Effects of Different Vegetation Restoration Modes on Soil Microbial Quantity and Biomass in a Degraded Karst Ecosystem in South China

Vegetation restoration projects have been implemented in China's degraded karst ecosystems (rocky desertification areas) for more than 20 years. There is an urgent need to evaluate the impact of different vegetation restoration modes on the ecological environment. The status of the soil environment under different vegetation restoration modes in degraded karst ecosystems was determined in the Guanling-Zhenfeng demonstration area of rocky desertification control in Guizhou, China. The differences in soil microbial quantity; soil microbial biomass carbon (MBC), nitrogen (MBN) and phosphorus (MBP); and soil nutrients were compared among five typical vegetation restoration modes (Hylocereus undatus 'Foo-Lon' (HUF), Lonicera japonica Thunb. (LJT), Zanthoxylum bungeanum Maxim. (ZBM), artificially accelerated forest regeneration (AFR), and hillclosing afforestation (HA)) implemented continuously for 13-15 years. Pearson correlation analysis and redundancy analysis (RDA) were utilized to analyse the environmental factors affecting the soil microbial quantity and biomass under the five vegetation restoration modes. The results showed that the soil organic carbon (SOC), total nitrogen (TN), total phosphorus (TP), calcium (Ca), and ammonium nitrogen contents under HA were significantly higher than those under the other vegetation restoration modes (P < 0.05). There were no significant differences in the soil microbial quantity or biomass among the different vegetation restoration modes, and the other microbial indicators, except MBP, reached their highest values at the HA site. The correlation analysis and RDA showed that TP, TN, vegetation type, and SOC were the main factors affecting the soil microbial quantity and biomass under the 5 vegetation restoration modes and that TP was the limiting factor for vegetation restoration in degraded karst ecosystems. The results of our study provide insights into the selection of appropriate vegetation reconstruction measures and modes for degraded karst ecosystems.