Soil and Belowground Processes

Soil characteristics and functions are critical determinants of rangeland systems and the ecosystem services that they provide. Rangeland soils are extremely diverse, but an emerging understanding is that paradigms developed in more mesic forest ecosystems may not be applicable. Vascular plants, biological soil crusts, and the soil microbial community are the three major functional groups of organisms that influence rangeland soils through their control over soil structure and soil carbon, water, and nutrient availability. Rangelands occur across a broad range of precipitation regimes, but local water status can be modified by management and land use. Important processes in carbon and nutrient cycling can be unique to arid rangelands. Physical drivers such as UV radiation and soil–litter mixing can be important factors for decomposition. Precipitation, vascular species composition and spatial pattern, presence of biological soil crusts, and surface disturbance interact to determine rates of carbon and nutrient cycling. The low resource availability in rangeland soils makes them very vulnerable to drivers of global change, and also excellent indicators of small changes in resource availability. Recent large-scale experiments demonstrate that rangelands are very susceptible to changes in precipitation regimes, warming, and atmospheric carbon dioxide. Growth of molecular tools in combination with other techniques has allowed scientists to increasingly link microbial community composition and function, thereby shedding light on what was formerly R.D. Evans (*) School of Biological Sciences and WSU Stable Isotope Core Laboratory, Washington State University, Pullman, WA, USA e-mail: [email protected] R.A. Gill Department of Biology and Evolutionary Ecology Laboratory, Brigham Young University, Provo, UT, USA e-mail: [email protected] V.T. Eviner Department of Plant Sciences, University of California, Davis, CA, USA e-mail: [email protected] V. Bailey Biological Sciences Division, Pacific Northwest National Laboratory, Richland, WA, USA e-mail: [email protected]