Articles | Volume 14, issue 3
Research article
10 Feb 2017
Research article |  | 10 Feb 2017

Interactions among temperature, moisture, and oxygen concentrations in controlling decomposition rates in a boreal forest soil

Carlos A. Sierra, Saadatullah Malghani, and Henry W. Loescher

Abstract. Determining environmental controls on soil organic matter decomposition is of importance for developing models that predict the effects of environmental change on global soil carbon stocks. There is uncertainty about the environmental controls on decomposition rates at temperature and moisture extremes, particularly at high water content levels and high temperatures. It is uncertain whether observed declines in decomposition rates at high temperatures are due to declines in the heat capacity of extracellular enzymes as predicted by thermodynamic theory, or due to simultaneous declines in soil moisture. It is also uncertain whether oxygen limits decomposition rates at high water contents. Here we present the results of a full factorial experiment using organic soils from a boreal forest incubated at high temperatures (25 and 35 °C), a wide range of water-filled pore space (WFPS; 15, 30, 60, 90 %), and contrasting oxygen concentrations (1 and 20 %). We found support for the hypothesis that decomposition rates are high at high temperatures, provided that enough moisture and oxygen are available for decomposition. Furthermore, we found that decomposition rates are mostly limited by oxygen concentrations at high moisture levels; even at 90 % WFPS, decomposition proceeded at high rates in the presence of oxygen. Our results suggest an important degree of interaction among temperature, moisture, and oxygen in determining decomposition rates at the soil core scale.

Short summary
Temperature, moisture, and oxygen are interacting variables that control the rates of soil organic matter decomposition. With a well-replicated experiment, the authors show that decomposition rates in a boreal forest soil are not limited at high temperatures in the presence of enough water and oxygen. Similarly, at high humidity, oxygen is the main limiting factor for decomposition. The authors conclude that interactions among the three variables are the main determinants of decomposition rates.
Final-revised paper