Changes in soil bacterial community characteristics in patches of different vegetation types under different stages of restoration in the desert of northern China.

In desert areas, the process of mobile sandy land changing to semi-fixed sandy land and eventually to fixed sandy land after undergoing vegetation restoration is inevitable. The presence of shrub patches and herb patches is common in this restoration process. No relevant studies have reported the soil bacterial community characteristics of different vegetation-type patches (shrub patches and herb patches) under different stages of restoration. Therefore, we utilized long-established experimental plots to collect soil from 0-20 cm soil layer under shrub patches (dominated by Salix psammophila) and herb patches under different stages of restoration (i.e., mobile sand land, semi-fixed sand land, and fixed sand land), by determining soil physicochemical properties, enzyme activities, and soil bacterial communities. Our results found that soil bacterial α-diversity under different restoration stages showed higher shrub patches than herb patches. The dominant bacterial communities (phyla) in shrub patches and herb patches at different recovery stages were Actinobacteria, Proteobacteria, and Bacteroidota. When the mobile sandy land returned to fixed sandy land, the relative abundance of Actinobacteria and Bacteroidota gradually decreased under shrub patches and herb patches, while the relative abundance of Proteobacteria increased significantly. In addition, herb patches significantly increased the relative abundance of bacteria (genus) relative to shrub patches at different stages of recovery. Soil nutrients, soil fine particles, and soil enzyme activities were significantly higher under shrub patches than under herb patches when fixed sandy land due to differences in life form and architecture between shrub patches and herb patches. Based on this, soil bacterial community composition and diversity under shrub patches were driven by more soil properties during the restoration of sandy land. This study complements the dynamic recovery processes and driving mechanisms of soil bacterial community structure under different vegetation patches in sandy areas, especially in the context of global climate change.

Responses of Soil Bacterial Communities to Nitrogen Deposition and Precipitation Increment Are Closely Linked with Aboveground Community Variation.

It has been predicted that precipitation and atmospheric nitrogen (N) deposition will increase in northern China; yet, ecosystem responses to the interactive effects of water and N remain largely unknown. In particular, responses of belowground microbial community to projected global change and their potential linkages to aboveground macro-organisms are rarely studied. In this study, we examined the responses of soil bacterial diversity and community composition to increased precipitation and multi-level N deposition in a temperate steppe in Inner Mongolia, China, and explored the diversity linkages between aboveground and belowground communities. It was observed that N addition caused the significant decrease in bacterial alpha-diversity and dramatic changes in community composition. In addition, we documented strong correlations of alpha- and beta-diversity between plant and bacterial communities in response to N addition. It was found that N enriched the so-called copiotrophic bacteria, but reduced the oligotrophic groups, primarily by increasing the soil inorganic N content and carbon availability and decreasing soil pH. We still highlighted that increased precipitation tended to alleviate the effects of N on bacterial diversity and dampen the plant-microbe connections induced by N. The counteractive effects of N addition and increased precipitation imply that even though the ecosystem diversity and function are predicted to be negatively affected by N deposition in the coming decades; the combination with increased precipitation may partially offset this detrimental effect.