关键词: CO₂浓度升高, 降雨量变化, 光合特性, 生物量, 红砂

Abstract: [Objective] At mospheric CO₂ concentrations would increase from approximately 350 μmol·mol^-1 today to over 700 μmo·mol^-1 by the end of this century. The elevated CO₂ islikely to have profound effects on the precipitation pattern in the future.This change would seriously affect the desert ecosystem,photosynthesis,above-and belowground biomass of desert plants,which could lead to the changes of ecosystem structure and function. Although many studies have examined the effects of precipitation and CO₂,the interaction of changing precipitation pattern and elevated CO₂ concentration on desert plantsis still not clear.[Methods] A pot experiment was conducted to study the interaction of elevated CO₂ concentration and changing precipitation pattern on photosynthesis parameters such as photosynthesis rate and transpiration rate and so on, andon growth characteristics such as plant height,biomass and root/shoot ratio(R/S) of Reaumuria soongarica thatis a dominant plant species of desert steppe in the arid region of China, in order to assess the possible effect of global climate change on desert ecosystem. The two-year-old seedlings were subjected to two CO₂ concentrations (350 and 700 μmol·mol^-1) and three precipitation levels[natural precipitationas control(0), precipitation minus 30% (-30%), precipitation plus 30%(+30%)].[Result] Doubled CO₂ concentration increased the photosynthesis rate and decreased the transpiration rate and stomatal conductance (P<0.05).The increase of precipitation by 30% had a significant promoting influence on the photosynthesis rateunder the elevated CO₂,and a certain compensation effect on the transpiration rate and stomatal conductance inhibited by the elevated CO₂.Long-term treatment with increased CO₂ led to the photosynthetic acclimation by reducing the photosynthetic capacity.Elevated CO₂ concentration and increasing precipitation were able to significantly stimulate the increase of plant height,aboveground biomass and total biomass of R.soongarica, and the elevated CO₂ concentration reduced the decrease of the R.soongarica growth caused by the decrease of rainfall.Root biomass were increased under precipitation reduction by elvated CO₂ concentration.

Key words: elevated CO₂ concentration, precipitation, photosynthesis, biomass, Reaumuria soongarica