Climate-mediated trade-offs between nutrient allocation and resorption efficiency in Phragmites australis along moisture gradients: A case study from an arid wetland in China

Arid wetland ecosystems face unprecedented challenges under accelerating climate change, yet the mechanistic understanding of how dominant species adapt their nutrient strategies remains critically limited. In this study, we use spatial moisture gradients as a proxy for long-term plant adaptation to differing water regimes, and interannual climate data to assess short-term modulation of nutrient strategies within these established gradients. Here, we present the comprehensive multi-year analysis of nutrient allocation and resorption trade-offs mediated by climatic variability in Phragmites australis , the keystone species of arid wetlands globally. Through three years (2021-2023) of field observations across spatial moisture gradients in China's Dunhuang wetland, we reveal fundamental trade-offs between belowground nutrient allocation and aboveground resorption efficiency that determine ecosystem functioning. Our results demonstrate that interannual precipitation variability regulates nutrient resorption strategies along spatial moisture gradients, while simultaneously exerting indirect effects through leaf N:P ratios and soil available phosphorus modifications. Specifically, leaf nitrogen resorption efficiency decreased significantly with increasing soil moisture across sites (from 75% in low moisture to 66% in high moisture), while phosphorus allocation to rhizomes increased under elevated moisture conditions. Structural equation modelling revealed that precipitation influences these responses through dual pathways: direct physiological effects and indirect modifications of leaf nitrogen-to-phosphorus ratios and soil available phosphorus. Critically, we discovered a negative correlation between rhizome-to-leaf nutrient ratios and leaf resorption efficiency (path coefficient = -0.53 and -0.27 for nitrogen and phosphorus, respectively), indicating that Phragmites australis employs contrasting nutrient conservation strategies depending on resource availability. Under water-limited conditions, plants prioritize leaf nutrient resorption, while under favourable moisture conditions, they enhance belowground nutrient allocation. These findings provide a conceptual framework for predicting plant nutrient responses to interannual climate variability as expressed through spatial moisture conditions in arid wetland ecosystems and offer insights that may inform wetland conservation strategies in water-limited regions. • The evidence of climate-driven trade-offs between nutrient allocation and resorption. • Plants shift from leaf resorption to root allocation under soil moisture thresholds (>25%). • Climate change alters plant-mediated nutrient cycling dynamics in arid wetlands.