摘要:全球气候变化改变了陆地生态系统植物的生理状态，使植物氮（N）、磷（P）代谢发生了变化。为揭示全球气候变暖及干旱环境下植物N、P代谢特征的变化，以典型的亚热带植物杉木（Cunninghamia lanceolata）为研究对象，按照两因素两水平试验设计设置对照、增温（+5℃）、隔离降雨（-50%）和增温×隔离降雨4个处理，根据"主干法"确定针叶龄级，采集一年生、二年生、三年生及四年生叶片，同时收集每个处理的凋落叶，分别测定鲜叶及凋落叶的生态化学计量学特征，并计算其N、P吸收率。结果表明：（1）增温及隔离降雨对凋落叶N浓度及C/N比值均无显著影响，隔离降雨使凋落叶P浓度显著增加23.32%，C/P比值显著下降18.57%（P < 0.05）。（2）增温、增温×隔离降雨处理使杉木二年生鲜叶N浓度较对照组均有显著差异（P < 0.05），三、四年生叶片N浓度在隔离降雨处理下分别极显著增加18.15%和25.33%（P < 0.01），增温及隔离降雨使P浓度均呈下降趋势但未造成显著差异。（3）N吸收率（NRE）在处理间及叶龄间均无显著差异；P吸收率（PRE）随叶龄增加呈下降趋势，其中仅隔离降雨处理下不同叶龄杉木叶PRE未有显著差异。（4）增温、隔离降雨及二者交互作用均增加鲜叶N浓度及NRE之间拟合关系，其中增温及增温×隔离降雨拟合度呈显著相关（P < 0.05），而增温、隔离降雨及二者共同作用均显著降低鲜叶P浓度及PRE的拟合关系（P < 0.05），其中隔离降雨处理对其影响最大。在中亚热带地区，杉木生长受P元素限制显著，土壤温度和水分都是叶片P素变化的重要因素，而杉木叶片N素对水分较为敏感，适当的水分亏缺能使叶片的N浓度增加，尤其对成熟叶片影响显著。



Abstract:Global climate change has altered the physiological status of plants in terrestrial ecosystems, causing significant changes in nitrogen (N) and phosphorus (P) metabolisms in plants. The objective was to investigate the responses of N and P metabolisms in a typical subtropical tree, Cunninghamia lanceolata, to simulated warming and drought. The experiment was completely randomized and fully crossed factorial design with five replicates. The treatments were control (CK), soil warming (+5℃, W), precipitation exclusion (-50%, Pe), and interactions of warming and precipitation exclusion (WP). Leaves at difference ages, including senesced-leaf, were collected to determine ecological stoichiometric characteristics and nutrients resorption efficiency. The W and Pe had no effects on N concentration and C/N ratio in the senesced-leaves. However, the Pe increased P concentration by 23.32% but reduced C/P ratio by 18.57% in the senesced-leaves (P < 0.05). In the biennial leaves, N concentration in W and WP treatments were different (P < 0.05) from the control. The N concentration in the three-and four-year-old leaves in the Pe treatment increased by 18.15% and 25.33%, respectively (P < 0.01) when compared to that of the control. No difference was found in N resorption efficiency (NRE) between the treatments and years. However, P resorption efficiency (PRE) decreased with increasing leaf age in all treatments, except for the Pe. The treatment of W, Pe, and WP improved the fitting relationship between N concentration and NRE, and it was significant in the W and WP treatments (P < 0.05). However, the fitting relationship between P concentration and PRE was lower in the W, Pe, and WP treatments (P < 0.05) than in the control with highest negative effect found in the Pe treatment. In subtropical regions, the growth of C. lanceolata is significantly limited by P. Soil temperature and water content are both important factors regulating P metabolism in leaves, while leaf N is more sensitive to changes in soil water and water deficits can increase its concentration, especially affecting mature leaves.





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