Effects of plant restoration on soil microbial biomass in an arid desert in northern China

•Plant restoration increases soil microbial biomass in an arid desert ecosystem.•Microbial biomass increases in stabilized chronosequence soils.•Effect of plant restoration on microbial biomass is independent of vegetation cover in arid regions.

Soil microbial biomass acts as both a source and sink of organic carbon and available nutrients, consequently affecting plant growth and production. However, our understanding regarding the effects of plant restoration practices on the patterns of soil microbial biomass remains limited. In this study, we established a 54-year chronosequence comprising moving sand dunes and adjacent sites that had been stabilized through different periods (10, 20, 29, 46, and 54 years) of plant restoration in the southeastern fringe of the Tengger Desert, China. Microbial biomass carbon (MBC), microbial biomass nitrogen (MBN), and their relationship with soil physicochemical properties were analyzed. The results showed that plant restoration significantly increased MBC and MBN in the arid desert. In all stabilized sites, MBC and MBN decreased with increasing soil depth, while they increased along the chronosequence with decreasing plant cover and successional biological soil crusts. MBC and MBN in moving dunes remained lower than those in stabilized sites and slightly increased from topsoil to subsoil. Both MBC and MBN were positively correlated with silt and clay contents, soil organic carbon (SOC), total nitrogen (TN), and MBC/SOC and MBN/TN ratios, whereas they were negatively correlated with sand content. Higher MBC and MBC/SOC were found in the later successional stages, suggesting a great potential for carbon sequestration and higher nutrient turnover for stand biomass. This study indicated that plant restoration plays an important part in the recovery of the biological functioning of soil in an arid desert.