Microbes require a relatively long time to recover in natural succession restoration of degraded grassland ecosystems

Using natural succession to restore degraded grassland is mainly achieved by self-adjusting the structure and relationship of the internal components of grassland ecosystems. Microorganisms play an important role in the restoration of grassland ecosystems; however, there is no systematic research summary on how microbial communities respond to natural restoration succession in degraded grasslands. In this study, related research results in recent years were summarized and analyzed using meta-analysis. Results showed that soil microbes displayed no significant changes at the early stage (≤5 years) of natural restoration succession, but significantly increased at the following stage (6–10 years) of restoration succession, before decreasing with the continuation of succession. Changes in microbial activity mainly occurred in the 0–20 cm soil depth layer. Numbers of bacteria, fungi, and actinomycetes significantly increased at the six to 10 year stage of restoration succession. When restoration succession ceased after 10 years, most microorganisms began to decrease. During natural restoration succession, the diversity of fungi and bacteroidetes increased, while chloroflexi diversity decreased. These results indicated that the optimal period for the natural restoration succession of degraded grassland was approximately 10 years to ensure that the microbes of the grassland system returned to relatively high levels.