Soil biogeochemical responses to multiple co-occurring forms of human-induced environmental change

Multiple forms of human-induced environmental change are impacting arid ecosystems. Climate change is increasing temperatures and altering precipitation patterns, and many rapidly-growing urban centers are in arid locations. Nitrogen deposition from air pollution accompanies urban activities in many of these locations. These forms of environmental stressors will certainly impact soil communities and the biogeochemical processes for which they are responsible. However, most studies investigate these multiple environmental change factors independently or sometimes in pairs, but rarely all together as co-occurring forms of change. We examined how the simultaneous manipulation of increasing temperatures, altered precipitation patterns (both pulse size and frequency), nitrogen deposition, and urbanization influenced soil respiration and mineral N pools in the Sonoran Desert. In a laboratory microcosm, we incubated soils collected from an urban vs. exurban site, from plots receiving ~20 yrs of experimental N fertilization vs. control plots. The microcosm soils were incubated at ambient vs. +2 degree C temperatures under a factorial precipitation treatment of decreased frequency and increased pulse size. We measured the response of soil respiration rates and inorganic N pools to these co-occurring forms of environmental change.