Continuous Forest Sites Research Articles

Drivers of functional diversity in small-bodied mammals across a deforestation frontier in the Southern Brazilian Amazon

Deforestation remains the most pervasive driver of biodiversity erosion across tropical forests. Understanding how species can cope with such habitat changes is particularly important along the rapidly expanding agricultural frontiers. To do so, we used a functional perspective examining small mammal responses to habitat loss, fragmentation, and degradation across the ‘Arc of Deforestation’ in the Southern Brazilian Amazon. Small mammals were surveyed using a combination of conventional and pitfall traps across 20 forest fragments—ranging from 42 to 4743 ha—in addition to two relatively continuous forest sites (> 7000 ha). These fragments lie isolated by a cattle pasture matrix of varying grazing intensity. We then analysed taxonomic and functional diversity patterns—represented by Simpson Diversity and Rao Quadratic entropy indices—in Generalised Linear Models containing local- to landscape-scale predictors of variation. Further, we used a functional trait composition approach based on community-weighted mean trait values to depict and predict small mammal functional variations across this degradation gradient. From a total of 847 individuals recorded belonging to 24 taxa, functional responses tended to follow the taxonomic diversity, both increasing with fragment area. The functional dimension further was promoted by low fire-related disturbance. Functional trait composition was mainly driven by habitat quality, represented by tree density, arthropod biomass, and fire-related disturbance. Our results reinforce that small forest fragments sustain depauperate small mammal assemblages both taxonomically and functionally. Accounting for habitat quality further allows for boosting the persistence across functional groups. Our findings can be used to improve the efficiency of management practices thereby maximising the multiple dimensions of small mammal diversity and their associated ecosystem services across tropical deforestation frontiers.

Demography of the understory herb Heliconia acuminata (Heliconiaceae) in an experimentally fragmented tropical landscape.

Habitat fragmentation remains a major focus of research by ecologists decades after being put forward as a threat to the integrity of ecosystems. While studies have documented myriad biotic changes in fragmented landscapes, including the local extinction of species from fragments, the demographic mechanisms underlying these extinctions are rarely known. However, many of them-especially in lowland tropical forests-are thought to be driven by one of two mechanisms: (1) reduced recruitment in fragments resulting from changes in the diversity or abundance of pollinators and seed dispersers or (2) increased rates of individual mortality in fragments due to dramatically altered abiotic conditions, especially near fragment edges. Unfortunately, there have been few tests of these potential mechanisms due to the paucity of long-term and comprehensive demographic data collected in both forest fragments and continuous forest sites. Here we report 11 years (1998-2009) of demographic data from populations of the Amazonian understory herb Heliconia acuminata (LC Rich.) found at Brazil's Biological Dynamics of Forest Fragments Project (BDFFP). The data set comprises >66,000 plant × year records of 8586 plants, including 3464 seedlings established after the first census. Seven populations were in experimentally isolated fragments (one in each of four 1-ha fragments and one in each of three 10-ha fragments), with the remaining six populations in continuous forest. Each population was in a 50 × 100 m permanent plot, with the distance between plots ranging from 500 m to 60 km. The plants in each plot were censused annually, at which time we recorded, identified, marked, and measured new seedlings, identified any previously marked plants that died, and recorded the size of surviving individuals. Each plot was also surveyed four to five times during the flowering season to identify reproductive plants and record the number of inflorescences each produced. These data have been used to investigate topics ranging from the way fragmentation-related reductions in germination influence population dynamics to statistical methods for analyzing reproductive rates. This breadth of prior use reflects the value of these data to future researchers. In addition to analyses of plant responses to habitat fragmentation, these data can be used to address fundamental questions in plant demography and the evolutionary ecology of tropical plants and to develop and test demographic models and tools. Though we welcome opportunities to collaborate with interested users, there are no restrictions on the use of this data set. However, we do request that those using the data for teaching or research purposes inform us of how they are doing so and cite this paper and the data archive when appropriate. Any publication using the data must also include a BDFFP Technical Series Number in the Acknowledgments. Authors can request this series number upon the acceptance of their article by contacting the BDFFP's Scientific Coordinator or E. M. Bruna.

Aerial insectivorous bat responses to 30 years of forest insularization in a dam-created Amazonian archipelagic landscape

Mega dams result in habitat loss and fragmentation in lowland tropical forests, compromising the diversity and ecosystem functioning in remnant habitat islands. We investigated the structure of aerial insectivorous bat assemblages within insular forest patches created by a vast ∼30-year-old hydropower reservoir and adjacent mainland continuous forests in Central Amazonia. Bats were surveyed using passive bat recorders across 34 sites. We assessed bat assemblage responses to landscape insularization and estimated the contribution of assemblage-wide components of β-diversity. Additionally, we assessed the effects of local vegetation, and both patch and landscape variables on bat species diversity. Continuous forest sites in the mainland retained higher species richness and bat activity compared to islands, leading to divergent species composition between forest sites. Larger islands (>100 ha) and continuous forests tended to share a similar assemblage composition manly drive by species richness differences with a minor contribution of species replacements. Moreover, local vegetation structure, island size, and landscape edge area exerted significant effects on species richness, bat activity, and species composition, with small degraded islands and landscapes dominated by forest edges exhibiting pervasive species loss. Our study highlights the detrimental impacts of forest fragmentation induced by large dams on aerial insectivorous bat assemblages. If new dam projects are inevitable, we recommend the creation of extensive protected areas in land-bridge island systems and their adjacent continuous forests. Those protected sites can minimize the negative impacts of small islands, safeguarding forest quality for forest-dependent bats, which ensures the continuity of their ecosystem services.

Foraging guild modulates insectivorous bat responses to habitat loss and insular fragmentation in peninsular Malaysia

Despite mounting evidence on the ecological impacts of damming for biodiversity, little is known regarding its consequences in the hyper-diverse Southeast Asian tropical forests. Here we assess the effects of habitat loss and fragmentation on the diversity and activity of insectivorous bats within the hydroelectric Kenyir Lake in peninsular Malaysia. We surveyed bat assemblages on 26 islands and two mainland continuous forest sites using passive acoustic monitoring. Echolocation calls were classified into sonotypes, each corresponding to either one or multiple species, and grouped into foraging guilds. We then examined bat overall assemblage (sonotype richness, activity, and composition), guild- and sonotype-specific activity. From 9360 h of recordings, we identified 16 bat sonotypes, including 10 forest (2854 bat passes), three edge (13703) and three open-space foragers (3651). Sonotype richness increased towards denser canopy structures, as indicated by higher Normalized Difference Vegetation Index values (NDVI). Sonotype composition varied across the gradient of forest area. Forest foragers were positively affected by NDVI and negatively affected by distance to the closest neighbour, whereas edge foragers' activity increased in smaller islands. Of the six sonotypes analysed, the activity of one forest sonotype increased with forest area, while that of one edge sonotype decreased. Ensuring habitat quality within insular forest remnants, in addition to their functional connectivity, maximises bat diversity, including the persistence of forest foraging species. Future hydropower development should therefore avoid the creation of a myriad of small, isolated, and habitat-degraded islands further characterised by altered levels of bat diversity and guild-level activity.

How do assemblages of epigeal Araneae and Coleoptera respond to changes in habitat structure caused by sugar cane crops in Northern Argentina?

ABSTRACT In Northwest Argentina, nothing is known about the relationship of Araneae and Coleoptera with sugar cane crops. Using pitfall traps in three continuous native forest sites (N) and three native forest windbreaks surrounded by sugar cane crops (W) in the province of Salta, we assessed a)- whether the native diversity of epigeal Araneae and Coleoptera in the Chaco Serrano forest changes as a result of the fragmentation of the habitat caused by the sugar cane plots, and b)- whether the diversity of predatory species increases in native forest windbreaks as a consequence of the contribution of species that come from crops. In the spring of 2006 and the summer of 2007, we collected 599 Araneae and 555 Coleoptera, with community W (S = 132, N = 535) containing much more species but fewer individuals than community N (S = 111, N = 619). We found that the spatial and phenological patterns of the alpha and beta diversities of N were altered in W communities. Thus, habitat fragmentation generated by sugar cane plots led to the local extinction of native Araneae and Coleoptera species. The abundance of generalist Araneae and herbivorous Coleoptera increased in W habitats, but the coprophagous and detritivorous beetles decreased. The diversity of predatory species (Araneae and some Coleoptera) increased in W habitats, although their abundance declined relative to N habitats. Species turnover determined beta diversity between N and W sites; however, between the W sites, nestedness increased and spiders showed a greater loss of species. The spatial heterogeneity between sites, seasons, and habitats had a substantial effect on the composition of the Araneae and Coleoptera assemblages, hence influencing regional diversity. Eight species were habitat indicators, particularly Leprolochus birabeni (Zodariidae), which responds unfavourably to perturbations in the agricultural landscape, and could be deployed as environmental monitors in the Chaco Serrano.

Emergent properties of species-habitat networks in an insular forest landscape.

Deforestation and fragmentation are pervasive drivers of biodiversity loss, but how they scale up to entire landscapes remains poorly understood. Here, we apply species-habitat networks based on species co-occurrences to test the effects of insular fragmentation on multiple taxa—medium-large mammals, small nonvolant mammals, lizards, understory birds, frogs, dung beetles, orchid bees, and trees—across 22 forest islands and three continuous forest sites within a river-damming quasi-experimental landscape in Central Amazonia. Widespread, nonrandom local species extinctions were translated into highly nested networks of low connectance and modularity. Networks’ robustness considering the sequential removal of large-to-small sites was generally low; between 5% (dung beetles) and 50% (orchid bees) of species persisted when retaining only <10 ha of islands. In turn, larger sites and body size were the main attributes structuring the networks. Our results raise the prospects that insular forest fragmentation results in simplified species-habitat networks, with distinct taxa persistence to habitat loss.

Homogenization of terrestrial mammals in fragmented rainforests: the loss of species turnover and its landscape drivers

Understanding the factors and mechanisms shaping differences in species composition across space and time (β-diversity) in human-modified landscapes has key ecological and applied implications. This topic is, however, challenging because landscape disturbance can promote either decreases (biotic homogenization) or increases (biotic differentiation) in β-diversity. We assessed temporal differences in intersite β-diversity of medium-bodied and large-bodied mammals in the fragmented Lacandona rainforest, Mexico. We hypothesized that, given the relatively short history of land-use changes in the region, and the gain and loss of some species caused by landscape spatial changes, β-diversity would increase through time, especially its nestedness component. We estimated β-diversity between 24 forest sites (22 forest patches and two continuous forest sites) in 2011 and 2017 to assess whether β-diversity is decreasing or increasing in the region, and calculated its turnover and nestedness components to understand the mechanisms responsible for changes in β-diversity, separately assessing mammal groups with different body mass, feeding guild, and habitat specialization. We then related such temporal changes in β-diversity to temporal changes in five landscape variables (forest cover, matrix openness, number of patches, edge density and interpatch distance) to identify the landscape drivers of β-diversity. In contrast with our expectations, β-diversity decreased over time, suggesting an ongoing biotic homogenization process. This pattern was mostly driven by a decrease in species turnover in all mammal groups, especially in landscapes with decreasing forest cover and increasing forested matrices. Although the nestedness component showed a three-fold increase through time, species turnover was 22 and six times higher than nestedness in 2011 and 2017, respectively. The decreased turnover appears to be driven by an increase in dispersal (i.e., spillover) of native species among patches. The prevalence of species turnover over nestedness indicates that different forest sites have a fairly distinct subset of species (i.e., high complementarity in species composition). Therefore, conserving all remaining forest patches and increasing forest cover is of utmost importance to effectively maintain β-diversity and conserve the total diversity (γ) of mammal assemblages in this Mesoamerican biodiversity hotspot.

Phylogenetic homogenization of Amazonian tree assemblages in forest islands after 26 years of isolation

AbstractQuestionLosses in species richness and functional diversity of tree assemblages have often been observed in Neotropical fragmented landscapes, but the way in which tree phylogenetic diversity responds to forest insularization over decadal timescales remains unclear. Here, we examine how tree phylogenetic diversity and structure have responded to profound landscape alteration and subsequent non‐random species losses within forest islands created within a vast hydroelectric reservoir.LocationBalbina Hydroelectric Dam Reservoir, Central Brazilian Amazonia.MethodsWe used a large tree data set including 435 subplots of 0.05 ha each in 34 forest islands of variable sizes and three continuous forest sites in the Balbina Hydroelectric Dam, which contained 11,000 stems representing 365 species and 188 genera. In each subplot we quantified tree phylogenetic diversity and structure and investigated their relationship with landscape structure metrics and the proportion of species within specific functional groups.ResultsWe uncovered a reduction in phylogenetic diversity in small (&lt;10 ha) isolated islands, particularly in more fire‐prone areas near forest edges and surrounded by low amounts of forest cover. Additionally, assemblage‐wide phylogenetic decay was a result of non‐random species losses, given that tree assemblages dominated by small‐seeded, soft‐wooded pioneer species exhibited lower values of phylogenetic diversity and structure. We also uncovered a phylogenetic signal in traits associated with disturbance‐adapted species within this major man‐made forest archipelago.ConclusionWe uncovered pronounced phylogenetic diversity decay that was mostly driven by the proliferation of disturbance‐adapted species, such as small‐seeded pioneer species exhibiting fast life histories. Our results undermine more optimistic views based on studies in fragmented landscapes dominated by terrestrial matrix habitats, and indicate that true land‐bridge forest islands experience more detrimental effects on different components of tree diversity. Our study contributes to elucidate a growing underestimation of the pervasive threats posed by mega‐dams to tropical forest biodiversity and ecosystem functioning.

Drivers of leafcutter ant populations and their inter‐trophic relationships in Amazonian forest islands

AbstractUnder habitat loss and fragmentation, the intensity of local ecological processes involving species interactions changes pervasively, accelerating local species extinctions, and disrupting essential ecosystem functions. We addressed this issue by examining the direct population drivers of apex predators (five felid species), armadillo mesopredators, leafcutter ants (Atta sexdens and Atta cephalotes), and the indirect effects mediated by their inter‐trophic relationships in a ~25‐yr‐old land‐bridge island system formed by a hydroelectric dam in the Central Amazon. These trophic groups and pioneer tree abundance were surveyed across 34 variable‐sized islands and three continuous forest sites. Leafcutter populations were characterized in relation to their occurrence, colony density, and proportion of inactive colonies, and for each leafcutter response, we considered the direct and/or indirect effects of forest area on each trophic group. Leafcutter occupancy was best explained by the direct model, colony density by either the direct or the indirect model, and proportion of inactive colonies by an indirect model via the effects of pioneer tree abundance. The direct forest area effects were positive for apex predators and leafcutter occupancy, but negative for armadillos and pioneer trees. Yet leafcutter colony density declined in increasingly larger forest areas. The absence or low abundance of apex predators on small islands released armadillo hyper‐abundance, which contrary to expectation from top‐down control, covaried positively with leafcutter colony density. Finally, the indirect model showed that leafcutter colonies were more active under higher pioneer tree abundances. That leafcutter density increases on smaller islands whenever present is likely attributed to the hyper‐abundance of pioneer plants and canopy gaps. Although apex predators apparently suppressed armadillos, the remaining fraction of the food web seems to be controlled by bottom‐up mechanisms most likely related the overall low foliage palatability typical of wet evergreen forests. Our findings can be used to inform the long‐term viability of forest ecosystems affected by hydropower development in lowland Amazonia.

Species-Area Relationships Induced by Forest Habitat Fragmentation Apply Even to Rarely Detected Organisms

Neotropical snakes have extremely low detection rates, hampering our understanding of their responses to habitat loss and fragmentation. We addressed this gap using a limited sample (50 individuals, 16 species) across 25 variable-size insular forest fragments within a hydroelectric lake and four adjacent mainland continuous forest sites, in Central Brazilian Amazonia. The number of species recorded on forest islands (1.55 [Formula: see text] 0.78) was much lower than that at continuous forest sites (5.0 [Formula: see text] 3.1), with no snakes being recorded at twelve islands smaller than 30 ha. As such, snake assemblages were positively affected by forest area, explaining 48% of the number of species, and negatively affected by island isolation. The markedly higher number of species recorded across continuous forest sites likely results from the availability of riparian habitats, which have virtually disappeared from the archipelagic landscape given the widespread inundation of lowland areas. To prevent further severe biodiversity loss, including those of poorly known rare taxa, conservation policies should avert the additional construction of mega-dams that create myriad of small islands, in addition to extensive reservoir lakes from which all riparian habitats are eliminated.

Riparian buffers act as microclimatic refugia in oil palm landscapes

Abstract There is growing interest in the ecological value of set‐aside habitats around rivers in tropical agriculture. These riparian buffers typically comprise forest or other non‐production habitat, and are established to maintain water quality and hydrological processes, while also supporting biodiversity, ecosystem function and landscape connectivity. We investigated the capacity for riparian buffers to act as microclimatic refugia by combining field‐based measurements of temperature, humidity and dung beetle communities with remotely sensed data from LiDAR across an oil palm dominated landscape in Borneo. Riparian buffers offer a cool and humid habitat relative to surrounding oil palm plantations, with wider buffers characterised by conditions comparable to riparian sites in continuous logged forest. High vegetation quality and topographic sheltering were strongly associated with cooler and more humid microclimates in riparian habitats across the landscape. Variance in beetle diversity was also predicted by both proximity‐to‐edge and microclimatic conditions within the buffer, suggesting that narrow buffers amplify the negative impacts that high temperatures have on biodiversity. Synthesis and applications. Widely legislated riparian buffer widths of 20–30 m each side of a river may provide drier and less humid microclimatic conditions than continuous forest. Adopting wider buffers and maintaining high vegetation quality will ensure set‐asides established for hydrological reasons bring co‐benefits for terrestrial biodiversity, both now, and in the face of anthropogenic climate change.

Determinants of population persistence and abundance of terrestrial and arboreal vertebrates stranded in tropical forest land-bridge islands.

Megadams are among the key modern drivers of habitat and biodiversity loss in emerging economies. The Balbina Hydroelectric Dam of Central Brazilian Amazonia inundated 312,900 ha of primary forests and created approximately 3500 variable-sized islands that still harbor vertebrate populations after nearly 3 decades after isolation. We estimated the species richness, abundance, biomass, composition, and group size of medium- to large-bodied forest vertebrates in response to patch, landscape, and habitat-quality metrics across 37 islands and 3 continuous forest sites throughout the Balbina archipelago. We conducted 1168 km of diurnal censuses and had 12,420 camera-trapping days along 81 transects with 207 camera stations. We determined the number of individuals (or groups) detected per 10 km walked and the number of independent photographs per 10 camera-trapping days, respectively, for each species. We recorded 34 species, and patch area was the most significant predictor of vertebrate population relative abundance and aggregate biomass. The maximum group size of several group-living species was consistently larger on large islands and in continuous patches than on small islands. Most vertebrate populations were extirpated after inundation. Remaining populations are unlikely to survive further ecological disruptions. If all vertebrate species were once widely distributed before inundation, we estimated that approximately 75% of all individual vertebrates were lost from all 3546 islands and 7.4% of the animals in all persisting insular populations are highly likely to be extirpated. Our results demonstrate that population abundance estimates should be factored into predictions of community disassembly on small islands to robustly predict biodiversity outcomes. Given the rapidly escalating hydropower infrastructure projects in developing counties, we suggest that faunal abundance and biomass estimates be considered in environmental impact assessments and large strictly protected reserves be established to minimize detrimental effects of dams on biodiversity. Conserving large tracts of continuous forests represents the most critical conservation measure to ensure that animal populations can persist at natural densities in Amazonian forests.

Spatiotemporal Variation in Bonobo (Pan paniscus) Habitat Use in a Forest–Savanna Mosaic

Understanding the ecological and behavioral variation of primates is central to improving conservation strategies. Studies of chimpanzees (Pan troglodytes) have shown marked behavioral variability across a wide range of habitats. By comparison, bonobos (Pan paniscus) occur mainly in continuous forest sites, and socioecological models explaining behavioral differences between the two species are based on the assumption that bonobo habitat is richer and more stable than chimpanzee habitats. The objective of this study was to assess bonobo ecology in a forest–savanna mosaic. We specifically explored 1) bonobo home range size, habitat use, and dietary composition; 2) forest fragmentation in a bonobo community’s home range; and 3) seasonality of dietary diversity, habitat use, and spatial distribution. Using 2 years of observational data on location, habitat type, and dietary composition, we found that the bonobo community's home range size, density, and dietary diversity were similar to those observed in continuous forest sites. Bonobos used areas with lower forest fragmentation than the surrounding areas and preferentially spent time in forested habitats. During the dry season, bonobos consumed a lower diversity of fruit species, spent more time in sparse forest with Marantaceae understory, and were closer to the seasonal center of their home range than during the rainy season. Our results contribute to our understanding of behavioral variation in bonobos and suggest that forest–savanna mosaic is valuable to bonobo conservation.

Small vertebrates are key elements in the frugivory networks of a hyperdiverse tropical forest

The local, global or functional extinction of species or populations of animals, known as defaunation, can erode important ecological services in tropical forests. Many mutualistic interactions, such as seed dispersal of large seeded plants, can be lost in large continuous forests due to the rarity of large-bodied mammalian frugivores. Most of studies that try to elucidate the effects of defaunation on seed dispersal focused on primates or birds, and we lack a detailed understanding on the interactions between ground-dwelling fauna and fleshy fruits. Using camera traps in forest areas with different degrees of defaunation, we described the organization of frugivory networks involving birds, mammals and plants. We recorded 375 frugivory interactions between 21 frugivores and 150 fruiting trees of 30 species of fleshy fruit plants in six sites in continuous Atlantic forest of Brazil. We found that small frugivores—particularly small rodents and birds—were responsible for 72% of the events of frugivory. Large frugivores, such as tapirs and peccaries, were responsible for less than 21% of frugivory events. Our results indicate that the interactions between flesh fruiting plants and frugivores are dominated by small frugivores, an indication of a functional loss of large frugivores in this endangered biome.

Changes in aboveground locomotion of a scansorial opossum associated to habitat fragmentation

AbstractHabitat fragmentation may affect animal movement patterns due to changes in intra- and interspecific interactions as well as in habitat quality and structure. Although the effects of habitat fragmentation on terrestrial movements are relatively well-known, it is unclear whether and how they affect aboveground locomotion of individuals. We compared aboveground locomotion of a Neotropical small mammal, the gray four-eyed opossum, Philander quica, between two forest fragments and two areas of continuous forest in the Brazilian Atlantic Forest. We 1) quantified support availability and tested for active selection of different support diameters and inclinations by individuals; and 2) compared support diameters and inclinations used (observed values) among areas and between males and females. Both males and females selected supports based on diameters and inclinations in forest fragments. In continuous forests sites, females selected supports based on diameters and inclinations, but males selected only support diameters. Frequency of support diameter use differed significantly between forest fragments and continuous forest sites and between males and females. Frequency of support inclination use differed significantly between areas only for females, and between sexes only in continuous forest sites. Sex-related differences in support selection and use are likely related to differences in body size and conflicting energetic and behavioral demands related to use of arboreal space. Site-related differences in aboveground movements likely reflect the effects of forest edges that result in increased use of thinner supports in forest fragments. These results complement our previous findings that habitat fragmentation reduces daily home ranges and increases the total amount of aboveground locomotion of P. quica, and provide a more thorough picture of how forest-dependent species are able to use and persist in small forest fragments.

Marked decline in forest-dependent small mammals following habitat loss and fragmentation in an Amazonian deforestation frontier.

Agricultural frontier expansion into the Amazon over the last four decades has created million hectares of fragmented forests. While many species undergo local extinctions within remaining forest patches, this may be compensated by native species from neighbouring open-habitat areas potentially invading these patches, particularly as forest habitats become increasingly degraded. Here, we examine the effects of habitat loss, fragmentation and degradation on small mammal assemblages in a southern Amazonian deforestation frontier, while accounting for species-specific degree of forest-dependency. We surveyed small mammals at three continuous forest sites and 19 forest patches of different sizes and degrees of isolation. We further sampled matrix habitats adjacent to forest patches, which allowed us to classify each species according to forest-dependency and generate a community-averaged forest-dependency index for each site. Based on 21,568 trap-nights, we recorded 970 small mammals representing 20 species: 12 forest-dependents, 5 matrix-tolerants and 3 open-habitat specialists. Across the gradient of forest patch size, small mammal assemblages failed to show the typical species-area relationship, but this relationship held true when either species abundance or composition was considered. Species composition was further mediated by community-averaged forest-dependency, so that smaller forest patches were occupied by a lower proportion of forest-dependent rodents and marsupials. Both species richness and abundance increased in less isolated fragments surrounded by structurally simplified matrix habitats (e.g. active or abandoned cattle pastures). While shorter distances between forest patches may favour small mammal abundances, forest area and matrix complexity dictated which species could persist within forest fragments according to their degree of forest-dependency. Small mammal local extinctions in small forest patches within Amazonian deforestation frontiers are therefore likely offset by the incursion of open-habitat species. To preclude the dominance of those species, and consequent losses of native species and associated ecosystem functions, management actions should limit or reduce areas dedicated to pasture, additionally maintaining more structurally complex matrix habitats across fragmented landscapes.

The role of baseline suitability in assessing the impacts of land-use change on biodiversity

We examined differences in species richness between reference and impacted sites to illustrate the extent to which estimated impacts of land-use change on biodiversity can be affected by the degree of baseline suitability (intactness of reference sites) and the species assemblage under consideration. We mist-netted birds at five continuous Amazonian forest sites and 33 land-bridge forest islands (0.63–1699 ha) within a large hydroelectric reservoir. We then produced a gradient of baseline suitability based on forest area of five sets of reference sites, namely continuous forest, 1000 ha, 500 ha, 250 ha and 100 ha, and contrasted these with all smaller islands combined considering two types of species assemblages. The first comprised only species captured at reference sites (baseline species assemblage), whereas the second comprised all species captured at all sites (overall species assemblage). We also examined biodiversity complementarity to define the minimum set of forest islands retaining the most number of species occurring both at continuous forest sites and across all sites. A focus on the baseline species assemblage from the most suitable baseline (continuous forest) resulted in an estimated decrease of 67% in species richness at impacted sites. In contrast, a focus on the overall species assemblage along with the use of the least suitable baseline (100 ha) as a reference condition reversed this trend, resulting in an estimated increase of 43% in species richness at impacted sites. We therefore underline the imperative of considering the intactness of reference sites to accurately assess the impacts of land-use change on biodiversity and establish conservation strategies.

Optimizing small mammal surveys in Neotropical fragmented landscapes while accounting for potential sampling bias

Maximizing cost-efficiency of biological surveys is of great importance to assess threats and monitor changes in tropical landscapes, particularly when survey costs are high as in Neotropical small mammals. Species detectability is mostly affected by local abundance but can further vary according to the forest size in fragmented landscapes. For example, species detection in smaller fragments may be higher due to either spatial constrains or forest vertical compression. Here, trade-offs between duration of trapping sessions and the cost of obtaining accurate small mammal individual and species data are investigated across a range of forest sizes, while accounting for potential sampling bias. Using a combination of live (Sherman and wire mesh) and pitfall traps, patterns of cumulative capture–recapture rates and community composition were examined across 16 night trapping sessions in 42 transects nested within 14 insular forest fragments of different sizes, and two continuous forest sites in the Central Brazilian Amazon. Based on 40,254 trap-nights, 604 captures were recorded from 22 identifiable species. Cumulative number of captures gradually increased along the entire trapping session, and on average, nearly half of all species required more than eight trapping nights to be detected at each sampling transect. Sampling bias was responsible for increased cumulative recapture rates in smaller fragments, but did not affect cumulative capture rates, or time to first detection of each species. Instead, time to first detection was mostly positively affected by species abundance. Our results highlight the higher effectiveness of long trapping sessions (i.e. > 10 nights) to detect uncommon species, increase sample sizes and recapture rates. Overall, if small mammal species abundance is high, sampling intensity can be reduced. However, regardless of species abundance, large fragments and continuous forest sites should be more intensively sampled to reduce any potential sampling bias.

Detection and characterization of birch pollen in the atmosphere using a multiwavelength Raman polarization lidar and Hirst-type pollen sampler in Finland

Abstract. We present the results of birch pollen characterization using lidar and in situ measurements based on a 11 d pollination period from 5 to 15 May 2016 at the European Aerosol Research Lidar Network (EARLINET) station in Vehmasmäki (Kuopio; 62∘44′ N, 27∘33′ E), Finland. The ground-based multiwavelength Raman polarization lidar PollyXT performed continuous measurements at this rural forest site and has been combined with a Hirst-type volumetric air sampler, which measured the pollen type and concentration at roof level (4 m). The period was separated into two parts due to different atmospheric conditions and detected pollen types. During the first period, high concentrations of birch pollen were measured with a maximum 2 h average pollen concentration of 3700 grains m−3. Other pollen types represented less than 3 % of the total pollen count. In observed pollen layers, the mean particle depolarization ratio at 532 nm was 10±6 % during the intense birch pollination period. Mean lidar ratios were found to be 45±7 and 55±16 sr at 355 and 532 nm, respectively. During the second period, birch pollen was still dominant, but a significant contribution of spruce pollen was observed as well. Spruce pollen grains are highly nonspherical, leading to a larger mean depolarization ratio of 26±7 % for the birch–spruce pollen mixture. Furthermore, higher lidar ratios were observed during this period with mean values of 60±3 and 62±10 sr at 355 and 532 nm, respectively. The presented study shows the potential of the particle depolarization ratio to track pollen grains in the atmosphere.

Sampling design may obscure species–area relationships in landscape‐scale field studies

We investigated 1) the role of area per se in explaining anuran species richness on reservoir forest islands, after controlling for several confounding factors. We also assessed 2) how sampling design affects the inferential power of island species–area relationships (ISARs) aiming to 3) provide guidelines to yield reliable estimates of area‐induced species losses in patchy systems. We surveyed anurans with autonomous recording units at 151 plots located on 74 islands and four continuous forest sites at the Balbina Hydroelectric Reservoir landscape, central Brazilian Amazonia. We applied semi‐log ISAR models to assess the effect of sampling design on the fit and slope of species–area curves. To do so, we subsampled our surveyed islands following both a 1) stratified and 2) non‐stratified random selection of 5, 10, 15, 20 and 25 islands covering 1) the full range in island size (0.45–1699 ha) and 2) only islands smaller than 100 ha, respectively. We also compiled 25 datasets from the literature to assess the generality of our findings. Island size explained ca half of the variation in species richness. The fit and slope of species–area curves were affected mainly by the range in island size considered, and to a very small extent by the number of islands surveyed. In our literature review, all datasets covering a range of patch sizes larger than 300 ha yielded a positive ISAR, whereas the number of patches alone did not affect the detection of ISARs. We conclude that 1) area per se plays a major role in explaining anuran species richness on forest islands within an Amazonian anthropogenic archipelago; 2) the inferential power of island species–area relationships is severely degraded by sub‐optimal sampling designs; 3) at least 10 habitat patches spanning three orders of magnitude in size should be surveyed to yield reliable species–area estimates in patchy systems.