Ecological - First Order
Recovery after fire
Cover data for plant species on eight environmentally similar sites that were each burned in a different year (from 2 to 36 years ago) were used to construct a composite sequence of vegetational change after fire on Artemisia-grassland sites in southeastern Idaho. Some species were early successional such as Lithospermum ruderale, and some late successional: Artemisia tridentata, A. tripartita, and Gutierreza sarothrae. But many species: Purshia tridentata, Symphoricarpos oreophilus, Amelanchier alnifolia, Chrysothamnus viscidiflorus, A chillea millefolium, Agropyron dasystachyum, and A. spicatum were present in both early and later stages. Shannon and Simpson indices of diversity and species richness indicated little change in alpha diversity through time. This was attributed mainly to the limited change in species composition from early to later stages. The general pattern of succession is compatible with the tolerance model of Connell & Slatyer (1977) in most respects. Species traits relating to persistence through a disturbance or re-establishment on the site, and tolerance of competition shape the course of succession on a site. Perennial grasses and forbs which sprout from the base after fire are the first species to dominate the sites. Sprouting shrubs, which require some years to regrow to their pre-fire form, are prominent by the sixth year. Shrubs which rely on dispersal become co-dominants in later stages, at which time some herbaceous species are reduced or eliminated. The pattern of succession can differ due to presence or absence of species with particular traits.