川西北高寒草甸蚁丘植物群落演替:种类组成与物种多样性

Plant Community Succession on Ant-hills of a Sub-alpine Meadow in Northwestern Sichuan,China:Species Composition and Diversity

蚂蚁通过构建蚁丘，提高了群落生境异质性，影响群落物种组成，甚至生态系统结构和功能。我们在川西北典型高寒草甸调查了平地（非蚁丘，即距离蚁丘4～5m的草地）和不同大小广布弓背蚁（Cam-ponotus herculeanus）蚁丘（小蚁丘、中蚁丘和大蚁丘3种，平均面积大小分别为309．45cm^2、948．45cm^2、2124．90cm^2）上的植物种类组成、物种多样性，以及每个物种的高度，盖度和多度，在此基础上分析了蚁丘植物群落演替进程中的优势种变迁及其机制。调查发现，与平地相比，天气晴朗条件下蚁丘的土壤温度在白天较高，而在夜晚较低，日变化的波动性较大；蚁丘中心的相对湿度低于边缘，更低于平地。群落结构分析表明，不同大小蚁丘之间植物物种丰富度和多样性差异不显著，但是优势种变化明显。随蚁丘增大，钩状嵩草（Kobresia uncinoides）的群落地位（重要值）逐渐上升，小、中、大蚁丘上的次优种分别为拉拉藤（Galium aparine）、羊茅（Festuca ovina）、垂穗披碱草（Elymus nutans）。蚁丘上禾草类优势度显著高于平地，而杂草类优势度则显著低于平地。平地上菊科（Compositae）和毛莨科（Ranunculaceae）植物占优势，蚁丘上莎草科（Cyperaceae）和禾本科（Gramineae）植物占优势。文中还讨论了蚁丘植物群落演替的可能机制，以及蚁丘对整个草甸群落组成和动态的潜在意义。

Ants may increase habitat heterogeneity by means of building ant-hills, thereby changing community species composition and ecosystem structure and functioning. We investigated plant height, coverage and abundance for each species and calculated species richness and diversity for ant-hills of Camponotus herculeanus differing in size （309.45 cm2, 948.45 cm2, 2124.90 cm2 for the small, intermediate and large ant-hills, respectively）. The dominant species was subsequently identified for the three size-classes of ant-hills and the mechanism underlying anthill community succession was derived. Our results showed that diurnal temperature fluctuation was greater in ant-hills than the surrounding flat soil, where the temperature of the ant-hills was higher in daytime but lower at night relative to the counterpart. The soil moisture was lower in center than in edge of ant-hills whose moisture was lower than the flat soil. Plant species diversity and richness were not significantly different among the three classes of ant-hills whilethe dominant species conspicuously changed. The importance value of the most dominant species, Kobresia unci- noides, increased significantly with increasing ant-hill size; the subdominant species was Galium aparine, Festuca ovina, Elymus nutans for the small, intermediate and large ant-hills, respectively. The dominance of grasses was significantly higher, but that of forbs was lower on ant-hills than in surrounding communities. The ant-hills were dominated by species from Cyperaeeae and Gramineae while Compositae and Ranuneulaeeae dominated the surrounding communities. In addition, we discussed the possible mechanisms driving ant-hill community succession and the potential significance of ant-hills to the whole community composition and dynamics in the alpine meadow.