Impacts of reseeding native grass and a legume on soil microbial community structure in the desert steppe of Ningxia

This study implemented three treatments: reseeded Agropyron mongolicum, Lespedeza potaninii, and a combination of A. mongolicum and L. potaninii, within a desert steppe in Ningxia. A grazed steppe was chosen as the control. Subsequently, the soil microbial community structure and its correlation with soil physicochemical properties were assessed. The results showed that compared to the grazed steppe, the three reseeding treatments did not significantly affect the species composition of the fungal community. However, the relative abundance of the dominant fungal phylum Ascomycota differed. Specifically, in the 0－20 cm soil layer, the relative abundance was significantly lower under the L. potaninii reseeding treatment compared to the mixed reseeding treatment of A. mongolicum and L. potaninii. Additionally, in the 20－40 cm soil layer, the relative abundance was significantly lower compared to both the A. mongolicum reseeding and mixed reseeding treatments (P < 0.05). Pearson correlation analysis revealed a significant positive correlation (P < 0.05) between the relative abundance of Proteobacteria and Ascomycota and soil active organic carbon across all replanting treatments. Moreover, compared to the grazed steppe, reseeding with L. potaninii enhanced both prokaryotic and fungal α-diversities. Prokaryotic α-diversity was negatively correlated with total nitrogen, whereas fungal α-diversity was negatively correlated with carbon fractions. β-diversity analysis indicated that reseeding with A. mongolicum and A. mongolicum + L. potaninii altered soil prokaryotic community structure within the 0－20 cm depth range (P < 0.05), while reseeding with L. potaninii altered soil prokaryotic community structure within the 20－40 cm depth range (P < 0.05). Furthermore, all reseeding treatments altered soil fungal community structure across the entire 0－40 cm depth range (P < 0.05). The RDA model indicated that soil organic carbon and total nitrogen are key factors affecting the structure of both prokaryotic microbial and fungal communities. As evident from the findings presented above, this study underscores that reseeding with native forages could potentially influence ecosystem functions within the desert steppe, particularly impacting carbon and nitrogen cycling through alterations in soil microbial community structure. These tentative changes emphasize the importance of researchers’ vigilance in monitoring and understanding such ecological shifts.