How phosphorus enrichment regulates the microbial community resistance and multifunctions tolerance to drying-rewetting cycles in paddy fields: the critical role of stoichiometry.

Abstract

With increased fertilization and water-saving irrigation, drying-rewetting cycles (DWCs) and phosphorus (P) accumulation occur more frequently in paddy soils. However, it remains unclear about the responses of microbial resistance to these disturbances. We established a microcosm experiment with five P accumulation gradients (P0-P4, 0.55-1.35 g P kg-1 soil) and four simulated DWCs to explore the resistances of microbial community and ecosystem multifunctionality (EMF). DWCs typically intensified microbial carbon limitation and suppressed EMF, while these responses varied markedly with P accumulation levels. The intermediate P accumulation level (P2, 0.75 g P kg-1) induced the slightest variations in soil and microbial C:N:P stoichiometry, while showing no statistically detectable decline in EMF and comparatively stable community attributes. By contrast, both low and high P levels were linked to greater stoichiometric imbalance, diminished microbial stability, and EMF loss under DWCs. Notably, both bacterial and fungal community stability remained statistically unaltered only under the P2+DWC treatment, fostering a more balanced trade-off between community composition resistance and multifunctional tolerance. Moreover, variations in soil nutrient and microbial stoichiometric ratios were more strongly correlated with this trade-off than ecoenzymatic stoichiometry. Collectively, our findings reveal a linkage between soil-microbial stoichiometric balance and microbial resistance to drying-rewetting disturbances along P accumulation gradients, offering crucial insights into how moderate P level stabilizes microbial community and EEM under intensified hydrological fluctuations in paddy soils.