SUMMER MOISTURE EVENTS AFFECT SOIL PROCESSES IN MULTIPLE ARID ECOSYSTEMS IN NEW MEXICO VIA A TANGLED-WEB OF MECHANISMS

Global change processes (GCC) and ecosystem conversions are significantly altering key ecosystem processes in multiple arid ecosystems. Additionally, GCC related phenomena are likely influencing the functional behaviors of established soil microbial communities, and the magnitude at which they affect multiple, fundamental soil processes. These processes likely include, soil organic matter turnover, soil nutrient cycling and soil carbon storage. Therefore to assess the aggregate influences of woody plant encroachment, fire, and drought on soil microbial community activity rates and their overall functionality, we collected soil samples from beneath plant canopies, and from adjacent bare soils. We collected dry season, and wet season samples, in both 2012 and 2013. We sampled from both burned and unburned grasslands, a shrub site, a shrub/grass ecotone, and a juniper savannah. We analyzed eleven soil physicochemical properties, none of which showed any significant trends across our different sampling locations, fungal biomass, and the activities of alanine aminopeptidase, alkaline phosphatase, β-D-glucosidase, and β-N-acetyl glucosaminidase (NAGase). Our one-way ANOVA results frequently showed that enzyme activity patterns were largely dependent on plant functional type, e.g. grass vs. shrub, sampling location, and sampling time. However, our PCA results suggested that the most influential variable on any single hydrolytic extracellular enzyme, was its interactions with the three other enzymes. In most cases all of these interactions lead to increases in enzyme activity rates, while interactions with soil nutrients led to decreased activity rates. These results suggest that any one factor that effectively changes the activity of one extra cellular enzyme, can thus significantly affect the overall functional behavior of root associated microorganisms. Further, the magnitude of these interactions can vary from one growing season to another.