Menu

Abstracts

IUFRO Spruce 2015 – Conference Abstracts

August 11, 2015

August 12, 2015

August 13, 2015

Poster Session Abstracts

  • Wiretapping of the plants: The bioelectrical activity in Norway spruce roots is modulated by environmental conditions
  • Root grafts serve as a morphological connections for combining trees.
  • Preliminary Sitka spruce (Picea sitchensis) early growth model for MOSES_GB
  • Development and dynamics of young aspen-spruce mixedwood stands in western Canadian Boreal Forests
  • Modeling of architectural development of black spruce (Picea mariana Britton., Stern & Poggenb. 1988) regarding climate
  • Is there evidence of overyielding in young aspen-spruce mixtures?
  • Norway spruce in Latvia – management history and future challenges
  • Importance of first thinning in young mixed stands with Norway spruce
  • Release response of black spruce and white spruce due to overstory lodgepole pine mortality following mountain pine beetle attack
  • Effects of Oriental beech (Fagus orientalis Lipsky), rhododendron (Rhododendron ponticum) and slope position on litter decomposition rates of Oriental spruce [Picea orientalis (L.) Link] in Turkey
  • WQ4MGM: a wood quality module for the Mixedwood Growth Model
  • Group planting of beech seedlings as the method of the spruce stand conversion in the Karkonoski National Park, the Giant Mountains, Poland.
  • Current situation of conversing pure larch plantations to mixed forests by underplanting of Picea koraiensis and Pi nus koraiensis in Northeast China

  • August 11 - Plenary

    An Overview of Forests and Forest Management in Alberta

    Janis Braze, Alberta Agriculture and Forestry, Forest Management Branch, Edmonton
    The natural beauty of Alberta attracts tourists from around the world and has inspired the creation of arguably the most spectacular national parks in Canada. Outside of the national parks, nearly 38 million hectares (60 per cent) of Alberta’s landscape is comprised of public forests, which are one of the province’s most important resources and provide many social and economic benefits to society. Alberta has a diverse and rich forest history that continues to shape its landscape, and today forestry is the province’s third largest economic sector.

    Albertans are proud of their environment, abundant natural resources, and provincial system of parks and protected areas, and the provincial government supports achieving a balance between environmental, economic, and social outcomes. The management process to achieve this balance is rooted in a collaborative environmental stewardship approach to development involving all Albertans. The Government of Alberta provides an environmental stewardship framework, and regulates natural resource access allocation and use through planning, policy, and policy assurance programs. As stewards of the environment, business, and non-governmental organisations, communities and individuals comply with timber, fish and wildlife harvest limits, water use limits, and timely reforestation, land reclamation and remediation requirements with the objective of achieving a sustainable level of usage that will meet the needs of future generations.

    The presentation will begin with a review of Alberta’s forests and ecosystems, and the distribution of forest cover types. A historical division between the so-called “White” (agricultural) and “Green” (forested) Areas and its importance in forest management planning will be identified. An economic overview of the forestry sector and a brief review of the forest tenure system will be presented. A review of Alberta’s forest products and their markets, mills and employment will be included.
    The presentation will then describe the provincial planning hierarchy, including the Land-Use Framework, Alberta’s new approach for managing its private and public lands for the achievement of long-term economic, environmental and social outcomes. Regional and sub-regional planning principles will be briefly discussed.

    Finally, a special focus will be given to Alberta’s forest management planning system as it is supported by a provincial commitment to the principles of sustainable forest management and responsible stewardship.

    A copy of the powerpoint presentations is available in pdf format at: p1-braze.pdf


    August 11 - Plenary
    A natural disturbance-based approach to Ecosystem Management in the mixedwood boreal forest: Lessons learned from the EMEND project

    S. Ellen Macdonald, Dept. of Renewable Resources, Univ. of Alberta, 751 General Services Bldg., Edmonton, AB T6G 2H1, Canada; Email: ellen.macdonald@ualberta.ca
    John Spence, Dept. of Renewable Resources, Univ. of Alberta, Edmonton, AB Canada
    Vic Lieffers, Dept. of Renewable Resources, Univ. of Alberta, Edmonton, AB Canada
    Colin Bergeron, Dept. of Renewable Resources, Univ. of Alberta, Edmonton, AB Canada

    The EMEND (Ecosystem Management Emulating Natural Disturbance) project was established in 1998 as a collaborative venture between university and federal governments researchers, the provincial government and the forest industry. Our purpose was to explore how we could implement a natural-disturbance based approach to ecosystem management at the stand level in the boreal mixedwood forest and to experimentally test some of the central hypotheses or assumptions of the natural disturbance paradigm. The experiment encompasses four different forest types (conifer-dominated, mixed conifer-broadleaf, broadleaf-dominated with a conifer understory, broadleaf-dominated) and six levels of green tree retention: 2%, 10%, 20%, 50%, and 75% plus unharvested control. Reconstruction of fire history and comparison of stand age distributions suggests that, in contrast to contemporary wisdom, these forests are subject to a mixed fire regime. Almost all mixed and conifer-dominated stands were multi-aged as were some broadleaf-dominated stands. Following harvesting, white spruce regeneration densities declined with the amount of retention and increased with the amount of conifer in the canopy. Variable retention harvesting in which seed trees are maintained can result in high levels of white spruce stocking. Forest cover type had a strong influence on diversity and composition for different biota. Inclusion of a spruce component was particularly influential. Composition and diversity of several biotic groups varied with the gradient of retention level but no clear threshold was apparent. Even 75% retention was substantially different than unharvested control. Some biotic groups have now begun to show recovery towards the unharvested condition. On-going research at the EMEND experimental site over the past 17 years has taught us much about ecological relationships in the boreal mixedwood forest, whether and how we can manage these forests under the natural disturbance paradigm, and what we might hope to achieve by doing so.

    A copy of the powerpoint presentations is available in pdf format at: p1-macdonald.pdf

     

    August 11 - Plenary
    Mixed Sitka spruce-red alder stands in southeast Alaska: The role of alder for improving biodiversity and enhancing ecosystem services
    Robert Deal, PNW Research Station, 620 SW Main Street, Suite 400., Portland, OR 97205, USA;
    Email: rdeal@fs.fed.us
    Paul Hennon, Juneau, AK, USA
    David D’Amore, Juneau, AK, USA
    Ewa Orlikowska, Skinnskatteberg, Sweden

    Native Sitka spruce forests of southeast Alaska have relatively simple species composition but complex stand structures with high diversity of tree ages, sizes and forest canopy levels, and an abundant understory plant community. Wildlife and fisheries resources also play an important role in the ecological functioning and maintenance of ecosystem services. Even-aged, pure conifer forest management has greatly altered these forest ecosystems with significant decreases in structural diversity of forest stands and greatly reduced wildlife habitat. In this talk we will synthesize information on management options in in younger forests to increase diversity of stand structures and their associated effects on biodiversity and the provision of important ecosystem services. In younger forests that develop after clearcutting, mixed alder-conifer stands provide more heterogeneous structures and significantly higher understory biomass than in pure conifer forests. Red alder is also a prolific nitrogen fixing species and can significantly increase nitrogen in soils with higher levels of stand productivity. Research in Alaska indicates that red alder benefits understory plants, provides forage for deer and small mammals and provides a broad suite of important ecosystem services. Results also show a clear linkage with increased invertebrate diversity in aquatic systems with an associated improvement of fisheries habitat. The inclusion of red alder in conifer-dominated forests could provide the greatest amount of diversity and maintain the complex stand structures that are an important component of these forest ecosystems.
    A copy of the powerpoint presentations is available in pdf format at: p1-Deal.pdf


    Session A1
    The influence of boreal tree species mixtures on ecosystem carbon storage and fluxes

    Jérôme Laganière, Natural Resources Canada, Canadian Forest Service, Laurentian Forestry Centre, 1055 du P.E.P.S., P.O. Box 10380, Stn. Sainte-Foy, Québec, QC, Canada G1V 4C7; Email: Jerome.Laganiere@RNCan-NRCan.gc.ca
    Xavier Cavard, Swedish University of Agricultural Sciences, Umeå, Sweden
    Brian W. Brassard, Faculty of Natural Resources Management, Lakehead University, Thunder Bay, ON, Canada
    David Paré, Natural Resources Canada, Canadian Forest Service, Laurentian Forestry Centre, Sainte-Foy, Québec, QC, Canada
    Yves Bergeron, Institut de recherche sur les forêts, Université du Québec en Abitibi-Témiscamingue, Rouyn-Noranda, QC, Canada
    Han Y. H. Chen, Faculty of Natural Resources Management, Lakehead University, Thunder Bay, ON, Canada

    Plant species mixtures may potentially achieve higher productivity and carbon (C) sequestration than their single-species counterparts, but it is unclear whether such occurrences are common in natural forests. Here we investigated whether naturally-regenerated mixtures of common North American boreal tree species were more productive and stored more C than single-species stands. We also examined how closely the different C pools and fluxes were interlinked and if these relationships varied with species composition. Single- and mixed-species stands of trembling aspen, black spruce and jack pine on mesic sites were selected in two regions of the Canadian managed forest to assess aboveground and belowground productivity and C storage. We found synergistic effects of tree species-mixing on specific C pools and fluxes such as greater organic layer C stocks and higher fine root productivity in some mixtures, but no effects were detected on combined C pools or fluxes at the ecosystem scale. While species-mixture effect on total ecosystem C stock was not apparent, aspen abundance was linked to greater aboveground tree productivity, greater aboveground living biomass and greater soil heterotrophic respiration. These results indicate that aspen acts as a key driver of ecosystem C storage and fluxes in these forest ecosystems. However, our results do not imply that greater productivity and C storage may not be achieved under some circumstances in mixed stands of the species considered because species interactions vary in space and time, along with light, water and nutrient availability. Furthermore, when the entire forest ecosystem is considered (not only tree parts), synergistic effect of tree species mixture may be more difficult to observe.

    A copy of the powerpoint presentations is available in pdf format at: a1-laganiere.pdf

    Session A1
    Linking multi-functional forestry goals with the legacy of spruce plantations in Scotland
    Maria Nijnik, The James Hutton Institute, Craigiebuckler, Aberdeen, AB15 8QH, Scotland, UK
    Email: maria.nijnik@hutton.ac.uk

    We demonstrate how different stakeholders perceive, interpret and deal with sustainable forestry objectives in Scotland; how they suggest implementing the forestry changes for people and nature; and how and why policy actors change their behaviour in response to changes on the ground. Within the ecosystem approach and considering a range of opportunities for and constraints on forestry development, we assess the ‘services’ that forest ecosystems can provide, as they are viewed by end-users. Research follows a semi-qualitative route and applies the Q-method which helps us to elucidate a range of existing attitudes, e.g. to woodlands development, and the spectrum of sustainability to which they may relate. Public attitudes towards changes in forest management policy options have been revealed; criteria of respondents’ perspectives have been identified and key factors influencing the attitudinal diversity have been explained. We have become aware of priorities and of factors that can hamper forestry development (e.g. concerning the reforestation, given the aspirational target of increasing Scotland’s forest cover to 25%). The revealed attitudes and perceptions concerning various ecological, socio-economic and aesthetic aspects of forestry changes have distinct policy relevance. Despite at times the opposite perspectives regarding the future of Scottish forestry, all (four) identified attitudinal groups have strong emphasis on regeneration of native woodlands and on the improvement of aesthetic values of forests. The mix of attitudinal groups identified and explained implies the recognition of ecosystem services types and the trade-offs between these. Also, findings allow us to suggest that, in Scotland, the Productivists position (for which the economic objectives of forestry development are important, and Sitka spruce is a predominant species) is strong. The research has also demonstrated comparability between public and stakeholder preferences in support of the multi-functional future of forestry, and this has important implications for decision-making.
    A copy of the powerpoint presentations is available in pdf format at: a1-nijnik.pdf



    Session A1
    Enabling wise forest management through the application of airborne laser scanning, with examples from biodiversity and riparian conservation

    Christopher W. Bater, Alberta Agriculture and Forestry, Forest Management Branch, 8th floor Great West Life Building, 9920 - 108 Street NW, Edmonton, AB, T5K 2M4;
    Email: chris.bater@gov.ab.ca

    Alberta’s Forest Management Branch (FMB) is an organization tasked with the stewardship of the province’s forests, and prides itself in its culture of innovation and capacity to adapt to advances in science and technology. Light detection and ranging (lidar) is arguably the most important remote sensing technology to emerge in forestry since aerial photography became widely used in the mid-20th Century. In response to the current mountain pine beetle infestation, FMB began purchasing lidar data at a rapid rate. Since 2008, licenses for more than 30 million hectares of data have been acquired. Although the initial driver of the purchase was the derivation of a quality digital elevation model for harvest planning, opportunities exist in many other areas. Within FMB, large-scale initiatives related to wet areas mapping, and enhanced forest inventory and vegetation characterization have been undertaken; both have fed more extensive research projects related to hydrological risk, access management, sustainable forest management, disturbed area reclamation, biodiversity conservation, and riparian conservation. I will present an overview of FMB’s publically available lidar-derived wet areas and vegetation datasets, and provide examples of their use for biodiversity and riparian vegetation conservation.

    A copy of the powerpoint presentations is available in pdf format at: a1-bater.pdf

    Session B1

    Allometric variation of Norway spruce trees from pure and mixed stands

    Ioan Dutca, Faculty of Silviculture and Forest Engineering (S building, SI5 room) Sirul Beethoven 1, 500123, Brasov, Romania; Email: idutca@unitbv.ro


    Tree allometry is important in the estimation of carbon accumulation in forests. Although known to be species and site specific, the current allometric equations are used to predict the biomass regardless of stand species association. The aim of this study was to assess the effect of species association on aboveground allometry and biomass allocation pattern of young Norway spruce trees, showing the uncertainty levels induced by the species association into biomass prediction. Young trees were preferred in order to confirm the transition from no effect of species association at the moment of planting to whether significant or not after the canopy closure. Biomass data measured for 70 young Norway spruce trees (35 from pure stands and 35 from mixed stands) randomly sampled from plantations in Eastern Carpathians of Romania was used. The diameter of the sampled trees ranged from 2 to 20 cm. To account for the effect of species association and also for the uncertainty induced, the Bayesian Generalized Linear Mixed Models (GLMM) were used. The response variable was the tree biomass (total and by components) and the explanatory variable was represented by tree diameter and/or height. As the trees were sampled from different plantations the random effect in each model was represented by the plantation. The ecological implications of the obtained results will be further discussed.


    Session B1

    White Spruce Annual Radial Area Growth and Wood Properties Averaged over Multiple Time Periods in Relation to Current Tree and Stand Attributes

    Francesco Cortini, Dept. of Renewable Resources, University of Alberta, Edmonton, AB, T6G 2H1; Email: fcortini@gmail.com
    Dan MacIsaac, Natural Resources Canada, Canadian Forest Service, Edmonton, AB Canada
    Phil Comeau, Dept. of Renewable Resources, University of Alberta, Edmonton, AB, T6G 2H1

    The relationships between white spruce growth (i.e. radial area increment) and wood properties (i.e. wood density, microfibril angle and modulus of elasticity) were investigated in relation to tree and stand attributes including estimates of competition and climate variables. Data for this study came from eight white spruce mature stands in the boreal forests of western Canada that underwent a wide range of understory protection treatments. The base models were built using annual averages (at DBH) over the three-year period prior to field sampling in relation to the crown, tree and stand attributes measured at the time of sampling. The base models developed were then applied to average annual radial area growth and wood properties calculated over longer periods of times (i.e. five, ten and 20 years). The base mixed effect models with the highest predictive ability were radial area growth and wood density with adjusted R-square values equal to 67% and 38%, respectively. The results indicated that live crown ratio was overall the best predictor of radial growth and wood properties of white spruce. The models consistently improved when using annual averages calculated over longer periods of time, which indicated that current tree and stand attributes could explain a significant portion of the variability related to past radial growth and wood properties up-to 20 years prior to sampling.

    A copy of the powerpoint presentations is available in pdf format at: b1-cortini.pdf


    Session B1

    Validation of existing and new models for wood stiffness in white spruce

    Derek Sattler, Quebec, QC Canada; Email: dsattler@ualberta.ca
    Jim Stewart, Canadian Forest Service, Northern Forestry Centre, Edmonton, AB Canada

    Wood stiffness, or modulus of elasticity (MoE), is a property which is used in grading machine stress rated lumber, but also gives insight into the biomechanical function of wood in trees. We evaluated an existing model for the prediction of pith to bark MoE (Mit-DS model) in white spruce (Picea glauca). The Mit-DS model was developed using MoE measured with static three-point bending tests and included samples taken across the central boreal mixedwood subregion of Alberta. We evaluated the model using samples collected from 9 sites located across west-central Canada, in a region defined as the Boreal Plains ecozone. In the evaluation dataset (BP dataset), MoE was measured using Silviscan-3. We also developed a new model after examining regional, climatic and growth-rate related effects on the development of MoE. Our evaluation of the existing Mit-DS model revealed that it consistently under-estimates MoE at all rings from pith. Mean percent difference indicated that predictions were about 31% lower than observed values. In developing the new model, we found that MoE increased with decreasing growth rate and greater potential evapotranspiration after the effect of ring number from pith was taken into account. Significant east-west regional differences in MoE were also detected suggesting that two sets of regional parameters are required for the Boreal Plains ecozone. The fixed effects from the final model explained 65% of the variability in MoE in the BP dataset. Using a leave-one-out cross-validation by site, we found the new model to be stable and unbiased. Finally, the new model derived from the SilviScan data was found to be biased when evaluated on MoE measures collected using three-point bending tests. This suggests that future efforts to calibrate the Mit-DS and new model must be performed using MoE measured with static bending tests or SilviScan, respectively.

    A copy of the powerpoint presentations is available in pdf format at: b1-sattler.pdf

    Session A2

    Managing canopy composition in boreal mixedwood forests: effects on understory plant communities

     

    S. Ellen Macdonald, Dept. of Renewable Resources, University of Alberta, 751 General Services Bldg., Edmonton, AB T6G 2H1, Canada; Email: ellen.macdonald@ualberta.ca
    Phil Comeau, Dept. of Renewable Resources, University of Alberta, Edmonton, AB Canada

    It is widely asserted that mixed stands support higher biodiversity than monocultures. In mature, unmanaged mixedwood boreal forests our studies indicate that the relative abundance ofwhite spruce and trembling aspen is an important correlate of understory composition and diversity at the stand scale and at the scale of small patches within forest stands. We examined the effects of manipulation of mixedwood canopy composition through: 1) underplanting white spruce in aspen-dominated forests; 2) managing densities of aspen and white spruce; and 3) retention of understory white spruce while harvesting the aspen canopy. For white spruce underplanted into mature aspen-dominated mixedwoods 15 years prior, forest floor pH and microbial biomass nitrogen were higher and understory community composition was slightly different in plots within 1 m of planted white spruce as compared to plots further away. For white spruce underplanted 48 years prior there were significant effects on understory environment (litter depth, FH layer depth, forest floor pH) and vegetation. Total understory cover, richness and diversity; cover and richness of herbs; shrub cover and richness; and soil temperature were lower and understory community composition differed between plots 1m of the base of white spruce than in plots farther away. In mixedwoods stands in which density of aspen and white spruce were manipulated by pre-commercial thinning, graminoid cover was negatively related to aspen basal area and positively related to spruce basal area. There was no relationship between overstory cover and total understory cover. Height of graminoids and willows was positively related to aspen basal area and overstory cover. Understory protection harvesting resulted in increased species richness, decreased species turnover, and changes in understory community composition as compared to control stands. These results suggest that there may be variable effects of manipulation of mixedwood canopy composition on understory plant communities.

    A copy of the powerpoint presentations is available in pdf format at: a2-macdonald.pdf

    Session A2

    Impacts of single and repeated glyphosate herbicide applications on plant community diversity and spruce growth in an Alberta spruce plantation

    Erin Fraser; Alberta Agriculture and Forestry, 8th floor Great West Life Building, 9920 - 108 Street NW, Edmonton, AB, T5K 2M4 Canada; Email: erin.fraser@gov.ab.ca
    Phil Comeau, Dept. of Renewable Resources, Univ. of Alberta, Edmonton, AB Canada
    Susan Humphries, Dept. of Renewable Resources, Univ. of Alberta, Edmonton, AB Canada

    Herbicide treatments, using glyphosate, are widely used to control the major competitive vegetation species bluejoint reedgrass (Calamagrostis canadensis) and trembling aspen (Populus tremuloides) in regenerating white spruce (Picea glauca) plantations in Alberta, Canada. Short-term impacts on vegetation cover and plant community diversity are evident, and literature from other parts of Canada suggests that a single application of glyphosate in boreal spruce plantations can result in increased early plant community diversity due to a reduction in the abundance of these two dominant competitive species. In some cases, two treatments timed 2 or 3 years apart can be used to control these species on very competitive sites.

    In 2004, we initiated a study to examine the longer-term effects of aerial herbicide application on plant community development and tree growth and survival following harvesting and planting of a mixedwood site near Calling Lake, Alberta. Four treatments were applied: a) no treatment (control); b) herbicide application in the first growing season after harvesting; c) herbicide application in the third growing season after harvesting; and d) herbicide application in the second AND fourth growing seasons after harvesting (two treatments). All herbicide treatments involved aerial application of glyphosate at a rate of 2.1 kg active ingredient per hectare.

    After 11 growing seasons, species richness was not significantly affected by herbicide treatment, regardless of timing or frequency of application. Species diversity was higher in the areas treated with herbicide in the first growing season. Community composition differed significantly between sites treated with herbicide in the first growing season and the untreated control, but other treatments did not differ from each other. Herbicide treatment did not have a significant effect on the cover of bluejoint reedgrass after 11 growing seasons, but did significantly reduce trembling aspen cover and height. The greatest impact to trembling aspen was observed after the application of herbicide in both the second and fourth growing seasons with aspen height averaging 181 cm and density 150 stems per hectare in this treatment, compared to an average height of 446 cm and density of 11,725 stems per hectare in the untreated control areas. White spruce survival was generally high (>65%) across all treatments. However, the application of herbicide in the second and fourth growing seasons resulted in the tallest spruce with the largest diameters. These results indicate that the application of glyphosate herbicide does not reduce species richness or diversity. However, it can result in some changes to the vegetation community composition, and it does contribute towards accelerated development of a spruce dominated ecosystem. Applying glyphosate in both the second and fourth growing seasons resulted in the greatest reductions to trembling aspen cover and height, which is expected to confer significant growth advantages to the planted white spruce.

    A copy of the powerpoint presentations is available in pdf format at: a2-fraser.pdf

    Session A2

    Prediction of Site index in boreal forests of central Alberta using environmental data

    Ivan Bjelanovic, Dept. of Renewable Resources, University of Alberta, 751 General Services Bldg., Edmonton, AB T6G 2H1 Canada; Email: bjelanov@ualberta.ca
    Phil Comeau, Dept. of Renewable Resources, University of Alberta, Edmonton, AB Canada
    Mike Bokalo, Dept. of Renewable Resources, University of Alberta, Edmonton, AB Canada
    Barry White, Alberta Agriculture and Forestry, Edmonton, AB Canada

    Accurate determination of site index is critical to determining potential yield of regenerating stands and is a key input into growth and yield models used in Alberta. Site index prediction models based on the relationship between environmental factors and site index can overcome some of the problems and challenges associated with determining site index due to variation in structure, age, stand density, composition, and suppression of trees. High resolution lidar generated Digital Elevation Model (DEM) combined with lidar derived depth-to-water and flow accumulation indexes from Wet Area Mapping (WAM) in Alberta provide access to potential high resolution estimates of soil moisture and other biophysical factors for predicting potential site index. The objective of this study is to evaluate the potential use of environmental variables derived from lidar and ground based determination of ecological site characteristics in the estimation of site index. A network of temporary sample plots was established in Central Alberta to examine these relationships. This region is typically composed of trembling aspen (Populus tremuloides), lodgepole pine (Pinus contorta), and white spruce (Picea glauca). In this presentation we will discuss relationships between site index and environmental factors determined from both ground sampling and remote sensing information. We will also discuss the effectiveness of lidar-derived metrics in characterizing key environmental factors.


    Session B2
    The level of intermixing of coniferous and deciduous trees and associated effects on forecast growth in juvenile managed stands in Alberta

    Lee Martens, Forest Management Branch, Alberta Agriculture and Forestry, 7th Floor, Great West Life Building, 9920 108 Street, Edmonton, AB, Canada T5K 2M4;
    Email: lee.martens@gov.ab.ca

     

    Defining and identifying mixedwoods in regenerating stands was an important consideration when developing Alberta’s new reforestation standards. It was widely acknowledged that a range of mixedwood types is desirable. Using data from Performance assessments completed using the Aerial Stratification System between 2010 and 2014, I examine the level of intermixing of coniferous and deciduous trees and associated growth within managed stands in the boreal region of Alberta. Managed stands were first stratified based on tree species composition and density using 1:20,000 scale or 20 cm resolution RGB aerial photography. Each resulting polygon was then assessed for a mixedwood pattern type (intimate mixture, aggregated clumped distribution, or pure coniferous or deciduous composition) and tree spatial distribution (spatial pattern of trees in the regeneration layer analogous to an assessment of stocking). Field tallies by tree species, top height tree total height and age, and the Growth and Yield Projection System (GYPSY) were used to calculate polygon-level coniferous and deciduous mean annual increment (MAI) at culmination age. Preliminary results suggest that of the approximately 59, 600 ha stratified, 49% of the area was considered aggregate mixedwood, 44% intimate mixedwood, and 7% pure. Forecast growth (MAI) is highest in intimate mixtures and lowest in pure stands.


    Session B2
    Picea abies and Fagus sylvatica regeneration niche partitioning within gaps of an Alpine forest

     

    Jurij Diaci, Department of Forestry, Biotechnical Faculty, Vecna pot 83, 1001 Ljubljana, Slovenia; Email: jurij.diaci@bf.uni-lj.si
    Jurij Rozman, Slovenia Forest Service, Kranj, Slovenia

    Mixed mountain forests composed of Picea abies, Abies alba and Fagus sylvatica represent one of the most important Alpine ecosystems, both in terms of economics, environmental impacts and social functions. However, most mixed stands are characterised by even-aged forest structure and altered species composition, making them more prone to disturbances and less effective in protection against natural hazards. Changes to the forest microclimate and nutrient cycling delay natural regeneration and favour successional development of ground vegetation. In this study, we hypothesized that creation of appropriate gap sizes and shapes will facilitate natural regeneration and forest conversion. In 2003 we selected 15 gaps, 0.01 to 0.62 ha in size and more than 50 years old, and three areas below closed canopy on a south facing Picea dominated mixed mountain forest (1380-1480 m a.s.l.). Within gaps we established 542 systematically distributed research plots (1.5 x 1.5 m) and analysed regeneration attributes according to height classes, ground vegetation coverage, light climate, soil moisture, microsite relief, and soil features. Measurements were repeated after five vegetation seasons and indicated minimal changes in vegetation structure and slow development of regeneration. Vegetation ordination and generalized linear mixed models showed a positive association of Picea seedling abundance with diffuse light, thickness of organic horizons, presence of CWD, and moss coverage and a negative association with ground vegetation cover, soil water content, Ellenberg N, and direct light. Fagus seedlings were more abundant closer to seed trees, on less acidic soils with higher moisture content and on concave microrelief. The results indicate that Picea and Fagus seedlings may successfully establish under slightly open forest canopies, but in a few years the former require amounts of diffuse light comparable with medium sized gaps in this study (0.15 ha). Due to the negative association between direct light and regeneration, gaps should be elliptical with the long axis oriented east-west.

    A copy of the powerpoint presentations is available in pdf format at: b2-diaci.pdf

    Session B2
    Thinning experiments in young Norway spruce stands affected by decline in the Czech Republic

    David Dusek, Forestry and Game Management Research Institute, Research Station at Opocno, Na Olive 550, Opocno 517 73, Czech Republic; Email: dusek@vulhmop.cz
    Jiri Novak, Forestry and Game Management Research Institute, Opocno, Czech Republic
    Dusan Kacalek, Forestry and Game Management Research Institute, Opocno, Czech Republic

    Norway spruce (Picea abies L., Karst.) is one of the most important commercial tree species in the forests of central Europe. Norway spruce occupies about 54% of forested area in the Czech Republic. This species is, however, also prone to suffer from many pests and harmful agents, especially in areas beyond its natural ecological conditions. In the last two decades, massive and chronic spruce stands decline has been occurred in the Czech Republic. The decline manifests itself by yellowing, defoliation and by dying of trees in all age stages. The main reasons are probably unsatisfactory state of forest soils due to former pollution deposition, precipitation deficiency and high temperature in vegetation seasons connected with global climate change. Honey fungus and bark beetle attacks should have been considered as just accompanying factors. Basically, cause of spruce decline lies in complicated complex of factors.

    Change of forest species composition toward mixed stands is one of the most important and promising measures. However, silviculture measures such as thinning in the affected young spruce stands are questioned today. Properly conducted thinning in the young spruce stands (especially monocultures), however, is a prerequisite for improving both stability and vitality of individual trees and for making stand structure appropriate to introduction of other forest species. Experimental thinning program in young spruce stands started in 2010. Four experiments lies in northeastern part of the Czech Republic, one of the most affected areas exhibiting the spruce decline today.

    Thinning contributed to modest acceleration of diameter increment. Relative diameter growth rate was about 2-5% higher in thinned treatment. Mortality in thinned treatment was slightly higher compared to control one, but the mortality has not endangered future stand development yet. Preliminary results of the experiments support active thinning of young spruce stands, even in the spruce decline regions.

    An extended abstract for this presentation can be opened by clicking on the following link: b2_dusek_extended_abstract.pdf

    Wednesday August 12 - Plenary

    How experiments that investigated growing Sitka spruce in mixture changed British forestry – and what happened afterwards

     

    W.L. (Bill) Mason, Forest Research, Northern Research Station, Roslin, Midlothian, Scotland EH25 9SY; Email: bill.mason@forestry.gsi.gov.uk

    From 1960 to 1990 rates of new planting in the United Kingdom averaged 25 thousand hectares per year. Much of this afforestation involved planting a range of non-native conifers such as Sitka spruce (Picea sitchensis), on nutrient poor soils in exposed conditions. In the last decade of the conifer afforestation ‘era’, pines (Pinus spp.) and larches (Larix spp.) were frequently planted in mixture with spruce on marginal sites where successful growth of pure spruce stands depended on intensive vegetation management and repeated fertilizer applications. The evidence base for these ‘nursing mixtures’ was provided by experiments planted in the 1960s which showed a positive interaction between the nurses and Sitka spruce at time of canopy closure (e.g. better nutrient status, improved spruce growth rate, and anticipated higher rates of return).The programme proved increasingly controversial during the 1980s, and following a change of policy in 1988, new planting rates have declined to one-third of previous levels with greater use of native species. However, no results have been published on the long-term performance of such mixtures to see whether early growth projections have been maintained. Four experiments in northern Scotland on a range of site fertility have been reassessed at 42-47 years of age (i.e. close to rotation age). On three sites of lower fertility, basal area of mixed stands was equivalent to that of pure Sitka spruce given several nitrogen applications. The basal area of the mixtures was significantly (p<0.05 to 0.001) greater than that of pure Sitka spruce ‘control’ plots grown without nitrogen. On the most fertile site, the highest basal area was found in the nitrogen treatments, while there was no difference between the mixtures and controls. The implications of these results for sustainable management of conifer planted forests in upland Britain will be discussed.

    A copy of the powerpoint presentations is available in pdf format at: p2-mason.pdf

    Wednesday August 12 - Plenary

    Replacing monocultures with mixed-species stands in Sweden: The socio-ecological implications of two prominent mixed-species alternatives

     

    Adam Felton, Inst för sydsvensk skogsvetenskap/ Southern Swedish Forest Research Centre SLU/ Swedish University of Agricultural Sciences Box 49, Rörsjöv 1 230 53 Alnarp
    Sweden Email: adam.felton@slu.se

    M. Ahlström, Swedish University of Agricultural Sciences, Alnarp, Sweden
    J. Bergh, Swedish University of Agricultural Sciences, Alnarp, Sweden
    and many others.

    Relative to monocultures, mixed-species approaches to production forestry are often suggested to provide a range of societal benefits, including increased stand-level biodiversity, higher recreational values, reduced risks of pest or pathogen outbreak, as well as providing managers with alternative directions for stand development vital to addressing the risks and uncertainties posed by anthropogenic climatic change. Whereas there is evidence that mixed-species approaches en masse can provide positive outcomes, it is less clear the extent to which multiple benefits can be simultaneously derived from individual mixed-species alternatives. More specifically, it remains to be determined how well individual mixed-species production-forest alternatives can balance the net tradeoffs and synergies among ecosystem services and adaptive capacity, to produce desirable packages of ecosystem services for a given level of investment. Providing relevant insights in this regard requires evaluations of the encompassing suite of ecosystem services provided by specific mixture versus monoculture forestry alternatives within a given biogeographical context. Here we conduct such an assessment by anchoring ourselves to a baseline starting condition provided by the extensive areas of rotationally clearcut even-aged Norway spruce stands (Picea abies) within Sweden’s production forests. We contrast this reference condition with mixed-species stands comprised of spruce and birch (Betula pendula or pubescens), or spruce and Scots pine (Pinus sylvestris), which together dominate scientific consideration and the public discourse involving mixed-species alternatives in this region. We evaluate the incentives, obstacles and implications of these production forest alternatives from the combined perspectives of policy, ecology, silviculture, production, economics, recreation and aesthetics. Due to the rarity of comprehensive interdisciplinary assessments of particular polyculture alternatives, we see this study as an internationally relevant case study of the extent to which multiple socio-ecological benefits and their associated costs are possible from specific polyculture alternatives.

    A copy of the powerpoint presentations is available in pdf format at: p2-felton.pdf

    Session A3
    Linking the Depth-to-Water topographic index to soil moisture on boreal forest sites in Alberta

    Gabriel S. Oltean, Dept. of Renewable Resources, Univ. of Alberta, 751 General Services Bldg., Edmonton, AB Canada T6G 2H; Email: oltean@ualberta.ca
    Phil Comeau, Dept. of Renewable Resources, Univ. of Alberta, Edmonton, AB Canada
    Barry White, Alberta Environment and Forestry, Edmonton, AB Canada

    The depth-to-water (DTW) index is a topographic index defined as the sum of slopes along the least-cost pathway from any cell in the landscape to the nearest flow channel. DTW is estimated using a gravitational water flow model applied to digital elevation models developed using LiDAR point clouds. Values can be determined using different flow initiation areas linked to climate and to the geological and topographical attributes of the area. We used data from 125 plots across five locations in the boreal forest of Alberta, Canada, to evaluate (1) the relationships between soil attributes and DTW, (2) the optimal flow initiation area, and (3) models to map the spatial variation of soil properties. Soil moisture regime (SMR), drainage class and depth-to-mottles were strongly related with DTW, whereas soil nutrient regime, organic matter thickness, soil texture and coarse fragment content exhibited weak relationships with DTW. A flow initiation area of 2 ha yielded the best representation for SMR, drainage class and depth-to-mottles. DTW, flow accumulation (FA) and local slope were included in a linear model to estimate and map SMR, whereas only DTW and FA were used to model drainage and depth-to-mottles. These results suggest that in the uniform boreal landscape the spatial variation of water-related soil properties can be captured by DTW calculated at a relatively small flow initiation area.

    A copy of the powerpoint presentations is available in pdf format at: a3-oltean.pdf


    Session A3
    Disturbance regime and establishment of an old-growth Taiwan spruce (Picea morrisonicola) stand in central Taiwan

    Biing T. Guan, School of Forestry and Resource Conservation, National Taiwan University, Taipei 10617, Taiwan; Email: btguan@ntu.edu.tw
    Sheng-Kun Huang, School of Forestry and Resource Conservation, National Taiwan University, Taipei, Taiwan
    William E. Wright, Laboratory of Tree-Ring Research, University of Arizona, Tucson, AZ USA

    Successful implementation of forest ecosystem management requires understandings of natural forest disturbance regimes. Based on a dendrochronological approach, we deciphered and reconstructed the stand dynamics and disturbance history of an alpine old-growth stand dominated by Taiwan spruce (Picea morrisonicola Hay.), the southern-most distributed species of the genus, in central Taiwan. The results revealed that on a temporal basis, stand establishment could be divided into three stages, namely, one stage prior to 1750, a second stage from 1750 to 1850, and a third stage from 1851 to 1950. This sequence corresponded spatially to stand topography, i.e., from gentle to steep slopes. Based on the annual relative release frequency, this study found that most of the disturbances were small-scale and occurred in two frequency modes. The higher-frequency mode may have been related to typhoon precipitation, while the lower-frequency mode likely resulted from low-frequency variability in the East Asian rainy season and summer southwest monsoon precipitation. Based on reconstructed spatial-temporal stand dynamics, we inferred that the stand is mainly shaped by small-scaled tree-replacement disturbance events. Although stand-replacing events are rare, one likely occurred before 1690 and that it took more than 250 years after the event for the stand to completely re-establish.


    Session A3
    Natural regeneration of Picea glauca in the mixedwood boreal forest of western Canada

     

    Stefanie M. Gärtner, Faculty of Environment and Natural Resources, University of Freiburg, Tennenbacherstr. 4, 79085 Freiburg, Germany; Email: stefanie.gaertner@waldbau.uni-freiburg.de

    Phil Comeau, Department of Renewable Resources, University of Alberta, Edmonton, AB Canada (presenting)
    Mike Bokalo, Department of Renewable Resources, University of Alberta, Edmonton, AB Canada
    S. Ellen Macdonald, Department of Renewable Resources, University of Alberta, Edmonton, AB Canada
    Ken Stadt, Alberta Agriculture and Forestry, Edmonton, AB Canada

    Picea glauca (white spruce) is a widely distributed and economically important tree species of the North American boreal forest. It may establish directly after a disturbance such as wildfire or several decades later. Typically it is found intermixed with other (usually deciduous broadleafs) boreal tree species, often becoming dominant in the later stages of stand development. In an empirical study we quantified the range of variation in post-fire regeneration in boreal mixedwoods in Alberta. We found high variability in the regeneration composition between and within five fires 10 to 20 years post-burn. Stands having a pre-fire deciduous component regenerated mostly to deciduous species, while pre-fire pure conifer (white spruce) stands had the highest proportion of unstocked plots. When conifer regeneration occurred it was almost always pine even when no pine component was indicated in the pre-fire forest inventory. In the 20 year old fire we found some small white spruce but almost none in the 10 to 13 year old fires. We also compared post-fire and post-harvest regeneration by pairing fires with nearby post-harvest plantations that had standard site preparation and planting treatments. The post-harvest plantations had a higher percentage of plots stocked to conifer whereas in the unmanaged, post-fire areas the plot stocking was of mixed species. We used a growth model (the Mixedwood Growth Model; MGM) to project the regeneration data forward to mature stands. The model suggested that post-fire areas will have substantially lower volumes of white spruce and a higher proportion of deciduous at rotation age than post-harvest areas. This suggests that natural, fire-origin stands achieve white spruce dominance considerably later than will post-harvest stands. This likely reflects a slow process of accumulation of spruce ingress as the deciduous canopy matures and breaks up.

    A copy of the powerpoint presentations is available in pdf format at: A3 - Gartner et al.pdf

    Session B3

    Overyielding in mixed forests decreases with site productivity

    Patrick Vallet, Irstea, domaine des Barres, 45290 Nogent sur Vernisson, France Email: patrick.vallet@irstea.fr
    Maude Toigo, Irstea, domaine des Barres, Nogent sur Vernisson, France
    Thomas Perot, Irstea, domaine des Barres, Nogent sur Vernisson, France
    Jean-Daniel Bontemps, AgroParisTech, Nancy, France
    Christian Piedallu, AgroParisTech, Nancy, France
    Benoit Courband, Irstea, St Martin d’Hères, France

     

    There is a rising interest in the role of species diversity in ecosystem functioning and services, including productivity. Yet, how the diversity–productivity relationship depends on species identity and abiotic conditions remains a challenging issue. We analyzed mixture effects on species productivity along site productivity gradients, calculated from a set of abiotic factors, in two biogeographic contexts (highlands and lowlands). We compared the productivity of 5 two-species mixtures with that of monocultures of the same species.
    Our data set was compiled from the 2006 to 2010 French National Forest Inventory data base and covers 2361 plots including pure and mixed stands.

    Overall productivity of mixtures in highlands, that is Norway spruce-European beech, European beech–silver fir and to a lesser extent, Norway spruce-silver fir, was found to be higher than expected from the productivity of corresponding monospecific stands. Overyielding was mainly due to European beech for the first two mixtures and to silver fir for the third one. No effect of mixture was found for sessile oak–Scots pine and sessile oak–European beech stands in lowlands. Overyielding of sessile oak mixed with Scots pine was not strong enough to significantly increase overall stand productivity. Overyielding of European beech was balanced by an underyielding of sessile oak.

    The mixture effect changed along site productivity gradients for six cases out of the 10 studied, with a stronger and positive effect on sites with low productivity. The magnitude of this change along site productivity gradients varied up to 89% depending on the tree species.

    The nature of species interaction in mixtures with regard to productivity changes with species assemblage and abiotic conditions.

    This talk is based on an article recently published in Journal of Ecology, with particular emphasis on the Spruce results.

    A copy of the powerpoint presentations is available in pdf format at: b3-vallet.pdf

     

    Session B3

    Linking stockability and stand productivity in Alberta’s boreal mixedwoods

     

    Valentín J.Reyes-Hernández, Colegio de Postgraduados, CampusMontecillo, Texcoco, México. 56230. Email: vareyhdz@gmail.com
    Phil Comeau, Dept. of Renewable Resources, Univ. of Alberta, Edmonton, AB Canada

    While it has been shown that total stand productivity might be benefited through the development of species mixtures it is not an easy task to assess the beneficial effects of species mingling. In this research, we used data from permanent sample plots to analyze the potential beneficial effects of mixtures on total stand productivity, in terms of periodic annual increment in volume (PAIv), for boreal stands comprised of trembling aspen and white spruce, in Alberta, Canada. We used measures of density, site occupancy (represented by Reineke’s Stand Density Index or SDI), height, and site quality, to examine the variation in PAIv for each component species and for the whole stand. Analyses also included examination of the effects of stand composition. Non-linear regression models were fit to combinations of variables representing these stand attributes. The best model explained up to 84 % of the total variation in spruce PAIv, with SDI and average spruce and aspen height among the most consistent explanatory variables. At the total stand level, SDI, basal area per hectare, and average height for each species, as well as stand composition, were the most consistent variables in the models evaluated. However, it was possible to explain only between 30-31 % of the variation in total stand PAIV. Reductions in total stand volume increment were associated with reductions in site occupancy of spruce, aspen, or both. The highest total stand volume increment is attained when site occupancy (SDI) of both species reaches its maximum, demonstrating the ecological combining ability of these two species. Thus, variation in maximum stocking densities (i.e. stockability) has a strong influence on volume growth in these forests.


    Session B3

    Modelling basal area growth in even- and uneven-sized mixed Picea abies stands in southern Finland as a function of growing stock and stand structure

    Eric K. Zenner, 305 Forest Resources Building, Penn State University, University Park, PA 16802 USA; Email: eric.zenner@psu.edu

     

    Picea abies dominated boreal forests of Europe typically develop into mixed multi-layered uneven-aged stands. Nonetheless, concerns about insufficient shade tolerances of their tree species convinced Finnish forest policy makers to strongly advise against uneven-aged management in the middle of the 20th century, which led to the cessation of most variants of continuous cover forestry. We studied growth responses of mixed Picea abies stands following two harvest treatments (thinning from below in even-aged and single-tree selection in uneven-aged management) that were applied in 62 circular plots of 0.03 ha on two sites in southern Finland in 1994 and 2002; residual basal areas ranged between 9–48 m2 ha-1. Here we report on absolute and relative basal area (RBA) growth of trees ≥ 2 cm DBH over a period of 8 years (1994–2002) and 6 years (2002–2008) following harvest. RBA growth was measured as proportional growth relative to post-cut residual basal areas and as relative growth rate (RGR) based on log-differences of BA. Structural stand characteristics were quantified using the standard deviation of the tree diameters, the tree mixture index, the diameter differentiation index, the proportions of basal area contribution by different tree species (i.e., spruce, pine, hardwoods), and the structural complexity index (SCI).

    After accounting for significant effects of residual growing stock (BA) and site effects, absolute and relative basal area growth was significantly smaller in plots that received a thinning from below over both growth periods. Basal area increment after the 1994 harvest entry was positively influenced by a more intimate species mingling, whereas increasing structural complexity negatively influenced growth following both harvest entries, particularly in the uneven-aged treatment at one site. Although structural complexity is often considered an important objective in contemporary forest management, too much structural complexity may result in some growth losses in uneven-aged stands.

    A copy of the powerpoint presentations is available in pdf format at: b3-zenner.pdf

    Session A4

    Growing Norway spruce in mixed stands in lowlands in Poland
    Dorota Dobrowolska, Forest Research Insitute, Braci Lesnej 3, 05-090 Raszyn, Poland;
    Email: d.dobrowolska@ibles.waw.pl

    Debate on natural distribution of main tree species in Poland took place in forestry recently. Distribution of silver fir (Abies alba Mill.) and Norway spruce (Picea abies Karst (L.) was the most controversial. The main goal of the study was to compare the growth, productivity, vitality and natural regeneration of silver fir within and beyond its natural range in Poland. The study was conducted in 48 mixed stands with different share of silver fir distributed within and beyond this species natural range. Growth and regeneration of silver fir were assessed on two dominated site types: fresh deciduous and fresh mixed deciduous forest site types. It was found that Norway spruce was one of the tree species in mixed stands with the share of fir. This tree species was mostly artificially planted, especially beyond the natural range of silver fir. The dominant tree species in the investigated stands were European beech (Fagus sylvatica L.) and oaks (Quercus robur L. and Q. petraea Liebl.), i.e. their number and volume were the highest. Norway spruce most often composed stands beyond silver fir natural range. Basal area of Norway spruce was significantly higher, whereas H/DBH ratio was significantly lower beyond silver fir range. Norway spruce regenerated naturally in the investigated area. Density of spruce seedlings (H≤0.5m) was higher beyond fir distribution. Density of small saplings (H>0.5 and DBH≤2) was also significantly higher beyond fir range and on fresh mixed deciduous site type. However, number of tall saplings was higher within silver fir natural range. So, Norway spruce is an important component of forest stands in lowlands, especially beyond silver fir range, and should grow and regenerate there.


    Session A4

    Evaluating the relative importance of direct and indirect impacts of climate change on European spruce forests

    Che Elkin, University of Northern British Columbia, Ecosystem Science and Management, 3333 University Way, Prince George, BC, V2N 4Z9, Canada; Email: che.elkin@unbc.ca
    Harald Bugmann, ETH Zürich,Department of Environmental Sciences, Zürich, Switzerland
    Tzvetan Zlatanov, Forest Research Institute, Sofia, Bulgaria
    Tomáš Hlásny, National Forest Centre, Zvolen, Slovak Republic

     

    The response of spruce forests to climate change is predicted to differ between regions as a result of different future climate drivers, differences in current and historic forest management practices, and region specific responses of climate sensitive disturbances. The relative importance of direct climate impacts vs. modified disturbances regimes will likely differ between regions due to the relative distance that vegetation and disturbance processes are to climate thresholds. We evaluated the projected importance of direct vs. indirect climate impacts on spruce forests in three European case study sites that under current conditions represent a range from cool and wet to warm and dry climatic conditions. Using a forest landscape model that includes climate sensitive representations of fire and bark beetle disturbances we simulated forest dynamics in each case study region for the next century under three climate scenarios that range from moderate to severe shifts in temperature and precipitation. At sites that are currently warm and dry increased drought stress under even moderate climate change is projected to be the major driver of spruce mortality and forest dynamics. Fire disturbances are also projected to increase at these sites, but net impact of fire on forest state and forest ecosystem services remained smaller than the direct impacts over the course of our simulations. In contrast, at comparably cooler and wetter sites climate change is projected to substantially increase the importance of European spruce bark beetle disturbances. At these sites direct climate impacts are also projected to influence forest composition, however these impacts are not observed until the latter part of the century while the impact of bark beetle disturbances on forests is projected to occur in the near future.

    A copy of the powerpoint presentations is available in pdf format at: a4-elkin.pdf

    Session A4

    Can mixedwood management mitigate climate change impacts on spruce in western Canada’s boreal forests?
    Phil Comeau, Dept. of Renewable Resources, Univ. of Alberta, 751 General Services Bldg, Edmonton, AB T6G 2H1 Canada; Email: phil.comeau@ualberta.ca

    Substantial temperature increases and associated increases in drought are forecast for the boreal forests of western Canada and these are expected to have significant impacts on the distribution of white spruce (Picea glauca (Moench) Voss). Since mixtures of aspen (Populus tremuloides Michx.) and white spruce are a common feature of upland sites, the potential for mixedwood management to mitigate climate change effects is of interest. While overtopping aspen have been shown to reduce the growth of white spruce, the presence of aspen has also been shown to mitigate frost injury and winter injury that may result in substantial damage to regenerating white spruce. In addition, aspen cover reduces the impacts of grass layer competition. In this presentation I will examine effects of aspen on air temperature, soil temperature and soil moisture monitored over an 8 year period following regeneration of aspen and spruce at one study site where treatments have created 6 plant community types: 1) an intact aspen canopy with planted spruce growing in the understory; 2) the same community as #1 with spot removal of aspen within a 2 m radius of planted spruce; 3) the same community as #1 with spot removal of all vegetation within a 2 m radius of planted spruce; 4) broadcast removal of aspen which created a spruce plantation with a well developed grass layer; and, 6) broadcast removal of all vegetation. Results demonstrate that aspen mitigates effects of drought and cold injury at this study site and indicate that on this site, aspen will mitigate impacts of global warming. However, the intact aspen canopy does substantially reduce growth of white spruce. Since they provide sufficient light for excellent tree growth while also providing the best microclimatic conditions for spruce, spot treatments show substantial promise.

    A copy of the powerpoint presentations is available in pdf format at: a4-comeau.pdf

    Session B4

    Early vegetation control for the regeneration of a single-cohort, intimate mixture of white spruce and aspen on upland boreal sites

    Michael Hoepting, Canadian Wood Fibre Centre, Canadian Forest Service, 1219 Queen St. E., Sault Ste. Marie, O, P6A 2E5 Canada.; Email: mhoeptin@NRCan.gc.ca
    Douglas G. Pitt, Canadian Wood Fibre Centre, Canadian Forest Service, Sault Ste. Marie, ON Canada
    Philip G. Comeau, Univ. of Alberta, Dept. of Renewable Resources, Edmonton, AB Canada.
    William C. Parker, Ontario Forest Research Institute, Ontario Ministry of Natural Resources, Sault Ste. Marie, ON Canada
    Dan MacIsaac, Canadian Wood Fibre Centre, Canadian Forest Service, Edmonton, AB Canada
    Scott McPherson, Science and Information Branch, Ontario Ministry of Natural Resources, North Bay, ON Canada.
    Milo Mihajlovich, Incremental Forest Technologies Ltd., Edmonton, AB Canada

    In Canada’s boreal forest region, mixedwood stands dominated by trembling aspen (Populus tremuloides Michx.) and white spruce (Picea glauca [Moench] Voss) are prominent and provide important timber and non-timber values. A paucity of silvicultural tools for regenerating mixedwood conditions prompted the establishment of an experiment in 2001, replicated in west central Alberta and northeastern Ontario, to test a strategy for regenerating a single-cohort, intimate mixture of aspen and white spruce. After ten growing seasons, spruce planted at 5-m spacing, each free of woody and early herbaceous competition within a 2-m radius, had equivalent or better survival, height growth and health status than spruce growing competition free for the duration of the experiment (α = 0.05). Select aspen situated in the vicinity of these spruce were at least as large as aspen crop trees situated in undisturbed plots. The early results of this long-term experiment suggest the hypothesized mixedwood regeneration strategy may offer a practical means of establishing mixedwoods capable of producing an early fibre rotation of aspen (~ age 30) and long term (> 60-years) sawlog crop of spruce.

    A copy of the powerpoint presentations is available in pdf format at: b4-Hoepting.pdf

    Session B4
    Managed mixtures of Aspen and White Spruce 21 to 25 years after Establishment
    Richard Kabzems, BC Ministry of Forests, Lands and Natural Resource Operations; 9000 17th St., Dawson Creek, B.C. Canada V1G 4A4; Email: Richard.Kabzems@gov.bc.ca
    Mike Bokalo, Univ. of Alberta, Dept. of Renewable Resources, Edmonton, AB Canada
    Phil Comeau, Univ. of Alberta, Dept. of Renewable Resources, Edmonton, AB Canada
    Dan MacIsaac, Natural Resources Canada, Canadian Forest Service, Edmonton, Alberta Canada

    Intimate mixtures of trembling aspen (Populus tremuloides Michx.) and white spruce (Picea glauca (Moench) Voss) are a key feature of boreal forests. These mixtures have the potential to produce high yields of merchantable fibre and provide numerous ecological services. Achievement of this potential has been difficult and often expensive to realize as a regeneration goal in managed forests. We report 21 to 25 year results of managed mixtures where the white spruce was planted, and the density of aspen natural regeneration manipulated within five years of stand initiation. Greater white spruce mortality occurred on the site where spruce planting was delayed at least two years after harvesting. On both sites, white spruce mortality was not affected by aspen density. While height and diameter growth of white spruce declined with increasing aspen density, the effect was not entirely consistent between the two sites. Abrasion from aspen branches was the most common source of damage to spruce crowns. Mixedwood Growth Model projections indicate that mixed stands will have greater merchantable volume production than pure spruce stands, particularly when aspen and spruce are harvested at two different times coinciding with their optimal rotation ages.

    A copy of the powerpoint presentations is available in pdf format at: b4-kabzems.pdf

    Session B4
    Sprucing up eastern Canadian mixedwoods: does white spruce (Picea glauca) respond to partial harvesting?

    Jessica Smith, Université du Québec en Abitibi-Témiscamingue, Institut de recherche sur les forêts (IRF), 445, boul. de l'Université, Rouyn-Noranda, Québec, J9X 5E4 Canada;
    Email: jessica.smith@uqat.ca
    Brian Harvey, Université du Québec en Abitibi-Témiscamingue, Institut de recherche sur les forêts (IRF), Rouyn-Noranda, Québec Canada
    Ahmed Koubaa, Université du Québec en Abitibi-Témiscamingue, Institut de recherche sur les forêts (IRF), Rouyn-Noranda, Québec Canada
    Suzanne Brais, Université du Québec en Abitibi-Témiscamingue, Institut de recherche sur les forêts (IRF), Rouyn-Noranda, Québec Canada
    Marc Mazerolle, Université du Québec en Abitibi-Témiscamingue, Institut de recherche sur les forêts (IRF), Rouyn-Noranda, Québec Canada

    Boreal mixedwood stands in the Abitibi-Témiscamingue region of north-western Quebec are often characterized by a dominant canopy of shade intolerant hardwoods like aspen (Populus tremuloides Michx.) with more shade tolerant conifers like balsam fir (Abies balsamea (L.) Mill.) and white spruce (Picea glauca (Moench.)Voss) distributed throughout the understory and sub-canopy. Partial harvesting has been promoted as an alternative treatment to clear-cutting and residual trees often exhibit increased growth rates above pre-treatment levels. We tested four partial harvesting treatments in mixed aspen - white spruce stands, consisting of different proportions of aspen removal (0, 50, 65 and 100% basal area (BA)). Ten years after treatments, 72 white spruce stems representing dominant, co-dominant and suppressed social classes were destructively sampled for stem analysis. Growth was analyzed as a function of treatment intensity, time since treatment, social status, pre-treatment growth rate and neighbourhood competition. Relative to control stands, radial and volume growth responses were detected only in the extreme treatment of 100% aspen BA removal. Compared to control trees, average annual radial and volume increments were, respectively, 23.5% and 7.1% higher for dominant trees, 67.7% and 24.1% higher for co-dominant trees and 115.8% and 65.6% higher for suppressed trees over the 10 years post-treatment. Growth response was proportional to pre-treatment growth rate with vigorous, younger trees having highest post-treatment growth rates. Based on Hegyi’s competition index, only coniferous neighbours had a negative effect on sampled white spruce growth. For these stand types and similar partial harvesting treatments, we conclude that it is necessary to remove a very high proportion of the shade intolerant hardwoods, and of total stand BA, in order to obtain accelerated white spruce growth rates. The removal of some dominant white spruce trees and thinning of dense conifers may further reduce intraspecific competition and have a positive effect on residual tree growth.

    A copy of the powerpoint presentations is available in pdf format at: b4-smith.pdf

    Session A5
    The Effect of Physical Interactions and Understory Light Conditions on Long-term Stand Dynamics in White Spruce and Aspen Boreal Mixedwoods.
    Dan A. MacIsaac, Natural Resources Canada, 5320 – 122 Street, Edmonton, Alberta T6H 3S5 Canada; Email: dan.macisaac@nrcan.gc.ca
    Phil Comeau, Univ. of Alberta, Dept. of Renewable Resources, Edmonton, AB Canada
    S. Ellen Macdonald, Univ. of Alberta, Dept. of Renewable Resources, Edmonton, AB Canada

    Trembling aspen (Populus tremuloides) and white spruce (Picea glauca) mixedwood forests cover much of the western Canadian boreal forest. Both species establish immediately post-disturbance. Over time, the slower growing understory white spruce grows through the aspen canopy, at which time it is subjected to physical abrasion by aspen swaying on windy days. This, along with the reduced light levels under the aspen canopy, can significantly reduce the growth rates and survival of the spruce. This study examined the importance of physical interactions and competition for light on the growth of white spruce into an aspen canopy.

    Research was conducted in CFS research plots established in 1951-1954 across the Prairie Provinces to determine the growth response of white spruce release from aspen. In 2001 detailed tree data and hemispherical images were recorded to quantify spatial variation in understory light conditions and crown architecture. Data analysis determined the effect of current and previous physical abrasion of spruce by aspen on spruce mortality and growth. The LITE model (Comeau 2012) provided an estimate of light levels in the proximity of each spruce tree. Physical abrasion has a significant effect on spruce growth and mortality, with a three-fold reduction in volume increment for trees with moderately to severely damaged leaders, compared to undamaged trees. Difference in growth between white spruce trees in control vs released plots accelerated since 1985, with a five-fold difference in total volume of individual trees in 2001. Several (27) competition indicies incorporating competition, physical proximity and light were developed, including Canham’s crowding index and the modified spacing factor. The best ci for each dependant variable was: annual volume increment 1951-85 – lorimer (all trees); annual height increment 1951-85 - lorimer (deciduous trees); annual volume increment 1985-01 – lorimer (taller trees);- annual volume increment 1985-01 – light at top of crown.


    Session B5
    Eighteen year results of white spruce underplanted beneath spaced and unspaced aspen stands in northeastern British Columbia
    Richard Kabzems, B.C. Ministry of Forests, Lands and Natural Resource Operations, 9000 – 17th Street, Dawson Creek, BC, V1G 4A4 Canada; Email: richard.kabzems@gov.bc.ca
    Phil Comeau, Univ. of Alberta, Dept. of Renewable Resources, Edmonton, AB Canada
    Cosmin Filipescu, Canadian Forest Service, Victoria, BC Canada
    Bruce Rogers, B.C. Ministry of Forests, Lands and Natural Resource Operations, Prince George, BC Canada
    Amanda F. Linnell Nemec, International Statistics & Research Corporation, Brentwood Bay, B.C. Canada

    Establishing white spruce by planting it under established aspen stands has substantial potential as a technique for regenerating mixedwood ecosystems in the western Canadian boreal forest. The presence of an aspen overstory serves to ameliorate frost and winter injury problems and suppresses competing understory vegetation that may compete with white spruce. Under future climatic regimes with more frequent and severe drought episodes, underplanting may provide a low risk, low input approach to mixedwood regeneration. In this study we examine the growth of white spruce during the first 18 years after being planted underneath a 39 year old stand of trembling aspen following thinning and fertilization. Spruce planted under thinned and unthinned aspen stands had successful establishment and reasonable growth even with aspen basal area over 45 m2 ha-1. Thinning of overstory aspen to 1000 or 2000 stems ha-1 did not increase the light reaching seedlings, but did result in improvements in light above the shrub layer and in diameter and height growth of the underplanted seedlings. Fertilization of these stands prior to planting had no effect on spruce growth. Growth of spruce underplanted at this site near Fort Nelson was similar to that at two other stands near Dawson Creek, B.C.

    A copy of the powerpoint presentations is available in pdf format at: b5-Kabzems.pdf


    Session B5
    Effects of intraspecific competition on growth of advance regeneration of white spruce following understory protection harvest

     

    Valerie S. Krebs, Univ. of Alberta, Dept. of Renewable Resources, 751 General Services Bldg., Edmonton, AB, T6G 2H1 Canada; Email: vkrebs@ualberta.ca
    Phil Comeau, Univ. of Alberta, Dept. of Renewable Resources, Edmonton, AB, T6G 2H1 Canada

     

    Understory protection harvesting, which removes mature aspen while leaving advance regeneration of white spruce is being used in many parts of northern Alberta. White spruce advance regeneration can grow vigorously following removal of overstory aspen in understory protection harvesting. In this study data were collected from four sites in northern Alberta to evaluate effects of competition from both coniferous and deciduous trees on growth of white spruce advance regeneration. We used dendroecological techniques to measure diameter and height growth responses. In this presentation we will discuss effects of neighboring spruce and aspen on both light levels and tree growth and the implications of these results in modeling and management of these stands.

    A copy of the powerpoint presentations is available in pdf format at: b5-krebs.pdf

    August 13 – Plenary

    Analyzing species mixing effects at the stand and tree level
    Hans Pretzsch, Technische Universität München, Hans-Carl-von-Carlowitz-Platz 2, 85354 Freising-Weihenstephan, Germany; Email: H.Pretzsch@lrz.tum.de

    Mixed-species forests can fulfil many functions and services better than pure stands and receive growing attention in forest science and practice. The presentation will show how mixing effects were traced in temperate forests from the stand to the tree level in order to better understand, model, and design mixed species production systems. I will discuss: (i) to what extent mixed stands can overyield pure stands, (ii) how productivity gains or losses result from the size distribution and growth partitioning in mixed versus pure stands, (iii) how differences in the size distribution and growth partitioning are reflected in the canopy space filling, (iv) how mixing can modify the individual tree allometry, and (v) how mixing effects are influenced by site conditions, which can change spatially and temporally. Finally, the relevance, the causes, and consequences of these mixing reactions will be discussed. Perspectives and concepts of further research will be presented.

    Some of my recent publications relating to the ecology and management of mixed-species stands:

    Pretzsch H., Block J., Dieler J., Dong P. H., Kohnle U., Nagel J., Spellmann H., and Zingg A. (2010) Comparison between the productivity of pure and mixed stands of Norway spruce and European beech along an ecological gradient. Annals of Forest Science, 67 (7): 712.

    Pretzsch H, Schütze G, Uhl E (2012) Resistance of European tree species to drought stress in mixed versus pure forests: evidence of stress release by inter-specific facilitation. Plant Biology, 15(3): 483-495.

    Pretzsch H., Bielak K., Block J., Bruchwald A., Dieler J., Ehrhart H-P., Kohnle U., Nagel J., Spellmann H., Zasada M., Zingg A. (2013) Productivity of pure versus mixed stands of oak (Quercus petraea (MATT.) LIEBL. and Quercus robur L.) and European beech (Fagus sylvatica L.) along an ecological gradient. Eur F Forest Res, 132 (2): 263-280.

    Pretzsch H and Dieler J (2011) Evidence of variant intra- and interspecific scaling of tree crown structure and relevance for allometric theory, Oecologia, 169(3): 637-649.

    Pretzsch H. (2014) Canopy space filling and tree crown morphology in mixed-species stands compared with monocultures. Forest Ecology and Management, 327: 251-264.

    Río M. del, Schütze G, Pretzsch H (2014) Temporal variation of competition and facilitation in mixed species forests in Central Europe. Plant Biology 16: 166-176.

    Pretzsch H., Rötzer T., Matyssek R., Grams T. E. E., Häberle K. H., Pritsch K., Kerner R., Munch J. C. (2014). Mixed Norway spruce (Picea abies [L.] Karst) and European beech (Fagus sylvatica [L.]) stands under drought: from reaction pattern to mechanism. Trees Structure and Function, 28:1305-1321.

    Pretzsch, H., del Río, M., …. & Bravo-Oviedo, A. (2015) Growth and yield of mixed versus pure stands of Scots pine (Pinus sylvestris L.) and European beech (Fagus sylvatica L.) analysed along a productivity gradient through Europe. Eur F Forest Res, DOI 10.1007/s10342-015-0900-4.

    A copy of the powerpoint presentations is available in pdf format at: p3-pretzsch.pdf

    August 13 – Plenary

    Scots pine-Norway spruce mixed forest experiments in northern Europe

     

    Lars Drössler, Southern Swedish Forest Research Centre, Rörsjövägen 1, SE-23053 Alnarp, Sweden; Email: Lars.drossler@slu.se
    Eric Agestam, Southern Swedish Forest Research Centre, Alnarp, Sweden
    Kamil Bielak, Department of Silviculture, Warsaw University of Life Sciences, Warsaw, Poland
    Małgorzata Dudzinska, Forest Research Institute, Department of Forest Management, Raszyn, Poland
    Bill Mason, Forest Research, Northern Research Station Roslin, Midlothian, UK
    Hans Pretzsch, Faculty of Forest Science and Resource Management, TU München , Freising, Germany
    Sauli Valkonen, Natural Resources Institute, Vantaa, Finland

     

    In northern Europe, the mixture of Norway spruce and Scots pine is one of the most common forest types. This tree species mixture occurs both in even-aged stands and old pine stands with advanced undergrowth of spruce. However, compared to pure spruce or pine forests, empirical growth studies and silvicultural experiments in mixed spruce-pine forest are much less frequent.
    We will give an overview of the existing long-term experiments in this region that compare the stand growth in mixed and pure stands of Scots pine and Norway spruce. All available experiments that contain both monocultures and mixture of these tree species will be presented. Location, contact person, site conditions, and stand characteristics will be provided for each site. The main contribution to the conference will be a joint analysis of growth comparisons between mixed forest and monoculture on similar sites documented in the literature. The published data from seven sites located in the UK, Sweden and northern Poland will be analyzed to calculate the difference of stand growth between tree species mixture and monocultures across all sites and stand ages. In a second step, the influence of site conditions (climate, latitude, soil fertility, etc.) and stand ages covered by the observation period will be investigated.

    In the discussion, the insights from the case-studies will be complemented by additional knowledge about growth patterns gained from inventory data and growth models in order to estimate production benefits by mixing both tree species over the whole rotation period. Information from other studies will be used to improve silvicultural guidelines for the management of even-aged, mixed Scots pine-Norway spruce stands in northern Europe. In addition, knowledge gaps and major research questions will be highlighted.

    A copy of the powerpoint presentations is available in pdf format at: p3-drossler.pdf

    August 13 – Plenary

    Why is Canadian policy governing boreal mixedwood forests so complicated?

    Victor Lieffers, Dept. of Renewable Resources, University of Alberta, 751 General Services Bldg., Edmonton, AB T6G 2H1 Canada; Email: victor.lieffers@ualberta.ca

    The usual development of a boreal mixedwood stand starts with aspen dominance in the early stages after disturbance, followed by a gradual transition to spruce dominance later in stand development. This seems like a simple ecological system and it should be easy to regulate. Over the years, however, Canadians have taken a sometimes crooked path in the development of policies that control industrial activities on public lands - and each province has taken a slightly different path. This presentation summarizes parts of the history and context of topics such as the development of a conifer bias; downloading of regeneration responsibilities to the industries that harvest the wood on public lands; taking the developmental phases of mixedwoods and locking them into fixed landbases with various proportions of spruce and deciduous trees; allocating different forestry companies with rights to the conifer or deciduous on the same landbase; implementing strict rules for limiting deciduous competition with conifers; and linking the annual allowable cut to the stocking and to the speed of regrowth of regenerating stands. Each of these policies, while well-intentioned, often produced unintended consequences. Today, while we may recognize the value of ecosystem management for mixedwoods, the history of policy development, professional biases as to what is good forestry, and longterm agreements and investment in mills, form an overwhelming inertia to change. If we could start over again, would we regulate these forests as we do?

    A copy of the powerpoint presentations is available in pdf format at: p3-lieffers.pdf

    August 13 – Plenary

    Understanding mixed forests in Europe – findings from EuMIXFOR

    W.L. (Bill) Mason, Forest Research, Northern Research Station, Roslin, Midlothian, Scotland EH25 9SY; Email: bill.mason@forestry.gsi.gov.uk
    Andrés Bravo-Oviedo, INIA-CIFOR Department of Silviculture and Forest Management & Sustainable Forest Management Research Institute Madrid Spain
    Hans Pretzsch, Faculty of Forest Science and Resource Management, TU München , Freising Germany
    Quentin Ponette, Forest science laboratory – Faculty of Bioengineering, Agronomy and Environment – Université Catholique de Louvain, Louvain-la-Neuve Belgium
    Maciej Pach, University of Agriculture, Krakow Poland
    Jerzy Lesinski, University of Agriculture, Krakow Poland

    EuMIXFOR is a European research network established in 2013 under the auspices of COST Association, a major pan-European mechanism for supporting knowledge exchange and cooperation in the fields of science and technology. 30 European countries have signed up to this network as well as four near-neighbour countries (Ukraine, Morocco, Tunisia, Algeria) and 5 institutions from four international partners (Argentina, Costa Rica, Canada and USA). The main aim of the network is to increase knowledge about all relevant aspects of mixed forests in Europe in order to enable the sustainable management of these forests and to enhance their future conservation, their expansion and their contribution to society. Participants within the network are organised into three working groups, namely:1) Understanding the dynamics and functioning of mixed forests; 2) Adaptive management of mixed forests; 3) Assessing the socio-economic values of mixed forests and policy measures for enhancing their benefits. Outputs from the network to data include a number of peer reviewed publications, scientific workshops, several training schools for early stage researchers, and exchange visits between researchers in different member states. Among major issues that have had to be addressed is agreeing a common definition of mixed forests applicable across a wide range of participants and mixed forest types. Preliminary analysis indicates that mixed forests exceed 25 per cent of the European forest area with Norway spruce (Picea abies) and Scots pine (Pinus sylvestris) being the species most commonly found in mixture. Other species commonly found in mixture include oaks (Quercus petraea and Q. robur), silver birch (Betula pendula) and European beech (Fagus sylvatica). This presentation will review some of the findings to date and indicate the challenges that remain to be addressed.

    A copy of the powerpoint presentations is available in pdf format at: p3-mason.pdf

    August 13 – Plenary

    Mixedwood management in the boreal plains of Canada – options for the future?

     

    Phil Comeau, Dept. of Renewable Resources, 751 General Services Bldg, Univ. of Alberta, Edmonton, AB T6G 2H1 Canada; Email: phil.Comeau@ ualberta.ca

     

    In the boreal forests of western Canada white spruce (Picea glauca [Moench] Voss) occurs primarily as a component of mixed stands with trembling aspen (Populus tremuloides Michx.). These mixedwood stands are the dominant forest type on productive uplands sites in the boreal plains and pure spruce stands are less common but do occur in later stages of succession. Mixtures are generally considered to be more resilient and more productive than monocultures. Growing spruce in a mixedwood setting may help mitigate impacts of climate change through reducing drought stress. In addition, aspen serves as a nurse species to small spruce primarily through reducing frost damage and suppressing competing herbaceous vegetation. However, aspen overstories suppress growth of white spruce by reducing available light. In aspen dominated ecosystems white spruce serves as an “ecological engineer”, contributing to increased yield, value, biomass, plant and ecosystem carbon, and biodiversity.

    Both coniferous and deciduous species are utilized commercially for a diversity of products. While aspen is regenerated naturally and requires no silviculture effort, white spruce is often managed intensively with mechanical site preparation, planting and stand tending used to accelerate succession toward the spruce dominated stages. While monocultures might be the simplest approach for managing stands in this region, growing managed mixed stands could provide higher yields, better wood quality, be more acceptable to the public, more likely to maintain biodiversity, and reduce risk relating to climate, insects, fire and other issues. Using thinning to reduce aspen density or using spot and patch treatments (cutting or herbicide ) can provide for good growth of white spruce seedlings within a mixedwood setting. Understory protection harvesting, that releases white spruce by harvesting the overstory aspen, is also a promising approach for providing both hardwood and softwood fibre from the same piece of land in a cost effective manner while making use of the nursing role of aspen as well as natural succession. A mix of approaches and practices should likely be used to maintain a diverse forest that is producing timber for commercial utilization while also satisfying increased recreational demands and meeting societies’ expectations that biodiversity in the boreal forest is protected. Selected approaches, their benefits, expected outcomes and costs will be discussed in this presentation.

    A copy of the powerpoint presentations is available in pdf format at: p3-comeau.pdf

    Poster Session Abstracts

    Wiretapping of the plants: The bioelectrical activity in Norway spruce roots is modulated by environmental conditions

    Robert Bernacik, Department of Plant Physiology and Biochemistry, Faculty of Biochemistry, Biophysics and Biotechnology, Jagiellonian University in Cracow, 7 Gronostajowa St. , 30-387 Cracow, Poland; Email: robert.bernacik@gmail.com
    Przemyslaw Malec, Department of Plant Physiology and Biochemistry, Faculty of Biochemistry, Biophysics and Biotechnology, Jagiellonian University in Cracow, Cracow, Poland.
    Pawel Jedynak, Department of Plant Physiology and Biochemistry, Faculty of Biochemistry, Biophysics and Biotechnology, Jagiellonian University in Cracow, Cracow, Poland.

    The harsh mountain climate beyond the level of the upper tree line usually eliminates single trees of Norway Spruce (Picea abies). In contrast, tree clusters, so called a biogroups, spatially isolated groups of tightly growing trees, can thrive in that conditions1. Root grafts (root fusions) are often observed between cluster members. The connections of vascular tissues have been suggested to facilitate the exchange of molecules and electrical signals between individual trees. However, the biological function of tree clusters still remains unclear. The trans-root potential (TRP) can be a parameter used to assess the intensity of the xylem transport in root system of trees in situ2.

    In this study we have monitored the TRP to investigate the influence of selected atmosphere parameters on the root transport activity in a population of Picea abies grown in the Carpathian Mts. The long-term TRP measurements were conducted on both selected single trees and tree cluster members, particularly individuals connected by root grafts. The weather-related parameters (including insolation, temperature, rainfall and humidity) were simultaneously monitored. The data analysis showed the influence of the atmospheric parameters on TRP measured in situ. Single trees and cluster members exhibited differences in response, as measured by TRP, to changes in environmental conditions. Moreover, data comparison revealed similarities (amplitude/phase) between TRP signals observed in particular tree cluster members connected by root grafts. Our data implies the role of root grafts in the formation of cooperative response of tree cluster members to the changes in the environment3.

    1 Danielewicz W., Pawlaczyk P., Community dynamics of Norway spruce.,(2007) In: Biology and Ecology of Norway Spruce, Tjoelker M.G., Boratyński A, Bugała W (Eds.), Springer, pp. 221- 254.

    2 Okamoto, H., Masaki, H., (1999), J. Plant Res. 112:123-130.

    3 This study is supported by the Ministry of Science and Higher Education (MNiSzW) of the Republic of Poland (DS-1277/HF/2013,“Generation of the Future”).


    Poster Session Abstracts
    Root grafts serve as a morphological connections for combining trees.

     

    Robert Bernacik, Department of Plant Physiology and Biochemistry, Faculty of Biochemistry, Biophysics and Biotechnology, Jagiellonian University in Cracow, 7 Gronostajowa St. , 30-387 Cracow, Poland; Email: robert.bernacik@gmail.com
    Przemyslaw Malec, Department of Plant Physiology and Biochemistry, Faculty of Biochemistry, Biophysics and Biotechnology, Jagiellonian University in Cracow, Cracow, Poland.
    Pawel Jedynak, Department of Plant Physiology and Biochemistry, Faculty of Biochemistry, Biophysics and Biotechnology, Jagiellonian University in Cracow, Cracow, Poland.

    A tree cluster (biogroup) is a spatially isolated group of 4 – 20 trees typically growing beyond upper tree line1. Noticeably, single trees usually vanish in such area. It was suggested that clustered individuals protect each other from harsh environmental conditions. Thus, a cooperation between cluster members was postulated to be the way to increase survival chances of individual organisms. Importantly, tightly growing trees promote formation of root grafts (fusion of tissues)2.

    Our field work focused on studying the root system grafting in a population of Picea abies grown in the Carpathian Mts. Magnetic resonance tomography (MRT) as well as dye penetrability and physiological analysis have proved that the accretion of xylems in root grafts formed by different trees, facilitates the exchange of molecules and electrical signals between cluster members. Thus, biogroups, contain individuals that are fused together and form the common vascular space. Moreover, the formation of root grafts can be considered as process with considerable stages observed especially in smaller biogroups (i.e. containing 2-3 individuals).

    We propose that, from ecophysiological point of view, the biogroup can be considered as a single, highly integrated system made of units connected by vascular tissues. It can serve as a model of the entire forest stand. Thus, understanding of tree cluster physiology is an important issue in the forest ecology, both in the mountains and in the lowlands3.

    1 Yli-vakkuri, P., (1953), Tutkimuksia puiden välisistä elimellisistä juuriyhteyksistä männiköissä: Untersuchungen über organische Wurzel verbindungen zwischen Bäumen in Kiefernbeständen. Acta Forestalia Fennica 60(3).

    2 Danielewicz, W., Pawlaczyk, P., Community dynamics of Norway spruce. (2007) In: Biology and Ecology of Norway Spruce, Tjoelker, M.G., Boratyński, A., Bugała, W., (Eds.), Springer, Dordrecht, The Netherlands, pp. 221- 254.

    3 This study is supported by the Ministry of Science and Higher Education (MNiSzW) of the Republic of Poland (DS-1277/HF/2013,“Generation of the Future”).


     

    Poster Session Abstracts

    Preliminary Sitka spruce (Picea sitchensis) early growth model for MOSES_GB

    Simone Bianchi, School of Environment, Natural Resources and Geography, Bangor University, Bangor, Gwynedd, LL57 2UW, United Kingdom; Email: afp462@bangor.ac.uk
    Sophie Hale, Forest Research, Northern Research Station
    Roslin, Midlothian, UK
    Catia Arcangeli, Forest Research, Alice Holt Lodge, Farnham, Surrey, UK
    Christine Cahalan, School of Environment, Natural Resources and Geography, Bangor University, Bangor, Gwynedd, UK
    Paul Henshall, Forest Research, Alice Holt Lodge, Farnham, Surrey, UK
    Gary Kerr, Forest Research, Alice Holt Lodge, Farnham, Surrey, UK
    Tom Jenkins, Forest Research, Aberystwyth Research Unit, Aberystwyth, UK

    Continuous Cover Forestry is an alternative management approach promoted in the UK Forestry Standard and in the UK Woodland Assurance Scheme. To support its implementation the Forest Research Agency is developing MOSES_GB, a distance-independent individual tree growth model suitable for use in mixed-species, uneven-aged stands. The model has been developed following the MOSES (MOdelling Stand rESponses) approach originally suggested by researchers at the University of Natural Resources and Life Sciences (BOKU), Vienna, Austria. The overstorey components of MOSES_GB are being adapted and re-calibrated for Sitka spruce (Picea sitchensis) growing under UK conditions. We present here the developments in the preparation of the early growth component for Sitka spruce regeneration, using both existing Forestry Commission datasets and data newly collected from coniferous stands. We prepared a preliminary model to predict the regeneration growth ratio (the ratio between the observed growth and the potential growth of the same tree growing in full light) based on the stand light transmittance and the tree size. Preliminary results are shown and discussed.

    A copy of the poster is available in pdf format at: poster_Bianchi.pdf

    Poster Session Abstracts
    Development and dynamics of young aspen-spruce mixedwood stands in western Canadian Boreal Forests

    Mike Bokalo, Dept. of Renewable Resources, Univ. of Alberta, 751 General Services Bldg., Edmonton, AB T6G 2H1 Canada; Email: mike.bokalo@ualberta.ca
    Phil Comeau, Dept. of Renewable Resources, Univ. of Alberta, Edmonton, AB Canada

    The Western Boreal Growth and Yield Association (WESBOGY) is a regional association of industrial, federal, provincial and university foresters and researchers interested in evaluating the dynamics of boreal forest development and the yield implications of silviculture practices. The four western provinces and the Northwest Territories are represented among the members. In 1992, WESBOGY began a long term study to evaluate the effects of aspen and spruce densities on the long-term dynamics of mixedwood stands. Eleven replicate installations of this study have been established in western Canada since that time. We will present and discuss results from recent analysis of spruce and aspen growth responses to the different treatments up to age 20.

    A copy of the poster is available in pdf format at: poster_bokalo.pdf

    Poster Session Abstracts
    Modeling of architectural development of black spruce (Picea mariana Britton., Stern & Poggenb. 1988) regarding climate

    Fabien Buissart, Irstea Aix en Provence, UR EMAX, 3275 route de Cézanne, CS 40061, 13182 Aix-en-Provence Cedex 5 France ; Email: Fabien.buissart@irstea.fr
    Michel Vennetier, Irstea Aix en ProvenceAix-en-Provence France
    Sylvain Delagrange, ISFORT - Institut des sciences de la forêt tempérée, Université du Québec en Outaouais, Ripon, QC Canada
    François Girard, Université de Montréal, department de géographie, Montréal QC Canada
    Alison Munson, Département des sciences du bois et de la forêt, Université Laval, Québec QC, Canada
    Régis Pouliot, ISFORT - Institut des sciences de la forêt tempérée, Université du Québec en Outaouais, Ripon, QC Canada

    Impacts of climate change on our forests is a major concern: how will the current stand respond to this change? Plant architecture is a science that allows studying the morphology of plants. Under contrasted climate (such as temperate climate), plant growth is not continuous: there are several breaks (particularly in winter). For several species these breaks remain visible for many years (leaving marks such as bud scars). Black spruce (Picea mariana Britton., Stern & Poggenb. 1988) follows this pattern. We studied architecture from mixed stand (Parc des Grands jardins, Québec) in order to assess the climate response of Black spruce architecture. We studied these parameters:

    • annual shoot length
    • ramification
    • needle length
    • reproduction

    For each parameter, we computed a PLS (Partial least square) regression (linear or logistic) with climatic parameters (monthly rainfall and temperature) and topologic variables (such as ramification order, age …). The results of this analysis show the active periods (organogenesis and elongation). We aggregated this result to build a simulator of Black spruce development depending on a climatic scenario.

    A copy of the poster is available in pdf format at: poster_buissart.pdf

    Poster Session Abstracts
    Is there evidence of overyielding in young aspen-spruce mixtures?

    Deogkyu Kweon, Dept. of Renewable Resources, Univ. of Alberta, 751 General Services Bldg., Edmonton, AB T6G 2H1 Canada; Email: kweon@ualberta.ca
    Phil Comeau, Dept. of Renewable Resources, Univ. of Alberta, Edmonton, AB Canada
    Mike Bokalo, Dept. of Renewable Resources, Univ. of Alberta, Edmonton, AB Canada
    Dan MacIsaac, Northern Forestry Centre, Canadian Forest Service, Edmonton, AB Canada

    Mixtures of trembling aspen (Populus tremuloides Michx.) and white spruce (Picea glauca (Moench) Voss) are a prominent component of the boreal forests in Western Canada, and overyielding indicating greater productivity in mixed species stands than monocultures has been observed in mature stands in this region. In this study we use data collected in 2006 (age=13), 2008 (age=15), and 2011 (age=18) from the Big River Saskatchewan site of the Western Boreal Growth and Yield Association (WESBOGY) Long Term Study to examine whether overyielding occurs in young mixtures of these species. At this site spruce was established at densities of 500 and 1000 stems per hectare, with aspen densities of 0, 200, 500, 1500, 4000 created by thinning, as well as an unthinned control. In addition, pure aspen treatments included unthinned, thinned to 4000 sph, and to 1500 sph. Stem biomass was calculated from diameter at breast height (DBH) and tree height and used as the production variable, and species proportions were calculated based on basal area. Productivity ratio (mixture production / expected production based on pure stands of the two species adjusted according to species proportion) was used to examine overyielding. Average productivity ratio indicated overyielding for the combination of 4000 aspen and 500 spruce (P-Ratio=1.38) and 4000 aspen with 1000 spruce (P-Ratio=1.18) at age 18 and these combinations are significantly different from pure stands (P-Ratio=1) for all 3 ages. The combination of 1500 aspen with 1000 spruce (P-Ratio=0.90) is not different from the productivity ratio of pure stands while all other treatments have P-ratios that are significantly lower than comparable pure stands.

    A copy of the poster is available in pdf format at: poster_kweon.pdf


    Poster Session Abstracts

    Norway spruce in Latvia – management history and future challenges

     

    Zane Libiete, Salaspils, Latvia; Email: zane.libiete@silava.lv
    Jurgis Jansons, Salaspils, Latvia
    Talis Gaitnieks, Salaspils, Latvia
    Peteris Zalitis, Salaspils, Latvia
    Talis Gaitnieks, Salaspils, Latvia

    Norway spruce is one of the main forest tree species in Latvia; spruce-dominated stands occupy 17% of 3.354 million ha of total forest area. It is economically important: in 2014, 13% of volume yield from final fellings and 34% of volume yield from thinnings was spruce timber and pulpwood. At the same time also the largest share, 34%, of total volume yield from sanitary fellings was spruce wood.
    After WWII spruce was mainly planted in monocultures with 80 years’ rotation age. In the 2nd half of 20th century spruce pulpwood plantations with 5000 to 7000 trees ha-1 were established on large areas, where intensive management, including fertilization, and felling at the age of 40 years were planned. With the collapse of Latvian pulpwood industry, these overstocked stands were left for conventional management.

    Even though Norway spruce is potentially highly productive, and mean annual increment in young stands can often reach 20 m3 ha-1, about 15 years ago unexplained productivity loss with consecutive tree dieback was observed in 30-50 years old stands. The first attempt to identify the problem and to propose solutions was in 2009 when a methodology to determine growth potential of spruce stands was developed and introduced into legislation. Although this initiative was successful, at present new, more profound knowledge is needed to face future challenges of growing timber demand, climate change and environmental issues. In 2014, a state-funded research program with following goals was launched: 1) development of management model for even-aged spruce stands; based on evaluation of spruce forests’ growth potential and response analysis to different thinning regimes; 2) evaluation of importance of genetic factors on spruce stand productivity; the impact of genotype and genotype-environment interactions; 3) analysis of phytopathological risks; occurrence of butt- and root-rot, identification of causal agents and population structure of Heterobasidion annosum s.l. 4) establishment of field experiment on fertile drained sites. This presentation illustrates this and several other research initiatives related to the management of spruce forests in Latvia.

    Participation in this conference was funded by State research programme “Forest and earth entrails resources: research and sustainable utilization – new products and technologies” (ResProd) project “Even-age spruce stands cultivation potential in fertile forest ecosystems”.

    A copy of the poster is available in pdf format at: poster_libiete.pdf


    Poster Session Abstracts
    Importance of first thinning in young mixed stands with Norway spruce

    Jiri Novak, Forestry and Game Management Research Institute, Research Station at Opocno, Na Olive 550, Opocno, CZ-51773; Email: novak@vulhmop.cz
    David Dusek, Forestry and Game Management Research Institute, Opocno, CZ
    Marian Slodicak, Forestry and Game Management Research Institute, Opocno, CZ
    Dusan Kacalek, Forestry and Game Management Research Institute, Opocno, CZ

     

    According to actual trends in European silviculture, mixed stands are established frequently in forest regeneration practice. Norway spruce is the most commercially important (also from its share point of view) tree species in Central Europe. Historically, spruce was grown mainly as monocultures but this approach often resulted in high risk of large-scale disturbances by abiotic and biotic harmful factors. As a result of recent trends, relatively large area of young mixed stands are established annually and recommendations for first (pre-commercial) thinning of these stands are required by forests practitioners. We will present results from a study focused on the effect of first thinning on development of young mixed stands with Norway spruce. We used both thinned and unthinned mixtures with European beech on two localities, which represented different conditions: (1) at an elevation of 440 m on Fagetum acidophilum site and (2) at an elevation of 900 m on Piceeto-Fagetum acidophylum site. Spruce has different ecological demands for successful development at young stage (it needs open space for individual stability development) compared to beech (it needs closed canopy for stem quality development). The most pronounced effect of thinning consisted in decreased amount of basal area (G), which had to be removed as salvage cut (dead trees). On control plots, 34-46% of G periodic increment had to be removed during the period of investigation (age of 19-35 years) as salvage cut, whereas salvage cut on thinned plots reached only 9-20% of periodic increment. On both localities, stability (by h/d ratio) of spruces was positively affected by thinning. Additionally, thinning supported spruce portion in lower elevation and beech portion in higher elevation. Results indicated that first thinning is a very important silvicultural measure to maintain future mixture.

    An extended abstract for this presentation can be opened by clicking on the following link: poster_novak_extended_abstract.pdf

    A copy of the poster is available in pdf format at: poster_Novak.pdf

    Poster Session Abstracts
    Release response of black spruce and white spruce due to overstory lodgepole pine mortality following mountain pine beetle attack
    Felix Oboite, Dept. of Renewable Resources, Univ. of Alberta, 751 General Services Bldg., Edmonton, AB T6G 2H1 Canada; Email: oboite@ualberta.ca
    Phil Comeau, Dept. of Renewable Resources, Univ. of Alberta, Edmonton, Alberta Canada

    Mountain pine beetle (Dendroctonus ponderosae Hopkins; MPB) has affected many lodgepole pine dominated stands in west-central Alberta. Advance regeneration of white spruce and black spruce is found in some attacked stands however its growth following death of the overstory is not well documented in Alberta.

    In 2014 we initiated a study aimed at determining and modeling the release response of black and white spruce in lodgepole pine forests in the upper and lower foothill natural subregions of western Alberta. We are examining how factors such as live and dead tree density, basal area (total basal area and basal area of larger trees by species), initial tree size, site index and release intensity influence release responses. Work also includes developing individual tree diameter and height growth functions for black and white spruce considering the influence of the above factors as well as parameterizing the Mixedwood Growth Model (MGM) for black spruce and evaluating and validating the performance of the model.

    A copy of the poster is available in pdf format at: poster_oboite.pdf


    Poster Session Abstracts
    Effects of Oriental beech (Fagus orientalis Lipsky), rhododendron (Rhododendron ponticum) and slope position on litter decomposition rates of Oriental spruce [Picea orientalis (L.) Link] in Turkey

    Temel Sariyildiz, Kastamonu University, Faculty of Forestry, Department of Forest Engineering, Soil Science and Ecology Division, 37100 Kastamonu/Turkey;
    Email: tsariyildiz@kastamonu.edu.tr

    The aim of this paper was to summarize information on litter decomposition dynamics of Oriental spruce [Picea orientalis (L.) Link] as affected by slope position, litter mixture with Oriental beech (Fagus orientalis Lipsky) and rhododendron (Rhododendron ponticum). Oriental spruce and beech are the two most common tree species in northeast Turkey. Their distribution, stand type and understory species are known to be influenced by topographical landforms. At high altitudes, Oriental spruce forms pure stands over a considerable area, while at low altitude it is often accompanied by Oriental beech. At high altitude, strong wind can result in creating small and big gaps. Within these gaps, ground flora is generally occupied by rhododendrons (Rhododendron ponticum L.), cherry laurel (Prunus laurocerasus L.) and blackberries (Rubus spp.). Because of those reasons, the decomposition of a single spruce of litter usually occurs in association with that of other species of litter, mostly beech and rhododendron litter. In order to understand how those factors (slope position, litter mixture with beech and understory cover by rhododendron) affect litter decomposition rates of Oriental spruce I have carried out a number of litter decomposition experiments in field since 2002. Most results have been published either in national or international journals. Here, a brief summary of those results will be presented. The objectives were to summarize (1) the effect of slope position on litter decomposition rates by placing Oriental beech and spruce litter at three slope positions on the north-facing site, (2) the effect of stand types (pure and mixed beech and spruce stands) on litter decomposition by placing beech, spruce and mixed beech–spruce litters under beech, spruce and mixed beech– spruce stands, (3) the effect of understory species by placing beech and spruce litter with and without purple-flowered rhododendron (Rhododendron ponticum) on the ground.

    An extended abstract for this presentation can be opened by clicking on the following link: poster_sariyildiz extended abstract.pdf

     

    Poster Session Abstracts
    WQ4MGM: a wood quality module for the Mixedwood Growth Model

     

    Jim Stewart, Canadian Forest Service, Northern Forestry Centre, 5320-122 St. NW, Edmonton, AB T6H 3S5 Canada; Email: Jim.Stewart@NRCan.gc.ca
    Chris Finlay, Edmonton, AB Canada
    Mike Bokalo, Dept. of Renewable Resources, Univ. of Alberta, Edmonton, AB Canada
    Derek Sattler, Quebec, QC Canada
    Phil Comeau, Dept. of Renewable Resources, Univ. of Alberta, Edmonton, AB Canada

    Wood density influences lumber strength and pulp yield and is related to many other wood quality properties. Modulus of elasticity (MoE) is a measure of the stiffness of wood and, along with density, determines the grade of Machine Stress Rated lumber. These and other wood quality properties are influenced by stand growth conditions and silvicultural treatments. Models predicting pith to bark wood density and MoE for white spruce (Picea glauca) have been developed and can be applied to ring level growth data, including data generated from tree-level growth simulators. To help silviculturalists make use of these models, we developed a “bolt-on” software module which links the wood property models to the Mixedwood Growth Model (MGM). The result is WQ4MGM, a stand-alone program written using C++. Wrapper code has been written which allows the module to interface with the Visual Basic programming code used in MGM. By applying WQ4MGM, predicted values for density, MoE and other wood properties can be obtained at the individual ring level. This output can be used to inform harvest operations and long-term silvicultural decisions in the context of value chain optimization. Predictions are also used as input to a second phase of the WQ4MGM module which estimates the transition point from juvenile wood (JW) to mature wood (MW), for any wood property of interest. Here, we present how WQ4MGM, in association with MGM, can be used to obtain estimates of the within-stem distribution of wood properties and the proportion of JW and MW for different growth conditions. In doing so, our objective is to show how WQ4MGM and MGM can serve as an important decision support tool. Similar wood property models for Lodgepole pine (Pinus contorta) are already programmed into WQ4MGM while models for properties such as micro-fibril angle are being prepared for inclusion.

    A copy of the poster is available in pdf format at:poster_stewart.pdf


    Poster Session Abstracts
    Group planting of beech seedlings as the method of the spruce stand conversion in the Karkonoski National Park, the Giant Mountains, Poland.

    Janusz Szmyt, Poznan University of Life Sciences, Faculty of Forestry, Silviculture Department, ul. Wojska Polskiego 69, 60-625 Poznań, Poland; Email: jszmyt@up.poznan.pl
    Jan Ceitel, Poznan University of Life Sciences, Faculty of Forestry, Silviculture Department, Poznań, Poland
    Jacek Zientarski, Poznan University of Life Sciences, Faculty of Forestry, Silviculture Department, Poznań, Poland
    Andrzej Raj, Karkonoski National Park,Jelenia Góra, Poland

    Large-scale forest decline was observed in the 1980’s through the 1990’s in the Sudety Mountains, south-western Poland. More than 15 000 ha of the forest have died due to air pollution, pest outbreaks and strong winds. Most of them (72%) were dominated by Norway spruce (Picea abies) and they were established artificially in the past. Spruce monocultures are very unstable ecologically and thus they are susceptible to abiotic and biotic factors influencing their growth. There is urgent necessity to find the best way to convert them into more resistant forest stand consisted of well adopted tree species.

    One of the methods of stand transformation is group planting of beech seedlings (Fagus sylvatica) under thinned (or dead) spruce canopies. Beech seedlings were planted in groups consisted of 20-30 seedlings, 200 groups per hectares.

    Conclusions are based on the linear correlations between seedling features (height growth, damage level) and characteristics of biogroups (e.g. seedling density, biogroup’s area, growing place of seedling). Five years after planting, both survival and growth of beech seedlings were satisfactory. Seedling growth depended mostly on the seedling location within the biogroup. Damage caused by wild game were of minor importance. Our initial results confirmed the usefulness of group planting method for stand conversion, even under large herbivore pressure.


    Poster Session Abstracts
    Current situation of conversing pure larch plantations to mixed forests by underplanting of Picea koraiensisand Pinus koraiensis in Northeast China

    Jiaojun Zhu, Shenyang , China; Email: jiaojunzhu@iae.ac.cn
    Lizhong Yu, Shenyang , China
    Yirong Sun, Shenyang , China
    Chunyu Zhu, Shenyang , China
    Deliang Lu, Shenyang , China

    Most forests in Northeast China are mixed broadleaved secondary forests resulting from excessive timber harvesting of original forests. Since the 1950’s, about 2 million ha of larch (Larix spp.) plantations have replaced the secondary forests to meet the increasing timber demand. However, these larch plantations are causing lower biodiversity and poor ecosystem services. In order to convert these pure larch plantations into mixed forests the local species Picea koraiensis (spruce) and Pinus koraiensis (pine) have been underplanted. To investigate the feasibility of the under-planting, we surveyed the survival and growth of spruce and pine saplings under-planted in the larch stands in 2006 (>20 ha, Plot A) and 1996 (3.25 ha, Plot B) by the local forestry farm. The results indicate that larch stem densities were 125±17 and 83±34 trees/ha with basal areas of 14.3±2.0 and 9.5±3.1 m2/ha in Plot A and Plot B, respectively. After 10 years, survival of spruce was 1167±367 saplings/ha, which was similar to that of pine (1158±72 saplings/ha) in Plot A. But the spruce growth (collar diameter: 2.0±3.1 cm, height: 94.0±26.9 cm and crown width: 79.9±22.4 cm) was less than pine (collar diameter: 2.5±0.2 cm, height: 141.0±13.7 cm and crown width: 99.5±3.4 cm). After 20 years, survival of spruce and pine were 406±63 and 694±309 saplings/ha, respectively in Plot B. The spruce growth (DBH: 6.4±0.9 cm, height: 4.6±0.5 m and basal area: 1.34±0.54 m2/ha) was better than pine (DBH: 4.2±1.0 cm, height: 3.5±0.5 m and basal area: 0.98±0.51 m2/ha). In addition, were some local broadleaved species such as Phellodendron amurense, Juglans mandshurica and Acer mono regenerated in Plot B(344±322 trees/ha, basal area: 1.44±1.08 m2/ha). It seems to be feasible to develop larch-spruce-pine, or conifer-broadleaved mixed forests through under-planting. Selective thinning may be necessary to further develop these mixed forests.

    A copy of the poster is available in pdf format at: Poster_zhu.pdf