Residual Trees Research Articles

Large scale biotic damage impacts on forest ecosystem services

ABSTRACTInsect outbreaks are natural phenomena that play a critical role in the development, senescence, and rebirth of forests. However, the damage caused by large-scale epidemics can have landscape scale consequences that are often poorly understood. The recent mountain pine beetle (MPB) outbreak in Canada has impacted a record >18.5 million hectares of pine forests, placing forest values at risk and significantly impacting forest-dependent communities within the region. To assess this impact, an ecosystem service-based approach was applied. Based on land cover information and monitoring data, four ecosystem services were assessed and mapped: merchantable timber, water provisioning, aboveground carbon storage, and vegetation diversity (supporting habitat). Timber is the most impacted provisioning ecosystem service followed by water provisioning, with peak stream flow in affected watersheds being positively related to mortality percent. Effects on carbon storage are substantial, with 20% of total timber aboveground carbon in dead pine trees. These effects may be mitigated, however, by the growth response of residual live trees and forest regeneration. The potential vegetation diversity showed a positive response to MPB-caused tree mortality. The results of our study may help with setting management priorities in response to large-scale biotic damage in forests in British Columbia and elsewhere.

Sustainability of wood harvesting in tropical rainforest of Nigeria

Over the years, Nigerian tropical rainforest has become the main source of timber supply to many countries which were in critical need of timber to feed their wood-based industries. The increase in population has led to increase in the demands for forest products, specifically wood for construction. Improper harvesting practices has substantially degraded the tropical forest that future timber values may be reduced. Sustainable wood harvesting focuses on the trees that are remaining rather than on the trees that are to be fell. Proper wood harvesting and management method must be adopted to facilitate the regeneration of the forest. Efficient wood harvesting in Nigeria requires the construction of landing sites as collection points for the harvested timbers and adequate training must be provided to the operators of the diverse harvesting equipment. With proper timber harvesting techniques, the damages caused by logging can be minimized. Functional forest policies that guide against over-exploitation of timber should be enacted. Reduced impact logging should be incorporated into sustainable forest management to reduce devastating damages to the residual trees in the forest.

Tree-level growth and survival following commercial thinning of four major softwood species in North America

Thinning is commonly applied to increase the tree growth in forest stands by improving the availability of water, light, and nutrients. However, thinning also can increase soil evaporation and intensify wind penetration into residual stands, potentially increasing moisture stress and wind damage. To strengthen our understanding of tree-level responses to thinning, we used long-term measurements from three controlled, replicated thinning experiments for four commercially important softwood species in North America, including the shade-intolerant loblolly pine (Pinus taeda L.), moderately shade-tolerant Douglas-fir (Pseudotsuga menziesii Mirbel), and shade-tolerant red spruce (Picea rubens Sarg.) and balsam fir (Abies balsamea L.). The objectives of this study were to assess the long-term (13–24 years) pattern of individual-tree growth and survival after a variety of commercial thinning treatments. Our results showed that on average tree volume growth was 31% higher in thinned stands relative to unthinned stands irrespective of species and tree size. However, the rate of growth decreased over time following thinning for loblolly pine and Douglas-fir, while a curvilinear relationship was observed for red spruce and balsam fir. Tree size was important only for loblolly pine where growth increased linearly with the size of residual trees. Tree survival was also higher in thinned stands than unthinned stands across all species in the long-term, but a significant initial decrease in survival was found in balsam fir and red spruce immediately after thinning due primarily to windthrow and breakage. Stand relative age and total basal area at time of thinning were negatively related with growth for all tree species, which may indicate that the trees examined in this study had reached their maximum growth potential or had a period of suppression prior to thinning. The relatively minor influence (i.e., 5% of total R2) of thinning intensity on growth may suggest that the timing of thinning (i.e., age of trees when thinned) and stand characteristics (species, tree age, and stand basal area) were more important in promoting individual-tree growth. However, a heavier intensity of thinning increased survival of loblolly pine and Douglas-fir trees. Overall, our results indicated that thinning can increase tree growth and survival across species of varying shade tolerance. To ensure the maximum benefits of thinning, the timing and intensity of the treatment needs to be adjusted for species characteristics, stand structure, and tree age.

Amount and Location of Damage to Residual Trees from Cut-to-Length Thinning Operations in a Young Redwood Forest in Northern California

A cut-to-length (CTL) harvest system using a harvester and forwarder has been recently introduced in northern California (USA) for thinning young (<25 years old) redwood forests (Sequoia sempervirens (Lamb. ex D. Don) Endl.). However, the severity of CTL damage to residual trees in this forest type are unknown. The goals of this study were to (1) determine the location, size, and number of scars resulting from CTL harvesting and (2) compare scar size differences between redwood clumps and individual trees in two units. Most scars occurred on trees located near the forwarding trails. Wider and longer scars were associated with clumped trees (9.1–12.2 cm wide and 28.1–46.2 cm long) as compared to scars on individual trees (8.1–9.5 cm wide and 16.7–31.3 cm long), and 16–32% of the residual trees were scarred. Determining a minimum scar size will define the severity of stand damage; larger scars result in a longer time until closure. However, counting all the smaller scars that result from CTL harvesting will result in a large number of counted damaged trees. Therefore, we suggest that scars smaller than 5–10 cm width are acceptable on coastal redwood after CTL thinning.

Damage to residual trees following commercial thinning by harvester and forwarder in a Pinus taeda stand in Southern Brazil

Damage to residual trees following commercial thinning by harvester and forwarder in a Pinus taeda stand in Southern Brazil

Trade-offs between carbon stocks and timber recovery in tropical forests are mediated by logging intensity.

Forest degradation accounts for ~70% of total carbon losses from tropical forests. Substantial emissions are from selective logging, a land-use activity that decreases forest carbon density. To maintain carbon values in selectively logged forests, climate change mitigation policies and government agencies promote the adoption of reduced-impact logging (RIL) practices. However, whether RIL will maintain both carbon and timber values in managed tropical forests over time remains uncertain. In this study, we quantify the recovery of timber stocks and aboveground carbon at an experimental site where forests were subjected to different intensities of RIL (4, 8, and 16trees/ha). Our census data span 20years postlogging and 17years after the liberation of future crop trees from competition in a tropical forest on the Guiana Shield, a globally important forest carbon reservoir. We model recovery of timber and carbon with a breakpoint regression that allowed us to capture elevated tree mortality immediately after logging. Recovery rates of timber and carbon were governed by the presence of residual trees (i.e., trees that persisted through the first harvest). The liberation treatment stimulated faster recovery of timber albeit at a carbon cost. Model results suggest a threshold logging intensity beyond which forests managed for timber and carbon derive few benefits from RIL, with recruitment and residual growth not sufficient to offset losses. Inclusion of the breakpoint at which carbon and timber gains outpaced postlogging mortality led to high predictive accuracy, including out-of-sample R2 values >90%, and enabled inference on demographic changes postlogging. Our modeling framework is broadly applicable to studies that aim to quantify impacts of logging on forest recovery. Overall, we demonstrate that initial mortality drives variation in recovery rates, that the second harvest depends on old growth wood, and that timber intensification lowers carbon stocks.

Corsican Pine (Pinus laricio Poiret) Stand Management: Medium and Long Lasting Effects of Thinning on Biomass Growth

With the aim of acquiring better comprehension of the ecological and productive aspects of the management of pine forests, we monitored logging damage and evaluated the effects of thinning on stand growth 20 years after the treatment in a Pinus laricio Poiret stand in central Italy. The objectives of the present study were to estimate the injury levels to the remaining trees after thinning; to assess logging damage in the long-term by monitoring residual trees at the end of thinning; to evaluate the effect of damage on the radial growth of trees; to assess the stand dynamics in relation to injury levels and the treatment applied in a twenty-year range; to understand a possible treatment return time; and to evaluate the existence of the “thinning shock”. The results were that 20 years after treatment, the stand dynamics showed a complete recovery; logging damage did not affect the radial growth of P. laricio over time; a second treatment seem to be sustainable starting from the fifteenth year after the previous treatment; and the thinning shock can be clearly evaluated in the first six to seven years after the treatment.

Overstory cohort survival in an Appalachian hardwood deferment cutting: 35-year results

Deferment cutting is a two-aged regeneration method in which the majority of the stand is harvested and a dispersed component of overstory trees—approximately 15–20% of the basal area – is retained for at least one-half rotation and up one full rotation for reasons other than regeneration. Careful consideration of residual trees, in both characteristics and harvesting, is necessary to improve the chances that individual trees will survive until the next planned harvest. A long-term experimental deferment cutting study was established on the Fernow Experimental Forest and Monongahela National Forest in West Virginia, USA in the early 1980s. Repeated tree measurements spanning the approximately 35-year study period permitted a survival analysis of the overstory cohort. The effects on survival were tested for three endogenous factors (dbh, species, crown class) and one exogenous factor (logging damage) using a Cox Proportional Hazards model, with stand effects (multiple trees measured within a stand) accounted for by using as frailty model. Survival rates were high, with 92% of trees surviving (910 of 985 trees). The mortality rate was low at six percent, (60 of 985 trees), and the number of trees cut or destroyed during logging was two percent (15 of 985 trees). Trees injured in the deferment harvest did not show increased risk of mortality, p = 0.91. Crown class also did not contribute to increased mortality, p = 0.35, as the majority of overstory trees retained were in the dominant and codominant classes. Six species, Liriodendron tulipifera L., Prunus serotina Ehrh., Quercus alba L., Quercus montana Willd., Quercus rubra L., Quercus velutina Lam., had sufficient sample sizes to test for species differences. However, species was not significant for survival, p = 0.10. The only significant factor in survival was dbh, p < 0.01, with larger trees having increased probability of survival. These results demonstrate that overstory trees in a deferment cutting can be acceptably maintained midway through the next rotation and likely until the next regeneration harvest.

Understory light predicts stump sprout growth in mixed multiaged stands in north coastal California

Regeneration of commercial species is central to long-term success of multiaged management for wood production. We examined relationships between understory light, varying overstory tree retention, and growth of coast redwood (Sequoia sempervirens; commercial species) and tanoak (Notholithocarpus densiflorus) stump sprouts initiated by group selection and single-tree selection harvesting in 80–100 year old mixed stands at four sites. Treatments included a complete harvest in 1-ha group selection openings, low-density dispersed retention, and either aggregated or dispersed high-density retention. Post-harvest stand density index and basal area were useful predictors of understory light. Mean and maximum understory light did not differ significantly between treatments with the same density where residual trees were retained in aggregated versus dispersed spatial patterns. However, the dispersed retention had lower minimum light levels when compared to the aggregated retention treatment. Aspect appeared to influence understory light more in dispersed treatments. At all light levels, the dominant sprout within clumps of redwood stump sprouts generally grew faster than dominant tanoak sprouts within tanoak sprout clumps. Differences in sprout height growth between aggregated and dispersed treatments were minimal. Stump size had a significant effect on redwood stump sprout height growth, with sprouts on the largest stumps growing approximately twice as quickly as sprouts on the smallest stumps. In the low density dispersed treatment, redwood sprouts outperformed tanoak sprouts by the greatest margin. Regeneration of redwood and tanoak was most rapid within group selection openings.

Survival and growth of residual trees in a variable retention harvest experiment in a boreal mixedwood forest

Abstract Long-term sustainability of forest resources is in question given wide-spread use of conventional clear-cut silviculture. In response, variable retention (VR) harvest has been increasingly promoted as a landscape-based approach to enhance sustainability by maintaining biodiversity and other ecosystem functions in managed forests. Although the success of the VR approach depends on post-harvest stand dynamics, little is known about growth and mortality of residual trees after harvest and how such trees respond to interactions between amount of retention and tree or site level covariates. We use data from three censuses distributed over a 10-year period of the main merchantable species to study the effects of retention level (i.e., percent of trees retained), mixedwood cover type, tree species, and three tree or terrain covariates (tree stem diameter, percent live crown, and soil wetness) on survival and growth of residual trees in a retention harvest experiment in NW Alberta, Canada. Both mortality and growth of residual trees were negatively related to retention levels. During the first five-year period after harvest, effects of retention levels on mortality were more evident for white spruce (Picea glauca) than for Populus spp., but effects on growth were weaker for white spruce. Tree mortality decreased through time following VR harvest for all species and in most cover types, while trends in tree growth varied by species. During the second five-year period after harvest, growth of residual Populus spp. had decreased from high levels observed in the first period. In contrast, growth of residual white spruce was greater in the second five-year period than in the first period. After the original harvest, re-entry of stands for additional harvest focused mainly on hardwoods may be economically rewarding and ecologically justified, depending on the overall objectives for retention. The positive effect of increased retention level on tree survival was strongest for trees with larger diameter and longer crowns. Thus, retention patches are a management option to protect large trees and trees with greater crown length when retaining such trees is a management goal.

Floating neighborhoods reveal contribution of individual trees to high sub-stand scale heterogeneity

Abstract Forest structure is typically characterized using approaches that fail to capture the sub-stand heterogeneity reflecting the processes shaping stand structure at neighborhood patch scales. We propose a focal-tree based approach that flexibly scales across natural tree neighborhoods and demonstrate it by quantifying small-scale structural heterogeneity using diameter distributions across multiple scales in an old-growth mixed conifer forest in western Oregon exhibiting a rotated sigmoid shape. Tree-centered delineation of neighborhoods via Delaunay triangulation (spatial tessellation) was used to connect natural tree neighbors. At the First-order neighborhood scale, each tree was connected to an average of 6 neighbors in 75 m2 of convex hull area, which increased to 118 neighbors covering 2542 m2 by the Fifth-order scale. Agglomerative clustering identified the ten most prevalent sub-stand diameter distribution types (DDTs). At the smallest scale, these ten DDTs were characterized by four different distribution shapes (negative exponential, concave, rotated sigmoid, and unimodal) and varied considerably in the abundance of trees in different size classes and species composition (Douglas-fir composing the larger trees and western hemlock and western redcedar the smaller). On average, each individual tree contributed to over 3 different DDTs at any given scale. Small-scale tree neighborhoods were tremendously heterogeneous, such that the stand-level diameter distribution represented an aggregation across extremely disparate sub-stand distributions. As expected, these distributions exhibited spatial smoothing (i.e., increasing homogeneity with increasing scale) as small, heterogeneous tree neighborhoods were expanded into larger neighborhoods with more similar average composition, which converged on a rotated-sigmoid shape by the Fifth-order scale. Structural complexity in the demonstration stand likely owes more to shade-tolerant ingrowth below residual trees than to gap processes. The diversity of structural contribution (e.g., the number of DDTs to which a tree contributes) may be a more informative measure of structural complexity than indices based on a fixed spatial perspective. The floating neighborhood delineation and scaling approach allows for the identification of natural neighborhoods, permits the assessment of multiple conditions for any given tree, and provides of a logical mechanism for exploring scale-dependent ecological phenomena.

Thinning regimes and initial spacing for Eucalyptus plantations in Brazil.

This study focuses on the effects of different thinning regimes on clonal Eucalyptus plantations growth. Four different trials, planted in 1999 and located in Bahia and Espírito Santo States, were used. Aside from thinning, initial planting density, and post thinning fertilization application were also evaluated. Before canopy closure, and therefore before excessive competition between trees took place, it was found that stands planted under low densities (667 trees per hectare) presented a lower mortality proportion when compared to stand planted under higher densities (1111 trees per hectare). However, diameter growth prior to thinning operations was not statistically different between these two densities, presenting an overall mean of 4.9 cm/year. After canopy closure and the application of the thinning treatments, it was found that thinning regimes beginning early in the life of the stand and leaving a low number of residual trees presented the highest diameter and height growth. Unthinned treatments and thinning regimes late in the life of the stand (after 5.5 years), leaving a large number of residual trees presented the highest values of basal area production. The choice of the best thinning regime for Eucalyptus clonal material will vary according to the plantation objective.

Mixed-Severity Fire Fosters Heterogeneous Spatial Patterns of Conifer Regeneration in a Dry Conifer Forest

We examined spatial patterns of post-fire regenerating conifers in a Colorado, USA, dry conifer forest 11–12 years following the reintroduction of mixed-severity fire. We mapped and measured all post-fire regenerating conifers, as well as all other post-fire regenerating trees and all residual (i.e., surviving) trees, in three 4-ha plots following the 2002 Hayman Fire. Residual tree density ranged from 167 to 197 trees ha−1 (TPH), and these trees were clustered at distances up to 30 m. Post-fire regenerating conifers, which ranged in density from 241 to 1036 TPH, were also clustered at distances up to at least 30 m. Moreover, residual tree locations drove post-fire regenerating conifer locations, with the two showing a pattern of repulsion. Topography and post-fire sprouting tree species locations further drove post-fire conifer regeneration locations. These results provide a foundation for anticipating how the reintroduction of mixed-severity fire may affect long-term forest structure, and also yield insights into how historical mixed-severity fire may have regulated the spatially heterogeneous conditions commonly described for pre-settlement dry conifer forests of Colorado and elsewhere.

Variable density thinning promotes variable structural responses 14 years after treatment in the Pacific Northwest

Abstract Young stands are commonly assumed to require centuries to develop into late-successional forest habitat. This viewpoint reflects the fact that young stands often lack many of the structural features that define late-successional habitat, and that these features derive from complex stand dynamics that are difficult to mimic with forest management. Variable density thinning (VDT) is a silvicultural strategy designed to accelerate development of late-successional habitat by applying a variety of harvest intensities within a stand. Previous reports indicate that VDT has had initial success increasing growth and regeneration. However, few studies have examined the effects of VDT at longer time scales. Here, we report 14-year growth response of residual trees in the thinned and unthinned VDT sub-treatments in five young mixed-conifer stands located on the Olympic Peninsula in western Washington. Our objectives were to investigate whether thinning has accelerated the recruitment of large trees (>80 cm dbh), recruitment of shade-tolerant species into the mid-story (40–65 cm), or development of longer crowns relative to the unthinned sub-treatment. In addition, we investigated whether the basal area distribution in the combined VDT sub-treatments has become more diverse compared to the unthinned sub-treatment. The response to thinning varied consistently across the diameter size class gradient. Thinning was ineffective at stimulating growth of upper canopy trees (65–80 cm). In this size class neither diameter growth nor crown length increased significantly compared to trees in unthinned patches. Further, only one stand has reached the restoration benchmark for large tree density. In contrast, thinning significantly increased diameter growth and crown length among trees in the mid-story (40–65 cm) and shade-tolerant species in the future mid-story (20–40 cm). Higher rates of recruitment into the mid-story were also observed from shade tolerant species growing in the thinned (34%) compared to unthinned (19%) patches, with two stands reaching the restoration benchmark for shade-tolerant mid-story density. Clear trends in basal area diversity and evenness have yet to develop in either the combined or unthinned sub-treatments. Collectively, our results demonstrate that VDT has partially accomplished its objectives. Although thinning has not yet accelerated recruitment of large trees, it has accelerated the advancement of shade-tolerant species into the mid-story and the development of deeper crowns among trees in smaller size classes. In addition, differing rates of diameter growth among smaller diameter trees in the various VDT sub-treatments suggest that increases in structural diversity may be developing more quickly than in untreated stands.

Does commercial thinning improve stand-level growth of the three most commercially important softwood forest types in North America?

Abstract Thinning is expected to improve both individual tree- and stand-level growth efficiency since more environmental resources (growing space, light, water, and nutrients) become available to fewer trees. However, thinning can also promote asymmetric competition among residual trees, and potentially increase mortality and growth stagnation by creating an immediate and often dramatic change in stand micro-environments. To strengthen our understanding of stand-level responses to thinning, we used long-term and replicated experiments for the three most commercially important softwood forest types in the North America, including: shade-intolerant loblolly pine (Pinus taeda L.), moderately shade-tolerant Douglas-fir (Pseudotsuga menziesii Mirbel), and shade-tolerant red spruce (Picea rubens Sarg.) and balsam fir (Abies balsamea L.). The primary objectives of this study were to quantify the stand-level and dominant tree (100 largest trees ha−1) response to various thinning treatments in terms of relative (RVG) and cumulative volume growth (CVG), while evaluating the effects of stand conditions, timing/intensity of thinning, and key stand-level biotic factors. Our results showed relatively limited differences between the stand-level and dominant-tree responses. Thinning generally increased the RVG of all three forest types, but the effect was dependent on time since treatment for spruce-fir. When compared to unthinned stands, thinning increased the overall RVG, but the pattern of change over time since thinning was negative for both loblolly pine and Douglas-fir. CVG was generally higher in unthinned than thinned stands across the three forest types. Thinning intensity had a positive effect on the RVG of Douglas-fir and loblolly pine, but negative on RVG of spruce-fir forest type. Relative age (based on age of maximum periodic annual increment) and stand density at time of thinning had negative effects on the RVG of dominant trees for all species examined, except spruce-fir. Overall, our results highlight a range of responses to thinning among three distinct softwood forest types, and revealed that thinning does not always improve the growth efficiency of dominant trees, and that the responses are governed largely by a variety of stand characteristics at the time of thinning.

Healing ability and diameter growth of lime-trees (Tilia begonifolia Stev.) following logging wounds

Lime-trees (Tilia begonifolia Stev.) have countless ecological and economical values in the northern forests of Iran. Bole wounds on residual trees are commonly caused by logging. The healing ability of bole wounds and the effect of bole wounds on diameter growth in lime-trees were assessed in a natural mixed uneven-age stand. The susceptibility to decay in relation to the wound severity was also evaluated. Condition and location of lime-trees before and after selective logging were determined through systematic plot sampling. The position of each lime-tree was identified on a topographical map using the global positioning system. After 10 years from wound occurrence, tree and wound characteristics were also re-measured. Overall, 68 stems (9.7 stem ha−1) of lime-trees were found in the sampled area, 25 stems (36.8%) were damaged in the form of bole wound, and 43 stems (63.2%) were undamaged. Statistical differences between wounded or non-wounded lime-trees in terms of diameter and height were not found. Most of the wounds occurred at the height of < 1 m; the average wound size was 370.5 cm2. Wound severity was related to wound size and wound position. Wound width healing rate was 6.2 mm year−1. The wound shape was found to be a healing factor as the healing rate by width was higher than that by length. Healed wounds were only 12, 60% of bole wounds resulted in decay. Diameter growth of wounded trees was 43.5% lower than undamaged trees. The average annual diameter growth decreased by increasing wound severity. The results indicated the lime-tree is a very sensitive species to damage caused by logging (bole wound). Single-tree selection cutting needs more careful logging operations to reduce damage on residual lime-trees in order to safeguard this species, valuable in ecologic and economic terms.

Partial harvest to reduce occurrence of American beech affected by beech bark disease: 10 year results

Beech bark disease stunts American beech (Fagus grandifolia Ehrh.) to unmerchantable size, and promotes heavy sprouting that outcompetes more desirable sugar maple (Acer saccharum Marsh.) and yellow birch (Betula alleghaniensis Britt.). We investigated whether selection harvest targeting removal of large beech can promote maple and birch regeneration while limiting beech competition. Forty plots were established in 2003 in north-western New Brunswick, Canada, with 26 plots harvested and 14 control plots. Harvested plots were re-measured the year after harvest and both harvested and control plots were re-measured 10 years later. Residual tree diameter increment doubled from 0.24 to 0.51 cm/year for maple, and 0.29 to 0.69 cm/year for birch. Harvest did not alter species composition of regeneration, with seedlings comprised of 88 per cent sugar maple in both treatments, 6 per cent beech in harvested plots vs 3 per cent in control plots, and other species ranging from 1 to 5 per cent. There were four times more beech seedlings/ha in control than in harvested plots, but beech still comprised ~60 per cent of the over 2000 stems/ha of saplings in harvested plots. Rapid growth from beech sprouts provided a strong competitive advantage. Residual tree mortality was negligible. Downed deadwood was 58 per cent greater and standing deadwood basal area 71 per cent lower in harvested plots. The harvest maintained strong overstory growth and survival, and did not benefit beech; however, beech remained a dominant species among the larger regenerating cohort. Our results suggest that similar treatments applied to stands with diseased beech can secure adequate regeneration of maple and birch, but will not control profuse regeneration of beech.

Habitat selection by Canada lynx: making do in heavily fragmented landscapes

Habitat loss and fragmentation result in landscapes where high quality habitat patches are surrounded by matrix habitats of low and variable quality. For mobile species to persist in such landscapes, individual animals often rely on the high quality habitats but also use matrix habitats for supplemental resources or while moving between higher quality patches. Determining what habitat features animals select when in these matrix areas is important, as retaining desirable features in lower quality habitats may enable species persistence. We examine a population of US federally threatened Canada lynx (Lynx canadensis) in northcentral Washington, near the southwestern range limit, where lynx habitat is fragmented by topography, wildfires, and human impacts. We used Global Positioning System radio-collar data from 17 lynx in the North Cascade Mountains during 2007–2013 to explore lynx habitat use. We used Random Forest models to analyze core hunting, resting, and denning habitat, and the habitats lynx select while between patches of core habitat. While selecting core habitat, lynx used spruce (Picea engelmannii)-fir (Abies lasiocarpa), lodgepole pine (Pinus contorta), and mixed sub-boreal-Douglas fir (Pseudotsuga menziesii) forests, and avoided dry forests and forest openings including new burns. When not in core habitat, lynx used a wider range of habitats, including new burns where fire skips and residual trees offered cover. Our results show clearly that Canada lynx tolerate a wider range of habitats where they occupy fragmented landscapes. Consequently, maintaining animals in fragmented landscapes requires that we identify and conserve not only the core habitats a particular species selects, but also the habitat features animals use while in less suitable environments.

Mortality of stocking commercial trees after reduced impact logging in eastern Amazonia

Forest harvest causes disturbances in the forest and affects the mortality of residual trees. The effects of this activity on trees of the residual stocking for future felling cycles are poorly known in post-harvest situations. Detecting mortality patterns and comprehending the factors that rule the post-harvest tree mortality may offer important subsidies for future sustainable harvests. In this study, the mortality of trees under Reduced Impact Logging (RIL) was assessed in a chronosequence of 13years in logging areas (2002–2015) in eastern Amazonia. The data were collected in five Units of Annual Production (UAP) and in a control plot. In each UAP, a Working Unit (WU) of 100ha was divided into 20 plots of 50m×1000m (5ha). Trees≥45cmDBH were inventoried one year before forest harvest and again in 2015. The mortality rates were calculated and compared among: (a) ecological groups; (b) different logging intensities and (c) diameter classes. The mortality rate is higher in the first five years (5.87%) and the effects of RIL are perceived up to seven years post-harvest (3.18%). The logging intensity, 3–40m3ha−1, did not affect the mortality of trees≥45cmDBH. Pioneer species are more susceptible to impacts of forest harvest than species of other ecological groups. In RIL plots, as well as in the non-logged plot, the mortality rate was not influenced by the size of trees≥45cmDBH.

Xylogenesis in stems and roots after thinning in the boreal forest of Quebec, Canada.

The reduction of competition through thinning increases radial growth in the stem and roots of many conifer species. However, not much is known about the effect of thinning on the dynamics of wood formation and intra-annual development of the growth ring, especially in the roots, which are an essential part of the tree for stability and resource acquisition. The aim of this study was to evaluate the effect of an experimental thinning on the dynamics and phenology of xylogenesis in the stem and roots of black spruce and balsam fir. Experimental and control trees were selected in two mature even-aged stands, one black spruce (Picea mariana (Mill.) BSP) and one balsam fir (Abies balsamea (L.) Mill.). Wood microcores were collected weekly in the stem and roots from May to October for a period of 4 years. The onset and ending of each cell differentiation phase were computed, as well as growth rate and total cell production. Results show that thinning increased the cell production rate of stem and roots of black spruce and balsam fir. This higher daily growth rate caused an increase in the total number of cells produced by the cambium. The intensity of the treatment was sufficient to significantly increase light availability for residual trees, but insufficient to modify soil temperature and water content to a point at which a significant change in the timing or duration of xylogenesis would be induced. Thus, thinning increased cell production rate and total number of cells produced in both stem and roots, but did not result in a change in the phenology of wood formation that could lead to increased risks of frost damage in the spring or autumn.