The impacts of shrub branch shelter and nitrogen addition on soil microbial activity and plant litter decomposition in a desert steppe
Shrub encroachment and nitrogen deposition are major drivers of global grassland - ecosystem degradation. Yet, the interactive impacts of shrub branch shelter and nitrogen deposition on soil microbial activity and litter decomposition in grasslands are not well - understood.In this research conducted in a desert steppe of Northwest China, four levels of branch shelter were set as main plots, with four nitrogen addition treatments as subplots. After two years, soil temperature, soil moisture, pH, nitrogen content, activities of carbon - and nitrogen - cycling related enzymes, and the microbial community structure in the 0 - 5 cm soil layer were measured. Litter decomposition of dominant plants was also determined.Findings showed that nitrogen additions elevated soil inorganic nitrogen content but reduced soil pH. In contrast, branch shelters increased soil moisture without affecting soil pH or nitrogen content. Nitrogen additions inhibited soil nitrogen - cycling related enzyme activities, while branch shelters promoted the activities of most extracellular enzymes tested. Branch shelters and nitrogen additions also had contrasting effects on soil microbial community structure.Overall, shrub shelters mitigated the negative impacts of nitrogen deposition on soil enzyme activity and microbial community structure. Both branch shelter and nitrogen addition promoted litter decomposition. Thus, branch shelter can be a viable strategy for restoring degraded grasslands affected by shrub encroachment and nitrogen deposition in arid and semi - arid regions.