Smith Melinda D, Knapp Alan K
Kansas State University, Division of Biology, Ackert Hall, Manhattan, KS 66506, USA e-mail:
Oecologia. 1999 Sep;120(4):605-612. doi: 10.1007/s004420050896.
We used data from a 15-year experiment in a C-dominated grassland to address the effects of community structure (i.e., plant species richness, dominance) and disturbance on invasibility, as measured by abundance and richness of exotic species. Our specific objectives were to assess the temporal and spatial patterns of exotic plant species in a native grassland in Kansas (USA) and to determine the factors that control exotic species abundance and richness (i.e., invasibility). Exotic species (90% C plants) comprised approximately 10% of the flora, and their turnover was relatively high (30%) over the 15-year period. We found that disturbances significantly affected the abundance and richness of exotic species. In particular, long-term annually burned watersheds had lower cover of exotic species than unburned watersheds, and fire reduced exotic species richness by 80-90%. Exotic and native species richness were positively correlated across sites subjected to different fire (r = 0.72) and grazing (r = 0.67) treatments, and the number of exotic species was lowest on sites with the highest productivity of C grasses (i.e., high dominance). These results provide strong evidence for the role of community structure, as affected by disturbance, in determining invasibility of this grassland. Moreover, a significant positive relationship between exotic and native species richness was observed within a disturbance regime (annually burned sites, r = 0.51; unburned sites, r = 0.59). Thus, invasibility of this C-dominated grassland can also be directly related to community structure independent of disturbance.
我们利用在以碳为主导的草原上进行的一项为期15年的实验数据，来研究群落结构（即植物物种丰富度、优势度）和干扰对外来物种入侵性的影响，入侵性通过外来物种的丰度和丰富度来衡量。我们的具体目标是评估美国堪萨斯州一片原生草原上外来植物物种的时空格局，并确定控制外来物种丰度和丰富度（即入侵性）的因素。外来物种（90%为碳植物）约占植物区系的10%，在这15年期间它们的更替率相对较高（30%）。我们发现干扰显著影响外来物种的丰度和丰富度。特别是，长期每年焚烧的流域中外来物种的覆盖度低于未焚烧的流域，火灾使外来物种丰富度降低了80 - 90%。在接受不同火烧（r = 0.72）和放牧（r = 0.67）处理的样地中，外来物种和本地物种丰富度呈正相关，并且在碳草生产力最高（即优势度高）的样地中，外来物种数量最少。这些结果有力地证明了受干扰影响的群落结构在决定这片草原入侵性方面的作用。此外，在一种干扰模式（每年焚烧的样地，r = 0.51；未焚烧的样地，r = 0.59）下，观察到外来物种和本地物种丰富度之间存在显著的正相关关系。因此，这片以碳为主导的草原的入侵性也可能与独立于干扰的群落结构直接相关。
