Tree Retention Research Articles

Long-term effects of prescribed burning, tree retention, and browsing on deciduous tree recruitment in European boreal forests

Silvicultural practices, effective fire suppression, and increased browser densities have profoundly altered structural diversity in boreal forests. Prescribed burning and retention forestry may counteract losses in structural diversity in managed forests by maintaining a higher deciduous admixture. We constructed an experiment on 18 sites with three types of timber harvesting (uncut, cut with retention, and clearcut) and burned half of these sites. Subsequently, we established a herbivore treatment with three compartments (unfenced, fenced excluding moose (Alces alces (Linnaeus, 1758)), and fenced excluding moose and hares (Lepus spp.)). In these compartments, we planted rowan (Sorbus aucuparia L.), European aspen (Populus tremula L.), and silver birch (Betula pendula Roth) seedlings and monitored these for 17 years. Birch and rowan mortality were lower on cut and burned sites, with retention further enhancing birch survival on these sites. Retention without burning did not lower seedling mortality of any tree species. While browsing resulted in greater mortality on cut sites, burning appeared to greatly reduce browsing on birch and rowan. On mature uncut sites, seedlings of all tree species exhibited high mortality. Our findings show that deciduous tree recruitment can be improved through prescribed burning, particularly for birch and rowan, and that browsing impacts on deciduous trees depend on forest age.

A meta-analysis of the effects of tree retention on shrubland birds

The effects of forest management on native fauna are of key interest to managers and conservationists. Individual studies have expanded our knowledge of management impacts, but meta-analyses of multiple studies are needed to summarize and integrate findings into a more generalizable form. Most meta-analyses on the effects of tree harvesting have focused on mature forest taxa because of concerns for these species; however, early-successional specialists, such as shrubland birds in the eastern United States, are also of key conservation concern. Using data from 34 studies that examined the effects of silvicultural treatments on bird communities, we conducted a meta-analysis to determine the effects of tree retention on a suite of bird species reported to be associated with shrubland habitats within the northeastern United States. Of 21 putative shrubland bird species for which we had sufficient sample sizes for analyses, most (62%) exhibited monotonic declines of density with increasing tree retention, defined as percent basal area or canopy cover retained. Five other species (24%) exhibited quadratic relationships with tree retention. Finally, three additional species (14%) considered to be shrubland birds did not exhibit significant relationships with tree retention. We also calculated density estimates of shrubland birds in three categorical classifications of basal area retention corresponding to common management regimes: regeneration harvests with little retention (clearcut and seed-tree methods), regeneration harvests with moderate retention (shelterwoods), and high retention management regimes (commercial thinning, selection methods, no management). Many of the shrubland species had high densities in clearcuts as well as in stands with low levels (5–25%) of mature tree retention, and some species had equally high densities in stands with moderate tree retention (30–70%), supporting the use of retention forestry approaches, which can provide other benefits associated with mature trees. Overall, our findings provide managers and conservationists with robust, quantitative relationships of shrubland birds with tree retention. Managers can use these quantitative relationships for more detailed planning and evaluation of silvicultural projects, more so than what was feasible using previous findings of shrubland bird responses to discrete silvicultural treatments from disparate studies.

Effects of small aggregates of mature tree retention on adjacent planted coastal Douglas-fir growth and survival

Long-term retention of mature trees at the time of harvesting, called variable retention, has increased significantly since the 1990s as a silvicultural practice for maintaining stand-level biodiversity. A common approach is aggregated retention where groups of trees are left to increase structural diversity and provide forest influence over the adjacent harvested area. Despite the increased global application of aggregated retention, the growth and survival of adjacent trees has received less research effort than biodiversity studies. This knowledge gap was addressed with a study of small (0.01 to 0.58 ha, mean 0.3 ha) retained mature tree aggregates in harvested areas on southeast Vancouver Island, British Columbia, Canada. Coastal Douglas-fir (Pseudotsuga menziesii var. menziesii (Mirb.) Franco.) seedlings were planted in ~10-m-wide belt transects (three planting rows), extending up to 10 m into and 50 m away from aggregate edges in four cardinal directions. Nitrogen fertilizer was applied at planting to some transects. Basal diameter, height and survival of the planted Douglas-fir were measured for an average of 11 years. We used nonlinear mixed-effects models to assess the relationships of planted-tree basal diameter and height growth to distance from aggregate edge, edge orientation, planted-tree age, fertilization and aggregate characteristics (basal area and height). We extended planting into the aggregates to model tree response on both sides of edges. Modeled growth rates were slower for 10-year-old planted trees under the aggregate canopy and along the edges of the harvested area compared to growth at about 10 m and greater distance from aggregate edges; i.e. trees achieved 90% of their potential height and diameter by about 10 m from the aggregate canopy. Impacts were greatest on north-facing edges and least on south-facing edges, although differences were very small. We examined planted-tree survival by proximity to aggregate edges using a Cox proportional hazards model. Survival was lower directly beneath the aggregate canopy and up to approximately 5 m into the harvested area and was also slightly lower adjacent to south-facing edges. Fertilized trees showed a minor increase in survival versus unfertilized trees. Structural characteristics of aggregates had only a minimal impact on planted-tree growth and survival. This study helps provide a better understanding of the relationships among planted-tree growth and survival and edge effects for implementation of aggregated retention.

Longer-term impacts of fuel reduction treatments on forest structure, fuels, and drought resistance in the Lake Tahoe Basin

Sierra Nevada mixed-conifer forests have undergone significant changes in structure and composition and are increasingly vulnerable to altered disturbance regimes and climate-related extreme events. Fuel reduction treatments, including thinning and follow-up surface fuel treatments, can reduce this vulnerability by creating forest structural and woody fuel conditions that not only allow forest stands to mitigate wildfire, but also alleviate individual tree stress. However, direct observations that quantify these longer-term effects are lacking. This study compares observed changes in forest structure, tree species composition, and downed woody fuel loads across three distinct time periods: pre-treatment, 1 yr post-treatment, and 10 yr post-treatment. Additionally, using tree ring data, we assessed whether treatments affected individual tree resistance to a severe statewide drought (2012–2015). Thinning treatments were able to effectively reduce tree density and basal area, increase the retention of both larger-sized and shade-intolerant trees, and mitigate tree mortality. Treatments were also associated with significantly lower coarse woody fuel and snag basal area. Snag basal area and time since treatment were related to the accumulation of fine and coarse woody surface fuel loads. Tree ring information indicated that treatments improved drought resistance as well, especially in units with lower residual live basal area. This study complements previous studies on fuel reduction thinning by demonstrating that these treatments have lasting effects on forest structure, which also confers a degree of drought resistance.

Boreal Owl (<i>Aegolius funereus</i>) and Northern Saw-whet Owl (<i>Aegolius acadicus</i>) breeding records in managed boreal forests

During the 2016 breeding season we monitored 169 nest boxes suitable for Boreal Owl (Aegolius funereus) and Northern Saw-whet Owl (Aegolius acadicus) in high-latitude (>55°N) boreal forests of northwestern Alberta affected by partial logging. Despite the large number of boxes deployed, the number of boxes used by Boreal and Northern Saw-whet Owls was small. Boreal Owls used nest boxes (n = 4) in conifer-dominated stands with three being in uncut blocks and the other in a 50% green tree retention cut-block. In contrast, Northern Saw-whet Owls used boxes (n = 4) in a broader range of cover types, breeding in boxes placed in stands with at least 20% post-harvest tree retention. Although both species successfully bred in the same landscape, Boreal Owls produced fewer eggs (mean = 2.5) and raised fewer young (mean = 0.5) than Northern Saw-whet Owls (5 and 2.25, respectively). Furthermore, our observed Boreal Owl egg production was lower than has been found for the same species nesting in nest boxes in different regions or forest types. In contrast, breeding parameters of Northern Saw-whet Owls were similar to that found in nest boxes in the eastern boreal region of Canada and in the southern part of its range.

Tree-Related Microhabitats: A Comparison of Managed and Unmanaged Oriental Beech–Dominated Forests in Northern Iran

Abstract Tree-related microhabitats (TreMs) provide ecological niches in features for a variety of species in forests and are suitable indicators of biodiversity for certain taxa. The study objective was to compare the abundance and occurrence of TreMs in managed versus unmanaged Oriental beech (Fagus orientalis Lipsky) forests of northern Iran to quantify the effect of forest management on biodiversity indicators. We inventoried 3,954 trees to identify the number of trees with TreMs and quantify the occurrence of different types of TreMs. Managed forests averaged 25 trees with TreMs per hectare, and unmanaged forests averaged 41 trees with TreMs per hectare. In both forests, larger-diameter trees (≥50 centimeters diameter at breast height [dbh]) had more TreMs than smaller-diameter trees. TreMs were found on trees larger than a minimum size (32 centimeters dbh) and were more common on trees in poor health, as indicated by vitality class. According to our findings, managed forests have a lower diversity of TreMs than unmanaged forests. However, if management plans in deciduous forests include the retention of large-diameter trees during harvesting events, it is possible to balance providing TreMs within the forest while maintaining growth of economically valuable timber. Study Implications Forest biodiversity is time and labor intensive to quantify, and researchers have begun using tree-related microhabitats (TreMs) as a proxy for biodiversity. This study found TreMs occurred at lower abundances but had a similar occurrence of TreM groupings (cavities, injuries and wounds, deformation/growth form, and epiphytes) in managed Oriental beech (Fagus orientalis Lipsky) forests compared with unmanaged Oriental beech forests. Managed hardwood stands provided 25 TreMs per hectare, which is similar to numbers recommended for managing for biodiversity, and thus it may be possible to promote TreM creation and retention as an opportunity to increase forest biodiversity while also managing forests for timber production. Abundance of TreMs was associated with large-diameter trees and low-vitality trees (poor health). In deciduous forests managed for timber production, the retention of large-diameter trees is likely to align more closely with other management objectives than the retention of trees in poor health.

Cutting practices in mature stands of Tilia cordata Mill.

Abstract The right timing for replacing mature and over-mature forest stands with a young generation of trees is evident as it ensures continuity in forest management. The study aimed to assess the efficiency of cutting practices in mature stands of Tilia cordata Mill. Mono-dominant and poly-dominant, even- and different-aged linden tree forests in the southern Urals were studied. The study found that in the first years following the small scale forest cutting practices (the Murakhtanov method), retention trees of Tilia cordata Mill. showed longer crowns (by 0.3 ± 0.01 m) and higher crown diameter indices (by 0.11 ± 0.04 m). A single selection showed that nectar secretion potential was 2.1 ± 0.06 mg/flower in the first assessment year, the index was 1.8 ± 0.03 mg/flower in the control forest area where no trees were cut. In the third assessment year, nectar secretion potential rose to 4.1 ± 0.04 mg/flower, while the index fell to 2.0 ± 0.01 mg/flower in the control forest area. The comparative analysis of the shoot growth capacity in stools of different diameters showed that shoots regrew from 82% of stumps. Shoots did not regrow from stumps affected by rot, those ones destroyed in the cutting process, and also from stumps of 59 – 62 cm in diameter.

Regeneration patterns of key pine species in a mixed-pine forest indicate a positive effect of variable retention harvesting and an increase in recruitment with time

BackgroundMany fire-dependent forests have experienced significant declines in species, structural, and functional diversity. These changes are attributed in part to traditional management approaches that were dominated by even-aged regeneration methods such as clearcutting. Variable retention harvesting (VRH) is an ecologically based forestry practice that involves retention of some mature overstory trees and other biological structures in the postharvest stand to emulate the effects of natural disturbance events. In this study, we examined the effect of a VRH treatment on recruitment of historically dominant pine species and understory vegetation two- and six years after its implementation in a naturally regenerated mixed pine forest in the Upper Peninsula of Michigan, USA.ResultsWe found greater regeneration of red pine (Pinus resinosa L.) and eastern white pine (Pinus strobus L.) in VRH stands compared to the unharvested controls. Although red pine recruitment was very low during the first 2 years, both species increased significantly from year two to year six. Recruitment responses for the two species did not differ significantly between the aggregated and dispersed retention treatments. We also found high recruitment of deciduous tree species, consisting primarily of sprouts, and red pine exhibited a negative correlation with these sprouts. Treatment, time, and the interaction of treatment and time were significant factors in red pine recruitment. Time had a strong effect on the understory vegetation, with significant decreases in shrubs and ferns over time.ConclusionsThe results suggest that VRH enhanced recruitment of red pine and eastern white pine and that this recruitment increased with time. We identify competition from sprouts and unfavorable seedbed conditions as the main factors that limited recruitment of red pine during the first 2 years. To reduce competing vegetation and improve seedbed conditions, we suggest following the VRH with a prescribed fire, mechanically removing sprouts, and implementing herbicide treatments. At a time when changes in global climate exacerbates the effects of traditional drivers of forest degradation, and with the need to maintain biodiversity, new ecologically based forest practices such VRH have the potential to facilitate regeneration of native trees and enhance the resilience of many fire-dependent forests.

Can’t see the Woodlark for the trees? Commercial forests as a habitat for a bird of conservation concern

This study investigated the extent to which intensive forest management practices influence a widespread bird of conservation concern, the Woodlark Lullula arborea. We compared trends of the studied population in Notec Forest, Poland during 2010–2014 against country-wide monitoring data, and populations of the forest interior versus forest edge dominated landscapes (forest-agricultural area mosaic). We also studied the influences of forest management practice (clearing size, stand structure, forestry activities on restock sites, harvesting in the neighboring habitat, and retaining tree aggregates) on the population of this species. Changes in woodlark numbers, habitat availability, and quality differences among studied sites and years were assessed using ANOVA. The influence of habitat characteristics on woodlark occupancy and abundances were tested by Generalized Estimation Equations, while the magnitude of influences in the study years was compared by Random Forest algorithm (as were population trends). Over the four study years, 419 woodlark pairs occupied 336 patches, with a maximum of 127 pairs. The number of woodlark pairs fell by 40% on the studied areas over the period, in line with declines across Poland as a whole. In our study system, population trends did not differ between forest and forest- agro mosaic landscapes. Size, age and number of available habitats did not differ either temporally or spatially during the study. Retention of unfelled trees in clearfell areas and forest works in the nearby sites, however, showed slight differences among the sampling polygons. Larger habitat patch size and restock areas under five years favored woodlarks. Less important but still significant positive influences were a higher proportion of retained trees and elongated shape of the habitat patches. Forestry activities on the neighbor stands were correlated with increased woodlark abundances, which is an unexpected result. Moreover, forestry provides suitable habitats for woodlarks in a dynamically changing arrangement. The magnitude of the studied factors’ influences on woodlarks showed a very high difference between study years, with the highest values in the years where woodlarks are the most numerous. In conclusion, we found no evidence that contemporary forestry adversely affects Woodlark habitat occupancy. Our study suggests that while managing land for one ecosystem service (timber), an apparent dis-benefit (loss of recreational attractiveness) might benefit some semi-open habitat species.

Adoption of Agroforestry Practices by Arable Farmers in Igabi Local Government Area of Kaduna State, Nigeria

The study examined the level of adoption of agroforestry practices among arable farmers in Igabi Local Government Area of Kaduna State, Nigeria. Data was collected from 100 randomly selected farmers with the use of structured questionnaire. The questionnaire focused on socio-economic characteristics of the farmers, level of adoption of agroforestry practices, types of agroforestry practices adopted, factors influencing the willingness of farmers to adopt agroforestry practices and constraints faced by the farmers in adopting agroforestry-based farming. Data was analysed using frequency, percentage, mean and probit model. The study found that male (78.00%) dominated farming activities in the study area, the majority (96.00%) of the farmers is in the age group of 21-60 years, most of the farmers (87.00%) are educated and the majority (76.00%) of them had more than 5 years farming experience. The study revealed that the adoption of agroforestry practices is high (79.00%) in the study areas. Retention of trees on farmland was mostly adopted (31.00%) while shifting cultivation is the least adopted (5.00%) agroforestry practice in the study area. The result of the probit model analysis showed that farm size (1.1122), farming experience (0.0231) and access to credit (0.1103) were the factors that significantly influence farmers’ willingness to adopt agroforestry practices at 10.00% probability level in the study area. However the level of adoption of agroforestry practices in the study area was hampered by constraints such as high capital intensive nature of agroforestry practices (87.00%), poor extension service (80.00%), inadequate capital (77.00%), poor technical know-how of agroforestry practices (45.00%), land tenure system (36.00%) and lack of access to credit (13.00%). The study suggests that to enhance the adoption level of agroforestry practices among farmers in the study area, improved agroforestry extension services should be provided to farmers; workshops, seminars and symposia should be organized for adequate training of farmers to understand the techniques of agroforestry; and farmers should be encouraged to form cooperative societies so that they can have access to credit facility to boost their capital.

Harvest Intensity Effects on Carbon Stocks and Biodiversity Are Dependent on Regional Climate in Douglas-Fir Forests of British Columbia

Temperate forests provide crucial ecosystems services as living sinks for atmospheric carbon (C) and repositories of biodiversity. Applying harvesting at intensities that minimize losses offers one means for mitigating global change. However, little is known of overstory retention levels that best conserve ecosystem services in different regional climates, and likewise as climate changes. To quantify the effect of harvest intensity on C stocks and biodiversity, we compared five harvesting intensities (clearcutting,seedtree retention, 30% patch retention, 60% patch retention, and uncut controls) across a climatic aridity gradient that ranged from humid to semi-arid in the Douglas-fir (Pseudostuga menziesii) forests of British Columbia. We found that increased harvesting intensity reduced total ecosystem, aboveground, and live tree C stocks one year post-harvest, and the magnitude of these losses were negatively correlated with climatic aridity. In humid forests, total ecosystem C ranged from 50% loss following clearcut harvest, to 30% loss following large patch retention harvest. In arid forests this range was 60% to 8% loss, respectively. Where lower retention harvests are sought, the small patch retention treatment protected both C stocks and biodiversity in the arid forests, whereas the seedtree method performed as well or better in the humid forests. Belowground C stocks declined by an average of 29% after harvesting, with almost all of the loss from the forest floor and none from the mineral soil. Of the secondary pools, standing and coarse deadwood declined in all harvesting treatments regardless of cutting intensity or aridity, while C stocks in fine fuels and stumps increased. The understory plant C pool declined across all harvesting intensities in the humid forests, but increased in arid forests. Shannon’s diversity and richness of tree and bryoid species declined with harvesting intensity, where tree species losses were greatest in the humid forests and bryoid losses greatest in arid forests. Shrub and herb species were unaffected. This study showed that the highest retention level was best at reducing losses in C stocks and biodiversity, and clearcutting the poorest, and while partial retention of canopy trees can reduce losses in these ecosystem services, outcomes will vary with climatic aridity.

Retention of large, old trees in alternatives to clearcutting with a comparison of ground- and helicopter-based assessments

Habitat trees (mature live and dead trees with hollows) are a keystone habitat in Australian eucalypt forests where tree hollows typically occur in large, old trees. These trees provide potential habitat for hollow-using birds, bats and arboreal marsupials, including many threatened species. Habitat trees may be felled during forest harvesting and can also be negatively affected by wildfires. Shortages of habitat trees in harvesting landscapes can be a limiting factor for populations of hollow-using vertebrates. Retention forestry systems are expected to retain a greater number of habitat trees within sites than traditional clearcutting silviculture, but there is a need to quantify how the pattern of retention (dispersed trees vs. retained clumps) will affect the numbers and types of trees retained. The method of assessment (ground-based vs. aerial surveys) may influence the estimated numbers of habitat trees. We investigated habitat tree retention at the Warra Silvicultural Systems Trial in Southern Tasmania, Australia. This trial was instrumental in developing alternatives to clearcutting in tall, wet, old-growth eucalypt forests. Our research has two objectives. Objective 1 is to assess the numbers of habitat trees retained in various alternatives to clearcutting by comparing: unlogged control areas, 0.5–1 ha clumps retained within a harvested matrix (aggregated retention), trees scattered throughout the harvested area (dispersed retention), and small ~0.08 ha machinery exclusion zones where trees were retained if they were not of commercial value (clearcutting with understorey islands). Objective 2 is to compare ground-based to aerial, helicopter-based, assessment of large live and dead trees. Although low replication of harvest treatments precluded statistical comparison of silvicultural systems, the results, based on 1,260 trees, were clear. Of the various alternatives to clearcutting, aggregated retention retained the greatest proportion of all classes of habitat trees, primarily because of higher retention targets, but possibly also because of greater survival with reduced wind exposure in aggregates. Substantially fewer habitat trees were retained with dispersed retention, and virtually none with understorey islands in clearcutting. Aerial and ground-based assessment methods provided similar estimates of numbers of trees with visible hollows in aggregates and understorey islands (R2 = 0.95). Choice of method for future studies should consider available resources and objectives, since there were advantages and disadvantages of each approach. In conclusion, aggregated retention was found to be the preferred silvicultural system for retaining habitat trees within sites for hollow-using vertebrates, and helicopter surveys provide a rapid alternative to traditional ground-based assessment.

Retention of tree-related microhabitats is more dependent on selection of habitat trees than their spatial distribution

Habitat trees, which provide roosting, foraging and nesting for multiple taxa, are retained in managed forests to support biodiversity conservation. To what extent their spatial distribution influences provisioning of habitats has rarely been addressed. In this study, we investigated whether abundance and richness of tree-related microhabitats (TreMs) differ between habitat trees in clumped and dispersed distributions and whether the abundance of fifteen groups of TreMs is related to tree distribution patterns. To identify habitat trees, we quantified TreMs in temperate mountain forests of Germany. We determined clumping (the Clark–Evans index), size of the convex hull, diameter at breast height, as well as altitude, slope and aspect of sites for their possible influence on TreMs. We additionally determined the difference in TreM abundance and richness among four options of selecting five habitat trees per ha from 15 candidates: (a) the most clumped trees, (b) five randomly selected and dispersed trees, (c) the single tree with highest abundance or richness of TreMs and its four closest neighbors and (d) a “reference selection” of five trees with known highest abundance or richness of TreMs irrespective of their distribution. The degree of clumping and the size of the convex hull influenced neither the abundance nor richness of TreMs. The reference selection, option (d), contained more than twice the number of TreMs compared to the most clumped, (a), or random distributions, (b), of five habitat trees, while option (c) assumed an intermediate position. If the goal of habitat tree retention is to maximize stand-level abundance and richness of TreMs, then it is clearly more important to select habitat trees irrespective of their spatial pattern.

Early-successional saproxylic beetles inhabiting a common host-tree type can be sensitive to the spatiotemporal continuity of their substrate

Intensive forest management has drastically reduced the amount and diversity of dead wood resulting in population decline of saproxylic species. Forestry practices can also disrupt spatiotemporal continuity of dead wood habitats. We studied the effects of stand- and landscape-level densities of host trees on the incidence (proportion of occupied trees) of saproxylic beetles inhabiting recently dead standing Scots pines, a common host-tree type both in natural and managed boreal forests. We compared the occurrence patterns of eight rare specialist and eight common generalist species. Saproxylic beetles were collected from a total of 315 trees in 67 forest stands, including both managed and natural forests, located in three regions which form a gradient in forest-use intensity. Species richness of the entire community at tree and stand level did not respond to the stand- and landscape-level host-tree density. The incidence of six common generalist species did not depend on the stand-level host-tree density, whereas the incidences of four rare specialist species increased with increasing host-tree density. Five out of eight rare specialist species were either significantly less common or absent from the region with the lowest landscape-level density of host trees. We conclude that rare specialist species living in recently dead pines are susceptible to changes in spatiotemporal dynamics of their host trees. To conserve rare early-successional species, it is necessary to ensure continuous input of dying trees by prolonging rotation times in mature forests, regenerating stands using seed-tree cutting and leaving as many permanent retention trees as possible.

Influence of Timber Harvesting Operations and Streamside Management Zone Effectiveness on Sediment Delivery to Headwater Streams in Appalachia

Disturbances created by timber harvesting equipment and associated haul roads and skid trails can create overland sediment flows (sediment paths), especially in steeply sloping terrain, leading to stream sedimentation. This study investigated the effect of variables associated with GPS tracked harvest equipment movement, skid trail development and retirement, topography, and streamside management zone (SMZ) width and tree retention on sediment delivery to streams. While the intensity of harvest equipment traffic was not correlated with sediment path development, the presence and location of skid trails were. All of the sediment paths were found to originate at water control structures, influenced by microtopographic features, on the skid trails directly adjacent to SMZs. Mesic slopes were associated with increased sediment path development across all SMZ configurations. Two factors, the accumulation of coarse logging debris in the SMZ and the increased distance of skid trails to streams, were both correlated with decreased sediment path development. The study provides insight into how these variables interact and can be used to develop site-specific guidelines for SMZs in steeply sloping terrain that could improve their efficiency and effectiveness.

Ecosystem Management of Eastern Canadian Boreal Forests: Potential Impacts on Wind Damage

Research Highlights: Windthrow can interfere significantly with ecosystem management practices. In some cases, their goal could still be reached but this may prove more complex in other cases, like the partial cutting of old-growth stands. In situations where windthrow is common without any human intervention, the use of partial cutting to maintain some stand structures may lead to a feedback loop leading to additional windthrow. Background and Objectives: Forest ecosystem management using natural disturbances as a template has become the management paradigm in many regions. Most of the time, the focus is on fire regime and effects. However, windthrow can be common in some places or can interfere with practices implemented in an ecosystem management strategy. This paper looks at interactions between ecosystem management and windthrow. Materials and Methods: The paper builds on three case studies looking at various elements that could be part of ecosystem management strategies. The first one looks at the impact of green tree retention, while the second one looks at the impact of reducing the size and dispersing clearcuts, and the last one examines the impact of a range of cutting practices in irregular old-growth stands. Results: Green tree retention leads to increased windthrow, especially when applied within mature even-aged stands. Reducing the size of clearcuts and dispersing them over the landscape also involves substantial windthrow along edges. Partial cutting in old-growth stands can lead to relatively high mortality, but part of it is not necessarily related to wind since it occurs as standing dead trees. Differences in the amount of damage with tree size and species have been found and could be used to reduce wind damage. Conclusions: Approaches to minimize wind damage in ecosystem management can be designed using existing knowledge. However, using windthrow as a template to design management strategies would prove more complex.

Browsing hinders the regeneration of broadleaved trees in uneven-aged forest management in southern Finland

ABSTRACT Uneven-aged forest management has attained increasing popularity. It may benefit biodiversity, buffer against pests and abiotic damages, decrease runoff from clearcuts and improve recreational values. We studied how gap cuttings and single-tree selection cuttings influence browsing damage in spruce-dominated forests in south-central Finland. Overall, browsing damage was especially frequent in aspen and rowan, but also in birch. The larger the basal area left in harvesting, the lower the browsing pressure on birch and rowan; neither the harvesting method nor the seedling density had an independent effect on browsing damage. Although larger tree retention levels may reduce browsing damage, the regeneration and recruitment of shade-intolerant broadleaved trees may be compromised.

Canopy cover is a key factor to preserve the ecological functions of dung beetles in the southern Atlantic Forest

In general, livestock activities affect the diversity and ecological functions of dung beetles. However, some practices associated with tree retention could reduce this problem while maintaining productivity. The objective of this study was to explore the influence of canopy cover on dung beetle biomass, their burial activity and changes in soil conditions associated with this activity, in the southern Atlantic Forest of Argentina. Four habitat types were compared: (i) native forest, (ii) silvopastoral systems with native trees, (iii) silvopastoral systems with exotic trees (Pinus taeda), and (iv) open pastures. Canopy cover, and microclimatic and soil conditions were also evaluated in each habitat type. The native forest and silvopastoral systems (both native and exotic) showed lower temperatures, higher relative humidity, higher electrical conductivity, and higher nitrate (N-NO3) and sand contents than open pastures, which showed opposite microclimatic conditions and higher clay contents. In addition, field experiments using acrylic plastic beads and cow dung were performed to evaluate the burial activity of dung beetles, and its influence on soil properties. Soil samples were collected after 30 days to compare the soil conditions among habitat types. Total burial (>95%) and depth (5–6 cm) of acrylic plastic beads were higher in habitat types with native trees than in livestock systems with exotic trees and open pastures; moreover, dung beetle total biomass was strongly and linearly related to burial activity among habitat types. We observed no direct influence of burial activity on soil properties. Our results support the idea that livestock systems with native trees improve the environmental parameters, biomass and ecological functions of dung beetles compared with silvopastoral systems with exotic trees and open pastures.

Effects of tree retention and woody biomass removal on bird and small mammal communities

Contemporary forest management is increasingly focused on maintaining ecosystem function and services including biodiversity conservation. As a result, harvest guidelines related to retention of live trees and woody biomass (fine and coarse residue arising from harvesting) have been developed to provide benefits for wildlife, but there is much uncertainty on the effectiveness of these guidelines depending on stage of succession, retention levels, and focal taxa. We used an operational-scale, fully replicated factorial experiment to determine the effects of both tree retention (none, dispersed, aggregated) and woody residue harvesting (no removal, 20% retention, all removed) on breeding bird and small mammal communities in aspen forests 7–8 years after harvest. Bird community metric responses showed a clear and consistent positive response to tree retention; both tree retention configurations resulted in higher total abundance, increased diversity, and higher species richness compared to stands with no tree retention. There was no difference in community metrics between the retention configurations and no evidence that early successional species were negatively affected by tree retention. Total abundance of small mammals was lower in clear-cuts compared to tree retention treatments; moreover, clear-cut stands had lower species diversity compared to stands with the aggregated tree retention. There were limited effects of biomass harvest treatments on small mammal communities, likely because actual biomass removal was much lower than experimental targets. Overall, our results provide conclusive evidence on the continued benefits of tree retention on wildlife communities se0ven and eight years post-harvest in regenerating aspen forests.

Changes in Deadwood and Understory Vegetation 12 Years after Partial and Clearcut Harvesting in Mixedwood Stands of Western Quebec, Canada

AbstractEcosystem management promotes the integration of knowledge of natural ecosystem dynamics into forest-management planning and practices, and provides a useful framework for understanding and mitigating the impacts of timber harvesting on biodiversity and ecosystem functions. Understory vegetation and deadwood are involved in many ecosystem functions including nutrient and carbon, and tree-regeneration dynamics. The study objective was to compare the 12-year post-treatment effects on forest floor attributes of two intensities of partial harvesting (gap harvesting [62 percent basal area retention; BAR] and diameter-limit harvesting [35 percent BAR]) to clearcutting (10 percent BAR). We quantified the standing and downed deadwood abundance and the understory plant community composition in mixed, northern temperate forests, in western Québec, Canada. Our results suggest that moderate-intensity gap harvesting can best preserve a standing deadwood stem density and a diameter structure comparable to unmanaged stands. Downed deadwood abundance of all diameter classes was not altered, 12 years following the gap harvesting. Finally, understory plant communities in the gap treatment were more similar to those of unmanaged stands than those in diameter-limit and clearcutting treatments. These results illustrate the importance of tree retention levels for the maintenance of deadwood and understory plant species associated with closed-canopy or old-growth forests.