南亚热带森林植物源挥发性有机物排放对氮沉降的响应

Biogenic volatile organic compounds (BVOCs) are volatile hydrocarbons emitted by plants with boiling point in the range of 50-260 ℃ and saturated vapor pressure at room temperature beyond 133. 322 Pa. Because these compounds have high reactive activities and participate in atmospheric chemistry process of troposphere, they potentially affect atmospheric environmental quality, global change and the cycling of carbon(C) and nitrogen (N). BVOCs belong to plant secondary metabolites and are considered to be plant defensive matters. Some species among BVOCs even take important ecological roles, such as resisting environmental changes, stresses and mechanical injuries, being transferred as signals among plants or between plants and insects. As a result, the functions of BVOCs and the relationship between BVOCs and global change are increasingly concerned. Nowadays, N deposition is globalizing and has become one of the new global change phenomena, and is projected to increase rapidly with development of industry, agriculture and urbanization. High atmospheric N deposition was also observed in China. Increasing atmospheric N deposition, as a new environmental factor, is stealthily and rapidly affecting BVOCs emission rates and species, and their functions in ecosystems. However, there have been so far few reports related to the effects of N deposition on BVOCs. In this item, based on the long-term simulated N deposition site established in 2002, we will plan to research the effects of N deposition on BVOCs from south China forest plants, compared with potted experiment. The aim of the research is to confirm whether increasing atmospheric N deposition affects BVOCs emission. The research on BVOCs affected by N deposition can increase our understanding on forest C sequestration, C and N cycles and their coupling into ecosystems; lay a strong basis to correctly evaluate C loss as BVOCs in ecosystems under the condition of increasing N deposition and to explore the roles played by BVOCs during the process of the reduction of forest biodiversity in the future; and further service the theory of plants surviving the environment with increasing atmospheric N deposition.

植物排放的挥发性有机物(Biogenic volatile organic compounds, BVOCs)，属于植物次生代谢物质，是植物重要的防御物质，亦是全球碳素循环的一个重要组成部分。它们具有很高的化学活性，参与对流层大气化学过程，承担重要的生态功能，并对全球变化和碳氮循环等具有潜在的影响。BVOCs的排放与环境变化密切相关。大气氮沉降正不断持续增加，并呈现全球化的趋势，尤其是中国。然而，氮沉降对BVOCs的影响迄今未有相关报道。本项目利用已建立的长期模拟氮沉降样地，拟研究大气氮沉降增加对南亚热带森林BVOCs的影响，并同期开展盆栽试验。拟确证大气氮沉降是否影响BVOCs排放，为评价植物排放BVOCs而导致的碳丢失对生态系统碳库的影响提供重要依据，为加深了解生态系统碳氮循环及其藕合提供参考，并为研究植物适应氮沉降增加提供重要基础及其进一步研究其适应机理提供理论依据。

氮沉降是一种新的全球变化现象，参与森林生态系统的碳素循环，并影响植物对光合产物的分配。然而氮沉降是否影响植物源挥发性碳的排放并未得到关注。本项目通过长期模拟氮沉降的森林样地研究平台，并同期开展苗圃试验，探索了植物源羰基化合物排放对氮沉降的响应。氮沉降还对植物赖以生存的土壤环境有重要影响。因此，我们还开展了氮沉降对土壤酸化的综述研究，并以珠三角的城市化为背景，研究该地区松林土壤的酸化情况；并利用氮磷添加手段，研究了与磷素和碳素相关的土壤酶活性变化。本项目取得的研究成果如下：.1）氮沉降对植物源挥发性碳的释放有季节差异。在湿季，氮沉降并不显著影响植物释放挥发性碳，但在干季，氮沉降会刺激氮饱和森林植物释放挥发性碳，却抑制氮限制森林植物挥发性碳的释放。苗圃试验亦证明：氮限制森林植物挥发性碳释放对氮沉降的响应趋势。.2）综述了氮沉降对森林土壤酸化的研究现状，总结了土壤酸化的特征和现用的研究方法。.3）利用珠三角高的氮沉降水平及城市化背景，研究了松林土壤酸化的状态及其特征，发现珠三角地区的土壤酸化有着自己的特色，与现有的氮沉降驱动的土壤酸化特征并不十分一致，但是，氮沉降仍是该地区土壤酸化的主要贡献者。.4）研究了土壤磷素和碳素相关的酶活性对氮磷养分添加的响应情况，结构表明：氮沉降加剧亚热带森林土壤的磷限制，尤其是氮饱和森林土壤的磷限制，并抑制氮限制森林土壤的碳可利用性；但磷添加能缓解氮沉降带来的负面效应，即增加土壤磷素和碳素可利用性。.我们的研究对氮沉降增加的背景森林碳氮耦合及其相关的机理探讨有重要的理论意义和学术价值。