克隆植物矮嵩草在放牧选择压力下的风险分散对策研究

对不同放牧强度下高寒矮嵩草草甸建群种矮嵩草Kobresia humilis构件数量的季节动态、构件数量和生物量的表型变化及死亡概率变化进行了研究.家畜放牧试验设4个放牧强度处理,于1999-2001年在中国科学院海北高寒草甸生态系统定位站的矮嵩草草甸内进行.研究表明,增加放牧强度会延迟部分分蘖抽秆开花,未影响所测其他性状的季节动态特征;每分株分蘖数、死分蘖数、叶片数和死叶片数均随放牧强度增加而显著提高,秆及死秆数在放牧处理间无显著差异,秆百分比、每分蘖秆质量及每分蘖地上生物量随放牧强度增加而显著下降;不放牧的对照处理中分蘖和分株死亡的概率大于重度放牧处理,在同一放牧处理中,分蘖死亡概率大于分株死亡概率,而分株死亡概率又大于源株死亡概率;构件较大的表型变化、分蘖的死亡以及贮藏资源共同构成了矮嵩草无性系风险分散对策.

Study on the risk spreading strategies of clonal plant Kobresia humilis under grazing selective pressures

A study of natural herbivory was conducted to investigate the seasonal dynamics of modular numbers, the phenotypic variation and the percentage mortality of modular members of clonal plant Kobresia humilis under different grazing treatments in an alpine meadow from 1999 to 2001. Study site was located at the Haibei Alpine Meadow Research Station in Menyuan Country, Qinghai Province, China. Field research for this study was conducted at a 5.46 hm~2 fenced experimental pasture, which was established in April 1998. A completely randomized experiment with four levels of grazing treatments was used. The results showed that the bolting and flowering time of some tillers of plants were delayed in moderate and heavy-grazed intensity, and the seasonal dynamics of the other measured traits of plant did not affected by grazing. The number of tillers, dead tillers, leaves and dead leaves per ramet of a genet increased significantly with increasing grazing intensity. On the contrary, the ratio of flowering tillers to total tillers, aboveground biomass per ramet, and culms weight per tiller decreased greatly with increasing grazing intensity. No significant difference in the number of culms and dead culms per ramet were found among grazing treatments. Death probabilities of tiller and ramet of a genet were greater in ungrazed treatment than in heavy-grazed treatment. The highest death probability was found in tiller level, lower in ramet level. In genet level it had the lowest death probability. The risk spreading strategies consisted of higher phenotypic variation of modular, higher death probability of tiller and storage resources.