Abstract
Increasing drought globally is a severe threat to fragile desert wetland ecosystem. It is of significance to study the effects of wetland drying on microbial regulation of soil carbon (C) in the desert. In this study, we examined the impacts of wetland drying on microbial biomass, microbial community (bacteria, fungi) and microbial activity [basal microbial respiration, microbial metabolic quotient (qCO2)]. Relationships of microbial properties with biotic factors [litter, soil organic carbon (SOC), total nitrogen (TN), total phosphorus (TP)], abiotic factors (soil moisture, pH and clay content) and biological processes (basal microbial respiration, qCO2) were also developed. Results showed that the drying of wetland led to a decrease of soil microbial biomass carbon (MBC) content, microbial biomass nitrogen (MBN) content and fungi and bacterial abundance, and an increase of the fungi:bacteria ratio. Wetland drying also led to increased soil basal respiration and increased qCO2, which was attributed to lower soil clay content and litter N concentration. The MBC:SOC ratios were higher under drier soil conditions than under virgin wetland, which was attributed to stronger C conserve ability of fungi than bacteria. The wetland drying process exacerbated soil C loss by strengthening heterotrophic respiration; however, the exact effects of soil microbial community structure on microbial C mineralization were not clear in this study and need further research.
Highlights
It is predicted that there will be severe and widespread droughts globally in the 30–90 years resulting from either decreased precipitation or increased evaporation [1,2,3]
Soil microbial biomass carbon (MBC) and microbial biomass nitrogen (MBN) contents decreased consistently, while MBC:soil organic carbon (SOC) ratios increased in the wetland drying process (Figure 2)
The drying of wetland led to a decrease of soil MBC content, MBN content and fungi and bacterial abundance, and an increase of fungi:bacteria ratios
Summary
It is predicted that there will be severe and widespread droughts globally in the 30–90 years resulting from either decreased precipitation or increased evaporation [1,2,3]. These changes are predicted to exacerbate processes leading to land degradation and desertification and a worldwide decrease in soil moisture by 5–15% has been predicted for the 2080–2099 period [2,4]. Soil microorganisms degrade litter and allocate the carbon to microbial biomass, exudate carbon as microbial derived organic matter or release carbon by heterotrophic respiration [11,12].
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