Topography as a driver of local terrestrial vascular plant diversity patterns

At landscape and regional scales topography is recognized as one of the most important determinants of vascular plant diversity, primarily due to the influence of mountains. As temperature changes markedly over the elevation ranges in mountain areas, topography offers a wide variety of different habitats as well as buffering against climate change. However, for local vegetation, notably in lowland areas, the general importance of topography is less well recognized and the mechanisms by which it exerts influence on local vascular plant diversity are not comprehensively understood. In this review, we provide an overview of the evidence for the different mechanisms involved in topography’s control of local patterns in potential vegetation drivers, namely incident solar energy, wind exposure, hydrology, geochemistry, and biotic conditions. Furthermore, we review the processes through which these factors shape local terrestrial vascular plant diversity patterns and provide directions for future studies on this topic. We find that topography is an important factor for local vascular plant diversity patterns in a broad range of habitats throughout the world, even in relatively flat lowlands. However, the mechanisms involved are varied and complex. Local patterns in soil moisture seem to be affected by topography through more mechanisms than other topographically controlled factors and have a strong and consistent influence on local plant diversity. Hence, local hydrology is probably the main mechanistic factor through which topography influences local terrestrial vascular plant diversity patterns. Future research should focus on employing high‐coverage fine‐resolution topographic data to comprehensively explore the role of topography in controlling local dynamics over large areas. Moreover, we recommend including several different habitats, particularly those in which the role of topography is poorly understood. Finally, we propose to integrate relevant functional topographic variables such as topographic wetness indices instead of simple topographic measures into future investigations.