Soil-Plant-Landscape Relationships In Arid Ecosystems: Factors, Functions, and Feedbacks.

Environmental factors influence the development of soils, including climate, relief/topography, parent material, time, and organisms. Plants are the primary producers of organic carbon in terrestrial ecosystems and thus are the most important group of organisms influencing soil development.  However, plant cover is low in water-limited ecosystems, and the relationships between soils, plants, and landscapes can be complex. Unique sets of soil physical and chemical properties occurring on distinct landforms often result in unique plant communities. The occurrence of unique plant communities can be influenced by various combinations of soil depth, coarse fragment volume, texture, mineralogy, salinity, saturation, and potentially toxic elements. Plant cover in arid ecosystems is typically heterogeneous, resulting in the patchy distribution of resources (e.g., soil organic carbon, nitrogen) and hydraulic properties (e.g., infiltration rate). The spatial variation in plant distribution and function can ultimately affect landscape evolution and ecosystem resistance and resilience to disturbance. Arid ecosystems also provide refuge to rare, endemic plants, which often occur on distinct landforms in soils that present physical (e.g., shallow soil depth) and/or chemical (e.g., high concentrations of gypsum, potentially toxic elements etc.) challenges for many common plants. The feedback relationships between soils, plants, and landscapes can be used to predict the spatial distribution of unique sets of soil properties in arid ecosystems. For example, digital elevation models (DEM) representing relief/topography, spatially explicit remotely sensed spectral data representing plant cover (e.g., NDVI) and texture/ mineralogy of parent material and/or surface soil, field observations, and laboratory characterization data can be incorporated into quantitative models used to predict spatial distribution of soil classes and properties – also known as digital soil mapping. The factors, functions, and feedbacks of selected soil-plant-landscape relationships in arid ecosystems will be illustrated with examples from the Great Basin, Colorado Plateau, Mojave, and Chihuahuan Deserts.