关键词: 植物种群, 群落, 生态系统, 大气CO2浓度增加

Abstract: World-wide current studies on responses of growth and competition of plant population and communities,exchanges of CO₂ and water vapor between forest ecosystems and atmosphere to rising atmospheric CO₂, and modeling forest response processes were reviewed in this paper.Gas measurement on crop population in response to elevated CO₂ showed that photosynthesis and instantaneous water use efficiency (the ratio f photosynthesis to transpiration) were increased with increasing atmospheric CO₂ concentration, but canopy conductance to water and CO₂ exchange were reduced. These responses were accompanied with an increase in leave area index, dry mass and seed yield. Population grown at elevated CO₂ was found to develop more quickly, reaching the stage of fruit production. The effect of CO₂ on thetiming of flowering and floral initiation Was not fully understood. The influence of the interaction between CO₂ concentration and population density on seed production varied with plant species. With increasing populationdensity, the positive effect of elevated CO₂ on seed production was increased, but negative response occurredwhen competitive species introduced. Very limited research on population differences in CO₂ responses indicated that within-and between-population differences were observed in the responses of the root to shoot ratio,seed weight, seed germination, leaf expansion and growth rate.Ideal research on response of plant community to elevated CO₂ was nearly impossible due to technical and practical problems as well as costs. Thus, the logical approach to study community responses to elevated CO₂ depended on developing ideas and theories from the population level of study. The response of a C₃ and C₄community to elevated CO₂ concentration was different regardless of using open-top chambers and in thecontrolled environment. In a community consisting of C₃ and C₄ species, the growth and productivity of the C₃ species was increased at elevated CO₂ concentration, particularly when in competition with the sensitive C₄ species. The leaf C/N ratio with CO₂ concentration resulting from a decrease in leaf nitrogen and protein wasincreased, and this increased the rate of leaf herbivore and the quantity of plant tissue consumed. These responsescould eventually lead to significant alterations in community structure and functioning.Experimental approaches can not directly employed to study ecosystem or biome response to risingatmospheric CO₂ concentration such as those instituted for plants, populations and communities, but the effectscan alternatively be achieved by remote observations of ecosystem optical reflectance. The seasonal changes inatmospheric CO₂ concentration were considered as a good estimators of ecosystem CO₂ exchange. Finallyrecommendations for future research was discussed, in which development of appropriate bottom-up models ofecosystems incorporating ecological feedback processes was strongly signified.

Key words: Plant population, communities, ecosystems, rising atmospheric CO₂ concentration