Biological soil crusts enhance nutrient availability and potential soil functions in waste dump soils

Abstract

Background

Open-pit coal mine waste dumps are typical degraded soil ecosystems caused by human activities. Biological soil crusts (BSCs) are crucial surface covers that promote plant growth and restore ecological balance, particularly in extreme or nutrient-poor environments. However, the functional roles of BSCs and their associated microbial communities in soil restoration remain poorly understood.

Methods

To address this gap, we investigated the Heidaigou open-pit coal mine waste dump, using amplicon sequencing and quantitative microbial element cycling (QMEC) to analyze six developmental stages of native waste dump soil and BSCs.

Results

BSCs improved soil pH and promoted microbial diversity and richness. Key microbial taxa, dominated by Aridibacter, Microvirga, and others, were closely linked to the ecological functions of BSCs. BSC development modulated functional genes in biogeochemical cycles, with genes involved in carbon fixation being more abundant than those associated with carbon degradation, while genes mediating organic phosphorus mineralization were more abundant than those related to inorganic phosphorus solubilization. Null model analysis showed that bacterial communities shifted progressively from deterministic to stochastic assembly processes during succession, while fungal communities were predominantly governed by stochastic processes.

Conclusions

BSCs enhanced the availability of soil nutrients more significantly than the total nutrient content, simultaneously improving the soil functional potential. We identified key microbial taxa associated with the functional roles of BSCs. This study advances our understanding of primary succession in degraded ecosystems and provides valuable insights for developing and optimizing ecological restoration strategies in waste dumps and similar environments.