Forest Specialists Research Articles

Severe wildfires promoted by climate change negatively impact forest amphibian metacommunities

AbstractAimChanges to the extent and severity of wildfires driven by anthropogenic climate change are predicted to have compounding negative consequences for ecological communities. While there is evidence that severe weather events like drought impact amphibian communities, the effects of wildfire on such communities are not well understood. The impact of wildfire on amphibian communities and species is likely to vary, owing to the diversity of their life‐history traits. However, no previous research has identified commonalities among the amphibians at most risk from wildfire, limiting conservation initiatives in the aftermath of severe wildfire. We aimed to investigate the impacts of the unprecedented 2019–2020 black summer bushfires on Australian forest amphibian communities.LocationEastern coast of New South Wales, Australia.MethodsWe conducted visual encounter surveys and passive acoustic monitoring across 411 sites within two regions, one in northeast and one in southeast New South Wales. We used fire severity and extent mapping in two multispecies occupancy models to assess the impacts of fire on 35 forest amphibian species.ResultsWe demonstrate a negative influence of severe fire extent on metacommunity occupancy and species richness in the south with weaker effects in the north—reflective of the less severe fires that occurred in this region. Both threatened and common species were impacted by severe wildfire extent. Occupancy of burrowing species and rain forest specialists had mostly negative relationships with severe wildfire extent, while arboreal amphibians had neutral relationships.Main ConclusionMetacommunity monitoring and adaptive conservation strategies are needed to account for common species after severe climatic events. Ecological, morphological and life‐history variation drives the susceptibility of amphibians to wildfires. We document the first evidence of climate change‐driven wildfires impacting temperate forest amphibian communities across a broad geographic area, which raises serious concern for the persistence of amphibians under an increasingly fire‐prone climate.

Isolation by resistance explains genetic diversity in the Arremon brushfinches of northern Mesoamerica.

Genetic differentiation between and within natural populations is the result of the joint effects of neutral and adaptative processes. In addition, the spatial arrangement of the landscape promotes connectivity or creates barriers to gene flow, directly affecting speciation processes. In this study, we carried out a landscape genomics analysis using NextRAD data from a montane forest specialist bird complex, the Mesoamerican Chestnut-capped/Green-striped Brushfinch of the genus Arremon. Specifically, we examined population genomic structure using different assignment methods and genomic differentiation and diversity, and we tested alternative genetic isolation hypotheses at the individual level (e.g., isolation by barrier, IBB; isolation by environment, IBE; isolation by resistance, IBR). We found well-delimited genomic structuring (K = 5) across Mesoamerican montane forests in the studied group. Individual-level genetic distances among major montane ranges were mainly explained by IBR hypotheses in this sedentary Neotropical taxon. Our results uncover genetic distances/differentiation and patterns of gene flow in allopatric species that support the role of tropical mountains as spatial landscape drivers of biodiversity. IBR clearly supports a pattern of conserved niche-tracking of suitable habitat conditions and topographic complexity throughout glacial-interglacial dynamics.

Many losers and few winners in dung beetle responses to Amazonian forest fragmentation

Tropical forest fragmentation is expected to result in the loss of forest-dependent species (‘losers’) and proliferation of disturbance-tolerant species (‘winners’). Here, we use multi-species occupancy modelling to quantify the effects of fragmentation on Amazonian dung beetles at the species and community level. We investigate the relationship between species' habitat preferences and fragmentation responses to understand how interspecific variation in fragmentation responses translates into patterns of alpha and beta diversity. We sampled dung beetles within 21 forest patches and 2 continuous forests. For each site, we quantified three fragmentation metrics (area, shape, and surrounding forest amount) and modelled their effects on species occurrence and community properties. Most species were most likely to occur within large forest patches, while surrounding forest amount had a positive impact on all species. Over 80 % of species were forest specialists and species' area responses were positively correlated with their level of forest specialization. Observed species-level responses were reflected at the community level, with greater representation of forest specialists in larger forest patches up to an 88-ha threshold, stabilizing thereafter; this threshold was met by only 1 % of patches in the landscape. Species richness also increased with patch area, although surrounding forest amount had a greater positive impact. Communities were structured by a gradient of species turnover from small to large patches, and among more isolated patches. Our findings show that most Amazonian dung beetle species become ‘losers’ within fragmented landscapes, particularly forest specialists. We recommend landscape-scale planning to retain forest connectivity including large forest remnants.

Tropical agricultural wooded land uses support high site use of forest birds

Agricultural expansion has been responsible for the large-scale modification of forest ecosystems globally. In many regions, this has resulted in the creation of heterogenous landscapes comprised of cleared agricultural lands, and semi-natural and natural wooded land uses such as agroforests and secondary forests. These wooded land uses can play an important role in supporting forest biodiversity. In a tropical agricultural landscape of Northeast India, we investigate how wooded land uses affect site use by forest specialist, forest generalist and open-country bird species, in comparison to a protected area. We also investigate the effects of site vegetation characteristics, surrounding forest cover and distance to the protected area. Using multi-species occupancy models, we found that wooded land uses support high site use of the three forest specialization groups. We attribute the high site use of forest species in wooded land uses to the similarity in site vegetation characteristics between these land uses and the protected area. In addition, high forest cover at, and neighbouring, our sampling sites, and habitat connectivity also contributed towards supporting high site use of forest species. However, for some species across the three groups, a few site vegetation characteristics and surrounding forest cover had a subtle influence. Our study showcases the supplementary role of low-intensity agricultural landscapes as habitat for forest birds, provided that wooded land uses outside protected areas are well maintained. In so doing, it contributes valuable insights into land management practices that support biodiversity in heterogeneous agricultural landscapes.

Agroforestry orchards support greater butterfly diversity than monoculture plantations in the tropics

Large-scale deforestation in the tropics, triggered by logging and subsequent agricultural monoculture has a significant adverse impact on biodiversity due to habitat degradation. Here, we measured the diversity of butterfly species in three agricultural landscapes, agroforestry orchards, oil palm, and rubber tree plantations. Butterfly species were counted at 127 sampling points over the course of a year using the point count method. We found that agroforestry orchards supported a greater number of butterfly species (74 species) compared to rubber tree (61 species) and oil palm plantations (54 species) which were dominated by generalist (73%) followed by forest specialists (27%). We found no significant difference of butterfly species composition between agroforestry orchards and rubber tree plantation, with both habitats associated with more butterfly species compared to oil palm plantations. This indicates butterflies were able to persist better in certain agricultural landscapes. GLMMs suggested that tree height, undergrowth coverage and height, and elevation determined butterfly diversity. Butterfly species richness was also influenced by season and landscape-level variables such as proximity to forest, mean NDVI, and habitat. Understanding the factors that contributed to butterfly species richness in an agroecosystem, stakeholders should consider management practices to improve biodiversity conservation such as ground vegetation management and retaining adjacent forest areas to enhance butterfly species richness. Furthermore, our findings suggest that agroforestry system should be considered to enhance biodiversity in agricultural landscapes.

Spatial and temporal non-stationarity in long-term population dynamics of over-wintering birds of North America.

Understanding population changes across long time scales and at fine spatiotemporal resolutions is important for confronting a broad suite of conservation challenges. However, this task is hampered by a lack of quality long-term census data for multiple species collected across large geographic regions. Here, we used century-long (1919-2018) data from the Audubon Christmas Bird Count (CBC) survey to assess population changes in over 300 avian species in North America and evaluate their temporal non-stationarity. To estimate population sizes across the entire century, we employed a Bayesian hierarchical model that accounts for species detection probabilities, variable sampling effort, and missing data. We evaluated population trends using generalized additive models (GAMs) and assessed temporal non-stationarity in the rate of population change by extracting the first derivatives from the fitted GAM functions. We then summarized the population dynamics across species, space, and time using a non-parametric clustering algorithm that categorized individual population trends into four distinct trend clusters. We found that species varied widely in their population trajectories, with over 90% of species showing a considerable degree of spatial and/or temporal non-stationarity, and many showing strong shifts in the direction and magnitude of population trends throughout the past century. Species were roughly equally distributed across the four clusters of population trajectories, although grassland, forest, and desert specialists more commonly showed declining trends. Interestingly, for many species, region-wide population trends often differed from those observed at individual sites, suggesting that conservation decisions need to be tailored to fine spatial scales. Together, our results highlight the importance of considering spatial and temporal non-stationarity when assessing long-term population changes. More generally, we demonstrate the promise of novel statistical techniques for improving the utility and extending the temporal scope of existing citizen science datasets.

Spatial predictions for the distribution of woody plant species under different land-use scenarios in southwestern Ethiopia

ContextDeforestation, forest degradation and intensification of farming threaten terrestrial biodiversity. As these land-use changes accelerate in many landscapes, especially in the Global South, it is vital to anticipate how future changes might impact specific aspects of biodiversity.ObjectivesThe objectives of this study were to model woody plant species richness in southwestern Ethiopia, for the present and for four plausible, spatially explicit scenarios of the future (‘Gain over grain’, ‘Mining green gold’, ‘Coffee and conservation’ and ‘Food first’).MethodsWe used cross-validated generalized linear models for both forest and farmland, to relate empirical data on total and forest-specialist woody plant species richness to indicators of human disturbance and environmental conditions. We projected these across current and future scenario landscapes.ResultsIn both farmland and forest, richness peaked at intermediate elevations (except for total species richness in farmland) and decreased with distance to the forest edge (except for forest specialist richness in forest). Our results indicate that the ‘Mining green gold’ and ‘Food first’ scenarios would result in strong losses of biodiversity, whereas the ‘Gain over grain’ scenario largely maintained biodiversity relative to the baseline. Only the ‘Coffee and conservation’ scenario, which incorporates a new biosphere reserve, showed positive changes for biodiversity that are likely viable in the long term.ConclusionsThe creation of a biosphere reserve could maintain and improve woody plant richness in the focal region, by forming a cluster with existing reserves, would be a major step forward for sustainability in southwestern Ethiopia.

Numerical Response of Owls to the Dampening of Small Mammal Population Cycles in Latvia.

Strong numerical and functional responses of owls to voles in cyclic environments are well known. However, there is insufficient knowledge from the boreonemoral region in particular, with depleted populations of small mammals. In this study, we describe the dynamics of the small mammal population in Latvia from 1991 to 2016 and link them to owl population characteristics. We used food niche breadth, number of fledglings, and population trends to lay out the numerical response of six owl species to dampened small mammal population cycles. We found temporarily increasing food niche breadth in tawny and Ural owls. There were no other responses in the tawny owl, whereas the breeding performance of three forest specialist species-pygmy, Tengmalm's, and Ural owls-corresponded to the vole crash years in Fennoscandia. Moreover, the populations of forest specialist owls decreased, and the change in the Ural owl population can be attributed to the depletion of small mammal populations. We found evidence of a carry-over effect in the eagle owl arising from a strong correlation of declining breeding performance with the small mammal abundance indices in the previous autumn. We conclude that dampening of the small mammal population cycles is an important covariate of the likely effects of habitat destruction that needs to be investigated further, with stronger responses in more specialized (to prey or habitat) species.

When forest loss leads to biodiversity gain: Insights from the Brazilian Atlantic Forest

Decades of research indicate that while native habitat loss often drives biodiversity loss and biotic homogenization, there are frequent exceptions. Relying on a multi-level landscape design, multiple biodiversity metrics and species habitat associations we explored one such exception. We investigated dung beetle responses to Atlantic Forest loss by modeling for both specialist and generalist species abundance, alpha and gamma diversities, and beta diversity through a null-model approach (βRC) that permits comparing observed values to those expected by chance. We found that both native forest specialist and habitat generalist communities gained species with native forest loss at local (ᾱ-diversity) and landscape (γ-diversity) levels, while community composition became increasingly dissimilar (β-diversity). Yet, abundance response to forest loss varied between groups. While for generalists, forest loss led to increased overall abundance and abundance distribution across species remained random among communities, for specialists, overall abundance did not change and abundance distribution across species became dissimilar. Such findings suggest that habitat loss does not always drive a decrease in the number of specialist species that compensate for the gain of generalist species, adding to evidence that habitat loss can drive biodiversity gain and biotic differentiation. These responses may be common in particular biogeographical contexts, where contemporary and/or historical regional dynamics may have influenced the resilience of forest biota and contribute to the availability of disturbance-adapted species. Our study highlights the importance of sampling across multiple spatial scales to understand the effects of habitat loss on biodiversity and suggest caution to silver-bullet conservation guidelines.

Amphibian communities along a forest degradation gradient in an East African forest reserve

The amphibian communities in Africa's tropical forests are of global conservation importance, but disturbances derived from anthropological activities threaten to dismantle this irreplaceable diversity. We explored the impacts of forest degradation on the amphibian community in Mabira Central Forest Reserve, Uganda. We sampled amphibians from March to July of 2015 in plots that were positioned along a gradient of forest degradation. We conducted visual encounter surveys across three categories of forest degradation with six 300-m transects in each (four surveys per transect). From 216 h of surveyor effort, we detected 3563 individual frogs representing 30 species from eight families and 13 genera. Hyperoliidae was the most diverse family represented by 13 species in four genera. Hyperolius had the highest number of species (nine) followed by four genera each represented by three species (Phrynobatrachus, Pytchadena, Leptopelis, and Sclerophrys). Comparisons among plots along a gradient of forest degradation revealed differences in species richness, composition, and frequency of encounters. The regenerating and degraded forest plots were similar in species composition to each other and were dominated by mostly widespread, open-canopy species. Several forest-dependent species were recorded in both the regenerating and mature forest plots but were absent from the degraded plots. In the regenerating and mature forests, species presence was significantly associated with high canopy cover, high relative humidity, and dense leaf litter, whereas the microhabitat variables of high grass cover and high temperature were most influential in the degraded forests. Our study provides important data on an Afrotropical amphibian community and suggests that forest degradation has dramatically altered the habitat to the detriment of forest specialist species.

Bark production of generalist and specialist species across savannas and forests in the Cerrado.

Bark allows species to survive fire, protecting their inner tissues and allowing new branches to resprout from aerial buds. Thus, bark production is likely to be selected with aerial bud protection in fire-prone ecosystems. By considering the coexistence of fire-prone and fire-free ecosystems, in addition to the different impacts of flames on different growth forms, in this study we tested whether: (1) species from areas with higher fire frequencies have a faster bark production; (2) bark growth rate differs between trees and shrubs; (3) generalists adjust their bark production according to their environment (fire-prone or fire-free ecosystems); and (4) fast bark production results in better aerial bud protection. We sampled two different types of forests and savannas in the Cerrado and registered every woody individual with height between 1.5 and 3 m tall (directly exposed to the flames). For the 123 species registered, we sampled three different individuals in each vegetation type where the species occurred to assess their bark production and aerial bud protection. We then checked, for each species, their preferred habitat (savanna and forest specialists or generalists) and their predominant growth form. A minimal threshold of 0.13 mm per growth unit of bark production differentiated woody communities from savannas and forests. Shrubs and trees did not differ in terms of bark growth rate, despite being exposed to the flames in a different manner. Generalist species in savannas were able to produce bark above the threshold. However, when these species were in forests they produced bark below the threshold. Finally, a higher bark growth rate accounted for a better aerial bud protection. Generalist species are likely to be capable of displaying plasticity in their bark production, which could be important for their success in contrasting ecosystems. The relationship between aerial bud protection and bark growth rate suggests that bark production plays an important role in protecting the dormant buds, in addition to being selected in fire-prone ecosystems.

The relationships between urbanization and bird functional traits across the streetscape

The urbanization process leads to changes in bird communities’ taxonomic and functional compositions. Highly urbanized areas generally exhibit a reduced number of bird species sharing few functional traits. However, most urban bird studies focused on vegetation patches in temperate cities. In this study, we investigate how urban environmental attributes – noise, height of buildings, and urban vegetation characteristics – modulate species occurrences and the distribution of functional traits across the streetscape of a tropical metropolis. We predicted diverse trait-environment relationships, but that highly urbanized contexts (e.g., noisy streets with tall buildings) would be mostly occupied b,y a lower number of species sharing generalist traits. We also predicted to observe streets with similar community composition (profiles) shaped by environmental conditions and interspecific interactions. We applied hierarchical modelling of species communities as a flexible framework for analysis of community data. We observed that, increased noise exposure and reduced green cover were negatively related with species richness due to their negative relationships with most species’ occurrences. On the other hand, larger number of trees and higher proportion of green cover presented mostly positive relationships with occurrences, and thus with species richness. Throughout our streetscape, community composition was highly heterogeneous and similar conditions led to similar profiles. For example, noisy streets may favor the presence of omnivorous and large-bodied species, while wooded streets may allow for the presence of smaller-bodied forest specialist species that exploit lower vegetation strata. Our results indicate that streetscapes may have the potential to harbor functionally and taxonomically diverse bird communities.

High-quality habitats and refuges from tourism reduce individual stress responses in a forest specialist

Context The assessment of suitable habitat for a species is often evaluated based merely on where the species is most abundant. However, a variety of environmental factors such as temperature, resources and human disturbances might force animals to avoid otherwise high-quality habitats. Additionally, individuals’ capacities to cope with such factors – as reflected in physiological stress responses – may also contribute to avoidance. Combining measures of stress response of individual animals with habitat suitability models may contribute essential insights to the development of species conservation plans. Aims We used a landscape-level approach to assess whether habitat quality, abiotic factors and human disturbance affect the physiological stress response of a forest specialist, the capercaillie (Tetrao urogallus), and to what extent these relationships are determined by variation between individuals. Methods We applied a non-invasive approach by collecting 1096 droppings across the entire species range in two adjacent national parks spanning the border between the Czech Republic and Germany. We measured faecal corticosterone metabolites (FCMs) to evaluate the physiological stress response. To test the influences of temperature, habitat quality, season and sex, as well as forest management and tourism intensity on FCM levels, we used generalised additive mixed effect models (GAMMs). The same models were applied for a reduced subset of randomly selected samples that were attributed to individuals via DNA profiling using 10 microsatellite loci. This approach allowed us to control for possible individual differences (through repeated measures within individual genotypes). Key results Both models revealed decreasing FCM levels with increasing habitat quality and showed no relationship between increasing forestry intensity and FCMs. When accounting for individual identity, we found a significant positive effect from increasing tourism intensity, although this relationship was not significant in the full dataset. Conclusions Our results highlight three conclusions for the conservation of capercaillie: (1) high-quality habitats reduce stress levels; (2) tourism-free refuge areas are important, and (3) individuality appears to be a strong determinant of response to environmental factors. Implications Generalising management recommendations from observations for single individuals to an entire population may be inappropriate.

Extensive protected area coverage and an updated global population estimate for the Endangered Madagascar Serpent-eagleEutriorchis astur

SummaryKnowledge gaps regarding distribution, habitat associations, and population size for rare and threatened range-restricted taxa lead to uncertainty in directing conservation action. Quantifying range metrics and species–habitat associations using Species Distribution Models (SDMs) with remote-sensing habitat data can overcome these setbacks by establishing baseline estimates for biological parameters critical for conservation assessments. Area of Habitat (AOH) is a new range metric recently developed by the International Union for Conservation of Nature (IUCN) Red List. AOH seeks to quantify inferred habitat within a species’ range to inform extinction risk assessments. Here, we used SDMs correlating occurrences with remote-sensing covariates to calculate a first estimate of AOH for the Endangered Madagascar Serpent-eagleEutriorchis astur, and then updated additional IUCN range metrics and the current global population estimate. From these baselines we then conducted a gap analysis assessing protected area coverage. Our continuous SDM had robust predictive performance (Continuous Boyce Index = 0.835) and when reclassified to a binary model estimated an AOH = 30,121 km2, 13% less than the current IUCN range map. We estimated a global population of 533 mature individuals derived from the Madagascar Serpent-eagle AOH metric, which was within current IUCN population estimates. The current protected area network covered 95% of AOH, with the binary model identifying three additional key habitat areas as new protected area designations to fully protect Madagascar Serpent-eagle habitat. Our results demonstrated that correlating presence-only occurrences with remote-sensing habitat covariates can fill knowledge gaps useful for informing conservation action. Applying this spatial information to conservation planning would ensure almost full protected area coverage for this endangered raptor. For tropical forest habitat specialists, we recommend that potential predictors derived from remote sensing, such as vegetation indices and biophysical measures, are considered as covariates, along with other variables including climate and topography.

Bird community structure and habitat association in Owabi Wildlife Sanctuary, Ashanti Region (Ghana)

Context Globally, an estimated 1.3% of the bird species have gone extinct over the past millennia, largely owing to habitat loss. Aims This study investigated bird–habitat associations and assemblages in the Owabi Ramsar wetland. Methods The study was conducted over 5 months (May–September 2019) in four habitat types (agricultural land, built-up, forest reserve, and open-water area). Data were collected in 84 plots across four habitats (i.e. built-up area = 25, forest reserve = 25, agricultural land = 25 and open-water area = 9 plots), using a point-count technique. The Gambin model, non-metric multidimensional scaling, Chao-1, and Hill numbers models were used to evaluate differences in bird diversity and composition among the habitat types. Key results In all, 1260 individual birds, belonging to 81 species, were encountered. Many of the species occurred in the forest habitat (n = 46, 56.8%. Species from the agricultural land (n = 37) and built-up (n = 30) were mainly habitat generalists that used these two habitats as their shared feeding station. Bird–habitat specialisation grouping equally showed the forest specialists to be the highest (n = 23, 38.4%), whereas the open water had the least number of habitat specialisation associations (e.g. white-faced whistling duck, n = 20, 24.7%). Five species were widely distributed in all four habitats (e.g. bronze-mannikins and white-throated bee-eaters), indicating their broad habitat preferences and ability to adapt to varied conditions. The forest reserve tended to be the most diverse, which was likely mediated by factors such as nesting microhabitats, varied food availability, and human-led activities. Conclusions This study highlighted bird dietary structure and associated habitat type and bird-habitat specialisation in four different land-use types at Owabi Ramsar wetland. Implications Given the increasing level of disturbance, there is the likelihood that the population of forest-dependent and open water-dependent birds will be lost or will have to change or modify their behaviour to be similar to that of open-tolerant or open-country birds if managers of the Owabi Wildlife Sanctuary fail to implement the recommended management interventions highlighted.

Bird species occupancy trends in Southeast Mexico over 1900-2020: Accounting for sighting record absences.

Long-term land-use change impacts tropical bird communities through population-level and functional diversity effects from habitat loss, degradation and fragmentation, leading to land management and conservation challenges. Assessing the temporal impacts of land-use change on occupancy patterns, population change and functional traits of bird species in tropical areas is limited by the treatment of nondetections as true absences or artefacts of low sampling effort during and throughout years. With this in mind, we developed a novel Bayesian species occupancy framework to account for species absences to evaluate bird community changes in Palenque, Chiapas, Mexico, where there is opportunity for study given exceptional records of change across habitats from rainforest to urban centres. We created a novel dataset of population trends for 244 bird species over the years 1900 to 2020 from published short-term field studies, expert field notes and community science pages. Our results show that open area species had higher population increases than forest specialists over time, represented most evidently by the turnover of rainforest specialists for urban species. Modelled influence of functional traits displayed the importance of main habitat types, body mass and habitat and dietary breadth as factors that associated with bird population trends. On average, species with body masses <6.6 and > 948.4g showed decreasing trends, while all other species showed increasing or stable trends. Our findings illuminate the value of accounting for species absences from several data sources to discover long-term species population trends and affiliated functional traits whose preservation requires conservation and land management action to protect bird ecosystem services. Primary forest conservation is key to maintaining populations of habitat and dietary specialists, such as small understorey insectivorous and large frugivorous species. Protecting rare natural savanna patches from conversion to cattle pasture is vital to prevent further extirpation of native granivores and to slow colonization by exotic and invasive species.

Stand Inventories as an Early Detection System for Forest Health Threats

Abstract Pest-specific inventories require substantial resources and are often infeasible, creating a need for alternative means of early pest detection. We examined the potential for stand inventories to detect forest health threats by using a unique dataset of mapped eastern spruce dwarf mistletoe (Arceuthobium pusillum Peck.) infestations in black spruce (Picea mariana Mill. B.S.P) stands of northern Minnesota, USA. We simulated stand inventories across a range of sampling intensities; that is, current standard (S) methods in Minnesota, adding one plot (S + 1), doubling the intensity (2S), and halving the intensity (S/2), using fixed-radius plots and transect buffers for detection. We categorized stands into low, moderate, and high infestation severity. We simulated detection at multiple viewing distances along S inventory transects in low severity infestation stands. Detection probability increased as sampling intensity increased. Plot-based detection averaged &amp;gt; 50% for moderate and high severity infestations except S/2 in moderate severity infestations. Notably, transect-based detection averaged ≥ 85% at viewing distances of 25 to 100 m. Results suggest stand inventories could provide opportunities to detect forest health threats with unique signatures when transect observations are included. Thus, forest health specialists may consider including pest-specific training for foresters in current inventory methods, requiring modest investment of time and effort.

Structural elements enhanced by retention forestry promote forest and non-forest specialist bees and wasps

Retention forestry promotes certain forest structural elements to enhance biodiversity. It is unclear however to what extent retention measures are suited to enhance the biodiversity of bees and wasps, and how relationships to structural elements promoted by retention may differ when habitat-based classifications are accounted for. Here, we analyze the abundance, diversity and species richness of forest and non-forest specialist cavity-nesting bees and wasps collected on 127 plots in the southern Black Forest, Germany. Our aim was to use habitat-based classifications, or groupings based on habitat occurrence of cavity-nesting bees and wasps to evaluate the effectiveness and importance of forest structural elements that are prioritized in biodiversity-focused conservation. We found that canopy cover, stand structural complexity and standing deadwood were principally important for abundance, diversity and species richness of bees and wasps, with differing responses among habitat classifications. Forest specialist biodiversity metrics and composition were related to forest structural variables indicating greater feeding and nesting resource availability, namely herb cover, standing deadwood and stand structural complexity. Non-forest specialist biodiversity metrics were related to primarily canopy cover and elevation while community composition was structured by only forest cover and understory species richness. Our results indicate the importance of considering habitat specializations of cavity-nesting bee and wasp communities for meaningful evaluation of retention forestry structural elements. The presence and arrangement of these forest elements can be altered by stand level management practices utilizing the cascading effects of structural changes, such as increasing herb cover and sun exposed standing deadwood via canopy opening, and high stump retention during tree harvesting.

Community Reserves Serve as Refugia Sites for Cavity-Nesting Owls in Northeast India

ABSTRACT Community Reserves, which are Community Conserved Areas, form the majority of the Protected Area Network in northeast India. Because this biodiverse region is threatened by a variety of anthropogenic activities, Community Reserves likely serve as refugia sites for stenotopic, cavity-nesting species such as some owls. To test this hypothesis, we conducted nocturnal surveys in 11 Community Reserves comprised of primary or secondary forest and outside Community Reserves in Meghalaya state, northeast India. We then used nonparametric tests to assess differences in the occurrence of owls among these three categories. We found that on average, occurrence of owls was higher inside Community Reserves. Inside Community Reserves with secondary forests, we found significantly higher occurrence of the Asian Barred Owlet (Glaucidium cuculoides) and Collared Scops-Owl (Otus lettia), while in Community Reserves with primary forest, we found significantly higher occurrence of the Brown Wood-Owl (Strix leptogrammica), a declining old-growth forest specialist. Hence, Community Reserves are serving as sites of refugia for owls in northeast India. However, anthropogenic pressures such as logging, shifting cultivation, and developmental activities threaten the forests of the region. Old-growth forests are also scarce in Meghalaya and were present in only two of the Community Reserves. Therefore, we find it of prime importance to conserve these reserves, especially those containing primary forests, and to allocate more areas as Community Reserves in the region.

Mega-disturbances cause rapid decline of mature conifer forest habitat in California.

Mature forests provide important wildlife habitat and support critical ecosystem functions globally. Within the dry conifer forests of the western United States, past management and fire exclusion have contributed to forest conditions that are susceptible to increasingly severe wildfire and drought. We evaluated declines in conifer forest cover in the southern Sierra Nevada of California during a decade of record disturbance by using spatially comprehensive forest structure estimates, wildfire perimeter data, and the eDaRT forest disturbance tracking algorithm. Primarily due to the combination of wildfires, drought, and drought-associated beetle epidemics, 30% of the region's conifer forest extent transitioned to nonforest vegetation during 2011-2020. In total, 50% of mature forest habitat and 85% of high density mature forests either transitioned to lower density forest or nonforest vegetation types. California spotted owl protected activity centers (PAC) experienced greater canopy cover decline (49% of 2011 cover) than non-PAC areas (42% decline). Areas with high initial canopy cover and without tall trees were most vulnerable to canopy cover declines, likely explaining the disproportionate declines of mature forest habitat and within PACs. Drought and beetle attack caused greater cumulative declines than areas where drought and wildfire mortality overlapped, and both types of natural disturbance far outpaced declines attributable to mechanical activities. Drought mortality that disproportionately affects large conifers is particularly problematic to mature forest specialist species reliant on large trees. However, patches of degraded forests within wildfire perimeters were larger with greater core area than those outside burned areas, and remnant forest habitats were more fragmented within burned perimeters than those affected by drought and beetle mortality alone. The percentage of mature forest that survived and potentially benefited from lower severity wildfire increased over time as the total extent of mature forest declined. These areas provide some opportunity for improved resilience to future disturbances, but strategic management interventions are likely also necessary to mitigate worsening mega-disturbances. Remaining dry mature forest habitat in California may be susceptible to complete loss in the coming decades without a rapid transition from a conservation paradigm that attempts to maintain static conditions to one that manages for sustainable disturbance dynamics.