Abstract: Biomass reflects the accumulation energy in plant,and the variation of biomass among various organs is determined by the growth strategies and the adaptability of plants to environment. Atmospheric CO₂ concentrations had increased from approximately 350μmol·mol^-1 today to over 700 μmo·mol^-1 in the late 21^th century and this is likely to have profound effects on the precipitation. This change would seriously affect on the above- and below-ground biomass allocation of desert plant. A pot experiment was conducted to study the interaction of elevated CO₂ concentration and changing precipitation on biomass of Reaumuria soongorica,which is a dominant in the arid region of China. The biomass allocation and isometric relationship were investigated in this study. The main plot was two CO₂ concentrations (350 and 700 umol·mol^-1) and three precipitation levels[natural precipitation as control(0),precipitation minus 30% (-30%),precipitation plus 30%(+30%). The results showed that elevated CO₂ stimulated the increase of above- and below-ground biomass of R.soongorica under three precipitation conditions(P<0.05). The ratio of below-ground biomass allocation was increased with the decrease of precipitation,and CO₂ fattening weakened this effect. Elevated CO₂ concentration and changed precipitation could change biomass among various organs through affecting the relative growth of above- and below-ground organs in R.soongorica,the slopes of the fitted equations at six treatments were not different from 1,which means the allocation patterns between above- and below-ground biomass were similar at six treatments and indicates an isometric allocation relationship between above- and below-ground biomass(P>0.05). With the elevated CO₂ concentration and changed precipitation in the future,responding of allocation patterns in above- and below-ground biomass of R.soongorica to climate changing partially support the optimal partitioning theory.

Key words: Elevated CO₂ concentration, Precipitation, Biomass allocation, Isometric relationship, Reaumuria soongorica

摘要： 植物的生物量在各器官中的分配可反映植物对环境的适应性及其生长策略。未来大气CO₂浓度显著升高将引起降水量的变化，而这种变化必将对荒漠植物的生物量分配产生严重影响。本研究以荒漠优势植物红砂（Reaumuriasoongorica）1年生苗木为试材，采用开顶式CO₂控制气室模拟CO₂浓度变化（350 μmol·mol^-1和700 μmol·mol^-1），研究了降水变化（-30%，0，+30%）及其与CO₂的协同作用对红砂生物量分配及相关生长关系的影响。结果表明：CO₂浓度升高对不同降水量下红砂地上和地下生物量均具有显著的促进作用（P<0.05）；降水减少，红砂生物量向地下分配的比例增加，但CO₂增加会减弱这一作用；CO₂浓度升高和降水变化通过影响红砂地上和地下器官的相对生长来影响生物量在不同器官中的分配，6种处理下的红砂地上-地下生物量分配斜率与1.0差异不显著，其相对生长关系均表现为等速生长。未来大气CO₂浓度升高及降水变化下，红砂生物量分配模式对环境变化的响应在一定程度上支持了最优分配假说。

关键词: CO₂浓度升高, 降水量变化, 生物量分配, 等速生长, 红砂