Responses Of Cropland Soil Microbial Community To Climate Changes Revealed By Metagenomics Approaches

Anthropogenic increases in the concentrations of greenhouse gases, including CO2, CH4, and N2O, have contributed substantially to the rise of global surface temperature, alteration of precipitation pattern, and frequency of extreme weather events. These climate changes would impose stresses on the habitats of soil microbial community and aboveground plants, resulting in the disorders of ecosystem functions. Therefore, we selected three typical cropland soil, namely, black soil in Hailun, Heilongjiang (cold temperate climate zone), Chao soil in Fengqiu, Henan (warm temperate climate zone), and red soil in Yingtan, Jiangxi (subtropical climate zone), along a climate gradient in East China, and then carried out a soil reciprocal transplant experiment between the three climate regimes to simulate climate changes.By transplanting red soil from Yingtan to Fengqiu and Hailun to simulate climate cooling, we found that soil nitrogen components and microbial community structure revealed by GeoChip3.0were altered after an adaptation period of four years. However, the effects of soil transplant on microbial communities were dampened by maize cropping. Further statistical analyses unveiled that climate conditions, soil geochemistry and aboveground biomass were all significantly correlated with microbial functional structures. In addition, average abundances of amoA-AOA (ammonia-oxidizing archaea) and amoA-AOB (ammonia-oxidizing bacteria) genes were positively and significantly correlated with soil nitrification capacity, hence both AOA and AOB contributed to the soil functional process of nitrification in cropland.We proceeded further to analyze three soil types at multiple years. By using advanced metagenomic approaches (e.g. Illumina sequencing and GeoChip4.6), we found that microbial community diversity, taxonomic and functional structures in the three types of cropland soil (including black soil, Chao soil and red soil) were significantly altered. Moreover, the alterations in microbial community were positively and significantly correlated with environmental attributes. Particularly, soil organic matter played a critical role in shaping microbial community structures, which resulted in corresponding variations of carbon cycling genes in the three types of cropland soil.When transplanted into different climate regimes, microbial community taxonomic and functional structures in the three types of soil were significantly changed. And microbial taxonomic structure was significantly correlated with microbial functional structure in black and chao soil. In addition, environmental variables, especially ammonium, played critical roles in shaping microbial community structures. And most of gene abundances involved in nitrogen cycling were decreased, implying that soil nitrogen cycling was dampened when confronted with climate changes.In summary, soil microbial communities in cropland were sensitive to climate changes, both microbial community compositions and functional genes were significantly changed. And the changes in microbial communities were not only closely related with climate conditions, but also with soil nutrient cycling. Particularly, ammonium was firstly found by metagenomics approaches as one of the most sensitive factors influencing microbial communities.