Exploring slope spatial heterogeneity by nitrogen transfer and arbuscular mycorrhizal community

Vegetated slope is an important ecosystem to protect the landslide and soil erosion. Although the heterogeneity of slope has received increasing attention, the understanding of soil microbial community and ecological process in the slope soil still remains limited. The purpose of this study was to figure out the slope spatial heterogeneity through measuring dynamics of nitrogen (N) diffusion, composition, and assembly patterns of arbuscular mycorrhizal fungi (AMF) community. In this study, stable isotope tracer (15N) was used to study the dynamics of the soil N diffusion in five slope ecosystems, and the soil was sampled on the 7th and 40th day after tracer addition at a small scale. At the same time, the community structure of AMF in slope soil was analyzed by Illumina MiSeq sequencing. The δ15N of downslope and upslope soil enriched gradually away the labeled plot with the treatment time. It indicated that N could be conveyed inversely from the labeled plot to its upslope. Among the five different plant communities, the amount of N isotope transferred to the upslope was significantly higher in Setaria viridis slope with the extension of time, and the difference in the N amount of transfer was accompanied by the fact that the proportion of Glomus of this slope was much higher than that of other slopes. Redundancy analysis (RDA) showed that the AMF community structure in the Setaria viridis slope soils was correlated with the pH. The composition of AMF community upslope and downslope was quite different. Mantel analysis showed that the difference in AMF community structure was poorly affected by plant communities. Our work highlighted an important role of neutral forces in the assembly of AMF community in the slope ecosystem. Our results revealed that N could be conveyed upward in the slope ecosystems. The AMF community in the five slopes seemed to be more randomly phylogenetically assembled. It was speculated that AMF community may play a major role in the transfer of N upward. Future works should test those conjectures and determine how the phylogenetic variation in AMF affects the N diffusion.