Soil carbon metabolizing microorganisms affect the storage and stability of carbon pool in degraded alpine meadows

The carbon pool of alpine meadows exerts an important impact on global climate change. Soil carbon metabolizing microorganisms play a crucial role in the storage and stability of carbon pools in ecosystems. However, the role and mechanism of soil carbon metabolizing microorganisms in alpine meadows’ carbon pools are not yet clearly understood. This study aims to fill this knowledge gap by selecting non-degraded alpine meadows (ND), slightly degraded alpine meadows (LD), moderately degraded alpine meadows (MD), and heavily degraded alpine meadows (HD) as the research objects. The response of soil carbon metabolizing microorganisms to meadow degradation and their impact on meadow carbon pools were analyzed via studying the carbon storage and the functional genes of carbon metabolism-related microorganisms (pmoA, cbbL, mcrA, chiA) in the four types of alpine meadow ecosystems. The results showed that the carbon storage in the MD and HD ecosystems decreased by 23.9 % and 32.9 %, respectively (P < 0.05), in comparison with ND. With the continuous degradation of alpine meadows, the α diversity of methanotrophs and chitinase-producing microorganisms gradually decreased, while the α diversity of soil carbon-fixing microbes and methanogens communities increased. Co-occurrence network analysis showed that two major methanotrophs modules (pmoA_Mod2,4), one major soil carbon-fixing microbe module (cbbL_Mod5) and two major chitinase-producing microorganism modules (chiA_Mod1,4) were significantly affected by meadow degradation. Due to changes in the β diversity of the soil carbon-fixing microorganism communities, and an increase in the α diversity of methanogens communities, the degradation of alpine meadows decreased the carbon sequestration capacity of the ecosystem, increased the decomposition ability, and ultimately reduced carbon storage in the meadow ecosystems. Additionally, the relative abundance of the chitinase-producing microorganism network module (chiA_Mod1) which primarily comprises genera capable of antibiotic production such as Janthinobacterium, Amycolatopsis methanolica, and Streptomyces, also significantly decreased due to meadow degradation (P < 0.05), thereby affecting carbon cycling in the ecosystems. This study reveals how four carbon-metabolizing microbial communities respond to alpine meadow degradation and their impact on carbon pool storage and stability, providing a theoretical basis for the protection and sustainable development of alpine meadows.