火烧和氮添加对亚热带—暖温带气候过渡区主要灌木光合特性的影响

Effects of Burning and Nitrogen Addition on Photosynthetic Characteristics of Major Shrubs in North Subtropical-Warm Temperate Climate Transition Zone

火烧和氮沉降是森林生态系统中重要的干扰因子,开展林下植物光合作用与火烧和氮添加的关系研究,揭示亚热带—暖温带气候过渡区主要灌木光合特性对环境扰动产生的响应,可为研究区森林生态系统的经营管理提供理论参考。本文采用原位培养法在火后5年的火烧迹地开展火烧和氮添加实验,以我国气候过渡区针阔混交林主要灌木黄荆(Vitex negundo L.)、山胡椒(Lindera glauca(Sieb.et Zucc.)Bl.)、华山矾(Symplocos chinensis)为研究对象,研究林下植物在火干扰和氮添加后光合特性的变化和光环境适应能力。主要结果如下:(1)火烧、火烧和氮添加交互处理显著提高林下层光合有效辐射以及土壤温度;(2)火烧显著增加三者的净光合速率和气孔导度,显著提高黄荆、山胡椒的光饱和点和最大净光合速率,显著增加黄荆和华山矾的水分利用效率;(3)氮添加对三种灌木的光合特性指标无明显影响,火烧和氮添加交互处理显著增加黄荆、山胡椒和华山矾的光合作用速率,但对其它光合指标协同作用不明显。研究表明,火烧对北亚热带—暖温带气候过渡区的3种优势灌木的光合特性影响显著,黄荆和华山矾比山胡椒更适应火烧后的干旱环境;全球气候环境变化的大背景下,在气候过渡区进行森林经营管理应考虑林下植被的适应性。

The burning and nitrogen deposition are important interference factors in the forest ecosystem.Studying on the relationship between the understory plant photosynthesis and the burning and nitrogen addition and revealing the effects of the main shrub photosynthetic characteristics on the environment disturbance in the subtropical-warm temperate climate transition zone can provide theoretical reference to the forest ecosystem management in the studied zone.In this study,the in-situ culture method was used to carry out the burning and nitrogen addition experiments in the burned area 5 years after burning.Vitex negundo L.,Lindera glauca(Sieb.et Zucc.)Bl.and Symplocos chinensis,the main shrubs of coniferous and broad-leaved mixed forest in the climate transition zone of China,were selected as the research objects to study the changes of photosynthetic characteristics and light environment adaptability of understory plants after the fire disturbance and nitrogen addition.The main results are as follows.(1)The burning and the intertreatment of burning and nitrogen addition can significantly increase the photosynthetically active radiation and soil temperature in the understory.(2)The burning can significantly increase the net photosynthetic rate and stomatal conductance of the abovementioned three shrubs,the light saturation point and maximum net photosynthetic rate of Vitex negundo L.and Lindera glauca(Sieb.et Zucc.)Bl.,and the water use efficiency of Vitex negundo L.and Symplocos chinensis.(3)The nitrogen addition has no pronounced effect on the photosynthetic characteristics of the three shrubs,and the interaction treatment of burning and nitrogen addition can remarkably accelerate the photosynthetic rates for the three shrubs,but no obvious synergistic effect on other photosynthetic indexes.The results show that the burning has a considerable effect on the photosynthetic characteristics of the three dominant shrubs in the north subtropical-warm temperate climate transition zone,and Vitex negundo L.and Symplocos chinensis are more suitable to the arid environment after burning than Lindera glauca(Sieb.et Zucc.)Bl.In the context of global climate change,the adaptability of understory vegetation should be considered for the forest management in the climate transition zone.