Patterns of nitrogen resorption in functional groups in a Tibetan alpine meadow

Abstract

Nutrient resorption from senescing leaves is an important plant nutrient conservation mechanism. Effects of functional groups on nitrogen resorption efficiency (NRE) are well known in woody perennials in forest ecosystems, but less is known from other ecosystems. We investigated green and senesced leaf nitrogen (N) concentrations of different functional groups in a Tibetan alpine meadow. We found legumes contained higher N in green leaves, with no significant differences in N between graminoids and forbs. Graminoids contained the lowest amount of N in senesced leaves, followed by forbs and legumes. NRE was higher in graminoids, with no significant difference between legumes and forbs. Our results showed that level of N was related to resorption in this ecosystem, with NRE decreasing as green leaf N concentration increased, regardless of the functional group. Furthermore, we found differences in N concentration in senesced leaves resulted from differences in both green leaf N concentration and NRE across functional groups. Our findings highlight that the ability to minimize N loss by both reducing the N concentration in senescing leaves and increasing NRE could explain the dominance of graminoids in this alpine meadow. Our results indicate that change in the dominance of different functional groups could influence soil N cycling in this ecosystem.