Interrelated impacts of water recirculation on soil physicochemical characteristics and bacterial co-occurrence networks: Consequences for yield sustainability in rice-crab systems
Water management methods are crucial determinants of ecosystem functionality in dry irrigation areas; yet, the processes by which water recirculation sustains rice-crab yields through the interrelated effects of soil physicochemical conditions and microbial networks remain unclear. This study contrasted traditional direct irrigation (CK) with a fish-rice-crab recirculating system (RS) in the Yellow River irrigation basin. By integrating high-throughput sequencing, neutral community models (NCM), network topology analysis, and structural equation modelling (SEM), we systematically elucidated the coupling properties of the soil-microbe nexus. The results indicated a notable physicochemical-microbial interaction under the RS mode: in addition to significantly increasing soil TN, TP, and SOM levels, the assembly rules of the bacterial community were altered. The contribution of abundance difference to beta-diversity rose from 19.81% (CK) to 31.90% (RS), alongside intensified stochastic migratory mechanisms. Moreover, network analysis identified a mechanism for enhanced micro-ecological resilience: the RS mode prompted a shift towards a multi-centered, high-modularity network structure. The mean stochastic turnover time (MST) rose by 6-7% relative to CK. In comparison, distance-based redundancy (DBR) decreased from 61% to 37%, indicating that water recirculation mitigated community vulnerability to environmental shocks by augmenting functional redundancy. SEM research validated the cascading impacts of physicochemical factorsnetwork traits, pinpointing TN as the principal determinant of microbial diversity and geographical distribution, with the strong negative association between network cohesion and the Shannon index indirectly endorsing crop growth. As a result, the RS mode attained synergistic yield enhancements for rice (+5.68%) and crab (+17.25%). This study demonstrates that recirculating irrigation improves ecosystem stability by optimising soil physicochemical properties and fostering stronger bacterial co-occurrence networks, thus offering a theoretical foundation for sustainable yield in integrated rice-crab co-culture systems.