The light shifts in ammonia nitrogen affected soil microbial communities with their related dissolved organic matter in the arid region

Abstract

Arid and semi-arid climates are vital components of ecosystem, however, the mechanisms by which microorganisms respond to soil dissolved organic matter (DOM) in these regions under the constraint of ammonium nitrogen remain unknown. In this study, we investigated the differences in microbial diversity, composition, abundance, and DOM composition in soils with varying ammonia-nitrogen (NH₄⁺-N) concentrations in arid and semi-arid regions. We also explored the connectivity between the co-occurrence networks of microorganisms and DOM. In high NH₄⁺-N environments, the phyla of soil microorganisms that showed an increase included Anabaena and Thick-walled Bacteria. Moreover, the abundance of microorganisms such as Reyranella, Actinophyfocala, and Arhrobacter also increased. The main metabolic modes of these microorganisms were lysine biosynthesis and D-amino acid metabolism. Metabolites that exhibited elevated levels along with the increase in NH₄⁺-N content included those related to chlorocyclohexane and chlorobenzene degradation, as well as geraniol degradation. NH₄⁺-N was identified as the most significant environmental factor influencing the relationship between microorganisms and DOM. In high-ammonia environments, the number of links, average clustering coefficient, density, and connectivity of the microorganisms and DOM co-occurrence network were significantly higher. This indicates that the co-occurrence network was more complex and stable. In contrast, low NH₄⁺-N environments restricted microbial metabolic processes and altered the DOM composition, leading to a further limitation of microbial activity. This study elucidated the response mechanism of soil microorganisms to DOM under the limitation of NH₄⁺-N in arid and semi-arid regions and emphasized the crucial role of soil NH₄⁺-N concentration in the soil biological cycle. It offers a reference for monitoring soil quality, preventing soil degradation, and maintaining ecological environment and food security.