Components Of Forest Structure Research Articles

Losing our palms: The influence of landscape-scale deforestation on Arecaceae diversity in the Atlantic forest

Understanding the effects of habitat loss on biodiversity has gained pronounced importance to inform conservation planning. Palms are a characteristic, important component of forest structure and the functionality of tropical forests, yet fragmentation-related studies have been poorly investigated in deforested landscapes. Here, we examine the influence of forest loss at the landscape scale on the entire palm community by evaluating species turnover at nine 16 km2 landscapes in the Brazilian Atlantic Forest with 9–71% forest cover. Additionally, we examine the influence of canopy openness at the local scale. We identified all live palms at the species level within 50×100m forest plots at each site and classified species into categories based on their habitat occurrence (“forest-interior” and “open-area” species). The number of Arecaceae species and stems greatly declined with lower amounts of forest cover at the landscape scale, with the power-law model best explaining these relationships. The community composition was also affected by forest cover, in which higher species dissimilarity was observed among severely deforested landscapes. Additionally, our results showed that palm assemblages have been shaped by non-random processes, with forest-interior species being negatively affected by reduced forest cover at the landscape scale. Landscapes embedded within less than 40% forest cover harbored fewer than 10palm species, mainly consisting of open-area forest species. Our study therefore demonstrates the pervasive influence of habitat loss on palm diversity in severely deforested landscapes in the Brazilian Atlantic Forest hotspot. Extensive management actions, including forest restoration and the reintroduction of animal dispersers, are urgent and serve as important tools to permit the successful recruitment, reproduction and establishment of palm species in the unique Atlantic Forest biome.

Assessing different components of three-dimensional forest structure with single-scan terrestrial laser scanning: A case study

Efficient quantification of the three-dimensional forest structure is of increasing importance for our understanding of forest functions and services, but it remains challenging with conventional methods. We used a single-scan ground-based laser approach in stands with a known difference in management history and associated differences in structures. The data were used to test whether the measurement approach could distinguish various structural measures among the stands, including overall density, vertical structure, competitive conditions for regeneration, horizontal visibility, and three-dimensional structural variability. In general, our data reflected known differences in stand structure. However, in some cases the different measures showed contradicting results, highlighting the limited information represented in each measure when considered in isolation. At the same time, our results suggested that all components of stand structure do not develop in sync. The variability of horizontal and vertical structural heterogeneity appears to be a good indicator of structural elements typically found in old-growth forests, i.e., spatially homogenous (scale independent) horizontal structural variability in combination with a scale-dependent vertical structural variability. In addition, our results provided information with direct management implications. For example, gap creation, a prominent practice in restoration treatments in the region, increased spatial variability, but the hard edges and removal of all trees inside the gap, are not reflecting structural conditions found in our old-growth stand. In summary, our results suggest that this new technology can efficiently provide objective and holistic inventories of stand structures. However, more work is needed to fully understand the implications of the novel structural measures for ecosystem processes and services.

Forest structure along a 600 km transect of natural disturbances and seasonality gradients in central‐southern Amazonia

Summary A negative relationship between stand biomass and the density of stems is expected to develop during the self‐thinning process in resource‐limited forests; this leads to a large proportion of the total biomass occurring in large trees. Nevertheless, frequent disturbance regimes can reduce self‐thinning and the accumulation of large trees. We investigated size–density relationships and the contribution of large trees (dbh ≥ 70 cm) to stand biomass in 55 1‐ha plots along a 600 km transect in central‐southern Amazonia. The effects of natural‐disturbance gradients (frequency of storms and soil characteristics) and seasonality on forest‐structure components (density of stems and mean individual mass) and stand biomass were examined. Contrary to self‐thinning predictions, stand biomass increased in forests with higher stem densities. Large trees contained only an average of 5% of stand biomass, and half of the stand biomass was represented by small trees with diameters < 27 cm. These findings indicate that persistent or strong disturbance plays a critical role in forest structure and biomass in the central‐southern Amazon. Frequent storms were identified as an important source of disturbance in the region. Forests under higher frequency of storms had trees with lower individual mass and higher stem packing. More physically restrictive soils seem to magnify the effects of exogenous disturbances limiting individual tree size. Forests in areas with longer dry seasons had lower stem densities; however, individual mass was higher in these areas. These structural components of biomass seem to counterbalance each other in generating total stand biomass. Seasonality affected forest structural components but not stand biomass. Synthesis. Forests of central‐southern Amazonia are not resource limited and accumulate most part of their biomass in small‐ to mid‐sized trees. The effects of environmental gradients on specific structural components of stand biomass differ such that strong positive effects on one component can mitigate strong negative effects on other component. Future work on the determinants of stand biomass should investigate forest structure and the contributions of individual components to stand biomass.

Deriving comprehensive forest structure information from mobile laser scanning observations using automated point cloud classification

The advent of mobile laser scanning has enabled time efficient and cost effective collection of forest structure information. To make use of this technology in calibrating or evaluating models of forest and landscape dynamics, there is a need to systematically and reproducibly automate the processing of LiDAR point clouds into quantities of forest structural components. Here we propose a method to classify vegetation structural components of an open-understorey eucalyptus forest, scanned with a ‘Zebedee’ mobile laser scanner. It detected 98% of the tree stems (N = 50) and 80% of the elevated understorey components (N = 15). Automatically derived DBH values agreed with manual field measurements with r2 = 0.72, RMSE = 3.8 cm, (N = 27), and total basal area agreed within 1.5%. Though this methodological study was restricted to one ecosystem, the results are promising for use in applications such as fuel load, habitat structure, and biomass estimations.

Burning the legacy? Influence of wildfire reburn on dead wood dynamics in a temperate conifer forest

AbstractDynamics of dead wood, a key component of forest structure, are not well described for mixed‐severity fire regimes with widely varying fire intervals. A prominent form of such variation is when two stand‐replacing fires occur in rapid succession, commonly termed an early‐seral “reburn.” These events are thought to strongly influence dead wood abundance in a regenerating forest, but this hypothesis has scarcely been tested. We measured dead wood following two overlapping wildfires in conifer‐dominated forests of the Klamath Mountains, Oregon (USA), to assess whether reburning (15‐yr interval, with >90% vegetation mortality) resulted in lower dead wood abundance and altered character relative to once‐burned stands, and how any differences may project through succession. Total dead wood mass (standing + down) following the reburn (169 ± 83 Mg/ha [95%CI]) was 45% lower than after a single fire (309 ± 87 Mg/ha). Lower levels in reburn stands were due to, in roughly equal parts, additional combustion and greater time for decay. Although a single fire in mature forest both consumed and created dead wood (by killing large live trees), a reburn only consumed dead wood (few large live trees to kill). Charred biomass (black carbon generation) was higher in reburned stands by a factor of 2 for logs and 8 for snags. Projecting these stands forward (notwithstanding future disturbances) suggests: (1) the near‐halving of dead‐wood mass in reburn stands will persist for ~50 yr until the recruitment of new material begins, and (2) the reburn signature on dead wood abundance will remain apparent for over a century. These findings demonstrate how a single stochastic variation in disturbance interval can impart lasting influence on dead‐wood succession, reinforcing the notion that many temperate forests exist in a state of dead‐wood disequilibrium governed by site‐specific disturbance history. Accounting for such variation in disturbance impacts is crucial to better understanding forests with complex mixed‐severity disturbance regimes and with increasing stochasticity under climatic change.

Above-ground biomass and carbon estimates of Shorea robusta and Tectona grandis forests using QuadPOL ALOS PALSAR data

Mechanisms to mitigate climate change in tropical countries such as India require information on forest structural components i.e., biomass and carbon for conservation steps to be implemented successfully. The present study focuses on investigating the potential use of a one time, QuadPOL ALOS PALSAR L-band 25m data to estimate above-ground biomass (AGB) using a water cloud model (WCM) in a wildlife sanctuary in India. A significant correlation was obtained between the SAR-derived backscatter coefficient (σ°) and the field measured AGB, with the maximum coefficient of determination for cross-polarized (HV) σ° for Shorea robusta, and the weakest correlation was observed with co-polarized (HH) σ° for Tectona grandis forests. The biomass of S. robusta and that of T. grandis were estimated on the basis of field-measured data at 444.7±170.4Mg/ha and 451±179.4Mg/ha respectively. The mean biomass values estimated using the WCM varied between 562 and 660Mg/ha for S. robusta; between 590 and 710Mg/ha for T. grandis using various polarized data. Our results highlighted the efficacy of one time, fully polarized PALSAR data for biomass and carbon estimate in a dense forest.

Integrating volunteered smartphone data with multispectral remote sensing to estimate forest fuels

Volunteered data sources are readily available due to advances in electronic communications technology. For example, smartphones provide tools to collect ground-based observations over broad areas from a diverse set of data collectors, including people with, and without, extensive training. In this study, volunteers used a smartphone application to collect ground-based observations. Forest structural components were then estimated over a broader area using high spatial resolution RapidEye remote sensing imagery (5 spectral bands 440–850 nm, 5 m spatial resolution) and a digital elevation model following a three nearest neighbor approach (K-NN). Participants with professional forestry experience on average chose high-priority fuel load locations near buildings, while nonprofessional participants chose a broader range of conditions over a larger extent. When used together, the professional and nonprofessional observations provided a more complete assessment of forest conditions. A generalized framework is presented that utilizes K-NN imputation tools for estimating the distribution of forest fuels using remote sensing and topography variables, ensuring spatial representation, checking attribute accuracy, and evaluating predictor variables. Frameworks to integrate volunteered data from smartphone platforms with remote sensing may contribute toward more complete Earth observation for Digital Earth.

Influences of forest structure and landscape features on spatial variation in species composition in a palm community in central Amazonia

Abstract:The mechanisms that maintain palm species diversity in tropical rain forests are still debated. Spatial variation in forest structure produces small-scale environmental heterogeneity, which in turn can affect plant survival and reproductive performance. An understanding of how palms respond to variation in forest heterogeneity may help to explain the diversity and structure of their assemblages. We used multivariate ordination statistics and multiple linear models to analyse how palm assemblages are affected by forest structure and landscape features in central Amazonia. In 72 (250×4 m) forest plots distributed over an area of 64 km2, we recorded all seedling and adult palms, and measured topographic and soil variables, and components of forest structure and tree abundance. We found 16976 adults and 18935 seedlings of 46 palm species and five varieties including two morphological forms making a total of 50 botanical entities. Results show that landscape features (altitude, slope, proportions of soil sand and clay) and various components of forest structure (such as degree of forest openness, abundance of forest trees, logs and snags, and leaf litter mass), influence spatial variation in richness, abundance and species composition of palms, creating ecological gradients in palm community composition. Despite the statistically significant effects of environmental variables, most species occurred throughout the full range of the ecological gradients we studied, indicating that there is either relatively weak niche specialization in the palms, or that the competition between the species is mediated by diffuse demographic processes that cannot be evaluated only through studies of species distributions.

Survey of the Patterns of Nest Box Use Among Squirrels (Sciuridae) in Managed Forest Stands in Clinton County, New York

Artificial habitat enhancements are important forest structural components that can increase the survival of squirrels (Sciuridae) and thus warrant study. Investigations of squirrel nest box usage can provide useful demographic and community information such as occupancy rates, litter size, habitat preference, species richness and abundance estimates. This artificial nest box study investigated the nesting patterns of squirrels from late winter through early fall 2011 in managed forest stands in Clinton County, New York. Squirrels are sensitive to forest disturbance, hence we compared sites of varying silvicultural activity (e.g., managed for production of timber or maple syrup versus an undisturbed reference stand). A total of 48 nest boxes were constructed and monitored across three separate sites (e.g., reference, logged, and sugaring). Prior research suggested that occupancy may be a function of nest box height (~3.5m and ~5m) and site-specific tree cavity/snags/drey abundance, thus height preference and alternative nesting options were monitored in the survey and analyzed to report detection probability and occupancy estimates in Program Presence. Visual confirmation of northern flying squirrels (Glaucomys sabrinus Shaw) was made in 81%, 44%, and 13% of the nest boxes in the reference, logged, and sugar site, respectively. Approximately 79% of the nest boxes showed evidence of wildlife visitation (e.g., scat, crushed seeds, or nesting material). Additionally, 87% of the high boxes (5m) versus 71% of the low boxes (3.5m) were utilized, and 17% of all occupancies contained multiple individuals. This survey provides additional multi-season occupancy data for an elusive mammal species under managed habitat regimes. We recommend that management plans include a wildlife habitat component that maintains snag trees and live cavity-trees in forest stands. When appropriate, stand management plans could also include installing habitat enhancement structures such as artificial nest boxes for squirrels.

Intraspecific root plasticity in agroforestry systems across edaphic conditions

Land-use practises converting forests to tree-crop systems commonly result in large expanses of intensively managed landscapes. However, some farming practices retain trees and other forest structural components during conversion as a means to confer favorable conditions through agroecological intensification. Understanding root plasticity in situ in response to such a multi-species rooting environment is important to avoid interspecific resource competition. This, however, is an often-understudied parameter due to methodological constraints. Here, we investigate two dominant parameters of root ecology, coarse root distribution and soil water acquisition, of the economically important tree-crop, Theobroma cacao, in monoculture and in mixture with shade trees (agroforestry systems) at two edaphically contrasting sites [sandstone (sandy loam) and phyllite-granite (loam) derived soils] in Ghana, West Africa. In monoculture and in mixture, we employed ground-penetrating radar to detect cocoa coarse root distribution and plant–soil δ18O isotopic signatures to estimate soil water acquisition zones. In monoculture, detected cocoa coarse root vertical distribution differed between sandy loams and loams, with a less dispersed distribution and a higher mean coarse root depth in sandy loams. Detected vertical coarse root distribution was also strongly differentiated between cocoa in monoculture and in mixture; cocoa exhibited restricted root allocation to a smaller zone in the presence of a shade tree, in sandy loam soils. In monoculture, cocoa plant δ18O isotopic signature matched a narrow soil δ18O isotopic zone, while this matched plant–soil zone expanded for cocoa in mixture, illustrating larger soil water acquisition zones in the presence of a shade tree but exclusively in sandy loam soils. We show that under certain conditions, root modification in the presence of a secondary species may limit competition as tree-crop root plasticity differentiates belowground allocation and resource acquisition zones in an agroforestry system.

Deadwood Density of Five Boreal Tree Species in Relation to Field-Assigned Decay Class

Aboveground deadwood, consisting of downed woody debris (DWD), snags, and stumps, is an important component of boreal forest ecosystem structure. Accurate deadwood density estimates are essential for evaluating ecosystem biomass and carbon stocks. The objective of this study was to examine the relationships between deadwood density, tree species, and decay status, identified in the field by morphological characteristics. We sampled DWD, snags, and stumps of trembling aspen (Populus tremuloides Michx.), paper birch (Betula papyrifera Marsh.), jack pine (Pinus banksiana Lamb.), black spruce (Picea mariana [Mill.] B.S.P.), and balsam fir (Abies balsamea [L.] Mill.) in the boreal forest of central Canada. A total of 240 samples (99 DWD, 94 snags, and 47 stumps) were collected. Decay class and tree species explained >80% of the variation in wood density of all deadwood types. Wood density decreased consistently from the lowest to the highest decay class. Tree species identity was also important in determining the relationships between wood density and field-assigned decay class for snags and stumps, but not for DWD, probably because of the five-class system used for DWD, rather than the three-class system used for snags and stumps. These results indicate that decay class and tree species are adequate predictors of deadwood density.

Quantifying spatial patterns of tree groups and gaps in mixed-conifer forests: Reference conditions and long-term changes following fire suppression and logging

Fire suppression and past logging have dramatically altered forest conditions in many areas, but changes to within-stand tree spatial patterns over time are not as well understood. The few studies available suggest that variability in tree spatial patterns is an important structural feature of forests with intact frequent fire regimes that should be incorporated in restoration prescriptions. We used a rare dataset consisting of mapped locations for all trees ⩾10cm in three 4-ha plots in 1929 before logging and in 2007/2008, 78 and 79years after logging, to assess changes in three spatial components of forest structure: individual trees, tree clusters and gaps. Comparing 1929 old growth to modern conditions, area in gaps decreased from 20% to zero, the percentage of stems that were single trees from 6% to 2% and in small or medium clumps (2–9 trees) from 28% to 9%, while trees in large clumps (⩾10trees) increased from 66% to 89%. Concurrent with these changes, canopy cover increased from 45% to 62%, and the average number of trees in a clump increased from 11 to 26, resulting in much more homogenous conditions across the stand. These changes also altered tree size and species associations within different structural groups (i.e., single tree, small, medium and large clumps). In an effort to account for the alteration of the fire regime that had already taken place in 1929 (the last fire recorded in tree rings was in 1889) we also analyzed spatial patterns of 1929 conditions removing all trees <25cm. In this analysis, 35% of the plot area was in gaps and canopy cover averaged 36%. Tree clusters had an average of 5.2 trees per clump, with 13% of trees being singles, 30% in small clumps, 24% in medium clumps and 33% in large clumps. Our results provide metrics that quantify spatial patterns and composition of individual trees, tree clumps, and gaps under the historical fire regime that may be useful to forest managers. Our study demonstrates that the contemporary forest is more homogeneous than it was historically, and variability that likely provided diverse microclimate and habitat conditions and fostered resilience to a variety of stressors and disturbances such as fire, insects and drought has been lost. Future management may benefit from restoring these structural components.

Assessing and modeling snag survival and decay dynamics for the primary species in the Acadian forest of Maine, USA

Snags are an important component of forest structure and a key carbon pool, but there is currently a limited understanding of their survival and decay in the Acadian region of North America. Using standing and fallen snag observations collected from permanent sample plot (PSP) remeasurements at a long-term, replicated silviculture methods experiment in central Maine, USA, the objective of this analysis was to develop quantitative models to better understand snag survival and decay dynamics. Species examined included the conifers Abies balsamea, Picea rubens, Thuja occidentalis, and Tsuga canadensis, and the hardwoods Acer rubrum and Betula papyrifera. Proportional hazards regression models that estimate the 5-year probability (Pr) of snag survival indicated that observed decay class (a measure of snag decomposition) could be used as a surrogate for years since death given the difficulties and errors associated with determining years since death for standing snags. Averaged across all species, Pr (5-year snag survival) estimated as a function of snag diameter at breast height (dbh) in decay classes 1, 2, 3, and 4 were predicted as 0.69±0.09 (mean±standard deviation), 0.36±0.09, 0.16±0.05, and 0.06±0.02, respectively. Where snag dbh was significant in estimating survival (3 of 6 species), hazard ratios indicated that snag survival would increase by as much as 24% for each 10cm increase in dbh, but was dependent on species. Probability matrices predicting the 5-year likelihood of snags transitioning to advanced decay classes or falling showed that T. canadensis and T. occidentalis snags were slowest to decay, as measured by the average time it takes for a snag to progress from decay class 1–4. Probability of snag height-loss, predicted using snag dbh and the harvest interval of the stand, was estimated to be highest for larger dbh snags found in stands with frequent harvest intervals (e.g. 40cm dbh and every 5years). Models predicting the amount of volume reduced in standing snags through time were related to the estimated total volume of a live tree with the same dbh, mode of death, and general decay stage (i.e. soft versus hard). When used together, these models quantifying snag dynamics and associated species and size differences can serve as tools for managers to estimating standing deadwood stocks in mixed-species stands found throughout the Acadian region.

Effects of variable canopy retention harvest on epixylic bryophytes in boreal black spruce – feathermoss forests1This article is one of a selection of papers from the International Symposium on Dynamics and Ecological Services of Deadwood in Forest Ecosystems.

Modification of forest attributes and structural components like downed wood (DW) during forest harvest can lead to local species loss. Epixylic bryophytes have been proposed as good indicators of such changes. Unharvested control, variable canopy retention, and single pass harvest represent a gradient in forest harvest impact and can be used to test the response of epixylic bryophytes to different levels of environmental change. The objective of this study was to see if variable canopy retention attenuates environmental change associated with harvesting, consequently maintaining an epixylic community more similar to unharvested stands than single pass harvesting. Environmental conditions and DW characteristics were sampled on 225 DW pieces distributed in 45 permanent plots. Results showed that treatment affected epixylic richness through its impact on canopy openness and DW diameter and decomposition class. Fewer species were found in more open habitats and more species were found on bigger and more decomposed DW. Most epixylic species were more commonly found on the forest floor than on the DW. In conclusion, variable canopy retention harvest offered microclimatic conditions and DW availability and quality more suitable for epixylic species than single pass harvest, which was less suitable for epixylic species.

Spatial variations in evapotranspiration over East Asian forest sites. II. Surface conductance and aerodynamic conductance

Evapotranspiration over forest surfaces is mainly constrained by environmental and forest structural components through their influence on surface conductance (Gs) and aerodynamic conductance (Ga). Tower based eddy covariance data from 16 forest sites in East Asia (2°S to 64°N) were used to examine the sensitivity of Matsumoto and Nakai models for predicting Gs and Ga, respectively. Daytime dry-canopy data for the growing season were used in this study. Comparisons between model predictions and observed Gs and Ga showed good agreement, suggesting that the models were suitable for predicting Gs and Ga with reasonable accuracy. However, the model for Gs was unable to predict Gs accurately when soil water content was low (∼10%). In this circumstance, effective soil water content and a more comprehensive method for modelling the soil water content function must be used. Gs in East Asia was largely depended on vapour pressure deficit and secondarily on soil water content. Ga was largely affected by leaf area index compared with stand density.

Microhabitat selection in an assemblage of crickets (Orthoptera: Ensifera) of a tropical evergreen forest in Southern India

. 1. Habitat selection is a universal aspect of animal ecology that has important fitness consequences and may drive patterns of spatial organisation in ecological communities. 2. Measurements of habitat selection have mostly been carried out on single species and at the landscape level. Quantitative studies examining microhabitat selection at the community level are scarce, especially in insects. 3. In this study, microhabitat selection in a natural assemblage of cricket species was examined for the first time using resource selection functions (RSF), an approach more commonly applied in studies of macrohabitat selection. 4. The availability and differential use of six microhabitats by 13 species of crickets inhabiting a tropical evergreen forest in southern India was examined. The six available microhabitats included leaf litter-covered ground, tree trunks, dead logs, brambles, understorey and canopy foliage. The area offered by the six microhabitats was estimated using standard methods of forest structure measurement. Of the six microhabitats, the understorey and canopy accounted for approximately 70% of the total available area. 5. The use of different microhabitats by the 13 species was investigated using acoustic sampling of crickets to locate calling individuals. Using RSF, it was found that of 13 cricket species examined, 10 showed 100% selection for a specific microhabitat. Of these, two species showed fairly high selection for brambles and dead logs, which were rare microhabitats, highlighting the importance of preserving all components of forest structure.

Deadwood abundance in recently harvested and old Nova Scotia hardwood forests

Deadwood – consisting of dead standing trees (snags), woody debris (WD; downed deadwood), buried wood and stumps – is an important yet poorly documented component of forest structure. Deadwood is important to carbon cycles (e.g. Kurz and Apps, 1993), provides growing and breeding habitat for a range of species, including saproxylic plants, fungi and animals (Kruys and Jonsson, 1999; Harmon et al., 2004; Norden et al., 2004). Deadwood is also an important habitat for southern flying squirrels (Glaucomys volans Linnaeus), which are endangered in Nova Scotia (Stabb, 1987). However, deadwood dynamics in northeastern North American hardwood forests have not received the same attention as other forest ecosystems and there is a dearth of information for Nova Scotia hardwood forests. Hence, forest dynamics of the northeastern USA and inland Canada are implied to apply to the whole of the Acadian Forest Region (Rowe, 1972), which includes Nova Scotia (e.g. Mosseler et al., 2003). Forests dominated by sugar maple (Acer saccharum L.), yellow birch (Betula alleghaniensis Britton), American beech (Fagus grandifolia Ehrh), white birch (Betula papyrifera Marsh) and red maple (Acer rubum L.) are common from the coast of New England, USA and Maritime Canada inland to southern Ontario and Quebec, Canada, Minnesota and Wisconsin, USA. Forests dominated by these species grow at their northeastern limit in Nova Scotia, which is more influenced by a maritime climate resulting in high winds, more frequent ice storms and cooler summers than most of their range. Thus, yields and tree dimensions of Nova Scotia’s hardwood forests are potentially lower than southern and inland hardwood forests, likely producing less deadwood consisting of smaller pieces that are less persistent on the landscape. Hardwood forests dominated by sugar maple, yellow birch and beech constitute 23 per cent of the potential late successional forests of Nova Scotia. Mixed woods composed of softwood, maple, birch and beech represent a further 11 per cent of the potential climax forests of Nova Scotia (Stewart et al., 2003). While the area of Nova Scotia dominated by the above species is unknown, Nova Scotia is estimated to contain a total merchantable volume of 132.1 million m3 of hardwood, consisting of 57.6, 19.4, Deadwood abundance in recently harvested and old Nova Scotia hardwood forests

Patterns of tree species richness in Jalisco, Mexico: relation to topography, climate and forest structure

The objective of this study was to identify the major environmental variables and components of forest structure associated with variability in tree species richness on a network of 806 permanent plots in the State of Jalisco, Mexico. Tree data recorded on the sample plots were used to characterize tree species richness by forest type and climatic conditions (temperature and precipitation) in the State. Species composition and other diversity indices were also calculated. Explanatory variables identified in a Poisson regression identified forest cover type, elevation, tree basal area, canopy closure, and winter precipitation as being important to changes in tree species richness. An “extreme quantile curve estimation” approach was then used to approximate the boundary that represented the maximum potential species richness response to the various levels of important variables. Maximum tree species richness decreased with increasing elevation. The relationships between maximum species richness and tree basal area, canopy closure, and winter precipitation followed a hump-back unimodal model, with intermediate values supporting the largest species richness. We believe that results of the current study will contribute to further development of a conservation plan for tree species in the State of Jalisco, Mexico.

Scale‐dependent environmental variables affecting red squirrel (Sciurus vulgaris meridionalis) distribution

We investigated the effects of habitat fragmentation on the endemic subspecies of red squirrel Sciurus vulgaris meridionalis in the Pollino National Park, Calabria, Southern Italy. Presence/absence of squirrels was monitored using drey (nest) counts in 51 1‐ha census plots. Squirrel dreys were found in 16 plots (31%). Patch size was not correlated to squirrel presence. Squirrels were found in patches ranging from 3.19 to 6051 ha. Small‐scale forest structure significantly affected the probability of occurrence. The proportion of conifers and average tree height positively predict squirrel presence; furthermore, nest density was positively correlated with high tree species diversity and the proportion of deciduous oaks (Quercus cerris, Q. ilex). Also at the home‐range scale the proportion of conifer forest and oak‐dominated deciduous forests positively predicted squirrel presence (200–300 m radius). At the even larger scale, corresponding with potential dispersal distances (3000 m radius), landscape parameters indicating a lower degree of fragmentation and proportion of oak seemed to favour squirrel presence. Our results emphasize that multi‐scale analyses can enhance our understanding of red squirrel distribution, and that their distribution and abundance were mainly determined by forest structure components, such as food availability, at the home‐range scale. We underline the importance of protection, and eventually increasing conifer and deciduous oak woods range in the Pollino National Park for the management and conservation of endemic Calabrian red squirrels.

Mapping snags and understory shrubs for a LiDAR-based assessment of wildlife habitat suitability

The lack of maps depicting forest three-dimensional structure, particularly as pertaining to snags and understory shrub species distribution, is a major limitation for managing wildlife habitat in forests. Developing new techniques to remotely map snags and understory shrubs is therefore an important need. To address this, we first evaluated the use of LiDAR data for mapping the presence/absence of understory shrub species and different snag diameter classes important for birds (i.e. ≥ 15 cm, ≥ 25 cm and ≥ 30 cm) in a 30,000 ha mixed-conifer forest in Northern Idaho (USA). We used forest inventory plots, LiDAR-derived metrics, and the Random Forest algorithm to achieve classification accuracies of 83% for the understory shrubs and 86% to 88% for the different snag diameter classes. Second, we evaluated the use of LiDAR data for mapping wildlife habitat suitability using four avian species (one flycatcher and three woodpeckers) as case studies. For this, we integrated LiDAR-derived products of forest structure with available models of habitat suitability to derive a variety of species-habitat associations (and therefore habitat suitability patterns) across the study area. We found that the value of LiDAR resided in the ability to quantify 1) ecological variables that are known to influence the distribution of understory vegetation and snags, such as canopy cover, topography, and forest succession, and 2) direct structural metrics that indicate or suggest the presence of shrubs and snags, such as the percent of vegetation returns in the lower strata of the canopy (for the shrubs) and the vertical heterogeneity of the forest canopy (for the snags). When applied to wildlife habitat assessment, these new LiDAR-based maps refined habitat predictions in ways not previously attainable using other remote sensing technologies. This study highlights new value of LiDAR in characterizing key forest structure components important for wildlife, and warrants further applications to other forested environments and wildlife species.