Abstract:

Aims: The dynamic changes of soil organic carbon pools are critical for evaluating the functional restoration of severely degraded ecosystems in mining areas, among which labile organic carbon is a vital aspect of soil carbon processes and functional recovery during the early restoration stage. This study aims to reveal the seasonal evolution mechanisms of soil labile carbon components during the early stage of vegetation reconstruction. 

Method: Based on a vegetation reconstruction experiment in the Baiyinhua mining area of West Ujimqin Banner, Nei Mongol, we measured soil physicochemical factors, dissolved organic carbon (DOC), microbial biomass carbon (MBC), and microbial community characteristics under different plant diversity configurations at key phenological stages (May, July, and August). 

Results: (1) Soil DOC and MBC contents exhibited significant seasonal fluctuations, and the impact of plant diversity on both variables differed significantly across seasons. In May, DOC showed a decreasing trend with increased plant diversity; in August, DOC significantly increased while MBC significantly decreased with higher plant diversity. (2) Fungal community characteristics and succession exhibited strong seasonal fluctuations. In August, both fungal diversity and r-strategy fungal richness significantly increased with increasing plant diversity. Further analysis revealed that fungal community composition is one of the important biological factors regulating DOC and MBC. During the early stages of vegetation reconstruction, high-diversity communities do not merely rely on increased biomass; they likely promote the growth of r-strategy fungi by enriching rhizospheric carbon inputs. Additionally, dry-wet cycles caused by August rainfall, coupled with nutrient competition, jointly resulted in the short-term depletion of MBC. 

Conclusions: This study reveals the micro-ecological evolution patterns during early vegetation restoration, providing scientific support for ecological reconstruction in mining areas. For ecological restoration in semi-arid mining areas, we recommend: promoting multi-species mixed sowing in community configurations to enhance carbon cycling; implementing surface moisture conservation during dry periods to reduce microbial carbon loss; and timely topdressing with available phosphorus fertilizer during the peak growth season to alleviate nutrient competition, thereby promoting the synergistic restoration of above-ground and below-ground processes in degraded mining ecosystems.

Key words: open-pit mine, vegetation restoration, plant diversity, soil microorganisms, seasonal dynamics, soil labile organic carbon, r-strategy/K-strategy