Dry-wet alternation in riparian zone affected chemical diversity of dissolved organic phosphorous at the molecular level and promoted its co-occurrence network stability with microorganisms

Dry-wet alternation frequently occurs in riparian zones, which significantly affects the availability of phosphorus-related nutrients. Information regarding the chemical molecular level transformations of dissolved organic phosphorus (DOP) driven by soil microorganisms under the dry-wet alternation is still lacking. In this study, the patterns of DOP molecular compositions in riparian zone and its underlying microbial drivers during the dry-wet alternation were investigated based on Fourier transform ion cyclotron resonance mass spectrometry and macrogenomic sequencing. The results showed that the dry-wet alternation increased the degree of humification of soil DOP, and wet conditions were more conducive to the conversion of inorganic phosphorus to organic phosphorus in soil. The dry-wet alternation also promoted the degradation of unsaturated hydrocarbons and the production of lignins/lignin-like molecules in DOP, accelerating the conversion of more chemically active substances. The microbial community associated with DOP was screened for lower species richness and more streamlined species under dry-wet alternation conditions; however, the network stability between DOP and microorganisms became much stronger. Consequently, Sorangium bacteria drove the inter-conversion between lipids and unsaturated hydrocarbons of DOP molecules, mainly involving dealkyl group reactions and oxygen reactions.