氮添加对黄河三角洲滨海湿地芦苇养分再吸收效率的影响

大气氮沉降增加能改变土壤养分可利用性，影响滨海湿地植物的养分再吸收。目前研究多关注氮沉降量对养分再吸收过程的影响，且研究集中于叶片，鲜有研究区分不同形态氮素对植物不同器官养分再吸收过程的影响。通过两年的野外控制实验，研究硝态氮、铵态氮添加对黄河三角洲滨海湿地芦苇(Phragmites australis)叶、茎养分再吸收效率的影响。结果表明：两类氮添加均显著增加叶、茎的氮、磷含量(P<0.001),增幅达32.74%—43.22%(氮)、30.91%—36.51%(磷)。叶片氮的再吸收效率为54.14%—67.66%,茎氮的再吸收效率为50.60%—62.85%。叶片磷的再吸收效率为56.80%—70.38%,茎磷的再吸收效率为77.43%—84.95%。两类氮添加均显著降低氮、磷的再吸收效率(P<0.001),但两类氮添加处理下的养分再吸收效率无差异。叶、茎氮的再吸收效率无差异，但茎磷的再吸收效率明显高于叶(P<0.01)。总之，氮添加降低芦苇对氮、磷的再吸收效率，且茎对养分的再吸收也具有不可忽略的贡献。

Effect of nitrogen additions on the nutrient resorption efficiency of Phragmites australis in coastal wetlands of the Yellow River Delta

Increased atmospheric nitrogen (N) deposition may adjust the nutrient resorption efficiency of the plant species in the coastal wetlands due to the changing of soil nutrients availability. Most studies concentrated on the nutrient resorption of the leaf, whereas the nutrient resorption of the non-leaf organs, such as culm, is still less known. Moreover, little attention is concentrated on differentiating the effects of nitrate and ammonium additions on nutrient resorption. In this study, an in situ experiment was conducted to investigate the effects of nitrate and ammonium additions on the nutrient resorption efficiency of leaf and culm for reed (Phragmites australis) in the coastal wetlands of the Yellow River Delta, China. Results showed that N additions increased the concentrations of N and phosphorus (P) in senesced organs, ranging from 32.71% to 43.22% for N, and ranging from 30.91% to 36.51% for P. The N resorption efficiency (NRE) ranged from 54.14% to 67.66% for the leaf and ranged from 50.60% to 62.85% for the culm. The P resorption efficiency (PRE) ranged from 56.80% to 70.38% for the leaf and ranged from 77.43% to 84.95% for the culm. Both two types of N addition had similar and negative effects on nutrient resorption efficiency (P<0.001). The NRE of leaf was similar to that of culm, whereas the culm had larger PRE than leaf (P<0.01). Overall, both N additions decreased the NRE and PRE of reed. Furthermore, the culm of reed had a non-negligible contribution to nutrient resorption.