Aggregate sizes regulate the microbial community patterns in sandy soil profile

Soil microorganisms play a key role in the function of soil ecosystem,yet our knowledge about how microbial communities respond to the typically sandy soil environmental properties along the soil profile is still insufficient.We investigated the soil microbial community patterns from top(0–20 cm)to clay-layer(>80 cm)of the typical sandy soils in three regions in China with different levels of precipitation,including Lishu County in Jilin Province(LS),Langfang City in Hebei Province(LF)and Zhengzhou City in Henan Province(ZZ).Our findings showed that small-size aggregates(<0.5 mm)rather than large ones(³0.5 mm)dominated the soil profile.The relative abundances of Actinobacteria,Crenarchaeota and Firmicutes were highly related to aggregate proportions of the deep clay-layer soil.The network analysis revealed the distinct community patterns among modules,evidencing niche differentiation along the soil profile.The keystone species OTU_11292 was observed having migrated clearly into the other module of the clay-layer soil.Different roles of the OTU_30(belonging to Gemmatimonadetes)in soil processes might partly explain the different microbial distribution between top-and clay-layer soils.These findings provided new insights into the candidate mechanisms of microbial diversity maintenance and community patterning of sandy soils,which were necessary for better understanding of ecological rules guiding long-term agricultural practice.

Different agricultural practices specify bacterial community compositions in the soil rhizosphere and root zone

We are only beginning to understand the influence of agricultural practices,together with soil properties and geographic factors,affect bacterial communities and their influence on the soil processes.Here,we quantify how typical agro-practices,i.e.,no-tillage,ridge tillage,continuous corn cropping,and crop rotation with corn and bean,and the corresponding soil physicochemical characteristics affect bacterial diversity and community compositions of the rhizosphere and root zone soils.Results show that species richness in the rhizosphere was significantly higher than that in the root zone soils(p<0.05),typically with more abundant Crenarchaeota and Firmicutes populations that are active members for C and N cycling.Specifically,crop rotation compared to other agro-practices was able to mediate soil pH value and the available P and thereby control the bacterial diversity pattern in the rhizosphere(p<0.05),while tillage practices regulated the relative abundance of bacterial populations in root zone soils by varying the soil available N(p<0.05).Analysis of biomarker patterns suggests that the observed differences in bacterial functional capabilities(e.g.,nutrient cycling)are strongly related to the physicochemical properties of surrounding soils.Our results highlight the importance of soil-plant interaction in shaping soil bacterial community structure typically in the rhizosphere and root zone soils and also illustrates the challenges in linking soil ecosystem function to microbial processes.