大气CO2浓度升高和N沉降对南亚热带主要乡土树种叶片元素含量的影响

大气CO₂浓度升高和N沉降以及二者之间的耦合作用对陆地森林生态系统的影响是当前国际生态学界关注的热点之一。该实验运用大型开顶箱(open-top chamber, OTC)研究: 1)高CO₂浓度(700 μmol×mol^-1) +高N沉降(100 kg N×hm^-2×a^-1) (CN); 2)高CO₂浓度(700 μmol×mol^-1)和背景N沉降(CC); 3)高N沉降(100 kg N×hm^-2×a^-1)和背景CO₂浓度(NN); 4)背景CO₂和背景N沉降(CK) 4种处理对南亚热带主要乡土树种木荷(Schima superba)、红锥(Castanopsis hystrix)、肖蒲桃(Acmena acuminatissima)、红鳞蒲桃(Syzygium hancei)、海南红豆(Ormosia pinnata)叶片元素含量的影响。研究结果表明, 大气CO₂浓度升高对5种乡土树种叶片元素含量有较大的影响, 除海南红豆叶片的Ca含量外, 其他树种的叶片元素含量在高CO₂浓度处理下都显著升高(p < 0.05); 而在N沉降处理下, 5个树种的叶片K和Ca含量都降低。大气CO₂浓度升高与N沉降处理对5种乡土树种植物叶片元素含量影响的交互作用不是很明显, 仅仅木荷和红鳞蒲桃的叶片Ca和Mn以及海南红豆的叶片Mn含量在大气CO₂浓度上升和N沉降交互处理下显著下降, 而肖蒲桃的叶片P含量在大气CO₂浓度上升和N沉降交互处理下显著上升。

Effects of elevated CO2 concentration and N deposition on leaf element contents of major native tree species in southern subtropical China

Aims The effects of elevated atmospheric CO2 concentration and N deposition on terrestrial ecosystems and plants are the focus of international ecological study.Changes of nutrient element content in plants induced by atmospheric CO2 concentration and/or N deposition directly affect the productivity of forest ecosystems;however,few studies have examined this in subtropical China.Our purpose is to study the effects of elevated CO2 and N deposition on leaf element contents of major native tree species in southern subtropical China.Methods Five tree species native in southern China were planted in model forest ecosystems.The species were exposed to elevated CO2 and N deposition in open top chambers in May 2005.The four treatments are:CN(elevated CO2 and high N deposition),CC(elevated CO2 and ambient N deposition),NN(high N deposition and ambient CO2) and CK(ambient CO2 and ambient N deposition).The elevated CO2 was(700 ± 20) μmol.mol-1,and the total amount of added NH4NO3-N was 100 kg N.hm-2.a-1.Leaves were harvested in January 2009,and elements in the leaves were measured.Important findings Compared to the control,elevated CO2 concentration significantly increased leaf-element contents in all species(p < 0.05) except for Ca content in Ormosia pinnata.High N deposition decreased K and Ca contents in the species.There was no interactive effect of high CO2 concentration and N deposition treatments on most leaf element contents.The interactive effect of high CO2 concentration and N deposition treatments only decreased leaf Ca contents in Schima superba and Syzygium hancei and leaf Mn contents in Schima superba,Syzygium hancei and Ormosia pinnata,as well as increased leaf P content in trees of Acmena acuminatissima.