The effects of grazing on local colonisation and extinction during early succession

摘要: Estimates of colonisation plant species were made at three spatial scales in an old-field on limestone subject to five experimental sheep grazing regimes. Local extinctions within treatments estimated 1-m2 permanent quadrats. These data used assess the effects treatment and scale process change over a period six years. Colonisation lOha field was virtually random draw from adj acent vegetation, irrespective life-history traits including dispersal strategy. The increased smaller scales. rates changed little during study 10 ha scale, but declined steeply with time short-lived more than those perennials, erratic episodes extinction which did not affect perennials. Short periods enhanced all species, same as ungrazed controls. Grazing for longer further rates, also rates. This produced diversity patterns consistent ‘hump-backed model’, except that no heavy enough decrease diversity. Ungrazed controls had low diversity, areas grazed diverse after years short periods.