Abstract:Nitrogen (N) and phosphorus (P) resorption from senesced leaves are hypothesized to improve plant nutrient conservation. However, whether the availability of nutrients in soil affects the resorption efficiency of N and P is still under debate. The present study investigated N and P contents in mature and senesced leaves of co-existing evergreen and deciduous tree species in evergreen broad-leaved forest at low altitude, beech mixed forest at middle altitude, and hemlock mixed forest at high altitude on Mao'er Mountain, Guangxi. The present study also determined if nutrient resorption was affected by leaf habit and altitude. N resorption efficiency (NRE) and P resorption efficiency (PRE) for the total species averaged 56.5% and 52.1%, respectively, supporting our hypothesis that nutrient resorption from senesced leaves is very important for plant nutrient conservation. NRE and PRE for the total evergreen species averaged 61.8% and 57.0%, respectively. NRE and PRE for the total deciduous species averaged 51.2% and 47.3%, respectively. Evergreen species exhibited significantly higher NRE (P < 0.001) and PRE (P < 0.01) than deciduous species, which were closely associated with lower N and P contents in senesced leaves in evergreen species. These shifts of NRE and PRE between leaf habits suggested that evergreen species were more conservative than deciduous species in terms of nutrient resorption. On average, at low, middle, and high altitude, NRE was 61.8%, 55.8%, and 52.0%, while PRE was 47.1%, 51.5%, and 57.8%, respectively. As altitude increased, NRE decreased significantly (P < 0.01), while PRE increased significantly (P < 0.05). NRE was negatively correlated to the soil N : P ratio (r=- 0.41, P < 0.05) and mature leaf N : P ratio (r=- 0.37, P < 0.05), whereas PRE was positively correlated to the soil N : P ratio (r=0.44, P < 0.05) and mature leaf N : P ratio (r=0.47, P < 0.01).The pattern of NRE vs. PRE was indicative of the plant adaptation from N limitation at low altitude to P limitation at high altitude. In addition, mean annual temperature was positively related to NRE (r=0.43, P < 0.05) but negatively related to PRE (r=- 0.45, P < 0.01), suggesting that air temperature was also an important factor in the regulation of nutrient resorption patterns in tree species. The combined effects of soil and temperature on nutrient resorption indicated that plants were not responding to altitude directly, but rather to a suite of factors such as soil and temperature that co-varied with altitude. Overall, this study suggests that surveying leaf nutrient content and resorption could provide information about plant adaptation to altitude-induced changes in soil and temperature and explain the bimodal distribution of evergreen tree species along the altitudes on Mao'er Mountain. This study also provides insight into the nutrient management and ecosystem conservation in montane forests and delivers information for future meta-studies and model simulations of global leaf nutrient resorption.