EFFECTS OF HYDROLOGIC CONNECTIVITY ON WATER CHEMISTRY, SOILS, AND VEGETATION STRUCTURE AND FUNCTION IN AN INTERMONTANE DEPRESSIONAL WETLAND LANDSCAPE

摘要

Historically, depressional wetlands have been viewed as small, closed basins without a naturally integrated inter-wetland surface drainage system. In this view, landscape-level connectivity is limited to surface water as overland flow. Contrasting with this view, conceptual prairie pothole ground-water models have relied on ground-water connectivity to explain inter-wetland differences in salinity, duration of inundation, and vegetation structure. To help clarify this contrast, we compared differences in hydrology, ground-water connectivity, near-surface soil moisture, geomorphology, water chemistry, and vegetation community structure and productivity for a suite of depressional wetlands in an intermontane prairie of western Montana. We compared depressional wetlands with and without temporary (< 4 wk) surface-water and/or soil-water connections. Connected wetlands had significantly smaller catchments, but stored more water, stored water longer, and had higher specific conductance than did isolated wetlands. Connected wetlands also had higher net primary productivity and a different plant community composition than did isolated wetlands. Comparisons of study site hydrology, water chemistry, and soil development found strong evidence for no ground-water exchange among any of the wetlands. The absence of ground water connection among these intermontane depressional wetlands emphasizes the importance of temporary surface-water and soil-water connections in depressional wetland ecology, as well as the need to understand the landscape scale variation of dissolved solutes and the distribution, abundance, and productivity of wetland plants among depressional wetlands and across wetland landscapes.