增温与氮沉降对高寒植物净光合速率的影响

Effect of climate warming and nitrogen deposition on net photosynthetic rate of alpine plants on Qinghai-Tibet Plateau

在青藏高原地区开展模拟增温试验和模拟氮沉降试验,在高寒草甸、高寒草原、高寒荒漠和栽培草地4类草地上各设置7组处理:对照[CK,0kg·(hm^2·a)^(-1)]、低氮Ⅰ[N_Ⅰ,8kg·(hm^2·a)^(-1)]、低氮Ⅱ[N_Ⅱ,24kg·(hm^2·a)^(-1)]、中氮[N_Ⅲ,40kg·(hm^2·a)^(-1)]、高氮Ⅰ[N_Ⅳ,56kg·(hm^2·a)^(-1)]、高氮Ⅱ[N_Ⅴ,72kg·(hm^2·a)^(-1)]、增温[W,0kg·(hm^2·a)^(-1)]、增温增氮耦合[W-N_Ⅰ,8kg·(hm^2·a)^(-1)],采用Li-6400光合仪,对各类草地优势植物的净光合速率进行实测分析。结果表明,1)随氮沉降和增温的加剧,高寒草甸中白花枝子花(Dracocephalum heterophyllum)和针茅(Stipa capillata)的净光合速率先增加后减少,高氮沉降条件下,猪毛蒿(Artemisia scoparia)、女娄菜(Silene aprica)等植物的净光合速率显著增加;2)高寒草原中披针叶黄华(Thermopsis lanceolate)、马蔺(Iris lactea var.chinensis)等植物的净光合速率随氮沉降而增加,矮生嵩草(Kobresia humilis)、平车前(Plantago depressa)等植物的净光合速率减少;3)栽培草地中披针叶黄华、冷地早熟禾(Poa crymophila)等植物的净光合速率随氮沉降量的增加呈现先下降后增加的趋势;4)在增温条件下,盐渍化草原中的华扁穗草(Blysmus sinocompressus)的净光合速率减少,高寒荒漠中垫状驼绒藜(Ceratoides compacta)净光合速率显著增加,高寒荒漠与盐渍化草原过渡带中赖草(Leymus secalinus)的净光合速率增加。

Simulated warming and nitrogen deposition experiments were conducted to examine the responses of the net photosynthetic rate of key dominant plants in four types of alpine grasslands,including alpine meadow,alpine steppe,alpine desert,and artificial grassland on Qinghai-Tibetan Plateau by using Li-6400.There were seven treatments:control[CK,0 kg·(ha·a)-1],low nitrogenⅠ[NⅠ,8 kg·(ha·a)-1],low nitrogenⅡ[NⅡ,24 kg·(ha·a)-1],medium nitrogen[NⅢ,40 kg·(ha·a)-1],high nitrogenⅠ[NⅣ,56 kg·(ha·a)-1],high nitrogenⅡ[NⅤ,72 kg·(ha·a)-1],warming[W,0 kg·(ha·a)-1],and the interaction of warming and nitrogen addition[W-NⅠ,8 kg·(ha·a)-1].The results showed that 1)the net photosynthetic rate of Dracocephalum heterophyllum and Stipa capillata increased initially and then decreased with the increasing gradients of warming and nitrogen addition.With increasing nitrogen deposition,the net photosynthetic rate of Artemisia scoparia,Silene aprica,Kobresia humilis,Poa crymophila,and P.attenuate in the alpine meadow increased markedly.2)The net photosynthetic rate of Thermopsis lanceolate,Iris lactea var.chinensis,and Potentilla multifida increased with nitrogen deposition,while that of K.humilis,Plantago depressa,A.scoparia,K.capillifolia,P.crymophila,Pedicularis kansuensis,Elymus nutans,and Dracocephalum heterophyllum decreased with nitrogen deposition.3)The net photosynthetic rate of T.lanceolate,P.crymophila,and Aster tataricus in the artificial grassland decreased initially and increased thereafter with the increase of nitrogen deposition.4)The net photosynthetic rate of Blysmus sinocompressus in soil-salinization grassland decreased,while that of Ceratoides compacta in alpine desert and Leymus secalinus in the transitional zone between soil-salinization grassland and desert increased with the experimental warming.