Nutrient resorption of coexistence species in alpine meadow of the Qinghai-Tibetan Plateau explains plant adaptation to nutrient-poor environment

Nitrogen (N) and phosphorus (P) resorption from senescing organs are important plant nutrient conservation mechanisms. However, whether nutrient resorption can indicate plant adaptation to nutrient-poor environment remains a controversy. We quantified nutrient resorption efficiency of major species in an alpine meadow of the Qinghai-Tibetan Plateau. N and P resorption for these species averaged 65.2% and 67.4%, respectively, which was at the high end of the values of global scale. Among three life forms, sedges contained least N and P and had highest resorption efficiency, indicating sedges had a competitive advantage over grasses and forbs in this nutrient-poor environment. This result was consistent with the fact that sedge was the typically dominant plant functional group in Qinghai-Tibetan Plateau. By fitting the allometric equations ([ nutrient](senescent) = A([nutrient](live))(B)) separately for N and P, we found much smaller B (N) than B (P), which suggested that relative to the resorption from senescent leaves, the cost of N uptake from soils increased more quickly than that of P as resource availability decreased. This phenomenon was contrary to the corresponding N and P acquisition pattern of the tropical ecosystem, which matched the large geographical gradients of N vs. P limitation (N for alpine ecosystem, while P for tropical ecosystem). This study suggests that surveying leaf nutrient concentration and resorption could provide indicative information about plant adaptation to nutrient-poor soil within and across ecosystems. Our finding offers insights to nutrient management and ecosystem restoration in nutrient-poor environment and delivers information for upcoming meta-studies and model simulation of global leaf nutrient resorption. Crown Copyright (C) 2012 Published by Elsevier B.V. All rights reserved.