No abstract

Microbes, especially abundant microbes in bulk soils, form multiple ecosystem functions, which is relatively well studied. However, the role of rhizosphere microbes, especially rhizosphere rare taxa vs. rhizosphere abundant taxa in regulating the element circling, multifunctionality, aboveground net primary productivity (ANPP) and the trade-offs of multiple functions remains largely unknown. Here, we compared the multiple ecosystem functions, the structure and function of rhizosphere soil bacterial and fungal subcommunities (locally rare, locally abundant, regionally rare, regionally abundant, and entire), and the role of subcommunities in the Zea mays and Sophora davidii sole and Z. mays/S. davidii intercropping ecosystems in subtropical China. Results showed that intercropping altered multiple ecosystem functions individually and simultaneously. Intercropped Z. mays significantly decreased the trade-off intensity compared to sole Z. mays, the trade-off intensity under intercropped S. davidii was significantly higher than under intercropped Z. mays. The beta diversities of bacterial and fungal communities, and fungal functions in each subcommunity significantly differed among groups. Network analysis showed intercropping increased the complexity and positive links of rare bacteria in Z. mays rhizosphere, but decreased the complexity and positive links of rare bacteria in S. davidii rhizosphere and the complexity and positive links of fungi in both intercropped plants rhizosphere. Mantel test showed significant changes in species of locally rare bacteria were most strongly related to nitrogen-cycling multifunctionality, ANPP and trade-offs intensity, significant changes in species of locally rare fungus were most strongly related to carbon-cycling multifunctionality, phosphorus-cycling multifunctionality, and average ecosystem multifunctionality. This research highlights the potential and role of rare rhizosphere microorganisms in predicting and regulating system functions, productivity, and trade-offs.

In this study, field experiments were used to set three cropping patterns: Sophora davidii Skeels monocropping pattern, Pennisetum sinese Roxb monocropping pattern, S. davidii and P. sinese intercropping pattern to explore the effect of different cropping patterns on soil nutrients and fertility. The results showed that the soil moisture content under different cropping patterns in the 0-30cm soil layer was as follows: S. davidii and P. sinese intercropping>P. sinese monocropping>S. davidii monocropping, and there were significant differences between different cropping patterns in the same soil depth (P<0.05); soil pH increased gradually with the increasing depth in soil, and the difference between different cropping patterns in the same soil depth was significant (P<0.05); S. davidii and P. sinese intercropping 0-10 cm soil layer of organic matter, total nitrogen, total phosphorus, available nitrogen and available phosphorus were significantly higher than that of S. davidii and P. sinese monocropping (P<0.05); In the 0-20cm soil layer, the ammonium nitrogen in P sinese monocropping pattern was significantly higher than that in S. davidii monocropping and S. davidii and P. sinese intercropping, while in the 20-30 cm soil layer, intercropping were significantly higher than that in the monocropping (P <0.05); in the 0-30cm soil layer, S. davidii monocropping pattern was significantly higher than P. sinese monocropping and S. davidii and P. sinese intercropping (P <0.05) (except for that of the P sinese monocropping 10-20 cm). The quality of soil integrated fertility index (FQI) showed that the rank of FQI value in the 0-30 cm soil layer was as follows: S. davidii and P. sinese intercropping>S. davidii monocropping>P. sinese monocropping. These fingdings suggest that the S. davidii and P. sinese intercropping could effectively improved 0-30 cm soil comprehensive fertility.