Foliar nutrient resorption responses of three life-form plants to water and nitrogen additions in a temperate desert

How nitrogen deposition and increasing precipitation would affect leaf nutrient concentration and internal nutrient cycling of desert plants is still unclear. The aim of our study was to test the responses of leaf nutrient resorption to increasing precipitation and N enrichment in a temperate desert. Green and senesced leaf nitrogen and phosphorus concentrations, and nitrogen (NRE) and phosphorus (PRE) resorption efficiency of three life-form plants (5 spring annuals, 2 summer annuals and 2 shrubs) were investigated. Both NRE and PRE showed remarkable variations among plant life-forms, being lowest in shrubs and highest in spring annuals, suggesting that plants may have different nutrient requiring strategies. Nitrogen addition promoted green and senesced leaf nitrogen concentrations in summer annuals and shrubs, while having no impacts on leaf phosphorus concentration, NRE and PRE. Water addition had no impacts on leaf nutrient concentration and resorption efficiency; combined nitrogen and water addition had no interactive effects. Our results suggest that spring annuals and shrubs exhibit conservative nutrient adaptation through increasing nutrient uptake but not changing nutrient internal cycle to increasing nitrogen and water.