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HISAE NAGASHIMA TAKASHI YAMANO KOUKI HIKOSAKA TADAKI HIROSE 《Global Change Biology》2003,9(4):619-629
To investigate the effect of elevated CO2 on the size inequality and size structure, even‐aged monospecific stands of an annual, Chenopodium album, were established at ambient and doubled CO2 with high and low nutrient availabilities in open top chambers. The growth of individual plants was monitored non‐destructively every week until flowering. Elevated CO2 significantly enhanced plant growth at high nutrients, but did not at low nutrients. The size inequality expressed as the coefficient of variation tended to increase at elevated CO2. Size structure of the stands was analyzed by the cumulative frequency distribution of plant size. At early stages of plant growth, CO2 elevation benefited all individuals and shifted the whole size distribution of the stand to large size classes. At later stages, dominant individuals were still larger at elevated than at ambient CO2, but the difference in small subordinate individuals between two CO2 levels became smaller. Although these tendencies were found at both nutrient availabilities, difference in size distribution between CO2 levels was larger at high nutrients. The CO2 elevation did not significantly enhance the growth rate as a function of plant size except for the high nutrient stand at the earliest stage, indicating that the higher biomass at elevated CO2 at later stages in the high nutrient stand was caused by the larger size of individuals at the earliest stage. Thus the effect of elevated CO2 on stand structure and size inequality strongly depended on the growth stage and nutrient availabilities. 相似文献
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The height ofChenopodium albumL. plants grown in monocultureat three different densities was followed throughout the growingseason to examine size-rank determination processes with specialreference to the effects of neighbourhood conditions. Changesin height rank of plants in the stands were assessed by therank correlation between final height and the height at eachmeasurement during the growing season. The height ranks of plantswere almost fixed 12 weeks after canopy closure whenthe stand height was 1020% of final stand height, andfixation occurred earlier in the denser plot. At each measurement,the effects of neighbourhood were evaluated as the partial correlationcoefficient between height growth and neighbourhood index withheight held constant (rGN.H), in which competitive asymmetrywas incorporated. During the early period of the growing season,rGN.Hwasnon-significant or positive (plants with taller and/or closerneighbours elongated faster), indicating no local competition.Just after canopy closure,rGN.Hbecame negative, indicating localcompetition. A plant's rank changed only in an initial shortperiod of the competition. Plants occupying the upper canopyof stands at the end of the growing season were distinguishedby greater height growth during the initial short period ofcompetition after canopy closure, although these plants werenot necessarily taller before the onset of local competition.These results suggest that the fate of a plant in a crowdedstand is determined in the early stage of stand development.Copyright1999 Annals of Botany Company Height growth, neighbourhood competition, local competition, height-rank of plants in population, size difference, asymmetric competition,Chenopodium albumL. 相似文献
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