Functional contributions of biological soil crust microorganisms to nitrogen and carbon cycling across diverse habitats on the Qinghai–Tibet Plateau

Abstract

The Qinghai–Tibet Plateau (QTP) is highly sensitive to global climate change and plays a pivotal role in global nitrogen and carbon cycles. However, the mechanisms by which biological soil crusts (BSCs) in diverse QTP habitats participate in nitrogen and carbon cycling, as well as the influence of habitat differences on BSC functional dynamics, remain poorly understood. This study investigates the functional contributions of BSC microorganisms across various habitats on the QTP. As ecosystems grow more stable and complex, nitrogen fixation, ammonia assimilation, and mineralization in the BSC nitrogen cycle gradually decrease, while nitrification and denitrification increase. These nitrogen cycling processes are primarily driven by factors such as total nitrogen (TN), nitrate (NO₃⁻), and pH. In the carbon cycling process, the contribution of BSC microorganisms in alpine deserts and Gobi habitats was significantly greater than in shrub meadows and forest grasslands. In alpine deserts and Gobi habitats, organic carbon shifts from recalcitrant to labile forms to regulate soil nutrients, whereas BSCs in shrub meadows and forest grasslands are more efficient at storing stable organic carbon to enhance carbon storage. Compared to the nitrogen cycle, the carbon cycle is more strongly influenced by the plateau environment. Furthermore, network analysis revealed a strong positive correlation between the nitrogen and carbon cycles. These findings provide valuable scientific insights into the functional roles of BSC microorganisms under future climate change scenarios.