Vertical stratification patterns of tropical forest vertebrates: a meta-analysis

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.

Global maps of soil temperature

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-km2 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-km2 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.

Ten simple rules for training yourself in an emerging field

The opportunity to participate in and contribute to emerging fields is increasingly prevalent in science. However, simply thinking about stepping outside of your academic silo can leave many students reeling from the uncertainty. Here, we describe 10 simple rules to successfully train yourself in an emerging field, based on our experience as students in the emerging field of ecological forecasting. Our advice begins with setting and revisiting specific goals to achieve your academic and career objectives and includes several useful rules for engaging with and contributing to an emerging field.

Forest microclimates and climate change: Importance, drivers and future research agenda

Forest microclimates contrast strongly with the climate outside forests. To fully understand and better predict how forests' biodiversity and functions relate to climate and climate change, microclimates need to be integrated into ecological research. Despite the potentially broad impact of microclimates on the response of forest ecosystems to global change, our understanding of how microclimates within and below tree canopies modulate biotic responses to global change at the species, community and ecosystem level is still limited. Here, we review how spatial and temporal variation in forest microclimates result from an interplay of forest features, local water balance, topography and landscape composition. We first stress and exemplify the importance of considering forest microclimates to understand variation in biodiversity and ecosystem functions across forest landscapes. Next, we explain how macroclimate warming (of the free atmosphere) can affect microclimates, and vice versa, via interactions with land-use changes across different biomes. Finally, we perform a priority ranking of future research avenues at the interface of microclimate ecology and global change biology, with a specific focus on three key themes: (1) disentangling the abiotic and biotic drivers and feedbacks of forest microclimates; (2) global and regional mapping and predictions of forest microclimates; and (3) the impacts of microclimate on forest biodiversity and ecosystem functioning in the face of climate change. The availability of microclimatic data will significantly increase in the coming decades, characterizing climate variability at unprecedented spatial and temporal scales relevant to biological processes in forests. This will revolutionize our understanding of the dynamics, drivers and implications of forest microclimates on biodiversity and ecological functions, and the impacts of global changes. In order to support the sustainable use of forests and to secure their biodiversity and ecosystem services for future generations, microclimates cannot be ignored.

Microgeography, Not Just Latitude, Drives Climate Overlap on Mountains from Tropical to Polar Ecosystems

AbstractAn extension of the climate variability hypothesis is that relatively stable climate, such as that of the tropics, induces distinct thermal bands across elevation that render dispersal over tropical mountains difficult compared with temperate mountains. Yet ecosystems are not thermally static in space-time, especially at small scales, which might render some mountains greater thermal isolators than others. Here we provide an extensive investigation of temperature drivers from fine to coarse scales, and we demonstrate that the degree of similarity in temperatures at high and low elevations on mountains is driven by more than just absolute mountain height and latitude. We compiled a database of 29 mountains spanning six continents to characterize thermal overlap by vertically stratified microhabitats and biomes and owing to seasonal changes in foliage, demonstrating via mixed effects modeling that micro- and mesogeography more strongly influence thermal overlap than macrogeography. Impressively, an increase of 1 m of vertical microhabitat height generates an increase in overlap equivalent to a 5.26° change in latitude. In addition, forested mountains have reduced thermal overlap-149% lower-relative to nonforested mountains. We provide evidence in support of a climate hypothesis that emphasizes microgeography as a determinant of dispersal, demographics, and behavior, thereby refining the classical theory of macroclimate variability as a prominent driver of biogeography.