ARS | Publication request: Soil microbial communities and enzyme activities in soils during historically extreme drought conditions in the USA

Submitted to: Eurosoil Congress
Publication Type: Abstract Only
Publication Acceptance Date: July 12, 2012
Publication Date: N/A

Technical Abstract: The Southern High Plains region of Texas experienced a significant reduction in 2011 crop production due a record drought as it experienced the hottest summer since 1911 (> 48 days of temperatures above 37.7oC and only 37.8 mm precipitation). Soil microbial communities and their associated enzymatic capacity are key drivers in soil ecosystem functioning, however, little is known about the effects of extreme weather on the microbial composition and functional capacity of soil. Therefore, we sampled a sandy soil (65% of sand) and a clay loam (38% of clay,) at 0-10 cm under a management history of monoculture (continuous cotton) or rotation (cotton-sorghum). Pyrosequencing was utilized to characterize bacterial and fungal diversity and enzyme activities important for C, N, P and S cycling were determined as indicators of biogeochemical cycling. Distance-based Redundancy Analysis (dbRDA) of pyrosequencing data demonstrated distinct microbial communities according to rotation and monoculture management history, regardless of the soil type. Thus, the microbiome continued to be a fingerprint of management despite extreme drought conditions. Enzyme activities were higher (>1.5X) compared to previous samplings (except for arylsulfatase and ß-glucosaminidase), indicating that soil colloids were essential for protecting the extracellular enzymes that can maintain the metabolic functioning of soil. High functional redundancy may explain the ability of these systems to resist short-term extreme drought conditions. However, global climate predictions of extended high temperatures and heavy precipitation events, may result in adverse effects on soil quality due to depletion of soil organic matter reserves and reduced ecosystem resistance and resiliency.