【摘要】 氮素对植物的生长发育十分重要,但持续、过量的氮沉降将可能对植物乃至生态系统产生深远影响。去除林下灌草是常用的林业管理措施,然而氮添加与去除灌草交互对植物生理生态特征的影响还具有很大不确定性。以中亚热带杉木（Cunninghamia lanceolata）人工林为研究对象,通过林冠氮添加(25kg·hm^-2·a^-1)和林下灌草去除,设置对照（CK）、灌草去除（UR）、氮添加（N）和氮添加加灌草去除（UR×N）处理。以正常生长、无病虫害的标准木为样本,通过测定杉木叶片饱和光强净光合速率(A_sat)、气孔导度（G_s）、叶绿素相对含量、全氮、全磷及非结构性碳水化合物含量以及δ¹³C来探讨氮添加及灌草去除对杉木生理生态特征的影响。结果表明,经过两年处理,林冠氮添加、灌草去除及其交互处理对杉木叶片的光合参数、叶片养分（氮、磷）、非结构性碳水化合物含量等各项指标均未有显著影响。N处理使杉木叶片的光合氮利用效率（PNUE）和光合磷利用效率（PPUE）较CK处理分别下降了30.1%、28.9%,而N×UR处理可以使PNUE和PPUE分别较N处理上升17.1%和13.6%。N处理使杉木叶片瞬时水分利用效率提高了15.9%。林冠氮添加、灌草去除及其交互处理对杉木人工林的影响可能是一个缓慢而长期的过程,短时间内（2年）不会对杉木生理生态特征产生显著的影响,但在实际的杉木人工林经营过程中,可以通过适当的氮添加,提高杉木人工林的抗旱性。研究结果可为全球变化背景下的杉木人工林的可持续经营措施的选择提供理论依据。更多还原

【Abstract】 Although nitrogen is crucial for plant growth and development, excessive nitrogen caused by continuing nitrogen deposition would not only affect plants, but also make substantial impacts to ecosystems. Understory removal is a common measure for forest management. However, how the combination of canopy nitrogen addition and understory removal will affect plant ecophysiology in forests remains unknown. In this study, we investigated the main and interactive effects of canopy nitrogen addition(N, 25 kg·hm^-2·a^-1) and understory removal（UR） on eco-physiological traits（including gas exchange, non-structural carbohydrates, chlorophyll content, nutrient concentration and resource use efficiency） of Cunninghamia lanceolata trees in a C. lanceolata plantation of subtropical China. After two-year treatment, branches from healthy trees were sampled for measurements. Results showed that both canopy nitrogen addition and understory removal had minimal effects on most eco-physiological traits of C. lanceolata. However, nitrogen addition significantly reduced leaf photosynthetic nitrogen efficiency（PNUE） and phosphorus use efficiency（PPUE） of by 30.1% and 28.9% respectively, but enhanced leaf instantaneous water use efficiency（WUE） by 15.9%. Our findings indicate that the impacts of canopy nitrogen addition and understory removal on C. lanceolata plantation would be a long-term process, while the effects of the two-year treatment would be absent or transient. Nonetheless, in the actual management of C. lanceolata plantation, the drought resistance of the plantation may be improved by appropriate nitrogen addition. These findings would provide insights into the management of C. lanceolata plantation under climate change.更多还原