中国东北典型森林生态系统植物叶片的非结构性碳水化合物研究

植物叶片的非结构性碳水化合物(NSC)不仅可以反应植物的碳供应状况,也能反应植物对外界环境的适应策略。利用传统的蒽酮比色法测定了东北3个典型森林生态系统(呼中、凉水和长白山)242种常见植物叶片的非结构碳水化合物,探讨了温带主要森林植物叶片NSC沿纬度梯度的变化趋势及其在物种-生活型-群落间的分布规律。实验结果表明:3个典型森林生态系统植物叶片可溶性糖、淀粉和NSC含量均呈偏正态分布,多数物种的含量偏中低水平;242种植物叶片可溶性糖、淀粉和NSC的平均含量分别为63.31、65.66和128.96 mg/g。在所调查的森林生态系统中,叶片可溶性糖、淀粉和NSC含量在不同生活型中表现各异。此外,乔木植物叶片的可溶性糖、淀粉和NSC含量从北到南呈递增趋势,呼中最低,凉水次之,长白山最高。乔木淀粉含量均表现为落叶树种大于常绿树种,可溶性糖和NSC含量变化趋势复杂。研究结果不仅为阐明东北主要森林生态系统植被碳代谢和生长适应对策提供数据基础,而且对理解植物对未来气候变化的响应机理提供数据支撑。

Evaluation of leaf non-structural carbohydrate contents in typical forest ecosystems in northeast China

Carbohydrates are utilized as an energy source during plant metabolism. Additionally, they are the primary photosynthates, and are important in other metabolic processes in plants. Plant carbohydrates are classified as either structural carbohydrates(SCs) or non-structural carbohydrates(NSCs). SCs, such as lignin and cellulose, are primarily used for the construction of plant morphology. NSCs, such as glucose and starch, are mainly used in metabolic processes. The NSC contents in leaves represent not only the supply of carbon, but also, to some extent, the adaptation mechanisms of plant species in response to the environmental changes. Leaf NSCs are mainly composed of soluble sugars and starch. The soluble sugars in leaves are primarily glucose, sucrose, and fructose, and play important roles in plant physical adaptation mechanisms. In contrast, starch is used for long-term energy storage.We used the anthrone colorimetric method to determine the NSC levels(soluble sugar+ starch) in the leaves of 242 plant species that are commonly found in three forest ecosystems in northeast China(Huzhong, Liangshui, and Changbaishan). We assessed the variations in NSC contents at the species, plant life form, and community levels. We also analyzed the changing trends in the leaf NSC content and its components with temperature. The frequency distributions for leaf NSC and its components were highly skewed, and the content levels of leaf NSCs and their components were medium to low in most plant species. The average concentrations of soluble sugars, starch, and NSCs in 242 plant species were 63.31, 65.66, and 128.96 mg/g, respectively. These values varied significantly across plant life forms. The leaf soluble sugar content in trees was 76.87 mg/g, which was significantly higher than that in shrubs and herbs. The leaf starch content in herbs was 71.92 mg/g, which was significantly higher than that in trees and shrubs. The NSC content in trees was 133.82 mg/g, and was higher than that in shrubs and herbs. Furthermore, leaf soluble sugars, starch, and NSC in trees increased from north to south in the three forest ecosystems. The average soluble sugars content in trees in Huzhong, Liangshui, and Changbaishan were 58.60, 65.91, and 99.96 mg/g, respectively, the average starch contents in trees in Huzhong, Liangshui, and Changbaishan were 55.83, 65.07, and 75.93 mg/g, respectively, and the average NSC contents in trees in Huzhong, Liangshui, and Changbaishan were 111.14, 121.32, and 153.72 mg/g, respectively. The leaf starch contents were higher in deciduous trees than in evergreen trees, but there were no apparent differences between the leaves of deciduous and evergreen trees in terms of soluble sugar. In conclusion, these data support the carbon limitation hypothesis, which states that NSC contents decline with decreasing temperature from south to north owing to reduced carbon assimilation. Our findings provide basic data on carbon metabolism and the adaptation strategies of plant species in a typical forest ecosystem in northeast China, and provide new insights into the underlying mechanisms and responses of plant species to future climate changes.