热带次生林不同林层植物叶片非结构性碳水化合物的季节变化及其对氮磷添加的响应

Abstract

非结构性碳水化合物（Non-structural Carbohydrates，NSCs）是植物生长代谢过程中重要的能量来源。通过在华南热带次生林进行氮磷添加试验，探究不同林层植物叶片NSCs的季节变化及其对氮磷添加的响应，取样时间为2019年1月、4月、7月和10月。结果表明：1）植物叶片NSCs存在显著的种间差异，磷（P）添加对叶片淀粉和NSCs含量具有显著影响，且物种与磷添加的交互作用显著影响叶片淀粉含量。2）黑嘴蒲桃和紫玉盘叶片NSCs含量对氮（N）添加的响应较为敏感，而白车和竹节叶片NSCs含量对P添加的响应较为敏感，氮磷同时添加（+NP）对植物叶片NSCs的增效作用最好。3）植物叶片NSCs存在显著的季节性变化，且季节与林层间的交互作用对叶片可溶性糖和NSCs含量具有显著影响。4）不同林层植物对氮磷添加的响应不同，氮磷添加使林下层植物叶片可溶性糖含量增高，林冠层降低，在干季，N添加会使林下层植物叶片淀粉含量增高，林冠层降低。P添加的影响恰好与之相反。在湿季，氮磷添加使林下层和林冠层植物叶片的淀粉含量增加。5）林冠层植物叶片NSCs含量高于林下层，且林下层植物叶片NSCs含量和可溶性糖与淀粉的比值均表现为干季高于湿季。因此，叶片NSCs之间的变化差异反映了不同植物的碳利用策略，NSCs含量对氮磷添加的响应变化可以反映出热带森林植物在生长发育过程中碳供给和消耗的动态变化情况，为探索热带次生林植物碳利用策略及共存机制提供科学依据。;Non-structural carbohydrates (NSCs) are important energy sources in the process of plant growth and metabolism. In this paper, we conducted field-based experiment with nitrogen (N) and phosphorus (P) addition, to explore the seasonal changes of leaf NSCs in different forest layers and its response to N and P additions in a secondary tropical forest in south China. Leaf samples were conducted in January, April, July, and October 2019. The results showed that:1) There were significantly interspecific differences on the leaf NSCs. Phosphorus addition had a significant impact on starch and NSCs contents, and the interactions between species and P addition significantly affected the starch content. 2) Leaf NSCs of Syzygium bullockii and Uvaria microcarpa were sensitive to N addition, while those of Syzygium levinei and Carallia brachiate were sensitive to P addition, and N and P co-addition (+NP) had the best synergistic effect on leaf NSCs. 3) There were significantly seasonal changes on leaf NSCs, and the interaction between seasons and forest layers significantly affected soluble sugar and NSCs content. 4) The responses of plants in different forest layers to N and P addition were different. N and P additions increased the leaf soluble sugar content in the understory and decreased those in the overstory plants. In dry season, N addition increased the leaf starch contents in the understory and decreased in the overstory species. However, P addition had the opposite effect. In wet season, N and P additions increased the starch content of plant leaves in understory and overstory. 5) Leaf NSCs content in overstory was higher than that in understory. The leaf NSCs content and soluble sugar/starch ratio of understory plants were higher in the dry season than those in wet season. Therefore, the variation of NSCs in different plant leaves reflects the carbon (C) utilization strategies, and the change of NSCs content in response to N and P addition can reflect the dynamic changes of C supply and consumption during the growth and development of tropical forest plants, which provides scientific basis for exploring C utilization strategies and coexistence mechanisms of plants in secondary tropical forest.