HR: 1330h
AN: NB33H-01    [Abstracts]
TI: Floodplain Vegetation Productivity and Carbon Cycle Dynamics of the Middle Fork Flathead River of Northwest Montana
AU: * Oakins, A J
EM: oakins@ntsg.umt.edu
AF: NTSG, College of Forestry and Conservation, The University of Montana, 32 Campus Dr, Missoula, MT 59812 United States
AU: Kimball, J S
EM: johnk@ntsg.umt.edu
AF: NTSG, College of Forestry and Conservation, The University of Montana, 32 Campus Dr, Missoula, MT 59812 United States
AU: Kimball, J S
EM: johnk@ntsg.umt.edu
AF: The University of Montana Flathead Lake Biological Station, 311 BioStation Lane, Polson, MT 59860 United States
AU: Relyea, S
EM: scott.relyea@umontana.edu
AF: The University of Montana Flathead Lake Biological Station, 311 BioStation Lane, Polson, MT 59860 United States
AU: Stanford, J A
EM: jack.stanford@flbs.umt.edu
AF: The University of Montana Flathead Lake Biological Station, 311 BioStation Lane, Polson, MT 59860 United States
AB: River floodplains are vital natural features that store floodwaters, improve water quality, provide habitat, and create recreational opportunities. Recent studies have shown that strong interactions among flooding, channel and sediment movement, vegetation, and groundwater create a dynamic shifting habitat mosaic that promotes biodiversity and complex food webs. Multiple physical and environmental processes interact within these systems to influence forest productivity, including water availability, nutrient supply, soil texture, and disturbance history. This study is designed to quantify the role of groundwater depth and meteorology in determining spatial and temporal patterns of net primary productivity (NPP) within the Nyack floodplain of the Middle Fork Flathead River, Northwestern Montana. We examine three intensive field sites composed of mature, mixed deciduous and evergreen conifer forest with varying hydrologic and vegetative characteristics. We use a modified Biome-BGC ecosystem process model with field-collected data (LAI, increment growth cores, groundwater depth, vegetation sap-flow, and local meteorology) to describe the effects of floodplain groundwater dynamics on vegetation community structure, and carbon/nitrogen cycling. Initial results indicate that conifers are more sensitive than deeper-rooted deciduous species to variability in groundwater depth and meteorological conditions. Forest productivity also shows a non-linear response to groundwater depth. Sites with intermediate groundwater depths (0.2-0.5m) allow vegetation to maintain connectivity to groundwater over longer periods during the growing season, are effectively uncoupled from atmospheric constraints on photosynthesis, and generally have greater productivity. Shallow groundwater sites (<0.2m) are less productive due to the indirect effects of reduced soil aerobic decomposition and reduced plant available nitrogen.
DE: 1818 Evapotranspiration
DE: 1851 Plant ecology
DE: 1878 Water/energy interactions
SC: North American Benthological Society [NB]
MN: 2005 Joint Assembly