Reduced precipitation neutralizes the positive impact of soil warming on soil microbial community in a temperate oak forest.

Changes in soil microbial community play an irreplaceable role in regulating nutrient cycling that shapes forest ecosystem responses to climate change. However, if the effect of experimental warming on soil microorganisms depends upon soil water availability, which is closely related to soil depth is generally not well decumented. We conducted an in situ simulation experiment in an oak forest to determine the response pattern of soil microbial community to manipulated drought and warming at different soil depths. The responses of soil microbial communities to reduced precipitation and soil warming were highly dependent upon soil depth. Reduced precipitation remarkably elevated top-soil microbial biomass carbon (MBC) and nitrogen (MBN) in the unwarmed plots but no effects occured in the warmed plots. Soil warming showed positive effects on top-soil MBC and MBN under ambient precipitation, whereas negative ones were found under decreased precipitation. Neither reduced precipitation nor soil warming displayed effects on sub-soil MBC and MBN. Reduced precipitation notably increased soil total phospholipid fatty acids (PLFA) as well as that of bacterial and gram-negative bacterial only at top-soil in the unwarmed plots. Soil warming showed positive effects on total PLFA, bacterial PLFA, and gram-negative bacterial PLFA at both top- and sub-soil under ambient precipitation. We found that the interactive effects of climate change on soil microorganisms varied with soil depth, indicating that multilayer soil models should be considered while assessing the relationship between soil and atmosphere carbon exchange. Further research is expected to explore the long-term response of soil microorganisms in soil vertical profiles to climate change.