Maximum air temperature controlled by landscape topography affects plant species composition in temperate forests
Abstract
Context Forest microclimates differ from regional macroclimates because forest canopies affect energy fluxes near the ground. However, little is known about the environmental drivers of understorey temperature heterogeneity and its effects on species assemblages, especially at landscape scales.
Objectives We aimed to identify which temperature variables best explain the landscape-scale distribution of forest vegetation and to disentangle the effects of elevation, terrain attributes and canopy cover on understorey temperatures. Methods We measured growing season air temperature, canopy cover and plant community composition within 46 plots established across a 400-km(2) area in Czech Republic.
We linked growing season maximum, mean and minimum temperatures with elevation, canopy cover and topographic proxies for heat load, topographic position, soil moisture and cold air drainage, and created fine-scale topoclimatic maps of the region. We compared the biological relevance of in situ measured temperatures and temperatures derived from fine-scaled topoclimatic maps and global WorldClim 2 maps.
Results Maximum temperature was the best predictor of understorey plant species composition. Landscape-scale variation in maximum temperature was jointly driven by elevation and terrain topography but not by canopy cover.
Modelled maximum temperature derived from our topoclimatic maps explained significantly more variation in plant community composition than WorldClim 2 grids. Conclusions Terrain topography creates landscape-scale variation in maximum temperature, which in turn controls plant species assembly within the forest understorey.
Maximum temperature is therefore an important but neglected microclimatic driver of species distribution across landscapes.