Leaf Stoichiometry and Edaphic Properties Jointly Shape Plant Nutrient Resorption in a Riparian Wetland Undergoing Water Table Fluctuations

ABSTRACT Variations in traits of plant leaves and roots affect both above‐ground and below‐ground resource exploitation strategies. However, little is known about the drivers of such variation in riparian wetlands undergoing water table fluctuation. We examined the links between strategies for nutrient conservation in leaves and nutrient acquisition by roots for two dominant species, Carex thunbergii and Phalaris arundinacea along a hydrological gradient. These linkages were assessed using a series of variables: (1) the N and P resorption efficiency of leaves, (2) nutrient acquisition‐related root and leaf morphological properties. We found that N resorption efficiency increases with increasing water table level, while P resorption efficiency was static for both species across different soil water conditions. Specifically, in C. thunbergii , we found a positive relationship between N conservation in above‐ground tissues and the below‐ground rate of nutrient acquisition that was driven by water table‐related variation in the leaf N content and the soil NH 4 + /NO 3 − ratio. Conversely, for P. arundinacea , its root traits shifted from conservation to acquisitive strategy along the hydrological gradient, coinciding with a shift in leaf strategies from conservation to acquisition, with higher leaf N at higher water table levels. The association of P and N resorption efficiencies with the N to P ratio in leaves in P. arundinacea suggested that resorption of nutrients responded to nutrient stoichiometry. We suggest that the characteristics of plant nutrient resorption are species‐specific and that the nutrient preferences of roots influence the nutrient availability in above‐ground tissues in this subtropical wetland ecosystem. Our study provides important insights into the nutrient balance and adaptation strategies of plants and helps us predict nutrient cycling under climate change in wetland ecosystems.