CONCLUSIONS ON THE ROLE OF SALT-AFFECTED SOILS IN PRIMARY SUCCESSION ON THE TANANA RIVER FLOODPLAIN, INTERIOR ALASKA

Results of the study of salt-affected soils on the Tanana River floodp lain in interior Alaska raised a number of key issues that are importa nt to resolve with future research in this fluvial environment. The re sults emphasized the prominent role of plant succession in ecosystem s tructure and function in northern boreal forests. For example, alder p lays a crucial role in organic matter and nitrogen dynamics in floodpl ain ecosystems. This plant species has an impact on ecosystem processe s in successional stages beyond its period of dominance on the floodpl ain. The potential facilitative nature of nitrogen accumulation, media ted by alder, to plant community development during and subsequent to the alder phase of succession should be examined in future studies. Or ganic matter chemistry and soil temperature appeared to be more import ant controls of soil processes than high soil salt content. Moreover, secondary plant chemicals may play a role in determining rates of soil nitrification in these floodplain ecosystems. The importance of ion b alance to plant nutrition and primary production in salt-affected soil s is an important topic for future research. Groundwater may be a uniq ue source of water and nutrients to floodplain plant communities. The magnitude of water flux to the rooting zone in relation to terrace ele vation and river level and its importance to plant growth is a signifi cant consideration in the semiarid environment of interior Alaska. The established plant community indicates which species are successful in this environment. Optimum species-terrace combinations may exist that maximize productivity through use of unique moisture and nutrient sup plies associated with a shallow water table. Results of this work sugg ested that new research initiatives are crucial to advance the fundame ntal understanding of controls of ecosystem processes and as a base of information to support forest resource management.