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We address the concerns that managed forest plantations may cause reductions of diversity of understory vegetation. We performed inventories of two mature ponderosa pine plantations in which multiple treatments were applied during plantation establishment. At stand age 35, we measured tree heights and diameters, understory plant cover and diversity, soil nutrients and chemical properties, and soil microbial biomass and diversity with phospholipid fatty acid. We found a significant, positive effect from both herbicide (H) and fertilizer (F) applications on subsequent overstory tree growth and development (P < 0.05); insecticide (I) effect was minimal. We observed negative effects on understory plant diversity decades later when herbicide was applied during stand establishment. However, lower plant diversity and ground cover appeared to have been caused primarily from overstory canopy closure, supported by the increased understory cover and diversity observed in the HI and HFI plots that had been thinned at age 12. Similarly, while fertilizer increased tree growth at both sites, it only negatively affected understory plants at the higher quality site. We did not find significant influence of treatment effects on soil nutrients and microbial communities. Therefore, to mitigate the potential loss of understory biodiversity in plantations, foresters can manage overstory trees with traditional pre-commercial thinning techniques and early tending. [ABSTRACT FROM AUTHOR]

Individual tree diameter at breast height (DBH) distribution is an important information for forest management planning. Forest managers obtain the DBH data either by field measurements or estimations using predictive models. However, probability distribution models are still lacking or need improvement. Therefore, we aimed to construct and fit diameter distribution models that reflect forest structure and composition change. We evaluated gamma, log-normal, and Weibull probability distribution functions (PDFs) for two commercially important tree species, black spruce (Picea mariana (Mill) B.S.P.) and jack pine (Pinus banksiana Lamb), grown in natural stands across Ontario, Canada. We modelled the parameters of the distributions as a function of stand-level variables for these species. We used DBH data from 735 permanent sample plots. Our results showed that all three evaluated PDFs reflected observed DBH distribution. We demonstrated that the moment-based recovered parameters could represent the maximum likelihood-estimated parameters precisely, and parameters of the PDFs can be modelled as a function of stand-level dynamic covariates. The models unbiasedly predicted the PDF parameters DBH means and DBH classes. The R2 of the model fit ranged between 0.35 and 0.98 for the predicted parameters and 0.90 and 0.97 for the predicted DBH. [ABSTRACT FROM AUTHOR]

Successional, second-growth forests dominate much of eastern North America; thus, patterns of biomass accumulation in standing trees and downed wood are of great interest for forest management and carbon accounting. The timing and magnitude of biomass accumulation in later stages of forest development are not fully understood. We applied a "chronosequence with resampling" approach to characterize live and dead biomass accumulation in 16 northern hardwood stands in the White Mountains of New Hampshire. Live aboveground biomass increased rapidly and leveled off at about 350 Mg/ha by 145 years. Downed wood biomass fluctuated between 10 and 35 Mg/ha depending on disturbances. The species composition of downed wood varied predictably with overstory succession, and total mass of downed wood increased with stand age and the concomitant production of larger material. Fine woody debris peaked at 30–50 years during the self-thinning of early successional species, notably pin cherry. Our data support a model of northern hardwood forest development wherein live tree biomass accumulates asymptotically and begins to level off at ∼140–150 years. Still, 145-year-old second-growth stands differed from old-growth forests in their live (p = 0.09) and downed tree diameter distributions (p = 0.06). These patterns of forest biomass accumulation would be difficult to detect without a time series of repeated measurements of stands of different ages. [ABSTRACT FROM AUTHOR]

Seedling establishment is crucial for the development of self-regenerating tree populations. Determinants of tree establishment vary widely and may compound in their effects. Using a factorial experiment, we manipulated invasive shrubs, downed woody debris (DWD), and rodent access to evaluate factors limiting the establishment of six woody species (five native trees, one invasive shrub). Our results suggest these factors independently contribute to tree seedling establishment. Exclusion of rodents increased establishment threefold. Invasive shrub removal (Elaeagnus umbellata; Lonicera maackii) and the presence of DWD promoted establishment of two native trees (Pinus strobus; Sassafras albidum). Notably, the presence of DWD halved L. maackii establishment. In identifying rodents as drivers of seed limitation, our results support findings that seed additions will likely promote woody seedling establishment when rodents are not abundant (e.g., low populations) or when seeds are physically or chemically protected (e.g., via taste deterrents). Management plans vary in DWD retention; results from our experimental cohort indicate retaining or introducing DWD promotes native tree recruitment and limits invasive shrub establishment. Future studies exploring the species-specific effects of invasive shrub removal and DWD amendments across multiple cohorts will help determine which woody species benefit most from these management practices. [ABSTRACT FROM AUTHOR]

Leaf area is an important ecophysiological variable for quantifying the potential production of trees, since it is closely related to tree growth. However, it is difficult to measure the leaf area completely because of the large number of leaves, so it is particularly important to develop accurate species-specific leaf area models. In this study, using 144 parse trees from 48 plots of different climate zones and ages of Chinese fir, tree leaf area models were developed based on sapwood area at breast height (SABH), diameter at breast height (DBH), and diameter at crown base (DCB), respectively. The results showed that the population-averaged levels of nonlinear mixed-effects (NLME) models were better than the plot-levels and base models, and the leaf area models based on DCB performed the best. Finally, the NLME model (16) based on DCB was used as the final model for tree leaf area of Chinese fir plantations, which was consistent with the pipe model theory. All the variables had certain biological and statistical significance and were easy to obtain in the field work (nondestructive). In addition, this study can also provide a reference for other tree species in predicting tree leaf area. [ABSTRACT FROM AUTHOR]

The black woodpecker Dryocopus martius is an ecologically disproportionately important forest species owing to its abundance. Its large cavities provide breeding sites and shelter for many species—large birds, mammals, and social insects. I evaluated the nest tree preferences of black woodpeckers in the Augustów Forest, northeast Poland. Approximately 400 black woodpecker cavities were observed. The Scots pine, Pinus sylvestris, was the most commonly selected tree species, accounting for 90%. The cavity trees were 55–225 years old. All trees younger than 90 years were broadleaved tree species. The trees used to excavate the cavities had a larger diameter at the breast height (DBH) than the average of the stand. The trees selected by black woodpeckers were significantly shorter than the average height of the stands. Over 60% of the cavities were excavated 10–16 m above ground level. I found that the DBH and the first branch height were critical factors affecting the cavity entrance height. In pine-dominated forests, black woodpeckers preferred dead trees. Approximately 44% of new cavities were excavated from dead trees. Leaving dead or dying large trees in commercial forests benefits black woodpeckers and large secondary cavity nesters that depend on it and promotes biodiversity conservation. Birds excavate new cavities at a high rate yearly, in contrast with beech-dominated forests. [ABSTRACT FROM AUTHOR]

Silvopastoral systems are one of the strategies proposed to manage natural forests in southern Patagonia for livestock and timber purposes. In the context of climate change, it is necessary to design new management proposals to improve forest carbon sequestration. The objective was to quantify the innate carbon stocking (t C ha−1) variation in Nothofagus antarctica forests under natural dynamics in even- and uneven-aged structures, and in harvested and transformed stands. Carbon stocks were sampled in 145 forest stands, identifying 14 different components in above- and belowground strata. Results showed that the carbon content of the stands varied significantly with age (e.g., C contribution of different tree components), ranging from 289 to 386 t C ha−1. Deadwood was the variable that varied most among the successional stages. In harvested stands, carbon content changed significantly with increasing harvesting intensity (from 84.6% to 55.7%) and was lower than in non-harvested stands. These changes were reflected in reduced carbon accumulation in trees, deadwood, and soil layer and increased accumulation in understory plants. Silvopastoral system management can achieve a balance between productive objectives and maintenance of carbon stocks in managed forests, resulting in higher resilience and lower carbon losses, thus promoting sustainable forest management. [ABSTRACT FROM AUTHOR]

Estimating the volume of standing trees is a fundamental concern in forestry and is typically accomplished using one or more measurements of stem diameter along with formulae that assume geometric primitives. In contrast, technologies such as terrestrial Light Detection And Ranging (LiDAR) can record very detailed spatial information on the actual surface of an object, such as a tree bole. We present a method using LiDAR that provides accurate volume estimates of tree stems, as well as 2D rasters that display details of stem surfaces, which we call the "unwrapping method." This method combines the concepts of cylinder fitting, voxelization, and digital elevation models. The method is illustrated and tested using a sample of standing trees, whereby we are able to generate accurate volume estimates from the point cloud, as well as accurate visualization of the scanned stem sections. When compared to volume estimates derived from Huber's, Smalian's, and Newton's formulae, the differences are consistent with previous studies comparing formula-derived volume estimates and water-displacement-derived volume estimates, suggesting the unwrapping method has comparable accuracy to water displacement. [ABSTRACT FROM AUTHOR]

We evaluated area-based approaches (ABAs) to light detection and ranging (lidar) predictions of plot- and stand-level forest attributes (tree count, height, basal area, volume, aboveground biomass, broadleaf/conifer, and diameter at breast height — "diameter"). ABA methods included post-stratification (PS), ordinary least squares (OLSs) regression, k nearest neighbors (kNN), and random forest (RF). This study was conducted on the Savannah River Site in South Carolina, USA. Plot- and stand-level predictions were validated against fixed-radius 0.04 ha (0.1 acre) plots in 49 ≈2.0 ha (5 acre) stands. Our findings demonstrate that lidar can be incorporated operationally into forest inventory systems to provide stand-level inferences for a wide range of forest attributes. Volume predictions for specific diameter classes, however, often fared poorly (root mean squared error (RMSE) > 100%) for the methods we explored, especially for larger (less common) diameter trees. Stand-level results were consistently better than pixel-level results (10–200+ percentage points). kNN and RF performed similarly and better than OLS and PS, but RF was the most robust to model configurations, while kNN has practical advantages such as simultaneous predictions of many attributes. [ABSTRACT FROM AUTHOR]

The predicted increase in frequency and intensity of boreal forest fires is considered a significant source of carbon dioxide emissions and linked with the degradation of permafrost covering more than half of Russia. Here we analyzed the stand structure and growth of East Siberian larch forests in response to fire severity. We measured 23 sites in the southern part of eastern Siberia along a latitudinal transect with a length of more than 1500 km. Live tree volume differed significantly across geographical regions (p < 0.05), decreasing from south to north (76–250 m3·ha−1), with higher values in forests burnt with low severity. Similarly, volume of coarse woody debris decreased from south to north. The volume of dead standing trees, on the other hand, increased from south to north. The distribution of trees by diameter class in some areas showed clear evidence of fires, with small trees being absent to rare in forests burnt at high severity. The impact of severe fires on stand volume was negligible at the southern sites, potentially associated with rapid regeneration of birch. Birch is an important component of larch forests near the southern boundary of the permafrost, which may contribute to larch forests in the southern part of the study transect being less vulnerable to wildfires compared to northern larch forests. [ABSTRACT FROM AUTHOR]

Effect of neighbor tree competition on crown shape of Korean pine plantation in Northeast China was studied. A total of 48 trees aged 7–58 years were felled, and all living branches were measured. A novel neighbor competition index that considered the overlap length between subject tree and neighbor tree crowns was created and incorporated into crown shape model. The effects of neighboring competition on crown shape, largest crown radius, and inflection point were analyzed. A dummy variable approach was used to detect crown asymmetry. The crown length index (CLI) of the subject tree was selected as the best neighbor competition index, and the mean square error reduction compared with that of the basic model was 2.0% after incorporating CLI. Crown radius displayed differences in the four cardinal directions and followed the order north > west > south > east. The crown radius in four directions for different ages decreased with increasing CLI and the difference increased with increasing tree age. The competition index, which considers horizontal and vertical competition effects, can significantly improve the performance of crown shape model. Both of inflection point and largest crown radius increased with increasing of CLI; however, the Pearson correlation coefficient was not significant (P > 0.05). [ABSTRACT FROM AUTHOR]

The article discusses the importance of unburnt patches (refugia) within the wildfire of Alberta for survival of organisms. Topics discussed include that the forests throughout Alberta experience wildfire as a naturally occurring disturbance that has dominated and molded the landscape, it defines the term refugia and its role in preserving the forest and the animal habitat of the forest; and presents an image showing examples of organisms using different refugia types and scales.

The article discusses the effect of climate change on vegetation in Yukon, Canada and on subarctic ecosystems. Topics discussed include that Yukon has a wide variety of vegetation communities, and paleoecological evidence indicates that vegetation changes have occurred throughout the territory; discussed adverse effect of the changes in climate in the Arctic and boreal regions and presents a table on Yukon's bioclimate zones and historical and natural changes in dominant vegetation communities.

In natural ecosystems, brown-rot fungi are major biodegrading agents of standing trees and dead wood. Decay caused by basidiomycetes results in structural instability and therefore negatively affects the quality and quantity of the produced wood. Fungal attack can also trigger defense mechanisms within the tree aimed at delaying or halting the progress of infection. As these defense mechanisms can decrease the value of the wood, their identification and study are of foremost importance. In this work, healthy trees of Eucalyptus grandis W.Hill — a widely commercialized species in Uruguay — were inoculated with Laetiporus sulphureus and Gloeophyllum trabeum. The decay process was characterized in terms of chemical and anatomical changes, and the defense mechanisms elicited by the tree were identified. Three months after inoculation, no symptoms of infection could be detected with the naked eye; however, microscopic analysis revealed anatomical and chemical changes (weakening, delamination, and rupture of vascular and parenchymal cells) and decreased holocellulose and lignin contents. Compartmentalization and the production of kino were used by the tree as defense mechanisms. [ABSTRACT FROM AUTHOR]

Large wood (LW) is an important structural feature in forested lake ecosystems, but little is known about the production of LW in riparian forests and its movement across the forest–lake ecotone, both of which we describe here for eight small (<30 ha) lakes in Ontario, Canada. The creation of snags through live-tree death varied by species, ranging from 0.24% year−1 for eastern white cedar to 5.60% year−1 for balsam fir. Snag breakage was best described as a function of snag height and snag fall described as a function of tree species, decay stage, and diameter. Long LW pieces and pieces generated close to the lake were more likely to be deposited at the shoreline. The density of LW at the shoreline was 125–550 pieces·km−1, and density and volume of LW were positively related to riparian slope. LW was a stable resource at the shoreline, with a recruitment rate about equal to the loss rate and average movement along the shoreline of 2.89 cm·year−1. LW volumes at the shoreline and in the littoral zone of the lake were positively related to lakebed slope. LW could reside in the littoral zone for centuries, providing physical structure for multiple generations of aquatic organisms in these small lakes. Our results indicate that critical habitat for fish that need aquatic LW extends at least 5 m into riparian forest and that removal of trees within 5 m of the forest edge would reduce LW input to the littoral zone. [ABSTRACT FROM AUTHOR]

The article focuses on post-fire early successional vegetation buffers surface microclimate and increases survival of planted conifer seedlings in the southwestern U.S.

The article focuses on effects of numbers of observations and predictors for various model types on the performance of forest inventory with airborne laser scanning.

The article focuses on measured differences in %C, %N, d13C, and d15N of plant functional types (PFTs) between burned and unburned ground surfaces soon after a wildfire on a north-facing slope in interior Alaska. Topics include the C and N were measured for 16 species and Sphagnum litter, and the shrub leaves showed the lowest d15N of PFTs and showed higher d15N on the burned surface, showing that N transfer from the soils to the leaves in the shrubs was slowed by the wildfire.

Effects of permanent (i.e., maintained) and temporary edges with north- and south-facing exposures were studied in sand pine (Pinus clausa var. clausa (Chapm. ex Engelm.) Vasey ex Sarg.) scrub, an open-canopied forest type in Ocala National Forest, Florida. On edges and interiors of four stands of each type, we measured canopy tree architecture in 5 m × 100 m plots and stand density and basal area in 5 m × 200 m plots. Edge effects were modest but often stronger on south- than north-facing edges and along permanent forest roads than temporary edges of clearcuts that were allowed to regrow. Compared with interior trees, those on edges were typically shorter, retained branches lower on their boles, oriented their first branches more towards the edge, and produced more asymmetrical crowns with the long axis extending into the opening; these trends were greater on south- than north-facing edges and along permanent than temporary edges. Contrary to expectations, there were no edge effects on total basal area, dead tree densities, proportions of sand pine trees with leaning trunks, directions of lean, or angles of lean. Instead of an edge effect, most trees leaned towards the southwest, which seems related to the northeastern origin of prevailing winds and wind gusts. [ABSTRACT FROM AUTHOR]

Northern red oak (Quercus rubra L.) wood is valuable for a variety of applications not only in its natural distribution range in North America but also in Europe. Timber quality and stem diameter largely determine timber prices and respective uses. Silvicultural management is key to influencing tree growth and stem quality. In Germany, crop tree thinning is currently the standard treatment, while in Canada the shelterwood system is common practice. The objective of this study was to compare stem characteristics related to stem quality of northern red oaks from Canada with those from Germany to determine effects of different silvicultural treatments on stem quality. We examined stem characteristics from a total of 150 dominant northern red oaks in Canadian and German forest stands using the terrestrial laser scanning approach. Northern red oak stems in Canada (shelterwood system) were significantly straighter, whereas German stems (crop tree thinning approach) were significantly smoother on the surface and rounder on the upper parts of the stems (height 4–8 m). The number of bark anomalies decreased with increasing tree competition, indicating that competition is the main driver influencing external stem form and the occurrence or persistence of bark anomalies. [ABSTRACT FROM AUTHOR]

Linear disturbances from geological exploration (i.e., seismic lines) have an extensive footprint across much of Canada's western boreal forest; however, how seismic lines interact with subsequent wildfire remains poorly understood. We assessed whether wildfires effectively mitigate the footprint of seismic lines by promoting forest recovery. We evaluated the forest structure of legacy seismic lines burned in 2001 and 2002 by comparing them against adjacent unburned control plots, using metrics derived from airborne laser scanning (ALS) data collected between 2007 and 2009. ALS metrics identified persistent differences in vegetation height and structure between seismic lines and adjacent forest controls, 7–9 years post-fire. Median canopy height was 2.90 m lower on upland seismic lines and 1.94 m lower on lowland seismic lines than on adjacent controls, corresponding to a 21% and 25% height reduction, respectively. Field surveys revealed greater graminoid and nonvascular plant cover, and lower tall-tree cover and dead vegetative matter, on seismic lines, in comparison with controls. Our results show that tree recovery remains significantly delayed on most upland and lowland burned seismic lines in our study area, and that additional management efforts or longer timescales may be required to restore these fragmented landscapes. [ABSTRACT FROM AUTHOR]

Live shrubs in forest understories pose a challenge for mitigating wildfire risk with prescribed fire. Factors driving shrub consumption in prescribed fires are variable and difficult to explain. This study investigated spatial patterns and drivers of Sierra Nevada mixed-conifer forest shrub consumption in prescribed fires through analysis of high-resolution imagery taken before and after prescribed fire. We applied a spatially explicit, generalized additive model to assess tree cover and coarse woody material as potential drivers of shrub consumption. Shrub cover in two experimental stands prior to burning was 38% and 59% and was 36% and 45% one-year post-burn. In both stands shrub patch density increased, while area-weighted mean patch size and largest patch index decreased. Increased local percent cover of coarse woody material was associated with increased shrub consumption. These findings provide information for prescribed fire managers to help better anticipate shrub consumption and patchiness outcomes under similar conditions. [ABSTRACT FROM AUTHOR]

Wood discoloration was investigated in 721 paper birch (Betula papyrifera Marsh.) trees from 146 sites across the managed forest of Quebec, Canada. Discoloration was present at breast height in 85% of trees, but its impact was limited in terms of tree basal area and volume, with proportions of 6.4% and 3.6%, respectively. These two measures were strongly correlated. Discoloration changed wood appearance but had no effect on microfibril angle and modulus of elasticity. Discolored wood was nevertheless denser, probably due to the accumulation of colored extractives. Predictive models were also developed and applied to 415 711 paper birch trees from 51 689 inventory plots across the province to study regional variation. Higher proportions of discolored basal area were obtained in the southwestern areas of the province where the climate is warmer and drier. In these areas, paper birch trees are larger and, likely, support bigger branches which can cause larger columns of discoloration when broken. Lower proportions were found in eastern regions where snowfall is more abundant. Smaller, more flexible branches in trees growing in these areas could explain this result. This study confirms the feasibility of large-scale mapping of wood discoloration in standing trees based on forest inventory and climate data. [ABSTRACT FROM AUTHOR]

The transition zone between the northern boreal forest and the Arctic tundra, known as the tundra–taiga ecotone (TTE) has undergone rapid warming in recent decades. In response to this warming, tree density, growth, and stand productivity are expected to increase. Increases in tree density have the potential to negate the positive impacts of warming on tree growth through a reduction in the active layer and an increase in competitive interactions. We assessed the effects of tree density on tree growth and climate–growth responses of Cajander larch (Larix cajanderi Mayr.) and on trends in the normalized difference vegetation index (NDVI) in the TTE of Northeast Siberia. We examined 19 mature forest stands that all established after a fire in 1940 and ranged in tree density from 300 to 37 000 stems·ha−1. High-density stands with shallow active layers had lower tree growth, higher stand productivity, and more negative growth responses to growing season temperatures compared with low-density stands with deep active layers. Variation in stand productivity across the density gradient was not captured by Landsat-derived NDVI, but NDVI did capture annual variations in stand productivity. Our results suggest that the expected increases in tree density following fires at the TTE may effectively limit tree growth and that NDVI is unlikely to capture increasing productivity associated with changes in tree density. [ABSTRACT FROM AUTHOR]

Mixedwood stands are composed of hardwoods and softwoods, with neither comprising greater than 75%–80% of basal area or aboveground biomass. By conferring associational resistance and greater resilience to forests when stressed or disturbed, the more diverse composition of mixedwood stands contributes to forest health. We analyzed three examples where mixedwood stands are more resistant to insect infestations in eastern North America. In balsam fir (Abies balsamea L. Mill.) and spruce (Picea spp.) forests, susceptibility and vulnerability to spruce budworm infestations is reduced with increasing hardwood density. In mid-Atlantic oak-dominated forests, oak mortality following gypsy moth infestations was much greater in oak-dominated forests than in oak–pine mixedwoods, while pine mortality during southern pine beetle infestations was greater in pine-dominated forests than in oak–pine mixedwoods. Overall, mixedwood stands have greater resistance to infestations of defoliators and bark beetles and recover more rapidly from disturbances, reducing economic losses associated with tree mortality and mitigating short-term impacts to ecosystem functioning resulting from insect damage, especially carbon sequestration. Finally, we discuss challenges and opportunities for mixedwood management to minimize insect damage. Management strategies that incorporate mixedwood stands may provide better continuity in supply of forest products and ecosystem services in the face of projected increases in insect infestations associated with changing climate. [ABSTRACT FROM AUTHOR]

It has been established that wood decay and cavities in tree stems contribute significantly to tree failures. Several techniques have been reported by researchers for detecting wood decay and cavities in living trees. These techniques are reviewed in this study under two broad categories: invasive and noninvasive methods. The invasive methods include traditional (decay detecting drill, increment borer, and boroscope), radiographic, acoustic, and electrical resistivity techniques. The noninvasive methods comprise microwave scanning, magnetic resonance imaging, X-ray tomography, and traditional techniques involving the use of mallets. Two or more methods are usually combined to investigate the health status of a tree for comparison and validation of results. The prospects and challenges of the various techniques in diagnosing wood decay, cavities, and other structural defects in living trees are reported. This review aims to help researchers in this field identify areas of further work towards the efficient monitoring and management of forest and urban trees. [ABSTRACT FROM AUTHOR]

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Long-term studies of vegetation succession can inform restoration of degraded forests. We examined resilience of a boreal mixedwood vegetation community, asking whether treatments employed to restore wood production in a degraded ecosystem could also restore diversity and composition of vegetation communities. The Inga Lake trial, established in 1987 in northeastern British Columbia, used mechanical, fire, and chemical and manual treatments, encompassing a gradient of restoration effort, and tree planting to restore a shrubland to white spruce (Picea glauca (Moench) Voss) forest. We monitored vascular plant, bryophyte, and macrolichen composition five times over 31 years on five to seven treatments replicated five times. We used mixed-effects models and nonmetric multidimensional scaling to compare diversity and composition among treatments and with mature reference forests. Low- to high-effort restoration created a gradient from broadleaf- to spruce-dominated overstories. Diversity increased with restoration effort. Four of 253 taxa occurred in mature forests only. There was no evidence that lower versus higher effort treatments followed divergent successional pathways toward broadleaved versus spruce reference communities. Our results suggest that these mixedwood vegetation communities lie within a broad domain of successional attraction that confers high ecological resilience to disturbance. Gap cuttings to stimulate understory re-initiation and provide woody debris are recommended to complete the restoration. [ABSTRACT FROM AUTHOR]

Modeling the number of branches in a tree is fundamental for simulating other branch characteristics and crown structure. In this study, a total of 77 Korean larch (Larix olgensis Henry) trees were destructively sampled from plantations in Northeast China. The number of first- and second-order branches was modeled using seven count data models, namely Poisson, negative binomial (i.e., NB, including NB-1, NB-2, and NB-P), and generalized Poisson (i.e., GP, including GP-1, GP-2, and GP-P) regression models. Generalized linear mixed models (GLMMs) were then applied to those models using the sampled trees as the random effects. The results showed that (i) the Poisson regression was preferred for modeling the number of first-order branches; (ii) the GP-1 regression was considered the optimal model for the number of second-order branches; (iii) the significant predictor variables included tree height increment, branch position, relative tree size, mean dominant height, and tree age; (iv) the GLMMs significantly improved both model fit and prediction performance; (v) the prediction accuracy of the GLMMs increased gradually with increasing sample size; and (vi) a relatively small sample size with an appropriate sampling strategy would be adequate to provide a good estimation at a specific crown section. [ABSTRACT FROM AUTHOR]

The article reports on a study which analyzed the changes in the moss community after more than 36 years following its disturbance by a volcanic eruption at Mount Saint Helens. The eruption resulted in large amounts of tephra (aerially transported volcanic ejecta) deposits on nearby forests in southwestern Washington. The research also examined the bryophyte succession in the area, particularly on mosses.

Widespread, rapid aspen (Populus tremuloides Michx.) mortality since the beginning of the 21st century, sometimes called sudden aspen decline (SAD), has been documented in many locations across North America, but it has been particularly pronounced in the southwestern United States. We investigated the relationship among aspen growth, mortality, and climate across three forest types in northern Arizona using cross-dated tree-ring samples from 126 live and 132 dead aspens. Aspen growth was negatively correlated with warm temperatures and positively associated with higher precipitation. Using survival analysis techniques to investigate the links between aspen mortality, tree traits, and climatic conditions, we found that tree traits played a larger role in mortality risk than climate factors. Trees with larger diameters, older trees, and trees with faster growth rates over the past 50 years had a reduced risk of mortality. Management actions aimed at maintaining the most vigorous, fastest growing aspen in the region could help mitigate the impacts of a warmer, drier future. [ABSTRACT FROM AUTHOR]

The article reports that natural disturbances to inform implementation of ecological forestry in Nova Scotia, Canada. Topics include the core of ecological forestry is the idea that natural forest structure, the processes may be approximated by designing management practices that emulate natural disturbances, and the natural disturbance emulation depends on fundamental knowledge of disturbance characteristics.

The article provides information on a study which examined whether species' shade tolerance regulate natural regeneration abundance and composition when partial harvestings are operated on a landscape scale. Topics discussed include how growth and mortality of natural regeneration influenced by partial harvestings over a 15-year period since harvesting, and difference between randomly selected unharvested control plots and partially harvested plots prior to the harvesting application.

Emerald Ash Borer (EAB; Agrilus planipennis Fairmaire (Coleoptera, Buprestidae)) has killed millions of ash (Fraxinus spp.) trees since its 2002 detection in southern Michigan and Ontario. Effects of EAB in riparian forests, where ash species are often abundant, could influence terrestrial and aquatic conditions but are largely unknown. We surveyed vegetation and coarse woody material within and between three gaps in riparian forests along stretches of three rivers in northwestern Michigan. Gaps were originally dominated by Fraxinus pennsylvanica Marsh. and Fraxinus nigra Marsh., which comprised 46%–71% of total basal area, while ash comprised <10% of basal area in forests between gaps. More than 95% of overstory ash were killed by EAB. Fraxinus pennsylvanica saplings were abundant in gaps but F. nigra regeneration was minimal. Few tree seedlings occurred in gaps, which were dominated by dense sedge mats. Aerial imagery showed the EAB invasion has resulted in 3.6–7.1 canopy gaps·km−1 and dead ash account for 13%–21% of total basal area within 100 m of the banks of all three rivers. Long-term monitoring will be useful to evaluate persistence of ash, particularly F. nigra, the stability of riparian buffers, and potential indirect effects of EAB invasion on the adjacent aquatic systems. [ABSTRACT FROM AUTHOR]

Wildfires may have serious and long-lasting impacts in Mediterranean Basin oak forests. Although cork oak (Quercus suber L.) is usually considered a highly fire-resistant tree species, post-fire recovery is not guaranteed. We assessed the mortality and regeneration of 729 cork oak trees that burned and were cut in six sites with the objective of identifying the main factors affecting the short- to medium-term post-fire recovery. We used linear mixed models to investigate potential relationships among tree stump status at the end of the second and fifth growing seasons and several tree- and site-level variables. Overall tree mortality in the second year was 44% and was negatively affected by bark thickness and positively affected by root exposure, trunk injuries, and diameter, in decreasing order of importance. Between the second and fifth years, mortality increased to 53%, but this increase was only observed in sites with high grazing pressure. Grazing also had a strong negative impact on the growth of basal resprouts, thereby compromising tree recovery. The results give useful information on the need for application of adequate forest management practices (particularly avoiding debarking injuries, soil erosion, and grazing pressure) to increase the resilience of these ecosystems and reduce the negative economic and ecological impacts of wildfires. [ABSTRACT FROM AUTHOR]

Climate-induced increases in tree mortality are reported for many forests worldwide. Understanding the potential effects on carbon pools requires long-term monitoring of changes in forest biomass. We measured aboveground biomass (AGB) of living trees over a 34-year period (1982–2016) in permanent plots with varying stand ages, species compositions, and topographic settings in a subalpine forest in the Colorado Front Range. Stand-level and species-level AGB varied spatially and temporally in relation to stand age, successional processes, and site moisture classification. Young (ca. 122 years) postfire stands composed of lodgepole pine (Pinus contorta var. latifolia Engelm. ex S. Watson) had lower mean AGB than older (>250 years) mixed-species stands. Mesic stands had higher AGB than xeric or hydric stands of similar age. At the level of individual species, significant shifts in AGB among species were primarily explained by successional replacement of shade-intolerant pines by shade-tolerant Engelmann spruce (Picea engelmannii Parry ex Engelm.) and subalpine fir (Abies lasiocarpa (Hook.) Nutt.). The permanent plot network recorded significant shifts in species dominance and tree densities between 1982 and 2016, reflecting successional patterns developing over several centuries and the effects of recent localized windthrow, insects, and pathogens. Despite increases in tree mortality, there was a general pattern of increasing AGB across the forest. [ABSTRACT FROM AUTHOR]

Where airborne laser scanning (ALS) measures the entire aboveground vegetation, the target of a stand-level forest inventory is usually the living tree stock above a given diameter but excluding standing dead trees. The aim here was to investigate the effects of varying field-measured minimum diameters (3-10 cm) and standing dead wood on ALS-based forest inventories. The characteristics considered in this case were volume, basal area, number of stems, mean diameter, and mean height for each species, as well as the total growing stock and the total aboveground biomass. The field data comprised measurements of all trees that were ≥3 cm at breast height (1.3 m) on 601 sample plots located in pine-dominated managed forests in eastern Finland. The results showed that the minimum diameter had a significant effect on the estimates obtained in young forests, for which the three smallest minimum diameter datasets (3, 4, and 5 cm) gave the most accurate estimates. Minimum diameter had no marked influence in the case of middle-aged or mature forests. The inclusion of standing dead trees did not have any effect on the estimates of living tree characteristics. The effect of minimum diameter is minor where large-area inventory applications are concerned; however, especially from a silvicultural point of a view, a minimum diameter of 3 cm should be employed in young forests, for which a large proportion of the tree stock usually consists of small trees, i.e., with diameters of <5 cm. [ABSTRACT FROM AUTHOR]

Effects of commercial thinning on downed coarse woody debris (CWD) and standing dead trees (snags) were examined in six intensively managed 22- to 30-year-old white spruce ( Picea glauca (Moench) Voss) plantations in northern New Brunswick, Canada. Four alternative treatments were applied: ( i) an unthinned control and three commercial thinning 40% basal area removals, with ( ii) slash and tops remaining on the site (status quo), ( iii) most of the branches and tops extracted from the site (biomass removal), and ( iv) clumps of unthinned trees left, with one-half of the trees in each clump girdled to create snags (enhanced structure). Three years after thinning, CWD volume increased by 14%-27% in the status quo and enhanced structure treatments, by 6% in the biomass removal treatment, and by 0.1% in the unthinned treatment. Mean snag volume changed little, i.e., less than 1 m3·ha−1 among treatments, and stumps of thinned trees were 4.6-4.9 m3·ha−1. The girdled trees added 0.7 m3·ha−1 of snags, and 1.3 m3·ha−1 is expected to be added from girdling the remaining live trees in the unthinned clumps in 2016. The girdled trees and future to-be-girdled trees added up to 50% of the new deadwood in the enhanced structure treatments, but thinning treatments did not significantly affect total deadwood. The results indicate that commercial thinning produced fine debris but had little effect on overall deadwood amount. Girdling trees during commercial thinning, at the intensity used in this study, is unlikely to produce sufficient snags. Leaving islands and clumps during harvest before plantation establishment would be a more effective way of adding structure. [ABSTRACT FROM AUTHOR]

Standing dead trees (snags) are an important component of forest ecosystems, providing foraging, nesting, and roosting substrate for a variety of vertebrates. We examined the effects of four forest regeneration treatments on residual snag density and compared those with densities found in unharvested, naturally regenerated forests (controls) during the second, fourth, and sixth year after timber harvest in mixed pine-hardwood forests of Arkansas and Oklahoma. Regeneration treatments were clearcut with snag creation, shelterwood, single-tree selection, and group selection. Density of large snags (≥25.0 cm DBH) differed only during the sixth year after harvest, with shelterwoods having a lower density of large snags (1.0 snags/ha) than the control or group selection stands (4.0 and 4.2 snags/ha, respectively). Density of small snags (10.0-24.9 cm DBH) mirrored residual basal area, with controls and group-selection stands having the greatest snag densities. Creation of snags in clearcuts by injection with herbicides caused initial snag density in these areas to be greater than other treatments, but density in clearcuts declined sharply by 6 years after harvest. In the absence of snag creation, treatments such as shelterwoods that remove most trees may have snag densities below that required to address some management objectives without additional snag creation. [ABSTRACT FROM AUTHOR]

Estimating residual tree survival and growth is crucial for evaluating the overall merit of partial harvesting. In this case study, we present the effects of different cutting intensities (0%, 40%, 50%, and 60% of merchantable (diameter at breast height ≥ 9.1 cm) basal area (BA)) on the response of residual trees in two mixed yellow birch ( Betula alleghaniensis Britt.) - conifer stands in eastern Quebec, Canada. Primarily aimed at promoting regeneration establishment, the experiment was conducted in two sites 90 km apart (Armagh and Duchesnay), each one containing four replicates of treatments in a randomized block design. Mortality after cutting decreased with increasing BA removal, but losses were two to three times higher at Armagh (62-138 stems/ha) than at Duchesnay (22-88 stems/ha). Loss of conifer stems involved primarily balsam fir ( Abies balsamea (L.) Mill.) under natural conditions (control), whereas fir and red spruce ( Picea rubens Sarg.) were equally affected in partial cuts. Red maple ( Acer rubrum L.) and paper birch ( Betula papyrifera Marsh.) were lost regardless of treatment. As a whole, growth in merchantable BA increased with cutting intensity. Uniform partial cuts produced good BA growth response from conifers at Armagh (0.27-0.28 m2·ha−1·year−1) and from hardwoods at Duchesnay (0.16-0.25 m2·ha−1·year−1), whereas BA growth was negligible for both species groups in the control. We examine the role of species composition and stand structure before cutting in the response of residual trees. [ABSTRACT FROM AUTHOR]

Yield tables used for stand-level predictions of standing volume typically do not account for the presence of dead trees and stem decay. Yet, recently dead trees, referred to as dead and sound wood (DSW), could be considered as a valuable supplemental wood source. Conversely, stem decay can cause important losses during product recovery. Accordingly, the general objective of this study was to characterize the patterns of change of stem decay and of DSW as functions of time since the last fire (TSF). The amount of stem decay and of DSW per tree species were measured in two chronosequences of 30 stands each, covering more than 1000 years in the northeastern Canadian boreal forest. Stand-level decay volume increased during the first 150 years following fire and then stabilized. This volume was mainly composed of black spruce ( Picea mariana (Mill.) BSP) when TSF <200 years and of balsam fir ( Abies balsamea (L.) Mill.) when TSF >200 years. Conversely, the volume of DSW declined rapidly after fire and increased gradually from about 200 years TSF. Hence, the loss of wood volume attributable to stem decay in old-growth stands was cancelled out by the increased availability of DSW, with a slightly positive balance of 3.5 m3/ha. This could be significant considering the large amount of old-growth stands in this part of the boreal forest. [ABSTRACT FROM AUTHOR]

Catastrophic mortality of North American ash ( Fraxinus spp.) caused by Agrilus planipennis Fairmaire has been attributed to the lack of coevolved resistance between native ash species and this Asian invader. Although A. planipennis host preference or tree resistance can vary, all North American ash species are presumably highly vulnerable to A. planipennis. We inventoried live and dead blue ash ( Fraxinus quadrangulata Michx.) and white ash ( Fraxinus americana L.) in two southeastern Michigan woodlots several years after the A. planipennis invasion to assess their survival. Agrilus planipennis populations in this area peaked in approximately 2005, and the region is now characterized by nearly complete ash mortality. At the Plymouth site, 71% of the original 380 blue ash were alive, whereas only 29 saplings of the original 187 white ash were alive. At the Superior Township site, 63% of the original 210 blue ash were living, whereas all 125 white ash were dead. More than 80% of the blue ash had evidence of previous A. planipennis colonization, but 87% appeared healthy in 2011. Tree diameter did not consistently affect survival, and live and dead trees of both species were distributed across sites, indicating that differential survival was not attributable to localized conditions. [ABSTRACT FROM AUTHOR]

Cavity-nesting birds are dependent on large declining and dead trees that are frequently removed during partial harvesting. We compared breeding densities, nest survival, nest site characteristics, food abundance, and reproductive parameters of six species of cavity-nesting birds in partially harvested and reference woodlots in southwestern Ontario, Canada. Silvicultural practices significantly altered woodlot structure, with treatment-specific effects on bark arthropod biomass, fledging dates for the Red-bellied Woodpecker ( (Linnaeus, 1758)), and site suitability for the Yellow-bellied Sapsucker ( (Linnaeus, 1766)). Red-bellied Woodpecker, Downy Woodpecker ( (Linnaeus, 1766)), and Hairy Woodpecker ( (Linnaeus, 1766)) experienced lower breeding densities in recently cut sites. Daily survival rates were generally greater for nests positioned higher up in large trees and for Northern Flicker ( (Linnaeus, 1758)) nests excavated in healthy and hard wood. Conversely, the Black-capped Chickadee ( (Linnaeus, 1766)) had higher daily survival rates in low, small trees (<10 cm diameter at breast height) and sites with lower arthropod abundance. We conclude that although partial harvesting has the potential to decrease cavity-nesting bird breeding densities, conscientious cavity tree retention during harvest may provide suitable nesting sites that maintain high rates of nest success, regardless of the silvicultural treatments that we examined. However, further research is required to monitor these trends beyond a single harvesting rotation. [ABSTRACT FROM AUTHOR]

Constructing models can be complicated when the available fitting data are highly correlated and of high dimension. However, the complications depend on whether the goal is prediction instead of estimation. We focus on predicting tree mortality (measured as the number of dead trees) from change metrics derived from moderate-resolution imaging spectroradiometer satellite images. The high dimensionality and multicollinearity inherent in such data are of particular concern. Standard regression techniques perform poorly for such data, so we examine shrinkage regression techniques such as ridge regression, the LASSO, and partial least squares, which yield more robust predictions. We also suggest efficient strategies that can be used to select optimal models such as 0.632+ bootstrap and generalized cross validation. The techniques are compared using simulations. The techniques are then used to predict insect-induced tree mortality severity for a Pinus radiata D. Don plantation in southern New South Wales, Australia, and their prediction performances are compared. We find that shrinkage regression techniques outperform the standard methods, with ridge regression and the LASSO performing particularly well. L'élaboration de modèles peut être compliquée lorsque les données à modéliser sont étroitement corrélées et de grande dimension. Cependant, les difficultés ne sont pas les mêmes si l'objectif est la prédiction plutôt que l'estimation. Nous nous concentrons sur la prédiction de la mortalité des arbres (mesurée par le nombre d'arbres morts) à partir de mesures de changement dérivées d'images satellitaires obtenues grâce au spectroradiomètre imageur à résolution moyenne. La grande dimensionnalité et la multicolinéarité inhérentes à de telles données sont particulièrement préoccupantes. Les techniques standards de régression sont peu performantes pour de telles données. Nous avons donc étudié les méthodes de régularisation de la régression, telles que la régression bornée, de type LASSO et des moindres carrés partiels, qui produisent des prédictions plus robustes. Nous proposons également des stratégies efficaces qui peuvent être utilisées pour choisir les meilleurs modèles, tels que 0,632+ l'auto-amorçage et la validation croisée généralisée. Les méthodes sont comparées à l'aide de simulations. Les méthodes sont ensuite utilisées pour prédire la sévérité de la mortalité induite par les insectes dans une plantation de Pinus radiata D. Don située dans le sud de l'État de la Nouvelle-Galles du Sud, en Australie et leurs performances prédictives sont comparées. Nous arrivons la conclusion que les méthodes de régularisation de la régression donnent de meilleurs résultats que les méthodes standards et que la régression bornée et de type LASSO sont particulièrement performantes. [ABSTRACT FROM AUTHOR]

We examined the relationship between the density of cavity trees and forest structure characteristics and explored the occurrence of cavity trees among different tree species and diameter breast height (DBH) size in a subtropical evergreen broad-leaved forest in the Ailao Mountains in southwestern China. Cavity trees accounted for 7.9% of living trees and 16.3% of dead trees. Average density of living cavity trees (86.3 trees·ha–1) was 6.9 times that of dead cavity trees. Density of living cavity trees was positively correlated with the density of living trees. Cavity trees showed a skewed distribution among DBH classes that peaked at DBHs of 20–40 cm. Moreover, the probability that a living tree was cavity-bearing was logistically related to DBH. Overall, the likelihood of trees being cavity-bearing differed significantly among species. The proportions of cavity trees among the 23 species having more than 63 trees were positively related to the average DBH and to the largest DBH recorded for each species. We suggest that (1) living tree density is important in determining density of cavity trees and (2) differences in proportion of living cavity trees among species is caused mostly by differences in average DBH of each species. [ABSTRACT FROM AUTHOR]

Worldwide, snags are an important, but often lacking, component of forest ecosystems. We revisited artificially topped Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco) trees 16–18 years after treatment in a replicated experiment in western Oregon. Some trees had been topped such that no live crown was retained (fatally topped), while others retained some portion of their live crown after topping (nonfatally topped). Topped trees were created under three different silvicultural regimes: clearcut, two story, and group selection. Twenty-three percent (61 of 262) of nonfatally topped trees remained living 16–18 years after treatment; 4% (19 of 482) of fatally topped trees had broken at some point up the bole by 16–18 years after treatment. Silvicultural regime, post-treatment height, stem diameter, stem lean, and ground slope were considered as potential explanatory variables in logistic regression models explaining mortality and breakage. A nonfatally topped tree’s odds of surviving 16–18 years after treatment was greater in the mature matrix of group selection stands than in clearcuts or two-story stands. A fatally topped tree’s odds of breaking within 16–18 years of treatment decreased as DBH increased. If carefully created, artificially topping trees can be a useful silvicultural tool to increase structural heterogeneity. [ABSTRACT FROM AUTHOR]

Partial cutting techniques are increasingly advocated and used to create habitat for priority wildlife. However, partial cutting may or may not benefit species dependent on deadwood; harvesting can supplement coarse woody debris in the form of logging slash, but standing dead trees may be targeted for removal. We sampled cerambycid beetles during the spring and summer of 2006 and 2007 with canopy malaise traps in 1- and 2-year-old partial cut and uncut bottomland hardwood forests of Louisiana. We captured a total of 4195 cerambycid beetles representing 65 species. Relative abundance was higher in recent partial cuts than in uncut controls and with more dead trees in a plot. Total species richness and species composition were not different between treatments. The results suggest partial cuts with logging slash left on site increase the abundance of cerambycid beetles in the first few years after partial cutting and that both partial cuts and uncut forest should be included in the bottomland hardwood forest landscape. [ABSTRACT FROM AUTHOR]

Policies have been enacted to encourage carbon (C) sequestration through afforestation, reforestation, and other silvicultural practices; however, the effects of wildfires on forest C stocks are poorly understood. We present information from Sierran mixed-conifer forests regarding how control, mechanical, prescribed-fire, and mechanical followed by prescribed-fire treatments affected C pools. Secondly, we report CO2 emissions from machinery and burning associated with the treatments. Lastly, the effects of treatments on the potential for C loss to wildfire are presented. The amount of aboveground C in live trees was significantly reduced in mechanical-only and mechanical plus fire treatments; C contained in dead trees was not significantly different. There was no significant difference in aboveground live and dead tree C between the fire-only and control treatments. Fire-only and mechanical plus fire treatments emitted significantly more CO2 than the mechanical treatment and control. Modeling results for the control demonstrated 90% of the live tree C had a high (>75%) chance of being killed in a wildfire; in contrast, all three active treatments had low vulnerabilities to C loss. With wildfire severity increasing in most Sierran forests, management actions designed to increase fire resistance are justified for long-term C sequestration. [ABSTRACT FROM AUTHOR]

Mortality rate is thought to show a U-shape relationship to tree size. This shape could result from a decrease of competition-related mortality as diameter increases, followed by an increase of senescence and disturbance-related mortality for large trees. Modeling mortality rate as a function of diameter is nevertheless difficult, first because this relationship is strongly nonlinear, and second because data can be unbalanced, with few observations for large trees. Parametric functions, which are inflexible and sensitive to the distribution of observations, tend to introduce biases in mortality rate estimates. In this study we use mortality data for Abies alba Mill. and Picea abies (L.) Karst. to demonstrate that mortality rate estimates for extreme diameters were biased when using classical parametric functions. We then propose a semiparametric approach allowing a more flexible relationship between mortality and diameter. We show that the relatively shade-tolerant A. alba has a lower annual mortality rate (2.75%) than P. abies (3.78%) for small trees (DBH <15 cm). Picea abies, supposedly more sensitive to bark beetle attacks and windthrows, had a higher mortality rate (up to 0.46%) than A. alba (up to 0.30%) for large trees (DBH ≥50 cm). [ABSTRACT FROM AUTHOR]

The amount and variability of living and dead wood in a forest stand are important indicators of forest biodiversity, as it relates to structural heterogeneity and habitat availability. In this study, we investigate whether light detection and ranging (lidar) can be used to estimate the distribution of standing dead tree classes within forests. Twenty-two field plots were established in which each stem (DBH >10 cm) was assigned to a wildlife tree (WT) class. For each plot, a suite of lidar-derived predictor variables were extracted. Ordinal regression using a negative log–log link function was then employed to predict the cumulative proportions of stems within the WT classes. Results indicated that the coefficient of variation of the lidar height data was the best predictor variable (χ2 = 106.11, p < 0.00; Wald = 4.83, p = 0.028). The derived relationships allowed for the prediction of the cumulative proportion of stems within WT classes (r = 0.90, RMSE = 6.0%) and the proportion of dead stems within forest plots (r = 0.61, RMSE = 16.8%). Our research demonstrates the capacity of lidar remote sensing to estimate the relative abundances of standing living and dead trees in forest stands and its ability to characterize vegetation structure across large spatial extents. [ABSTRACT FROM AUTHOR]