Growing season temperature and precipitation affect nutrient resorption in herbaceous species through foliar stoichiometric control strategies

Abstract Aims: Nutrient resorption affects ecosystem nutrient cycling. Previous studies have described the independent responses of nutrient resorption to climatic factors, plant traits, and soil nutrient status. Little is known about the comprehensive effects of all above factors on nutrient resorption, especially based on observations in situ. Methods: We conducted an eight-year field survey in a semi-arid grassland for exploring interannual variation in foliar nutrient resorption in two herbaceous functional groups (i.e., graminoids and forbs) and the factors driving this variation. Results: Results showed nitrogen and phosphorus resorption efficiencies (NRE and PRE) in graminoids, not in forbs, varied significantly among years, indicating more flexible nutrient resorption strategies in graminoids. There was no significantly direct effect on nutrient resorption because of the insignificant changes of soil nutrients across the selected years. However, NRE was positively related to the N:P ratio in green leaves ([N:P]g) and PRE negatively related, supporting a foliar “stoichiometric control” strategy on nutrient resorption. Moreover, growing-season temperature and precipitation had positive and negative effects on nutrient resorption in graminoids, respectively, via the regulation of [N:P]g. Comparatively, precipitation affected forbs NRE positively and PRE negatively, again acting through regulating [N:P]g. Conclusion: Our study showed growing season hydro-thermal factors control foliar nutrient resorption by foliar [N:P]g, emphasizing the role of both climatic variables and foliar “stoichiometric controls” on foliar nutrient resorption under low nutrient-variability conditions. Meanwhile, more positive responses of graminoids could help explain their current and future dominance in this grassland.