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Tropical forests harbour the highest levels of terrestrial biodiversity and represent some of the most complex ecosystems on Earth, with a significant portion of this diversity above ground. Although the vertical dimension is a central aspect of the ecology of forest communities, there is little consensus as to prominence, evenness, and consistency of community-level stratification from ground to canopy. Here, we gather the results of 62 studies across the tropics to synthesise and assess broad patterns of vertical stratification of abundance and richness in vertebrates, the best studied taxonomic group for which results have not been collated previously. Our review of the literature yielded sufficient data for bats, small mammals, birds and amphibians. We show that variation in the stratification of abundance and richness exists within and among all taxa considered. Bat richness stratification was variable among studies, although bat abundance was weighted towards the canopy. Both bird richness and abundance stratification were variable, with no overriding pattern. On the contrary, both amphibians and small mammals showed consistent patterns of decline in abundance and richness towards the canopy. We descriptively characterise research trends in drivers of stratification cited or investigated within studies, finding local habitat structure and food distribution/foraging to be the most commonly attributed drivers. Further, we analyse the influence of macroecological variables on stratification patterns, finding latitude and elevation to be key predictors of bird stratification in particular. Prominent differences among taxa are likely due to taxon-specific interactions with local drivers such as vertical habitat structure, food distribution, and vertical climate gradients, which may vary considerably across macroecological gradients such as elevation and biogeographic realm. Our study showcases the complexity with which animal communities organise within tropical forest ecosystems, while demonstrating the canopy as a critical niche space for tropical vertebrates, thereby highlighting the inherent vulnerability of tropical vertebrate communities to forest loss and canopy disturbance. We recognise that analyses were constrained due to variation in study designs and methods which produced a variety of abundance and richness metrics recorded across different arrangements of vertical strata. We therefore suggest the application of best practices for data reporting and highlight the significant effort required to fill research gaps in terms of under-sampled regions, taxa, and environments., (© 2022 Cambridge Philosophical Society.)

In tropical forests, large, old trees (LOTs) can be considered keystone structures for provisioning unique habitats such as decaying wood, roots, cavities, and epiphytes, including those that hold water (phytotelmata). These habitats may also be stratified in vertical space, for example, root structures occur at ground level and below, whereas epiphytes occur above-ground. Canopy habitat is utilized by a diversity of amphibians, but canopy habitat may only be viable in the wet season when epiphytes and surfaces are sufficiently saturated. Here, we examine how the provisioning of microhabitats and structures by LOTs influence the horizontal, vertical, and seasonal distribution patterns of phytotelmata-breeding poison frogs. We conducted ground-to-canopy surveys over 4 years, constituting 6 seasons, in Panama and used mark-recapture techniques on a population of the yellow-bellied poison frog, Andinobates fulguritus. We found that A. fulguritus migrated vertically, tracking seasonal rainfall, and displayed strong philopatry to individual trees. Furthermore, A. fulguritus almost exclusively inhabited the largest trees at the study location, which provided disproportionately high-quality microhabitats and epiphytes compared to other trees. LOTs, and specifically Anacardium excelsum at our site, appear to serve as keystone structures with high conservation value due to their provisioning of unique habitats. We conclude that the distribution of A. fulguritus is defined vertically by the stratification of arboreal microhabitat resources, horizontally by the presence of LOTs providing the resources, and temporally by the seasonal viability of the resources., (© 2022. The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature.)

Research in global change ecology relies heavily on global climatic grids derived from estimates of air temperature in open areas at around 2 m above the ground. These climatic grids do not reflect conditions below vegetation canopies and near the ground surface, where critical ecosystem functions occur and most terrestrial species reside. Here, we provide global maps of soil temperature and bioclimatic variables at a 1-km 2 resolution for 0-5 and 5-15 cm soil depth. These maps were created by calculating the difference (i.e. offset) between in situ soil temperature measurements, based on time series from over 1200 1-km 2 pixels (summarized from 8519 unique temperature sensors) across all the world's major terrestrial biomes, and coarse-grained air temperature estimates from ERA5-Land (an atmospheric reanalysis by the European Centre for Medium-Range Weather Forecasts). We show that mean annual soil temperature differs markedly from the corresponding gridded air temperature, by up to 10°C (mean = 3.0 ± 2.1°C), with substantial variation across biomes and seasons. Over the year, soils in cold and/or dry biomes are substantially warmer (+3.6 ± 2.3°C) than gridded air temperature, whereas soils in warm and humid environments are on average slightly cooler (-0.7 ± 2.3°C). The observed substantial and biome-specific offsets emphasize that the projected impacts of climate and climate change on near-surface biodiversity and ecosystem functioning are inaccurately assessed when air rather than soil temperature is used, especially in cold environments. The global soil-related bioclimatic variables provided here are an important step forward for any application in ecology and related disciplines. Nevertheless, we highlight the need to fill remaining geographic gaps by collecting more in situ measurements of microclimate conditions to further enhance the spatiotemporal resolution of global soil temperature products for ecological applications., (© 2022 The Authors. Global Change Biology published by John Wiley & Sons Ltd.)

Current analyses and predictions of spatially explicit patterns and processes in ecology most often rely on climate data interpolated from standardized weather stations. This interpolated climate data represents long-term average thermal conditions at coarse spatial resolutions only. Hence, many climate-forcing factors that operate at fine spatiotemporal resolutions are overlooked. This is particularly important in relation to effects of observation height (e.g. vegetation, snow and soil characteristics) and in habitats varying in their exposure to radiation, moisture and wind (e.g. topography, radiative forcing or cold-air pooling). Since organisms living close to the ground relate more strongly to these microclimatic conditions than to free-air temperatures, microclimatic ground and near-surface data are needed to provide realistic forecasts of the fate of such organisms under anthropogenic climate change, as well as of the functioning of the ecosystems they live in. To fill this critical gap, we highlight a call for temperature time series submissions to SoilTemp, a geospatial database initiative compiling soil and near-surface temperature data from all over the world. Currently, this database contains time series from 7,538 temperature sensors from 51 countries across all key biomes. The database will pave the way toward an improved global understanding of microclimate and bridge the gap between the available climate data and the climate at fine spatiotemporal resolutions relevant to most organisms and ecosystem processes., (© 2020 John Wiley & Sons Ltd.)

Global warming is having impacts across the Tree of Life. Understanding species' physiological sensitivity to temperature change and how they relate to local temperature variation in their habitats is crucial to determining vulnerability to global warming. We ask how species' vulnerability varies across habitats and elevations, and how climatically buffered microhabitats can contribute to reduce their vulnerability. We measured thermal sensitivity (critical thermal maximum-CT max ) of 14 species of Pristimantis frogs inhabiting young and old secondary, and primary forests in the Colombian Andes. Exposure to temperature stress was measured by recording temperature in the understorey and across five microhabitats. We determined frogs' current vulnerability across habitats, elevations and microhabitats accounting for phylogeny and then ask how vulnerability varies under four warming scenarios: +1.5, +2, +3 and +5°C. We found that CT max was constant across species regardless of habitat and elevation. However, species in young secondary forests are expected to become more vulnerable because of increased exposure to higher temperatures. Microhabitat variation could enable species to persist within their thermal temperature range as long as regional temperatures do not surpass +2°C. The effectiveness of microhabitat buffering decreases with a 2-3°C increase, and is almost null under a 5°C temperature increase. Microhabitats will provide thermal protection to Andean frog communities from climate change by enabling tracking of suitable climates through short distance movement. Conservation strategies, such as managing landscapes by preserving primary forests and allowing regrowth and reconnection of secondary forest would offer thermally buffered microhabitats and aid in the survival of this group., (© 2020 British Ecological Society.)

In tropical forests, epiphytes increase habitat complexity and provision services rare to canopy environments, such as water retention, nutrient cycling, and microclimate refuge. These services facilitate species diversity and coexistence in terrestrial ecosystems, and while their utility in forest ecosystems is appreciated for the Bromeliaceae of the Neotropics, fewer studies have examined the role of Paleotropic epiphytes in ecological niche theory. Here, we compare herpetofaunal presence, abundance, and diversity of in bird's nest fern (Asplenium nidus complex; BNF) to other microhabitats in Madagascar and the Philippines. We measure BNF fern microclimates, examine temporal use of canopy microhabitats, and test models of fern characteristics hypothesized to predict herpetofaunal use. In both countries, one in five BNFs were occupied by herpetofauna, mostly amphibians, and species using BNFs were highly dissimilar from those in other microhabitats. Herpetofaunal presence and abundance were greater in BNFs than in other canopy microhabitats and were most commonly used during the day when fern temperatures were highly buffered. Finally, BNF area was the best predictor of herpetofaunal presence and abundance, compared to canopy cover and BNF height. Importantly, these patterns remained consistent despite the distinct phylogenetic histories of our two communities (Asian versus African). Our results suggests that BNFs and their microclimate services play a critical role in the ecology of two Paleotropic forests, and facilitate the use of canopy habitats by climate-sensitive species. However, future studies are needed to assess the consistency of BNFs' utility as a microclimate refuge across their large range.

Assemblage similarity decays with geographic distance-a pattern known as the distance-decay relationship. While this pattern has been investigated for a wide range of organisms, ecosystems and geographical gradients, whether these changes vary more cryptically across different forest strata (from ground to canopy) remains elusive. Here, we investigated the influence of ground vs. arboreal assemblages to the general distance-decay relationship observed in forests. We seek to explain differences in distance-decay relationships between strata in the context of the vertical stratification of assemblage composition, richness and abundance. We surveyed for a climate-sensitive model organism, amphibians, across vertical rainforest strata in Madagascar. For each tree, we defined assemblages of ground-dwelling, understory, or canopy species. We calculated horizontal distance-decay in similarity across all trees, and across assemblages of species found in different forest strata (ground, understory and canopy). We demonstrate that within stratum comparisons exhibit a classic distance-decay relationship for canopy and understory communities but no distance-decay relationships for ground communities. We suggest that differences in horizontal turnover between strata may be due to local scale habitat and resource heterogeneity in the canopy, or the influence of arboreal traits on species dispersal and distribution. Synthesis. Biodiversity patterns in horizontal space were not consistent across vertical space, suggesting that canopy fauna may not play by the same set of "rules" as their conspecifics living below them on the ground. Our study provides compelling evidence that the above-ground amphibian assemblage of tropical rainforests is the primary driver of the classical distance-decay relationship., (© 2018 The Authors. Journal of Animal Ecology © 2018 British Ecological Society.)