Leaf nitrogen and phosphorus resorption of woody species in response to climatic conditions and soil nutrients: a meta-analysis

Nutrient resorption before abscission is an important nutrient conservation mechanism regulated by climatic conditions and soil nutrients. However, our current understanding of leaf nutrient resorption is primarily derived from site-specific studies or from the use of green-leaf nutrient concentrations to represent those in soils. It remains unknown how nutrient resorption responds to natural soil-nutrient concentrations at a global scale. The effects of plant functional groups, climatic conditions, and soil nutrients and their interactions on leaf nutrient resorption are also unknown. In this study, we established a global database derived from 85 published papers, including 547 reports of nitrogen and phosphorus resorption efficiency (NRE and PRE), climatic factors (LAT, latitude; MAT, mean annual temperature; MAP, mean annual precipitation) and soil-nutrient data (STN, soil total nitrogen; STP, soil total phosphorus) across 111 research sites. The results demonstrated that mean NRE and PRE were 48.4 and 53.3%, respectively. NRE of trees was lower than those of shrubs. NRE and PRE of coniferous species were both higher than those of broad-leaved species. Evergreen species had higher PRE than did deciduous species. NRE was negatively related to STN, but PRE and STP were not related. Both NRE and PRE decreased with increasing MAT and MAP but increased with increasing LAT. Plant functional groups, climate and soil nutrients jointly explained 22 and 32% of the variations in NRE and PRE, respectively. It is important to note that climate (especially MAT) explained 12 and 29% of the variations in NRE and PRE, respectively, implying that continuing global warming will exert an increasingly profound influence on plant nutrient cycles.