Dense Understory Vegetation Research Articles

A comparative assessment of the vertical distribution of forest components using full-waveform airborne, discrete airborne and discrete terrestrial laser scanning data

Laser scanning has the potential to accurately detect the vertical distribution of forest vegetative components. However, limitations are present and vary according to the system’s platform (i.e., terrestrial or airborne) and recording method (i.e., discrete return or full-waveform). Terrestrial configurations detect close objects (i.e., lower vegetation strata) in more detail while airborne configurations detect a more detailed upper strata, with weak backscattered signals from lower strata. Moreover, discrete lidar systems record single or multiple hits from a given pulse at intercepted features in contrast to full-waveform systems, which register the pulse’s complete backscattered signal providing complete vertical profiles. In this study, we examine for a boreal and a Mediterranean forest with contrasted conifer canopy densities: (i) the characterization of the vertical distribution and signal occlusion from three laser scanning configurations: full-waveform airborne (ALSFW), discrete airborne (ALSD), and discrete terrestrial (TLS); (ii) the comparison in the detection of understory vegetation by ALSFW and ALSD using TLS as reference; and (iii) the use of a methodological procedure based on the Gini index concept to group understory vegetation in density classes from both ALSFW and ALSD configurations. Our results demonstrate, firstly, that signal occlusion can be quantified by the rate of pulse reduction independently for data from all three laser scanning configurations. The ALSD configuration was the most affected by signal occlusion, leading to weak signal returns at the lower strata (z < 4 m) where the rate of pulse reduction was highest as a result of dense canopy covers. Secondly, we demonstrated the capabilities for both airborne laser scanning configurations to detect understory vegetation, albeit significantly more accurately with ALSFW. Lastly, we demonstrated the use of the Gini index as an indicator to determine understory vegetation density classes, particularly for ALSFW data in dense canopy cover. We proceed to explain the limitations in detecting the vertical distribution from different configurations, and indicate that understory vegetation density classes may be successfully assigned with ALSFW in contrasted conifer canopy densities.

Stream water quality in relation to watershed‐scale practical forest management in a cool‐temperate natural forest in northern Japan

AbstractThe water chemistry of a stream reflects the biogeochemical processes occurring in upstream forests. Anthropogenic disturbances in forests, such as cutting trees, altering the nitrogen (N) cycle, and increase in N leaching from the soil to streams, potentially cause acidification or eutrophication downstream. In forests with dense understory vegetation, mechanical site preparation following tree cutting is commonly used to improve the early establishment of tree seedlings. In cool‐temperate forests in northern Hokkaido, Japan, dense understory vegetation (mainly comprising Sasa dwarf bamboo) inhibits forest regeneration after tree cutting. Soil scarification is a common site preparation technique for eliminating Sasa bamboo and improving forest regeneration. Long‐term data are useful for examining the temporal changes in stream water chemistry exposed to different specific forest management practices under changing environment (e.g., climate change and atmospheric N deposition). For 14 years (2003–2016), we observed the stream water chemistry in naturally forested watersheds and at one point after the confluence of all streams in Uryu Experimental Forest of Hokkaido University (North Hokkaido Experimental Forests Site of JaLTER) in northern Japan. We also monitored stream discharge, water level and stream water temperature in each watershed. Water samples were collected from the outlets of 10 watersheds. The forest management practice in each watershed includes clear‐cutting, soil scarification in sparse forest with dense understory Sasa, and clear‐cutting and soil scarification followed by soil replacement. Long‐term data in the six unmanaged watersheds are also valuable as a background information to analyze the effect of long‐term climate, environment and vegetation changes on stream water chemistry. The measured water quality data of 1,873 water samples include the ion concentrations (Cl−, NO3−, SO42−, Na+, NH4+, K+, Mg2+, and Ca2+), pH, and electrical conductivity (EC) in the stream water. The range of the concentrations of Cl−, NO3−, SO42−, Mg2+, and Ca2+ in the stream water across all the watersheds throughout the observed periods (minimum to maximum) were 3.35–23.67, 0.01–8.68, 0.83–4.01, 0.45–2.55 and 0.72–6.16 mg L−1, respectively. Similarly, the stream pH and EC ranged from 6.04 to 7.53 and 3.14 to 9.47 mS m−1, respectively.The complete data set for this abstract published in the Data Paper section of the journal is available in electronic format in MetaCat in JaLTER at http://db.cger.nies.go.jp/JaLTER/metacat/metacat/datapaper%202020‐04.1/jalter‐en. [Correction added on 7 September 2020, after first online publication: JaLTER URL has been updated.]

Differential responses of the acidobacterial community in the topsoil and subsoil to fire disturbance in Pinus tabulaeformis stands.

Acidobacteria is found to be dominant and abundant in forest soil, and performs specific ecological functions (such as cellulose decomposition and photosynthetic capacity, etc.). However, relative limited is known about its changing patterns after a fire interruption. In this study, the response of soil Acidobacteria to a wildfire disturbance was investigated using the Illumina MiSeq sequencing system. The research area was classified by different severities of fire damage (high, moderate, and low severity, and an unburnt area), and samples were collected from various soil layers (0–10 cm as topsoil; 10–20 cm as subsoil). We obtained a total of 986,036 sequence reads; 31.77% of them belonged to Acidobacteria. Overall, 18 different Acidobacteria subgroups were detected, with subgroups 4, 6, 1, 3, and 2 the most abundant, accounting for 31.55%, 30.84%, 17.42%, 6.02%, and 5.81% of acidobacterial sequences across all samples, respectively. Although no significant differences in acidobacterial diversity were found in the same soil layer across different fire severities, we observed significantly lower numbers of reads, but higher Shannon and Simpson indices, in the topsoil of the high-severity fire area than in the subsoil. Non-metric multidimensional scaling (NMDS) analysis and permutational multivariate analysis of variance (PERMANOVA) also revealed significant differences in the acidobacterial community structure between the two soil layers. Soil pH, total nitrogen, NH4+-N, the Shannon index of understory vegetation and canopy density were the major drivers for acidobacterial community structure in the topsoil, while soil pH and organic matter were significant factors in the subsoil. A variance partitioning analysis (VPA) showed that edaphic factors explained the highest variation both in the topsoil (15.6%) and subsoil (56.3%). However, there are large gaps in the understanding of this field of research that still need to be explored in future studies.

Defaunation of large mammals alters understory vegetation and functional importance of invertebrates in an Afrotropical forest

Hunting has reduced or eliminated large-bodied vertebrates in many areas across the tropics, contributing to the global process of defaunation. Elucidating the ecological consequences of hunting has important implications for managing ecosystems and for our understanding of community and ecosystem ecology. We present data collected through a combination of comparative and experimental approaches to assess how faunally-intact and heavily-hunted forests in Gabon differ in understory vegetation structure, macroinvertebrate fauna, ecological processes, and the relative importance of different taxa driving those processes. Our results show that hunted sites had denser understory vegetation and hosted approximately 170 times fewer termites compared to faunally-intact sites. While web-building spiders were positively associated with understory vegetation density, this effect did not translate to significantly higher abundances in heavily-hunted forests. Additionally, the overall rates of decomposition, insectivory, and seed predation/removal on the forest floor appeared robust to both defaunation and the associated increases in understory vegetation density. However, our exclosure experiments revealed that the contribution of invertebrates to decomposition was approximately 25% lower in hunted sites compared to faunally-intact sites. Results suggest potential resilience in this complex ecosystem such that microbial or other taxa not measured in this study may compensate for the reduced functional contribution of invertebrates to decomposition. However, while our results illustrate potential resilience, they also indicate that indirect effects following defaunation, such as increases in the density of understory vegetation, may alter invertebrate communities on the forest floor, with potential consequences for the mechanisms, and therefore the dynamics, driving critical ecosystem processes.

Forest Road Status Assessment Using Airborne Laser Scanning

Abstract Forest roads allow access for silvicultural operations, harvesting, recreational activities, wildlife management, and fire suppression. In British Columbia, Canada, roads that are no longer required must be deactivated (temporarily, semipermanently, or permanently) in order to minimize the impact on the overall forested ecosystem. However, the remoteness and size of the road network present challenges for monitoring. Our aim was to examine the utility of airborne laser scanning data to assess the status and quality of forest roads across 52,000 hectares of coastal forest in British Columbia. Within the forest estate, roads can be active or deactivated, or have an unknown status. We classified road segments based on the vegetation growth on the road surface, and edges, by classifying the height distribution of airborne laser scanning returns within each road segment into four groups: no vegetation, minor vegetation, dense understory vegetation, and dense overstory vegetation. Validation indicated that 73 percent of roads were classified correctly when compared to independent field observations. The majority were classified as active roads with no vegetation or deactivated with dense vegetation. The approach presented herein can aid forest managers in verifying the status of the roads in their management area, especially in remote areas where field assessments are costly and time-consuming.

Forest adaptation strategies aimed at climate change: Assessing the performance of future climate-adapted tree species in a northern Minnesota pine ecosystem

Climate change is expected to impact the function, health, and productivity of many northern latitude forests, including North American mixed-pine ecosystems. Additionally, forest managers face increasing challenges to sustaining forests in the face of high uncertainty associated with response to climate change. The Adaptive Silviculture for Climate Change (ASCC) project was developed to provide operational-scale research opportunities to assess and demonstrate various adaptation approaches to forest management in regionally important forest types. The ASCC project framework includes three treatments (resistance, resilience, and transition) representing a gradient of silvicultural approaches aimed at climate change. The first of five ASCC installations is located on the Cutfoot Experimental Forest-Chippewa National Forest (CEF), Minnesota USA, in a mixed-species northern pine forest. Using habitat suitability models under projected future climates, as well as expert opinion, we chose eight future climate-adapted species for planting as part of the transition treatment, consisting of four native species to the CEF: eastern white pine (Pinus strobus L.), northern red oak (Quercus rubra L.), bur oak (Quercus macrocarpa Michx.), and red maple (Acer rubrum L.); and four novel species to the CEF: white oak (Quercus alba L.), bitternut hickory (Carya cordiformis Wangenh.), black cherry (Prunus serotina Ehrh.), and ponderosa pine (Pinus ponderosa C. Lawson). The seedlings were planted under two canopy conditions, a thinned matrix (14–18 m2 ha−1 residual basal area) and 0.2-ha gap openings (through harvesting). We measured how overstory canopy conditions (gap openings versus a thinned matrix) and understory shrub/herbaceous cover affect species performance. We measured 45 plots over the course of three growing seasons (Spring 2016 – Fall 2018), taking measurements of seedling basal diameter and survival, as well as estimates of understory vegetation density. Our findings highlight strong variations in species performance across treatment conditions. While overstory canopy condition was found to be a weak predictor of seedling survival and growth, our results show post-treatment colonization of understory shrub/herbaceous cover being a strong predictor of seedling survival (p < 0.001), with 86.67% (±8.04; 1 standard error) of seedlings surviving in the lowest understory cover class, and 74.23% (±3.04) surviving in the highest understory cover class. Seedling growth did not appear affected by understory shrub/herbaceous cover. Additionally, growth and survival varied significantly among native and novel seedlings, with ponderosa pine exhibiting the highest growth rates at 0.31 cm cm−1 year−1 (±0.004), while also having the lowest survival of any species at 45.66% (±1.2). Results from this study can be directly used by managers to inform planting decisions and species selections that align with management planning to promote forest health and sustainably in the face of climate change.

Stochomys longicaudatus (Rodentia: Muridae)

AbstractStochomys longicaudatus (Tullberg, 1893) is a monotypic African murid rodent called the target rat because long bristle-like hairs in its fur resemble arrows stuck into a target, giving it a unique appearance. Although occurring in comparatively low densities, it is widely spread throughout the lowland rainforests of equatorial western and central Africa. Inhabiting dense understory vegetation, it is a secretive and perhaps nomadic species and little is known about its behavior. S. longicaudatus is herbivorous, climbs well and often, and builds nests from shredded grass. The International Union for Conservation of Nature and Natural Resources classifies it as a species of “Least Concern.”

Testing the Ability of Airborne LiDAR to Measure Forage Resources for Wild Ungulates in Conifer Forests

AbstractVegetation in the forest understory is a key food resource for wild ungulates like deer (Odocoileus spp.) because the amount of nutritious forage influences animal productivity and density. Therefore, measuring the abundance of understory vegetation available to wildlife populations is often a key objective for wildlife managers. Field-based methods for measuring understory vegetation across remote landscapes are time- and resource-intensive, so we compared estimates of understory vegetation density derived from airborne light detection and ranging (LiDAR) returns with vegetation biomass sampled directly on 65 field plots across 4 years and &gt;250,000 hectares of xeric conifer forests in northeastern Washington. We found that LiDAR-derived estimates of understory vegetation density were only able to predict field-sampled vegetation biomass when the two sampling methods occurred within 3 years of each other, and overstory canopy cover was &lt;50 percent. Our results demonstrate limitations in the ability of LiDAR, at the intensity and frequency currently applied for multiuse purposes, to measure the quantity of forage. However, further testing with synchronous field sampling and higher-density laser pulses holds promise.

Persistent effects of fragmentation on tropical rainforest canopy structure after 20yr of isolation.

Assessing the persistent impacts of fragmentation on aboveground structure of tropical forests is essential to understanding the consequences of land use change for carbon storage and other ecosystem functions. We investigated the influence of edge distance and fragment size on canopy structure, aboveground woody biomass (AGB), and AGB turnover in the Biological Dynamics of Forest Fragments Project (BDFFP) in central Amazon, Brazil, after 22+ yr of fragment isolation, by combining canopy variables collected with portable canopy profiling lidar and airborne laser scanning surveys with long-term forest inventories. Forest height decreased by 30% at edges of large fragments (>10ha) and interiors of small fragments (<3ha). In larger fragments, canopy height was reduced up to 40m from edges. Leaf area density profiles differed near edges: the density of understory vegetation was higher and midstory vegetation lower, consistent with canopy reorganization via increased regeneration of pioneers following post-fragmentation mortality of large trees. However, canopy openness and leaf area index remained similar to control plots throughout fragments, while canopy spatial heterogeneity was generally lower at edges. AGB stocks and fluxes were positively related to canopy height and negatively related to spatial heterogeneity. Other forest structure variables typically used to assess the ecological impacts of fragmentation (basal area, density of individuals, and density of pioneer trees) were also related to lidar-derived canopy surface variables. Canopy reorganization through the replacement of edge-sensitive species by disturbance-tolerant ones may have mitigated the biomass loss effects due to fragmentation observed in the earlier years of BDFFP. Lidar technology offered novel insights and observational scales for analysis of the ecological impacts of fragmentation on forest structure and function, specifically aboveground biomass storage.

Survival, Movements, and Habitat Use of Fledgling Veeries (Catharus fuscescens) in Northeastern Pennsylvania

For most passerines, survival and behavior during the postfledging period are poorly known, even though these population characteristics are potentially important to demography and conservation. In 2013–2014 radiotelemetry was used to measure survival, movements, and habitat use of juvenile Veeries (Catharus fuscescens) during the postfledgingdependent period in a landscape dominated by mature forest in northeastern Pennsylvania. In total I tracked 29 juvenile Veeries and conducted habitat sampling at sites used by fledglings and at associated random sites. Survival during the first 21 d postfledging was high (0.78), with most mortalities occurring during the first 7 d, and all deaths attributed to predation. Fledglings moved gradually away from their nests as they aged, averaging 333±62 m by 19–21 d. However, there was much variation in movement patterns among individuals, perhaps reflecting differences in spatial distribution of important microhabitats or differences in timing of postfledging dispersal. Like fledglings of many other species of forest passerines, Veery fledglings preferred microhabitats with dense woody understory vegetation: compared to random sites, sites used by fledglings had, on average, greater woody ground cover, midstory cover, and sapling density but had lower density of eastern hemlock trees. However, unlike many other forest passerine species, Veery fledglings did not exhibit broad shifts to other nonnesting habitat types. These results provide the first detailed study of postfledging survival and behavior of the Veery and add generally to our understanding of postfledging ecology in forest passerines.

Evaluación del uso de LiDAR discreto, full-waveform y TLS en la clasificación por composición de especies en bosques mediterráneos

&lt;p&gt;LiDAR technology –airborne and terrestrial- is becoming more relevant in the development of forest inventories, which are crucial to better understand and manage forest ecosystems. In this study, we assessed a classification of species composition in a Mediterranean forest following the C4.5 decision tree. Different data sets from airborne laser scanner full-waveform (ALS&lt;sub&gt;FW&lt;/sub&gt;), discrete (ALS&lt;sub&gt;D&lt;/sub&gt;) and terrestrial laser scanner (TLS) were combined as input data for the classification. Species composition were divided into five classes: pure Quercus ilex plots (QUI); pure Pinus halepensis dense regenerated (HALr); pure P. halepensis (HAL); pure P. pinaster (PIN); and mixed P. pinaster and Q. suber (mPIN). Furthermore, the class HAL was subdivided in low and dense understory vegetation cover. As a result, combination of ALS&lt;sub&gt;FW&lt;/sub&gt; and TLS reached 85.2% of overall accuracy classifying classes HAL, PIN and mPIN. Combining ALS&lt;sub&gt;FW&lt;/sub&gt; and ALS&lt;sub&gt;D&lt;/sub&gt;, the overall accuracy was 77.0% to discriminate among the five classes. Finally, classification of understory vegetation cover using ALS&lt;sub&gt;FW&lt;/sub&gt; reached an overall accuracy of 90.9%. In general, combination of ALS&lt;sub&gt;FW&lt;/sub&gt; and TLS improved the overall accuracy of classifying among HAL, PIN and mPIN by 7.4% compared to the use of the data sets separately, and by 33.3% with respect to the use of ALS&lt;sub&gt;D&lt;/sub&gt; only. ALS&lt;sub&gt;FW&lt;/sub&gt; metrics, in particular those specifically designed for detection of understory vegetation, increased the overall accuracy 9.1% with respect to ALS&lt;sub&gt;D&lt;/sub&gt; metrics. These analyses show that classification in forest ecosystems with presence of understory vegetation and intermediate canopy strata is improved when ALS&lt;sub&gt;FW&lt;/sub&gt; and/or TLS are used instead of ALS&lt;sub&gt;D&lt;/sub&gt;.&lt;/p&gt;

Conifer tree plantations for land rehabilitation: an ecological‐functional evaluation

Plantations of exotic fast‐growing tree species have been widely used for maintaining or restoring ecosystem functions. Despite this, in tropical countries with high biodiversity, these plantations have been the subject of heated debate. We evaluated the long‐term effect of coniferous tree plantations (Cupressus lusitanica, Pinus patula, Pinus elliottii) on the ecological rehabilitation of the Andean highlands in Colombia. To determine degree of rehabilitation, we assessed whether there were differences in the structure or density of native understory vegetation or soil ecological properties between plots established within tree plantations and plots established within other vegetation cover types (secondary forests, ferns, pastures, and abandoned mining areas). Measured variables were combined to create an index of ecological rehabilitation (ERI). We found significant differences in the ERI values among vegetation cover types: secondary forest (11.78) &gt; conifer plantations (P. elliottii: 6.23, P. patula: 5.33, C. lusitanica: 5.24) &gt; ferns (4.16) &gt; pasture (2.50) &gt; abandoned mining areas (0.43). The results obtained showed that, from the structure of native understory vegetation and soil ecological properties, conifer plantations favored the rehabilitation process. However, among them, it was highlighted that the P. elliotii plantations showed significant differences in the density of native understory species, their values being 1.7 and 2.1 times higher than those corresponding to P. patula and C. lusitanica, respectively. Thus, unlike these plantations that could represent an ecological barrier over time, P. elliottii plantations have enabled the advancement of natural succession, showing a high diversity of native species.

Ungulate exclusion accentuates increases in woody species richness and abundance with canopy gap creation in a temperate hardwood forest

Forest biodiversity is declining due to a wide variety of anthropogenic factors. Forest and wildlife management can be part of the problem or part of the solution. Our objective was to examine the influence of white-tailed deer exclusion on the response of understory communities to a gradient in overstory disturbance. We expected that greater overstory disturbance would act synergistically with deer exclusion to increase understory species richness and abundance. In northern Wisconsin, USA, we monitored changes in understory vegetation in a temperate hardwood forest following four overstory treatments (no-harvest controls and three gap sizes) and two deer treatments (deer access or exclosure). By the seventh year following gap creation, understory species richness and the abundance of multiple species groups had increased, especially when deer were excluded. Effects were most pronounced in larger gaps, particularly among saplings of less shade-tolerant tree species. The tree seedling community responded similarly, but less strongly, to treatments. In contrast, change in the short-stature shrub and herbaceous community seven years following gap and deer treatments was limited and species-specific. Environmental conditions at the groundlayer, such as light availability and soil moisture content, rarely differed by treatment in our study. Increased density of understory vegetation at seven years post-treatment may have negated early pulses in resource availability resulting from gap creation. Gap creation alone increased species richness and abundance of woody taxa, whereas deer exclusion alone had little effect on the understory community. When treatments were applied in combination, we saw the greatest change in the plant community. Our study provides evidence that, when accompanied by a reduction in deer population density, relatively intense overstory disturbance (e.g., group-selection harvest) may be an effective management strategy for restoring forest heterogeneity.

Quantifying understory vegetation density using small-footprint airborne lidar

The ability to quantify understory vegetation structure in forested environments on a broad scale has the potential to greatly improve our understanding of wildlife habitats, nutrient cycling, wildland fire behavior, and wildland firefighter safety. Lidar data can be used to model understory vegetation density, but the accuracy of these models is impacted by factors such as the specific lidar metrics used as independent variables, overstory conditions such as density and height, and lidar pulse density. Few previous studies have examined how these factors affect estimation of understory density. In this study we compare two widely-used lidar-derived metrics, overall relative point density (ORD) and normalized relative point density (NRD) in an understory vertical stratum, for their respective abilities to accurately model understory vegetation density. We also use a bootstrapping analysis to examine how lidar pulse density, overstory vegetation density, and canopy height can affect the ability to characterize understory conditions. In doing so, we present a novel application of an automated field photo-based understory cover estimation technique as reference data for comparison to lidar. Our results highlight that NRD is a far superior metric for characterizing understory density than ORD (R2NRD = 0.44 vs. R2ORD = 0.14). In addition, we found that pulse density had the strongest positive effect on predictive power, suggesting that as pulse density increases, the ability to accurately characterize understory density using lidar increases. Overstory density and canopy height had nearly identical negative effects on predictive power, suggesting that shorter, sparser canopies improve lidar's ability to analyze the understory. Our study highlights important considerations and limitations for future studies attempting to use lidar to quantify understory vegetation structure.

Does density of green infrastructure predict preference?

Green Infrastructure (GI) refers to the natural spaces in a city that improve urban ecology and bring social, economic, and environmental benefits to residents and communities. Although we know a good deal about people’s preference for urban forests, we know little about how people reaction to other types of GI and even less about how varying levels of vegetation density influence preference. Without this knowledge, planners and designers risk creating landscapes that people experience as insufficiently restorative.To understand people’s preference for different types and vegetation density levels of GI, we conducted three GI preference surveys and utilized a new technology called Brown Dog’s Green Index Extractor to calculate vegetation density. We found that, overall, tree density and understory vegetation density are positively associated with preference in a power-curve relationship. The nature of the relationship between bioretention density and preference remains unclear, even though it is significant and positive.The findings presented here expand our knowledge of landscape preference to the emerging field of GI. Designers and planners can use these results to create preferred landscapes that manage stormwater that also promote human well-being. Future studies might explore the relationship between GI density and preference further by investigating other aspects of GI such as planting designs and maintenance and the relationships between GI’s vegetation density and various health and well-being indicators.

Vertical stratification of invertebrate assemblages in water-filled treeholes of a temperate deciduous forest

Water-filled treeholes provide temporal habitats and resources to detritus-based aquatic organisms in the aboveground forest strata. Treeholes are found at different vertical positions, and are often surrounded by dense understory vegetation, which may affect water volume and litter weight. Differences in water volume and litter weight are indicative of the habitat quantity and the quality of treehole communities. Therefore, in the present study, we used containers as artificial treeholes to examine the effects of these characteristics on treehole invertebrate assemblages in a broad-leaf deciduous forest in central-eastern Japan. We first generated two models: a direct-effect model that reflected the physical and chemical properties of treeholes (water volume, litter weight, and other measurable properties that might directly influence invertebrate survival and fitness); and an indirect-effect model that reflected the differences in vertical position and surrounding understory vegetation per se. We compared these models and found that species richness is better explained by the direct-effect model, whereas the indirect-effect model plausibly explains the differences in invertebrate abundances. Further analyses revealed that some species such as Tripteroides bambusa utilized lower treeholes, while higher treeholes had a greater abundance of Ceratopogonidae sp. A within dense understory vegetation. Our study demonstrates that treehole invertebrates are not only influenced by simple physicochemical properties, but also by ambient conditions. However, the response patterns were highly variable across species. Our approach provides insight for elucidating the key drivers of treehole detritivore diversity in vertically stratified environments.

Habitat heterogeneity affects predation of European pine sawfly cocoons.

Habitat heterogeneity is thought to affect top‐down control of herbivorous insects and contribute to population stability by providing a more attractive microhabitat for natural enemies, potentially leading to reduced population fluctuations. Identifying the parameters that contribute to habitat heterogeneity promoting top‐down control of herbivorous insects by natural enemies could facilitate appropriate management decisions, resulting in a decreased risk of pest insect outbreaks because of a higher level of predation. In our study, we measured the top‐down pressure exerted by small mammals on the cocoons of a notorious pest insect in pine forests, the European pine sawfly (Neodiprion sertifer), which is known to be regulated by small mammal predation. The forest stands used differed in heterogeneity measured in terms of differences in tree diversity and density, understory vegetation height, presence/absence, and density of dead wood. We found higher predation in more dense spots within forest stands. Further, the effect of dead wood on sawfly cocoon predation depended on the pine proportion in forest stands. The addition of dead wood in a manipulation experiment had a slight positive effect on cocoon predation, while dead wood removal caused a clear decrease in predation rate, and the decrease was more pronounced when the proportion of pine increased. Our results show that habitat heterogeneity affects predation by generalist predators on herbivorous insects. This knowledge could be applied to reduce the risk of insect outbreaks by applying management methods that increase heterogeneity in perennial systems such as forests and orchards, thus decreasing the levels of insect damage.

Snowshoe hare multi‐level habitat use in a fire‐adapted ecosystem

ABSTRACTPrescribed burning has the potential to improve habitat for species that depend on pyric ecosystems or other early successional vegetation types. For species that occupy diverse plant communities over the extent of their range, response to disturbances such as fire might vary based on post‐disturbance vegetation dynamics among plant communities. Although responses of snowshoe hares (Lepus americanus) to fire have been studied in conifer‐dominated forests in northern parts of the species’ range, there is a lack of information on snowshoe hare habitat use in fire‐dependent communities in southern parts of their range. We used global positioning system (GPS) and very high frequency (VHF) radio‐collars to monitor the habitat use of 32 snowshoe hares in a scrub‐oak (Quercus ilicifolia)‐pitch pine (Pinus rigida) barrens complex in northeastern Pennsylvania where prescribed fire has been used for habitat restoration. The area contained stands that underwent prescribed burning 1–6 years prior to our study. Also, we investigated fine‐scale determinants of habitat use within stands. We found that regardless of season, hares did not select for areas that had been burned within 6 years prior. Hares primarily used stands of older scrub oak, conifer, or hardwoods, which contained dense understory vegetation and canopy cover. Hare habitat use also was positively associated with stand edges. Our results suggest that hares do not respond to prescribed burning of scrub oak in the short‐term. In addition, by focusing on structural determinants of habitat use, rather than broad‐scale characteristics such as stand type, management strategies for snowshoe hares can be adapted over the extent of their range despite the multitude of different land cover types across which the species occurs. © 2017 The Wildlife Society.

A new species of tapaculo (Rhinocryptidae: Scytalopus) from the Western Andes of Colombia

We describe Scytalopus alvarezlopezi from the Western Andes of Colombia. The new species forms part of a distinctive clade of Scytalopus tapaculos (Rhinocryptidae) that also includes S. robbinsi from Ecuador and S. stilesi and S. rodriguezi, which occur on the Central and Eastern Andes of Colombia. S. alvarezlopezi is easily diagnosable from its near relatives by its song and mitochondrial DNA; differences in plumage exist but are more subtle. The species inhabits dense understory vegetation on the floors and lower slopes of ravines in cloud forest at elevations of 1,300 to 2,100 m. On the Pacific slope, its altitudinal distribution is sandwiched between those of S. chocoensis (below) and S. vicinior (above); the latter in turn is replaced higher up by S. spillmanni and S. latrans, but S. alvarezlopezi also occurs at ∼2,000–2,100 m on eastern slopes just below the low ridgeline. All of the latter species are distinguished by vocal and plumage characters. Marked sexual differences in plumage exist in stilesi, but females have yet to be collected for alvarezlopezi and rodriguezi. We consider that S. alvarezlopezi is not threatened at present, but could be potentially vulnerable due to its restricted distribution; it is endemic to Colombia.

Reproductive and denning ecology of the Central Georgia American black bear population

Understanding biological and ecological requirements of small populations of American black bears (Ursus americanus) is important for maintaining or promoting population growth. During 2012–2015, we studied reproductive biology, cub survival, and den selection of black bears in an isolated population in central Georgia, USA. We visited dens of 15 females and documented production of 39 cubs of the year (COY). We tracked and obtained visual observations of COY for 11 family units (19 COY) to estimate survival for a 6-month period. Cub survival for the first 6 months of life was 0.765 ± 0.102 (mean ± SE). We assessed effects of microhabitat and landscape characteristics on den selection. We found that early successional habitats associated with upland forests were important to denning females, presumably because of their higher elevation and availability of dense understory vegetation.