Abstract
AbstractDrying 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 µg 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.
Highlights
Soils are exposed to natural drying and rewetting cycles which result in the perturbation of nutrient cycling, mainly resulting from changes in microbial activity (De Nobili et al, 2006; Butterly et al, 2010) and diversity within the microbial community (Fierer et al, 2003; Steenwerth et al, 2005; Gordon et al, 2008; Butterly et al, 2009)
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
Previous studies have shown that the rewetting of dry soil stimulates microbial activity, resulting in increased mineralization of soil organic matter (SOM) (Fierer and Schimel, 2003) and pulses of carbon dioxide (CO2) and nitrous oxide (N2O) emissions along with enhanced macronutrient availability (Franzluebbers et al, 2000; Wu and Brookes, 2005; Butterly et al, 2010, 2011)
Summary
Soils are exposed to natural drying and rewetting cycles which result in the perturbation of nutrient cycling, mainly resulting from changes in microbial activity (De Nobili et al, 2006; Butterly et al, 2010) and diversity within the microbial community (Fierer et al, 2003; Steenwerth et al, 2005; Gordon et al, 2008; Butterly et al, 2009). Fierer and Schimel (2003) observed that drying and rewetting cycles affected soil carbon (C) cycling in the short term by increasing the microbial mineralization of cytoplasmatic solutes accumulated during drying, with a spike in soil respiration after rewetting when microbial communities re-grew in response to available nutrients. During rewetting, those microorganisms that passively equilibrated to the dry conditions are able to rehydrate (Kieft et al, 1987) and are able to multiply rapidly exploiting the increase in available nutrients (Nguyen and Marschner, 2005). Gordon et al (2008) observed that drying and rewetting stress significantly reduced the quantities of MBC, fungal phospholipid fatty acids (PLFAs) and microbial biomass nitrogen in both low and high productivity grassland soils
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