干旱区生态环境知识资源中心

Foliar nutrient resorption is an important strategy which allows leaf nutrients to be reused rather than lost with leaf fall, particularly in nutrient-poor ecosystems where even small nutrient losses can have significantly negative impacts on plant survival, competitive ability, and fitness. However, plants vary greatly in nitrogen (N) and phosphorus (P) resorption among plant growth forms during leaf senescence, which may be vital to understand the role of plant growth forms in ecosystem functioning. Green and senesced leaf N and P concentrations of 39 plant species in sandy grassland (Horqin Sand Land) of northern China were analyzed to detect variations of nutrient resorption efficiency among plant growth forms. The results showed that nitrogen resorption efficiency (NRE) ranged from 29% to 74%, with an average (+/- SD) of 50.3 +/- 11.2%, and phosphorus resorption efficiency (PRE) varied among species between 46% and 82%, with a mean (+/- SD) of 68.4 +/- 6.9%, suggesting that nutrient resorption is a vital nutrient conservation strategy in this ecosystem. In addition, NRE and PRE differed significantly among the dominant plant growth forms in this sandy grassland. NRE for N-fixing species and graminoids were significantly lower relative to NRE for shrubs and forbs, but mean PRE of graminoids was significantly higher than those of N fixers, shrubs and forbs. These data give indirect evidence that the differentiation of N and P conservation serve as an important mechanism permitting the co-existence of growth forms in arid systems.