Liu Nan, Liu Fangyan, Sun Zhongyu, Wang Zhihui, Yang Long
Key Laboratory of Vegetation Restoration and Management of Degraded Ecosystems, Guangdong Provincial Key Laboratory of Applied Botany, South China Botanical Garden, Chinese Academy of Sciences, 510650 Guangzhou, China; College of Life Sciences, Gannan Normal University, 341000 Ganzhou, China.
Key Laboratory of Vegetation Restoration and Management of Degraded Ecosystems, Guangdong Provincial Key Laboratory of Applied Botany, South China Botanical Garden, Chinese Academy of Sciences, 510650 Guangzhou, China.
Sci Total Environ. 2023 Dec 1;902:165914. doi: 10.1016/j.scitotenv.2023.165914. Epub 2023 Jul 29.
Many studies have focused on the impact of nitrogen deposition on plants, but due to technical limitations, research on the responses of forest canopy to manipulated nitrogen deposition is relatively scarce. Based on a canopy nitrogen addition (CN) platform, this study used laboratory analysis and unmanned aerial vehicle (UAV) observations to assess the impact of CN on the canopy traits of dominant tree species (Engelhardia roxburghiana, Schima superba, and Castanea henryi) in an evergreen broad-leaved forest in China. The results showed that nitrogen application at 25 kg N ha y (CN25) and 50 kg N ha y (CN50) significantly increased the actual net photosynthetic rate (A) of all the three tree species. CN25 significantly increased superoxide dismutase (SOD), catalase (CAT), and ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco) activities in C. henryi. CN50 significantly increased the leaf area of all the three tree species and significantly reduced the leaf thickness of C. henryi, and significantly increased the POD and Rubisco activities in S. superba and C. henryi. CN significantly changed the number of forest gaps, but did not significantly change the area of forest gaps within the sample plots. CN25 significantly decreased the vertical projection area but increased the canopy flowering coverage of S. superba in dominant directions. CN25 and CN50 significantly increased the flowering coverage of C. henryi in favorable directions. It is found that under long-term (10-year) nitrogen addition, the balance between carbon fixation and antioxidant defense functions of E. roxburghiana may be broken down, but the carbon assimilation, antioxidant capacity and reproduction potential of S. superba and C. henryi may be well coordinated, which will have a potential impact on the species composition and ecological functions of the evergreen broad-leaved forest. This study may also provide scientific basis for forest management in the context of enhanced atmospheric nitrogen deposition.
许多研究都聚焦于氮沉降对植物的影响，但由于技术限制，关于森林冠层对人为控制氮沉降响应的研究相对较少。基于一个冠层氮添加（CN）平台，本研究利用实验室分析和无人机（UAV）观测，评估了CN对中国一个常绿阔叶林优势树种（黄杞、木荷和锥栗）冠层性状的影响。结果表明，25千克氮·公顷·年（CN25）和50千克氮·公顷·年（CN50）的施氮量显著提高了所有这三种树种的实际净光合速率（A）。CN25显著提高了锥栗中超氧化物歧化酶（SOD）、过氧化氢酶（CAT）和核酮糖-1,5-二磷酸羧化酶/加氧酶（Rubisco）的活性。CN50显著增加了所有这三种树种的叶面积，显著降低了锥栗的叶厚度，并且显著提高了木荷和锥栗中过氧化物酶（POD）和Rubisco的活性。CN显著改变了林窗数量，但未显著改变样地内林窗面积。CN25显著减小了木荷在优势方向上的垂直投影面积，但增加了其冠层开花覆盖率。CN25和CN50显著增加了锥栗在有利方向上的开花覆盖率。研究发现，在长期（10年）氮添加条件下，黄杞的碳固定与抗氧化防御功能之间的平衡可能会被打破，但木荷和锥栗的碳同化、抗氧化能力和繁殖潜力可能会得到良好协调，这将对常绿阔叶林的物种组成和生态功能产生潜在影响。本研究也可为大气氮沉降增强背景下的森林管理提供科学依据。
