摘要：

This paper provides an overview of the environmental setting, rationale, and organization of a multidisciplinary research programme designed to examine the role of salt-affected soils in primary succession on the Tanana River floodplain of interior Alaska. The association of pedogenic salts and forests is largely restricted to northern latitudes where both low precipitation and moderate potential evapotranspiration occur simultaneously. In contrast with upland secondary-successional sites, where fire is the principal determinant of forest type distribution and successional change, ecosystem processes on the floodplain are determined by the fluvial nature of the environment. Consequently, the research presented an opportunity to evaluate some of the markedly contrasting mechanisms that control development of soils and forests in upland ecosystems and on floodplains. Three central hypotheses are presented: (1) the presence and growth of tree and shrub species in early-successional locations on the Tanana River floodplain are controlled by the occurrence of high solution salt concentrations; (2) the genesis and maintenance of surface salt crusts are controlled by the soil physical and chemical environments on early-successional seedbeds; and (3) the disappearance of salt crusts and reduction in mineral soil salt concentration are controlled by forest succession, which mediates the changing soil physical, chemical and biological environment. Within each of 2 replicate sites plots were established in 1985 on terraces representing early to late stages of forest succession [I-XII]. Adjacent to stage III and V plots, 30x50 m areas were cleared and maintained free of vegetation. Adjacent to stage VIII control plots (mature white spruce, Picea glauca) cleared areas of about 8 ha were established and allowed to revegetate or planted with seedlings.

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