• Energy Research

AbstractAimClimate change is causing shifts in the range of species worldwide. In high‐altitude areas forests are often observed to be shifting their upper limits to higher altitudes in response to warming temperatures. Although this phenomenon is well described, the possible consequences of this for the wider forest community have not been fully considered. In this study, we used epiphytic macro‐lichens to investigate the impacts of tree line advance on associated organisms. We hypothesized that the rate of forest advance should influence the species richness and composition of associated communities.LocationThe Hehuanshan area, Central Mountain Range, Taiwan (24°08–09′ N, 121°15 – 16′ E).MethodsLichen communities were sampled on trees occurring at 33 tree line sites displaying varying degrees of advance. Habitat variables were recorded.ANOVA,GLMM, nestedness analysis and indicator species analysis were used to investigate patterns of species richness and community composition and their association with tree line advance and habitat variables.ResultsSpecies richness was lower in tree lines exhibiting rapid advance; reductions were related to tree size (considered here as a proxy for age) and the distance over which advance had occurred. Community composition varied with tree line form and forest position. Only a subset of species found in slowly advancing or stable forest edges occurred in rapidly advancing tree lines.Main conclusionsDifferential migration rates between co‐occurring species and differences in habitat structure associated with tree line advance can result in community change, but this depends, amongst other factors, on the speed of tree line advance. The importance of advance rate in determining the response suggests that reductions in species richness at tree line could be transitory. However, this will depend on whether advance continues, and on the changes in habitat associated with advance. Given the complexity of tree line behaviour, the findings that we report represent an essential step in understanding community responses to climate change. This understanding is of importance for biodiversity and conservation, especially given the high rate of endemism reported for this and other alpine regions.

AbstractResearch 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‐km2resolution 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‐km2pixels (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.