Submitted to: ASA-CSSA-SSSA Annual Meeting Abstracts
Publication Type: Abstract Only
Publication Acceptance Date: 10/16/2011
Publication Date: 10/19/2011
Citation: Bell, C.W., Acosta Martinez, V., Tissue, D., Zak, J. 2011. Understanding Soil Microbial Community Structural and Functional Responses to Climate Change[abstract]. American Society of Agronomy, Crop Science Society of America, Soil Science Society of America Annual Meeting. October 16-19, 2011, San Antonio, TX. Interpretive Summary:
Technical Abstract: Global climate models (GCM) predict increased temperature and precipitation variability across arid regions in North America within the next century, resulting in fewer rain events of greater magnitude. Increased inter-pulse periods (dry days between rain events) along with increased temperature will increase evapotranspiration stress and reduce soil moisture availability. Reductions in soil moisture can lead to declines in soil microbial biomass and diversity, subsequently altering microbial ecosystem processes that facilitate decomposition and nutrient cycling in this region. While many studies have addressed soil-microbial responses to short-term changes in precipitation magnitudes, few efforts have assessed microbial response to long-term shifts in seasonal precipitation. This research examined soil microbial and nutrient properties as affected by GCM predictions of 25% increased seasonal shifts in rainfall over a 7-year period (2002-2008) in a Chihuahuan Desert grassland. We hypothesized that over time, these minor but realistic increases in soil moisture would produce cumulative changes in soil microbial communities (species assemblage and functional attributes). Our results demonstrated clear shifts in microbial community dynamics by the third year of this study. Microbial community structural responses (identified using fatty acid methyl ester (FAME) analysis) revealed increased abundances of saprophytic, arbuscular mycorrhiza, and gram-negative bacteria within plots subjected to 25% seasonal rainfall additions when compared to ambient (control) conditions. Microbial function (enzyme activity) also demonstrated increases; as ß-Glucosidase and phosphodiesterase activity (involved in cellulose degradation and phosphorus mineralization, respectively) was elevated in plots subjected to minor shifts in seasonal precipitation during this same period. Our findings suggest that microbial community structure and function is linked to climate. Furthermore, different microbial community-assemblages occur as a result of varying seasonal precipitation scenarios; but provide similar ecosystem functional contributions at varying degrees. Consequently, the ability of soil microbial communities to maintain functional resilience may be reduced in this desert grassland ecosystem.