Characteristics of leaf nutrient resorption efficiency in Tibetan alpine permafrost ecosystems.

Nutrient resorption is an important strategy for nutrient conservation, especially in permafrost ecosystems where plant growth is limited by nutrients. Based on the measurements mainly derived from tropical, subtropical and temperate regions, current projections suggest that resorption efficiency is higher for leaf nitrogen (N) than for phosphorus (P) in cold regions. However, these projections have not been fully validated due to the lack of observations in permafrost ecosystems. Here, we carry out a large-scale sampling campaign along a permafrost transect on the Tibetan Plateau. Our results show that, in contrast with the prevailing view, resorption efficiency is higher for leaf P than N in permafrost ecosystems (75.1 ± 1.8% vs. 58.7 ± 1.5%; mean ± standard error). Our results also reveal that leaf P resorption efficiency is higher in permafrost ecosystems than in global herbaceous plants, while there is no difference for leaf N resorption efficiency. Interestingly, there is a trade-off between leaf N resorption efficiency and soil N mineralization rate, but no such pattern exists for P. These results illustrate the unique characteristics of plant nutrient resorption in permafrost ecosystems and advance our understanding of nutrient conservation strategies in little-studied permafrost regions.