几种海南岛热带雨林优势种植物挥发性有机物排放对模拟氮沉降的短期响应

Short-term response of BVOCs emissions from several dominant tropical rainforest tree species in Hainan Island to simulated nitrogen deposition

BVOCs(Biogenic Volatile Organic Compounds)是植物向大气释放的一类重要气态化合物,能参与大气化学过程和陆地生态系统碳素循环。分析环境因子对BVOCs排放的影响,对科学认识未来气候变化具有重要意义。氮素作为植物生长、发育所需的大量营养元素之一,其沉降增加是当前全球气候变化的主要驱动因素之一,但学者对BVOCs如何应对氮沉降增加知之甚少。因此以海南岛热带雨林树种:木荷(Schima superba)、厚壳桂(Cryptocarya chinensis)和线枝蒲桃(Syzygium araiocladum)为研究对象,通过温室盆栽实验模拟氮沉降对3个树种BVOCs释放的短期效应。主要结论如下:(1)自然状态下,从木荷、厚壳桂和线枝蒲桃的枝叶中鉴定出14、34和24种挥发性有机化合物,包括异戊二烯、单萜烯、倍半萜烯和其他挥发性有机化合物(烷烃、羰基、醛、醇、酯、醚和酸),此外三个阔叶树种释放BVOCs的速率呈厚壳桂>木荷>线枝蒲桃;(2)外源施氮均促进了三种植物幼苗VOCs释放,其中总VOCs释放速率和成分数量均随施氮浓度的升高而增加,且叶面施氮的影响效果显著高于土壤施氮。(3)三种植物幼苗对氮沉降的敏感性大小表现为木荷>厚壳桂>线枝蒲桃。(4)外源施氮对植物的生理参数和土壤肥力均产生了影响,且叶面施氮的影响效果更为突出。生理参数中,净光合速率与幼苗释放BVOCs关系最为密切,其次是气孔导度。施氮主要对土壤pH、NH^(+)_(4)-N和NO^(-)_(3)-N有显著影响,其次是有效磷(Available phosphorous,AP)和总磷(Total phosphorus,TP)。

Biogenic volatile organic compounds(BVOCs)are low-boiling,small-molecule secondary metabolites released by plants,and play an important role in the biosphere,such as herbivore deterrence,fungal toxicity,and pollinator attraction.Besides,BVOCs are also important gaseous compounds in the atmosphere,which can react with active free radicals in the atmosphere to form secondary organic aerosols(SOA)and prolongs the life of greenhouse gases such as CH4 in the atmosphere.Analyzing the impact of environmental factors on Biogenic Volatile Organic Compounds(BVOCs)emissions is of great significance for accurately understanding future climate change.As we all know,nitrogen is one of large numbers of nutrients for plant growth,however,it′s increasing in deposition is the main driver of current global climate change.Besides,the emission of BVOCs in response to the elevated N deposition is poorly understood.In this study,Schima superba,Cryptocarya chinensis,and Syzygium araiocladum were chosen as the research objects,which are the tropical rain forest tree species in Hainan Island,the short-term effect of nitrogen deposition on the release of BVOCs of three tree species were also simulated through a greenhouse test.A dynamic headspace method was used to collect BVOCs released by the three broad-leaved tree species.The main conclusions are as follows:(1)Under natural conditions,14,34 and 24 kinds of volatile organic compounds were isolated and identified from the branches and leaves of S.superba,C.chinensis,and S.araiocladum,including isoprene,monoterpene,sesquiterpene and other VOCs(alkanes,carbonyls,aldehydes,alcohols,esters,ethers and acids),and the rates of BVOCs released by three broad-leaved tree species showed C.chinensis>S.superba>S.araiocladum..(2)Nitrogen application promoted the release of BVOCs from the three plant seedlings,and the effect of foliar nitrogen application was significantly higher than that of soil nitrogen,and the emission rate of Total Volatile Organic Compounds(TVOCs)and the number of components increased with the increase of nitrogen concentration.(2)The sensitivity of the three plant seedlings to nitrogen deposition was expressed as Schima superba>Cryptocarya chinensis>Syzygium araiocladum.(3)Nitrogen application had an impact on plant physiological parameters and soil fertility,and the effect of foliar nitrogen application was more prominent.Among the physiological parameters,the net photosynthetic rate had the closest relationship with the BVOCs released by the seedlings,followed by the stomatal conductance.Nitrogen application mainly had a significant effect on soil pH,NH^(+)_(4)-N and NO^(-)_(3)-N,followed by Available phosphorous(AP)and Total phosphorus(TP).