Challenges of species distribution modeling belowground

Understanding the relationship between soil biodiversity, habitat, and function is one of the main issues of soil-ecological research. The description of spatiotemporal distributions of soil organisms at relevant scales and in relation to their activity is a prerequisite to understand and quantify the factors that control soil functions. Species distribution models can help to explain the functional relationships between organisms and their habitat by estimating occurrence probabilities from spatial-distribution data and environmental predictors for single species or species groups. Here, I present a brief overview of recent developments in species distribution models and illustrate this tool with a case study using a carabid beetle species in a small-scale highly heterogeneously structured environment. In the light of the peculiarities of soil organisms and habitat, several implications and challenges of species distribution models are discussed referencing some instructive studies on the spatial distribution of soil organisms over a range of spatiotemporal scales. The most important challenges of species distribution models for soil organisms comprise the spatiotemporal heterogeneity of soil habitat on a hierarchy of nested scales; the overwhelming diversity of soil organisms with largely unknown life histories, habitat requirements, and dispersal characteristics; taxonomic and technical limitations regarding sampling and measurements; feedbacks between soil biota and their habitat. There is a clear theoretical and practical basis for considering both environmental and geographic drivers of species distributions in soil studies, and for doing so across multiple scales. This would yield a habitat-based soil ecology by combining the spatially explicit approach proposed by Ettema and Wardle (2002) with the niche-based approach of species distribution modeling.