气候变化领域集成服务门户

Drying and rewetting cycles are known to be important for the dynamics of carbon (C), phosphorus (P), and nitrogen (N) in soils. This study reports the short-term responses of these nutrients to consecutive drying and rewetting cycles and how varying soil moisture content affects microbial biomass C and P (MBC and MBP), as well as associated carbon dioxide (CO2) and nitrous oxide (N2O) emissions. The soil was incubated for 14 d during which two successive drying-rewetting episodes were imposed on the soils. Soils subjected to drying (DRW) were rewetted on the seventh day of each drying period to return them to 60% water holding capacity, whilst continually moist samples (M), with soil maintained at 60% water holding capacity, were used as control samples. During the first seven days, the DRW samples showed significant increases in extractable ammonium, total oxidized nitrogen, and bicarbonate extractable P concentrations. Rewetting after the first drying event produced significant increases only in CO2 flux (55.4 mu g C g(-1) d(-1)). The MBC and MBP concentrations fluctuated throughout the incubation in both treatments and only the second drying-rewetting event resulted in a significantly MBC decrease (416.2 and 366.8 mg kg(-1) in M and DRW soils, respectively). The two drying-rewetting events impacted the microbial biomass, but distinguishing the different impacts of microbial versus physical impacts of the perturbation is difficult. However, this study, having a combined approach (C, N, and P), indicates the importance of understanding how soils will react to changing patterns of drying-rewetting under future climate change.