SENSITIVITY OF MICROBIAL PROCESSING OF SOIL CARBON TO SOIL MOISTURE IN DIFFERENTLY-TEXTURED SOILS

Soil temperature and moisture are two key factors driving microbial respiration of soil carbon (C). Compared to the huge number of studies on temperature effects, relatively few experimental studies were focused on moisture sensitivity of soil microbial and C dynamics. The aim of this study was (i) to examine how soil moisture treatments in different soil textural classes influence heterotrophic respiration and (ii) to describe the dependence of microbial and extracellular enzyme activities on soil moisture in differently-textured soils. Soil samples of two distinct textures − sandy and loamy − were collected from mixed forests at a depth of 15 cm from locations in Georgia and Missouri. Five moisture levels were set up for each soil type; air dried, 25% water holding capacity (WHC), 50% WHC, 100% WHC and 100% water filled pore space. After pre-incubating for 7 days, soils were incubated aerobically in mason jars for a period of 90 days at room temperature in the dark. Soil respiration was measured from these microcosms on a weekly basis. Destructive sampling was conducted at different time points (day 1, day 5, day 15, day 30, day 60 and day 90) to determine microbial biomass C, dissolved organic C, and hydrolytic enzyme activities. Data analysis is currently underway and the results will be presented at the conference. This study will shed light on how soil moisture and soil texture interactively control the microbial processing of soil organic C.