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尽管气候变化很可能会导致干旱生态系统的降水量变化幅度增大,但沙漠灌木群落对降水变化的响应模式尚不清楚.因为适应干旱的植物具有多种生存机制以利于其物种的共存,所以认识沙漠灌木群落对降水变化的响应具有重要的意义.我们在美国大盆地地区(美国加利福尼亚州欧文斯谷)开展了一项同质园实验,对8种干旱适应性植物(其中包括了禾本科植物、灌木和杂类草植物)在3种不同夏季降水量(分别为每月1.3、2.6和3.9 cm)的响应进行了测定.检测了上述植物在矿物养分吸收(碳、氮、磷、钾、钙、镁、锰、铜、硼、锌、铁和钠)和气体交换参数(光合速率和气孔导度)方面的变化.研究结果显示,两种禾本科植物[鼠尾粟草(Sporobolus airoides)和匍匐野麦赖草(Leymus triticoides)]与一种耐盐灌木物种[密叶滨藜(Atriplex confertifolia)]在水分供给增加时,光合速率和/或气孔导度增加.在这8个物种中,有5个物种表现出了水分供给与营养物质吸收之间的显著相关性.光合速率更高的三齿蒿(Artemisia triidentata)含有更多的钾、铜和硼,而光合速率更高的北极灯心草(Juncus arcticus)具有更高的镁和铁含量以及更低的钠含量.北极灯心草以及3种适盐性物种[密叶滨藜、盐草(Distichlis spicata)和鼠尾粟草]在气孔导度和营养素浓度方面表现出了相关性.这些结果表明,干旱适应性物种之间对水分增多情形的生理响应机制的差异以及相关的营养吸收策略可能有助于它们在夏季雨水增多时的相互共存.“,”Aims Although increases in precipitation variability in arid ecosystems are projected due to climate change,the response of desert shrub communities to precipitation change has not been fully elucidated.Such knowledge is important since drought-adapted plants exhibit varied mechanisms of survival that may contribute to species coexistence.Methods We tested the responses of eight drought-adapted plants,a mix of graminoids,shrubs and forbs to three summer precipitation scenarios(1.3,2.6 and 3.9 cm per month)in a common garden experiment in the Great Basin(Owens Valley,California).Changes in mineral nutrient uptake(carbon,nitrogen,phosphorus,potassium,calcium,magnesium,manganese,copper,boron,zinc,iron and sodium)and gas exchange parameters(photosynthetic rate and stomatal conductance)were investigated in the studied species.Important Findings Two graminoids(Sporobolus airoides and Leymus triticoides)and one salt tolerant shrub species(Atriplex confertifolia)responded to increased water availability with increases in photosynthetic rate and/or stomatal conductance.There was a significant correlation between water availability and uptake of nutrients for five out of eight species.Artemisia tridentata,with higher rates of photosynthesis,contained greater amounts of potassium,copper and boron,while Juncus arcticus,with higher rates of photosynthesis,contained greater amounts of magnesium and iron,and less sodium.Juncus arcticus and three salt-adapted species(A.confertifolia,Distichlis spicata and S.airoides)exhibited correlations with stomatal conductance and concentrations of nutrients.Results indicate that differential physiological response mechanisms to increased moisture and associated nutrient uptake strategies in drought-adapted species may mediate coexistence under increased summer precipitation.