模拟CO_2浓度升高及降雨变化对荒漠灌木红砂光合及生长的影响

Influences of Elevated CO_2 and Precipitation Regimes on Photosynthesis and Growth of Desert Shrub Reaumuria soongarica

【目的】未来大气CO_2浓度显著升高将引起降雨格局的变化,必将对荒漠生态系统产生严重影响。研究CO_2浓度及降水变化对荒漠优势植物光合特性及生长的影响有助于预测荒漠生态系统对全球气候变化的响应。【方法】以荒漠优势植物红砂2年生苗木为试材,采用开顶式CO_2控制气室模拟CO_2浓度(350和700μmol·mol^(-1))变化,研究降水变化减少30%(-30%)、自然降水0、增加30%(+30%)及其与CO_2的协同作用对红砂光合速率、蒸腾速率等光合生理参数以及株高、生物量和根茎比等生长特性的影响。【结果】1)CO_2浓度倍增可显著提高红砂的光合速率,降低蒸腾速率和气孔导度(P<0.05),降水增加30%对高浓度CO_2下红砂叶片的光合速率有显著促进作用,对蒸腾速率和气孔导度的降低有一定补偿效应。2)长期高浓度CO_2处理使红砂存在光合适应现象,光合能力下调。3)CO_2浓度倍增和降雨量增加可显著增加红砂的株高、地上生物量和总生物量,且CO_2浓度增加可以减缓因降雨量减少而引起的红砂生长量减小。4)降雨减少,红砂的根生物量增长,导致根茎比增加;CO_2浓度升高则显著促进地上部分生长,导致根茎比减小。【结论】未来CO_2浓度升高条件下,降雨量增加地区红砂因充足的碳源和水分而得以恢复;降雨减少地区,CO_2浓度升高对降雨减少有一定的补偿作用,红砂以较高的根茎比来维持其在荒漠生态系统中地位。

At mospheric CO 2 concentrations would increase from approximately 350μmol·mol-1 today to over 700μmo·mol-1 by the end of this century.The elevated CO 2 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 CO 2,the interaction of changing precipitation pattern and elevated CO 2 concentration on desert plantsis still not clear.【Methods】A pot experiment was conducted to study the interaction of elevated CO 2 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 CO 2 concentrations(350 and 700 0x0E?SymbolmA@0x0Fmol·mol-1)and three precipitation levels[natural precipitationas control(0),precipitation minus 30%(-30%),precipitation plus 30%(+30%)].【Result】Doubled CO 2 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 CO 2,and a certain compensation effect on the transpiration rate and stomatal conductance inhibited by the elevated CO 2.Long-term treatment with increased CO 2 led to the photosynthetic acclimation by reducing the photosynthetic capacity.Elevated CO 2 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 CO 2 concentration reduced the decrease of the R.soongarica growth caused by the decrease of rainfall.Root biomass were increased under precipitation reduction by elvated CO 2 concentration.