Temperature and Moisture Effects on Microbial Biomass and Soil Organic Matter Mineralization
- Denis Curtin *a,
- Michael H. Bearea and
- Guillermo Hernandez-Ramireza
Concern over climate change has stimulated interest in the temperature and moisture dependence of soil organic matter decomposition. In particular, there has been intense debate in relation to the factors that determine the temperature dependence of C mineralization. We examined temperature and moisture responses of C and N mineralization in an 85-d laboratory incubation (factorial combination of four temperatures [5, 12, 18, 25°C] and five moisture treatments [matric potential from −5 to −1200 kPa]) using three agriculturally important New Zealand soils (soils with a history of pasture, arable, or vegetable cropping). Mineralization was linearly related to gravimetric moisture content, except in the high-C pasture soil where O2 supply apparently limited mineralization at high (25°C) temperature–moisture combinations. Temperature responses were adequately described by a Q10 function (Q10 values for C mineralization ranged 1.9–2.8). The pool of mineralizable C, estimated using a first-order kinetic model, increased as temperature and moisture increased, whereas the rate constant did not show a consistent trend with either temperature or moisture. Part of the C mineralized during the incubation was from the microbial biomass (post-incubation biomass C decreased by an average of 0.22–0.31 mg kg−1 for each 1 mg kg−1 CO2–C evolved). Microbial biomass C (MBC) was particularly sensitive to temperature (post-incubation biomass C decreased 18–35% between 5–25°C). The decline in MBC between 5 and 12°C represented an average of 40% of the C mineralization increase in that temperature interval. Between 18 and 25°C, the decline in MBC was equivalent to only 20% (on average) of the C mineralized in that temperature interval. High Q10 values reported in laboratory incubations at low temperature may be partly due to mineralization of microbial C.Please view the pdf by using the Full Text (PDF) link under 'View' to the left.
Copyright © 2012. . Copyright © by the Soil Science Society of America, Inc.