Influence of slope and aspect on long‐term vegetation change in British chalk grasslands

作者：Jonathan Bennie, M. O. Hill, Robert C. Baxter, Brian John Huntley · 发表于：Journal of Ecology · 年份：2006 · DOI：10.1111/j.1365-2745.2006.01104.x · 被引用次数：372 · 研究领域：Ecology and Vegetation Dynamics Studies、Pasture and Agricultural Systems、Botany and Plant Ecology Studies

1 The species composition of fragmented semi-natural grasslands may change over time due to stochastic local extinction and colonization events, successional change and/or as a response to changing management or abiotic conditions. The resistance of vegetation to change may be mediated through the effects of topography (slope and aspect) on soils and microclimate. 2 To assess long-term vegetation change in British chalk grasslands, 92 plots first surveyed by F. H. Perring in 1952–53, and distributed across four climatic regions, were re-surveyed during 2001–03. Changes in vegetation since the original survey were assessed by comparing local colonization and extinction rates at the plot scale, and changes in species frequency at the subplot scale. Vegetation change was quantified using indirect ordination (Detrended Correspondence Analysis; DCA) and Ellenberg indicator values. 3 Across all four regions, there was a significant decrease in species number and a marked decline in stress-tolerant species typical of species-rich calcareous grasslands, both in terms of decreased plot occupancy and decreased frequency within occupied plots. More competitive species typical of mesotrophic grasslands had colonized plots they had not previously occupied, but had not increased significantly in frequency within occupied plots. 4 A significant increase in Ellenberg fertility values, which was highly correlated with the first DCA axis, was found across all regions. The magnitude of change o...