272 / 2023-10-05 18:43:58

Effects of vegetation restoration on soil microbial community, and the functional groups related to carbon, nitrogen and phosphorus cycles in open-pit mining area of the Loess Plateau, China

land reclamation,vegetation restoration,microbial community,assembly process,functional genes,carbon nitrogen phosphorus cycles

Vegetation restoration is an important indicator of ecosystem health in mining areas. Understanding the impact of vegetation restoration on the characteristics and assembly process of soil microbial community is very important to explore the resilience and self-sustaining mechanism of the restored ecosystem in a mining area. Moreover, the ecology of mining areas in the Loess Plateau is relatively fragile, while the vegetation restoration is closely related to soil microbe-mediated nutrient cycling. This study was designed to clarify the influence and regulatory roles of vegetation restoration on the functional groups related to soil carbon, nitrogen and phosphorus cycles, which are significantly important to rebuilding the ecological resilience and self-sustaining mechanism of mining areas. Therefore, this study uses MiSeq high-throughput sequencing and zero model to detect the composition of soil microbial communities, the characteristics of molecular ecological network, the key flora and its assembly mechanism in the shrubs (BL), coniferous forests

(CF), broad-leaved forests (BF), mixed forests (MF), that have been reclaimed for 18 years in Antaibao open-pit mining dump, and the control plots (CK, undisturbed surrounding poplar forests that have continued to grow for more than 30 years) in Pingshuo mining area, the Loess Plateau. Meanwhile, high-throughput qPCR chip technology, random forest model and structural equation model were used to reveal the changes and mutual feeding mechanism of soil characteristics, enzyme activities, carbon, nitrogen and phosphorus functional groups under different vegetation restoration modes. The results show that: ① The effects of different vegetation restoration types on the bacterial community α-diversity are significant (P < 0.05). Compared with CK, the Sobs and Shannon index of MF and CF have increased by 35.29%, 3.50% and 25.18%, 1.05%, respectively, whereas there is no significant difference in the α-diversity of fungal community among different vegetation restoration types. Actinobacteria, Chloroflexi, Proteobacteria and Acidobacteria dominate in the bacterial community, and the first two dominant phylum are significantly higher than CK, while the latter two are opposite (P < 0.05). Ascomycota and Basidiomycota are the dominant fungi in the fungal community. The former is significantly higher than CK, while the latter is opposite (P < 0.05). ② The stochastic process dominates the construction process of the soil bacterial community. In addition to the MF soil fungal community dominated by deterministic process, other fungal communities are also dominated by a stochastic process. However, no matter which type of vegetation is restored, the dominant role of the randomness process on the assembly of the bacterial community is much higher than that of the fungal community. Moreover, Proteobacteria and Acidobacteria are key taxa of the bacterial network, while Mortierellales, Thelebolales, Chaetothyriales, and Hypocreales are the key taxa of the fungal network. Vegetation restoration affects microbial community diversity, BL, CF, and MF increase the stability of the bacterial network, and MF makes fungal network more complex. The soil bacterial assembly process is dominated by stochastic processes, except for MF, and the fungal assembly process is also dominated by stochastic processes. ③ The different modes of vegetation restoration significantly changed the relative abundances of functional groups related to carbon, nitrogen and phosphorus (P<0.05), whereas the variation tendencies always keep a consistent correspondence. The functional groups related to carbon, nitrogen and phosphorus were significantly positively correlated with soil nitrate nitrogen (P<0.001), but they presented negative correlations with ammonium nitrogen (P<0.01). The functional groups involved in the carbon cycle, nitrification process and organic phosphorus mineralization were significantly positively correlated with available phosphorus (P<0.01). In addition, results of the structural equation model showed that vegetation restoration could directly affect catalase (CAT) and available phosphorus (AP), thereby regulating the carbon, nitrogen and phosphorus cycle. Otherwise, the vegetation restoration could affect soil AP indirectly, thereupon then regulating the abundances of carbon, nitrogen and phosphorus functional groups, together with other soil characteristics, such as nitrate nitrogen or ammonium nitrogen. This study might help deepen the knowledge about soil microbiology mechanism of vegetation restoration, which will furtherly help the ecological restoration of damaged mines in the Loess Plateau.