Effects of simulated rainfall events on soil carbon transformation

Abstract

The storage of carbon (C) in soils can be influenced by rainfall patterns that affect both inputs from plant productivity and losses through soil respiration. The aim of this study was to investigate the effect of rainfall on the soil C transformation. A laboratory experiment was conducted using soil columns with different treatments, including a control with constant water content, and rainfall treatments with applications of 3, 6, and 10 simulated rainfall events during an experimental period of 31 days. Results showed that pulses of soil respiration rates occurred after the first 3 rainfall events, associated with soil water content and CO2 concentration pulses in the soil profile, while subsequent rainfall events did not result in similar increases in CO2 concentrations and respiration rates. Relative to the control treatment, the treatments with low (3 rainfall events) and moderate (6 rainfall events) amounts of total water applied resulted in 181% and 72% increases, respectively, in cumulative CO2 emission. In contrast, the high frequency rainfall treatment with the greatest amount of water resulted in a 40% reduction in cumulative CO2 emission. Soil microbial biomass C slightly increased under treatments with low and moderate rainfall treatments, but decreased under the treatment with 10 rainfall events. The results indicate that rainfall events with a high frequency and increased amount of water, and associated saturation of soils, can significantly reduce soil C losses during the wet season. The rainfall frequency and amount are of importance in controlling soil C emissions and should be incorporated into models of soil C dynamics.