A model of created wetland primary succession

Abstract

A descriptive model of primary succession processes on hydric soils is described. The processes of wetland primary succession and temporal change were examined through comparison of eight created wetland sites of different ages (spanning 11 years). Field data were collected on sites that were initially void of any organic matter and had similar hydrologie conditions. Conditions and patterns of covariation in temporal change were assessed for plant species associations, diversity, composition, frequency dominance, character, origin, life form characteristics; and for soil particle size, pH, electrical conductivity, moisture, and organic carbon that naturally evolved on the sites. During the Arrival and Establishment Phase (within the first three growing seasons), plant species aerial cover was between 50 and 60%, annuals dominated species composition, and plant richness and diversity were highest. During the Autogenic Dominance Phase (after the first three growing seasons), aerial cover was over 90% and perennials became dominant. Very few if any vegetative perennial (tree or shrub) seedlings grew on the older sites. The occurrence of native species was above 80% for all sites. Soil organic carbon content was less than typical (for content in natural wetland soils) on the oldest sites. Groups of plant species were found unique to sites in each age class, some species covaried positively in occurrence (i.e. increased in frequency together on successively older sites), some species covaried negatively (i.e. decreased in occurrence as others increased over time), and others were common to all sites. The following conclusions were made: (1) primary succession is the underlying process effecting the evolution of newly created wetland conditions; (2) wetland design strategies should be derived from wetland primary succession theory; (3) existing succession theory can serve to guide the development of wetland primary succession theory; (4) primary succession on created wetlands can be analyzed within the context of complex natural systems.