Soil microbial community composition and respiration along an experimental precipitation gradient in a semiarid steppe.

Cancan Zhao,Lin Jiang,Chengde Yu,Shiqiang Wan,Yuan Miao,Lili Zhu,Dafeng Hui,Feng Wang

doi:10.1038/srep24317

Abstract

As a primary limiting factor in arid and semiarid regions, precipitation strongly influences soil microbial properties. However, the patterns and mechanisms of soil microbial responses to precipitation have not been well documented. In this study, changes in soil microorganisms along an experimental precipitation gradient with seven levels of precipitation manipulation (i.e., ambient precipitation as a control, and ±20%, ±40%, and ±60% of ambient precipitation) were explored in a semiarid temperate steppe in northern China. Soil microbial biomass carbon and respiration as well as the ratio of fungal to bacterial biomass varied along the experimental precipitation gradient and peaked under the +40% precipitation treatment. The shifts in microbial community composition could be largely attributable to the changes in soil water and nutrient availability. The metabolic quotient increased (indicating reduced carbon use efficiency) with increasing precipitation due to the leaching of dissolved organic carbon. The relative contributions of microbial respiration to soil and ecosystem respiration increased with increasing precipitation, suggesting that heterotrophic respiration will be more sensitive than autotrophic respiration if precipitation increases in the temperate steppe as predicted under future climate-change scenarios.

Highlights

Given the species- or functional group-specific sensitivity to water availability, shifts in microbial composition could lead to changes in microbial-associated processes and consequent changes in ecosystem functions
Soil temperature (ST) declined along the precipitation gradient and reached the minimum of 19.6 and 18.6 °C under the + 40% precipitation treatment in 2011 and 2012, respectively (Fig. 1)
In the present study, decreased precipitation increased the relative mole percentage of fungal phospholipid fatty acids (PLFAs) and fungal to bacterial PLFAs (F/B) PLFAs, suggesting that the fungi in these communities are more drought-tolerant than the bacteria (Table 1; Fig. 3)

Summary

Introduction

Given the species- or functional group-specific sensitivity to water availability, shifts in microbial composition could lead to changes in microbial-associated processes and consequent changes in ecosystem functions. Accurate determination of heterotrophic respiration responses to precipitation variation could provide parameter estimates required for model simulations concerning future atmospheric CO2 concentrations[28]. Arid and semiarid steppes are water-limited and sensitive to altered precipitation regimes[29]. To investigate precipitation effects on microbial community and respiration, a field experiment with seven levels of precipitation manipulation (i.e., ambient precipitation as a control, and ± 20%, ± 40%, and ± 60% of ambient precipitation) that cover the natural range in precipitation variation has been conducted in a semiarid temperate steppe in northern China since 2010. 2) Microbial respiration could be enhanced by increasing precipitation. This positive relationship may not be persistent when water no more limit. This positive relationship may not be persistent when water no more limit. 3) Shifts in microbial composition could lead to changes in microbial respiration

Methods

Results

Conclusion