高寒退化草地甘肃棘豆小尺度点格局

Fine-scale spatial patterns of Oxytropis kansuensis population in degraded alpine grassland

植物种群的空间格局是植物与环境协同适应的结果,体现了植物种群的生活史对策。采用草地群落学调查与点格局分析方法,在祁连山北坡选择未退化(Ⅰ)、轻度退化(Ⅱ)、中度退化(Ⅲ)和重度退化(Ⅳ)4种高寒草地,研究了甘肃棘豆(Oxytropis kansuensis)种群小尺度格局的空间异质性。结果表明:随着天然草地退化程度的加剧,甘肃棘豆种群高度、盖度、地上生物量和密度增大,小株丛(一级)比例逐渐减小,大株丛(二、三级)比例逐渐增大;甘肃棘豆的分布格局表现出与尺度关联的变化趋势,在未退化(梯度Ⅰ)和轻度退化(梯度Ⅱ)草地,甘肃棘豆种群在较小尺度上表现为聚集分布,较大尺度上表现为随机分布;在中度(梯度Ⅲ)和重度(梯度Ⅳ)退化草地,种群空间分布格局则表现出相异的格局特征。随着草地退化程度加剧,甘肃棘豆种群的聚集分布格局由小尺度转向较大尺度,体现了植物种群的扩散和更新策略。

The spatial patterns of plant populations are the results of coordinated adaptation of plants to environment, reflecting the life history strategy of plant populations. The heterogeneity of fine-scale spatial patterns in Oxytropis kansuensis population was studied by using the methods of community survey and point pattern analysis. Four kinds of alpine grassland were chosen, inclu- ding undegraded grassland （ I ）, lightly degraded grassland （ lI ）, moderately degraded grass- land （ m ） and severely degraded grassland （IV） in the northern slope of Qilian Mountains. The results showed that, with the increasing degree of natural grassland degradation, the population height, coverage and aboveground biomass and branch density increased, and the proportion of small bunch decreased, while the proportion of big bunch increased. The spatial distribution pattern of O. kansuensis showed a scale-associated change trend. In the undegraded and lightly degraded grasslands, the distribution pattern of O. kansuensis showed a clumped distribution on a smaller scale, while showed a random distribution on a larger scale. Meanwhile, in the moderate and heavy degradation grasslands, the spatial distribution pattern of the population showed distinct pattern characteristics. With the increasing degree of natural grassland degradation, the clumped distribution patterns of plant populations shifted from a smaller scale to a larger scale, which reflected the dispersion and regeneration strategy of O. kansuensis population.