【摘要】 植物群落空间异质性及其动态是认识生态系统生物多样性和稳定性维持机制的基础,而目前对蒙古高原典型草原植物群落空间异质性及其维持机制尚没有专门的研究。本研究在内蒙古温带典型草原区选定针茅(Stipa grandis)和羊草(Leymus chinensis)为优势种的典型草原群落,测定了216个样点(在面积为13.5 hm~2的草地上规则排列12行×18列,样点间距25 m)的植物群落和土壤性质,探讨植物群落的斑块结构及其与土壤性质的关系。结果表明,草原群落具有明显的斑块结构,不同斑块间植物组成的差异促进了群落的生物多样性;草原群落不同斑块之间没有观测到明显的微地形差异且土壤含水量差异不显著(P> 0.05),但土壤容重和养分与不同斑块间植物养分含量的变化具有对应性;草原放牧会降低土壤的养分,增大土壤紧实度和容重,可以推论草原植物群落斑块尺度上的空间异质性可能与放牧影响的空间异质性相关;多年生丛生禾草针茅为优势的群落斑块具有聚集养分的作用,土壤有机碳和氮、磷元素相对丰富,而猪毛菜(Salsola collina)为优势的群落土壤养分低,限制了原生草原优势植物的生长及其对群落伴生植物的抑制,为一年生植物夏雨后快速生长提供了条件。本研究加深了对草原空间异质性的认识,有益于草原生物多样性保护和可持续管理。更多还原

【Abstract】 Spatial heterogeneity in a grassland ecosystem is associated with grassland species diversity and production stability. Understanding the drivers and mechanisms of grassland spatial heterogeneity is essential for the development of best practices in grassland management. To our knowledge, patch-scale spatial heterogeneity of the grassland communities on the steppes on the Mongolian Plateau has not been investigated to date. Here, we investigated the spatial variation of plant communities and soil properties in 216 sites in a rectangular area of 13.5 hm~2 in a typical steppe dominated by Stipa grandis and Leymus chinensis in Inner Mongolia. Our results showed that plant community patches at these sites could be clustered into four groups, dominated by S. grandis, L. chinensis, Salsola collina, or jointly by S. grandis, L. chinensis, and Cleistogenes squarrosa(mixed patch). The differences in the species compositions among these patches indicated an enhancement of species diversity due to spatial heterogeneity. Soil bulk density, organic carbon(SOC), and nutrients(total nitrogen, TN; total phosphorous, TP) and pH differed among the 4 patch types(P < 0.05), but soil moisture did not(P >0.05), which suggests that soil nutrients and bulk density are associated with the spatial heterogeneity of plant communities.The differences in soil bulk density and nutrients among these patch types are most likely related to the heterogeneity of grazing impacts at the patch scale. The grassland patches dominated by perennial S. grandis had higher SOC, TN, and TP,and lower soil bulk density than those of patches dominated by annual S. collina. The low nutrient content of the S. collina patches suggests that the growth of dominant species, S. grandis and L. chinensis, was limited on these patches, which provided a favorable condition for the fast growth of annuals such as S. collina using the pulse of water and nutrients following the summer rainfall. Our research provides new insights into the spatial heterogeneity of steppe grasslands, and is helpful for conservation and sustainable management of the steppes.更多还原