中文摘要：

为揭示白羊草（Bothriochloa ischaemum（L.）Keng.）对全球气候变化的光合生理特征响应规律,采用盆栽控制试验,研究了白羊草在不同CO2浓度、水分条件和施氮水平下叶片的叶绿素含量和光响应曲线特征。结果表明：随CO_2浓度升高和施氮量增加,白羊草叶片SPAD值,最大净光合速率（Pmax）,表观量子效率（AQE）和光饱和点（LSP）均呈增加趋势;干旱胁迫降低了SPAD值,Pmax和LSP。多因素方差分析表明,CO2浓度,水分处理和施氮水平对SPAD值,Pmax和LSP有极显著影响,施氮水平对AQE有极显著影响。CO2浓度和水分处理对Pmax,AQE和LSP有显著的交互作用;CO2浓度和施氮水平对Pmax,AQE和光补偿点（LCP）有极显著的交互作用;水分处理和施氮水平对Pmax,AQE和LSP有极显著的交互作用。RDA分析表明氮素是影响白羊草光合特征的最重要因素。全球CO2浓度升高和氮沉降增加对干旱胁迫引起的白羊草光合速率下降有显著的缓解作用。

英文摘要：

In order to study the photo-physiological characteristics of old world bluestem（Bothriochloa ischaemum（L.）Keng.）from loess hilly-gully region under the background of global climate change,the chlorophyll content（SPAD）and photosynthesis light response curves were determined under potted conditions with different atmospheric CO2 conditions,soil moisture conditions and nitrogen deposition treatments.The results showed that elevated CO2 and nitrogen deposition increased the SPAD value,maximum photosynthetic rate（Pmax）,apparent quantum efficiency（AQE）,light saturation point（LSP）;drought stress decreased the SPADvalue,Pmaxand LSP.Multi-factor analysis of variance indicated that CO2 concentration,soil water conditions and nitrogen deposition level all had highly significant influence on SPAD value,Pmaxand LSP;and nitrogen deposition level had significant influence on AQE.CO2 concentration and soil water conditions had significant interaction effects on Pmax,AQEand LSP;CO2concentration and nitrogen deposition level had significant interaction effects on Pmax,AQEand light compensation point（LCP）;soil water conditions and nitrogen deposition levels had significant interaction effects on Pmax,AQEand LSP.RDA analysis indicated that nitrogen was the most important factor that affected thephotosynthesis characteristics of B.ischaemum.Elevated CO2 concentration and nitrogen deposition had compensation effect on the photosynthetic reduction of B.ischaemuminduced by drought stress under the background of global climate change.