大气氮沉降对海北高寒草甸优势种叶片光合作用过程的影响  

Effects of Atmospheric Nitrogen Deposition on Photosynthesis of Dominant Plant Species in the Haibei Alpine Meadow Ecosystem

作　　者：吕琳玉 张黎[2] 刘利民[1] 何洪林[2] 闫霜 方华军[2] 李英年[4] 

机构地区：[1]沈阳农业大学农学院,辽宁沈阳110866 [2]中国科学院地理科学与资源研究所生态系统网络观测与模拟重点实验室,北京100101 [3]北京市密云区气象局,北京101500 [4]中国科学院西北高原生物研究所,青海西宁810008

出　　处：《环境科学研究》2016年第11期1617-1625,共9页Research of Environmental Sciences

基　　金：国家自然科学基金项目(31000235);国家自然科学基金重大项目(31290221);中国科学院先导专项项目(XDA05050600)

摘　　要：为研究大气氮沉降对海北高寒草甸光合作用过程的影响,对不同施氮水平和氮沉降类型〔KNO3、(NH4)2SO4和NH4Cl〕下5个群落优势种叶片w(TN)、异针茅叶片光合参数和冠层LAI(叶面积指数)进行测定和分析,并利用Farquhar植物光合作用模型估算光合参数变化对GPP(总初级生产力)的可能影响,其中,氮沉降设置4个水平,即对照〔0 kg/(hm2·a)〕、低氮〔10kg/(hm2·a)〕、中氮〔20 kg/(hm2·a)〕和高氮〔40 kg/(hm2·a)〕,均以N计.结果表明:除了施加(NH4)2SO4、低氮处理下甘肃棘豆叶片w(TN)显著增加9.4%以外,其他施氮水平和施氮类型对5个优势种叶片w(TN)均无显著影响.高氮处理下Vcmax25(25℃时最大羧化速率)、J25(25℃时电子传输速率)、TPU25(25℃时丙糖磷酸传输速率)和Rd25(25℃时暗呼吸速率)分别较对照处理高出38.6%、30.4%、27.8%和164.3%.氮添加后,Rd25的增加抵消了因Vcmax25增加引起的光合作用增强效果,使得整体上GPP的增加趋势不显著.不同施氮水平和施氮类型下海北高寒草甸群落优势种的LAI均未发生显著变化.研究显示,当大气氮沉降量低于40 kg/(hm2·a)时,氮沉降量的增加会促进海北高寒草甸植物叶片光合作用的反应速率,但对植物叶片w(TN)、LAI和GPP的影响并不显著.To quantify the effects of nitrogen deposition on photosynthetic processes in the Haibei alpine meadow,we analyzed the differences in observed leaf nitrogen content（ w（ TN）） of five dominant species,leaf photosynthetic parameters of Stipa aliena and canopy leaf area index（ LAI） measured in simulated atmospheric nitrogen deposition treatments with various nitrogen levels（ control of-0 kg/（ hm^2·a）,low nitrogen treatment of 10 kg/（ hm2·a）,medium nitrogen treatment of 20 kg/（ hm^2·a） and high nitrogen treatment of 40 kg/（ hm2·a）） and forms（ KNO_3,（ NH4）2SO4and NH4Cl）. We also used a photosynthesis model to estimate the possible effects of photosynthetic parameters on gross primary productivity（ GPP）. The results showed that nitrogen levels andforms had no significant effects on leaf nitrogen content for five dominant species,except for Oxytropis kansuensis,the leaf nitrogen content of which increased by 9. 4% significantly in the low level nitrogen treatment when using（ NH_4）_2SO_4fertilizer. Values of the maximum carboxylation rate at 25 ℃（ Vcmax25）,electron transfer rate at 25 ℃（ J25）,triose phosphate transfer rate at 25 ℃（ TPU25）,and dark respiration rate at 25 ℃（ Rd25） in the high level nitrogen treatment were 38. 6%,30. 4%,27. 8% and 164. 3% higher than those in the control. Increasing Rd25 offset the increase in GPP induced by increasing Vcmax25 after nitrogen addition,which caused no significant change in GPP. Observed LAI had no significant responses to nitrogen levels and forms. These results suggest that nitrogen input within the level of40 kg/（ hm2·a） accelerated the reaction rates in leaf photosynthesis,but did not significantly affect leaf nitrogen content,LAI,and GPP.

关 键 词：氮沉降 光合参数 叶片w(TN) 叶面积指数(LAI) 高寒草甸 

分 类 号：X171.1[环境科学与工程—环境科学]