Soil microbial communities' contributions to soil ecosystem multifunctionality in the natural restoration of abandoned metal mines.

On a global scale, the restoration of metal mine ecosystem functions is urgently required, and soil microorganisms play an important role in this process. Conventional studies frequently focused on the relationship between individual functions and their drivers; however, ecosystem functions are multidimensional, and considering any given function in isolation ignores the trade-offs and interconnectedness between functions, which complicates obtaining a comprehensive understanding of ecosystem functions. To elucidate the relationships between soil microorganisms and the ecosystem multifunctionality (EMF) of metal mines, this study investigated natural restoration of metal mines, evaluated the EMF, and used high-throughput sequencing to explore the bacterial and fungal communities as well as their influence on EMF. Bacterial community diversity and composition were more sensitive to mine restoration than fungal community. Bacterial diversity exhibited redundancy in improving N-P-K-S multifunctionality; however, rare bacterial taxa including Dependentiae, Spirochaetes, and WPS-2 were important for metal multifunctionality. Although no clear relationship between fungal diversity and EMF was observed, the abundance of Glomeromycota had a significant effect on the three EMF categories (N-P-K-S, carbon, and metal multifunctionality). Previous studies confirmed a pronounced positive association between microbial diversity and multifunctionality; however, the relationship between microbial diversity and multifunctionality differs among functions' categories. In contrast, the presence of critical microbial taxa exerted stronger effects on mine multifunctionality.

Tillage activates iron to prevent soil organic carbon loss following forest conversion to cornfields in tropical acidic red soils.

Previous studies have shown that deforestation and planting of corn resulted in the loss of soil organic carbon (SOC). However, this is not inevitable in regions with acidic red soil. We selected six cornfields that have been planted for 34 years and adjacent forest plots in southwest China. Using a structural equation model, we identified the SOC contents and 42 soil environmental factors in 11 soil layers that are conducive to SOC storage, and evaluated their relative weights hierarchically (0-40, 40-100, and 100-140 cm). Our results surprisingly indicated that after forest had been converted into cornfield, the SOC density did not change in any layer. In acidic red soil, reactive iron (Feo), soil water content, nitrogen, and pH were the main soil environmental factors that affected the storage of SOC. In the 0-40 cm soil layer, compared to forests, the contribution of Feo in cornfields increased significantly (by 11.65%), due to farming promoting the activation of iron, while the contribution of nitrogen decreased significantly (by 9.65%). In the 100-140 cm soil layer, the contribution of soil environmental factors was similar to that in the forest system, but the pH in cornfields increasing significantly (by 21.5%) may result from the leaching of hydrogen ions. Although the cultivation of cornfields caused a loss of nitrogen in the 0-40 cm soil layer, the increase in Feo promoted combination of iron and soil organic carbon, avoiding the soil layer from SOC loss.