【目的】叶片氮含量是植物重要功能性状之一,定量分析不同截雨干旱时间对毛竹(Phyllostachys edulis)叶片氮含量影响,为季节性干旱条件下毛竹氮肥管理提供决策依据。【方法】以钱江源森林生态系统定位研究站野外毛竹林为研究对象,通过“顶棚法”人工截雨干旱处理2年试验数据测定,定量分析不同截雨干旱时间下毛竹叶片氮含量的时空分布特征及其对干旱的响应。【结果】截雨干旱处理1和2年后,干旱毛竹叶片氮含量年平均值均高于自然生长条件下(对照)。截雨干旱处理2年后的毛竹叶片氮含量年平均值比干旱处理1年后的高,但差异不显著。与对照相比,截雨干旱1年使夏季、冬季毛竹叶片氮含量增加;随着干旱处理时间延长,叶片氮含量在夏季、秋季、冬季保持稳定。截雨干旱1年后,除冬季毛竹冠层上部叶片外,夏季和冬季冠层各叶片氮含量显著比对照高(P<0.05);截雨干旱2年后,仅冬季毛竹冠层上部叶片氮含量显著高于对照。截雨干旱1年后夏季毛竹冠层上部与下部叶片氮含量显著差异(P<0.05)。随着干旱时间延长,毛竹叶片氮含量与对照差异显著且受季节和竹龄双重影响,但干旱处理下春季不同年龄毛竹叶片氮含量与对照差异不显著、冬季1度竹(1~2年生)叶片氮含量显著高于对照的趋势比较稳定。截雨干旱1年和2年后,不同年龄毛竹间春季和夏季叶片氮含量均无显著差异,但秋季和冬季1度竹叶片氮含量与4度竹(7~8年生)间差异显著(P<0.05)。相比干旱1年,较长时间干旱下老龄竹叶片年平均氮含量保持较高值。【结论】 截雨干旱处理2年的数据表明,干旱毛竹叶片平均氮含量高于对照但不显著,截雨干旱处理年限对毛竹叶片氮含量的影响受生长季节和竹龄双重调节。随着截雨干旱时间延长,毛竹叶片氮含量高于对照处理的季节发生频率增加;干旱与对照处理毛竹叶片氮含量显著差异发生的冠层部位减少,局限于个别冠层的差异显著。今后气候变化下毛竹养分管理需要考虑季节和竹龄因素。

【Objective】 The foliar nitrogen content is an important functional trait of plants. Herein, the effect of drought on the nitrogen content of Moso bamboo (Phyllostachys edulis) leaves was quantitatively analyzed. The study provides a theoretical basis for the sustainable and efficient management of bamboo forests under the current global climate change scenario.【Method】A wild bamboo forest located in Miaoshanwu Forest Farm of Qianjiangyuan Forest Ecosystem Research Station was selected as the research object in this study. The 2-year experimental data pertaining to precipitation exclusion in the bamboo forest, and the spatiotemporal distribution characteristics of the nitrogen content per unit mass of Phyllostachys edulis leaves under different drought periods and their response to drought stress were analyzed. 【Result】 The annual average nitrogen content per unit mass of bamboo leaves following 1 and 2 years of precipitation exclusion was high than that under natural growth conditions (CK). Although the annual average nitrogen content after 2 years of precipitation exclusion was higher than that after 1 year of exposure to drought, the difference was not significant. Exposure to drought for 1 year increased the foliar nitrogen content during summer and winter, compared to that of the CK; however, the foliar nitrogen content remained stable in summer, autumn, and winter following prolonged exposure to drought. With the exception of the nitrogen content of the leaves in the upper canopy in winter, the foliar nitrogen content following 1 year of precipitation exclusion was significantly higher than that of the CK in summer and winter (P < 0.05). The nitrogen content of the upper leaves was significantly higher than that of the CK in winter after 2 years of precipitation exclusion. The nitrogen content of the upper and lower leaves differed significantly in summer (P < 0.05) after 1 year of precipitation exclusion. The prolongation of drought exposure caused significant differences between the foliar nitrogen content of drought-exposed and CK plants, depending on the season and age of the bamboo. However, the foliar nitrogen content of different degrees of bamboo did not differ significantly from that of the CK during spring. The foliar nitrogen content of first degree (1-2 years old) bamboo plants under drought stress was significantly higher than that of the CK in winter. There were no significant differences between the foliar nitrogen content of different degrees of bamboo plants in spring and summer, following 1 or 2 years of precipitation exclusion. However, the foliar nitrogen content of the first (1-2 years old) and fourth (7-8 years old) degree bamboo plants differed significantly in autumn and winter (P < 0.05). The annual average foliar nitrogen content of the elderly bamboo plants exposed to prolonged drought was relatively high compared to that of the plants exposed to drought for 1 year. 【Conclusion】Analysis of the 2-year data obtained during precipitation exclusion demonstrated that the average foliar nitrogen content of bamboo following precipitation exclusion was higher than that of the CK, but the differences were not significant. The effects of the duration of drought exposure on the foliar nitrogen content were influenced by the season and plant age. The prolongation of precipitation exclusion increased the number of seasons during which the foliar nitrogen content of the drought-exposed plants was higher than that of the CK. Additionally, the number of canopy layers of drought-exposed and control plants that exhibited significant differences in foliar nitrogen content was reduced following the extension of precipitation exclusion, and the differences were limited to individual canopies. The season and age of the bamboo plants need to be considered for the nutrient management of Moso bamboo in future, under the current climate change situation.