Harry Jenter, Virginia Carter (retired), Jonathan Lee (deceased)
U.S. Department of Agriculture - Natural Resources Conservation Service (NRCS) Department of the Interior - U.S. Geological Survey Department of Commerce - National Oceanic and Atmospheric Administration (NOAA) Environmental Protection Agency (EPA) Smithsonian Institution - National Museum of Natural History (NMNH)
Nancy B. Rybicki, Justin T. Reel, Henry A. Ruhl
Reel, J. , Ruhl, H. A., Gammon, P. T., Carter, V., Lee, J. K.
Justin T. Reel, Henry A. Ruhl, Patricia T. Gammon, Virginia Carter
Justin T. Reel, Henry A. Ruhl, Patricia T. Gammon, Virginia Carter, Jonathan K. Lee
Water velocity and water surface slope were measured, and vegetation was sampled at each site (Lee and Carter, 1996). An 0.5 m x 0.5 m quadrat was delimited by poles, and the vegetation was cut and bagged in layers starting with the layer >100 cm above the sediment/water interface. Layers were 20 cm in height between 60 to 100 cm and were 10 cm in height between 0 and 60 cm above the sediment/water interface. All periphyton was collected in layers below the water surface. The water depth, plant height, and depth of the litter layer (the dense layer of decomposed plant material just above the sediment/water interface) were recorded. Water depth was measured to the contact with peat or marl.
Plant material in each layer was sorted by species after all dead material not standing erect and periphyton were separated out. Sawgrass was separated into leaves and culms: leaves were separated into small, medium, and large leaves and culms into small and large culms and counted. Dead standing sawgrass leaves and culms were counted separately. The widths of six leaves in each live group were measured. Rushes and grasses were separated into live leaves or stems and dead standing leaves or stems and their widths estimated. All other plants were counted as individual stems with attached leaves. Numbers of leaves, culms, or stems were normalized to a square meter. Leaf area index (LAI) was calculated for the standing material (live or dead) in each layer as square meters of plant material per square meter using the formula:
LAI = (LL x AW for the LL + ML x AW for the ML + SL x AW for the SL + LC x AW for the LC + SC x AW for the SC) x DL, where AW = average width in meters, LL = number of large leaves, ML = number of medium leaves, SL = number of small leaves, LC = number of large culms, SC = number of small culms, and DL = depth of the layer in meters. When the widths of the dead leaves and culms were not measured, we used the average width of the live leaves or culms in the same layer. In this case, LAI accounted only for the resistance of the live and dead standing leaves. In order to account for the resistance of the remaining dead material, we determined the ratio of dead material/standing biomass for each layer and then multiplied the LAI by the ratio to calculate a litter LAI. This litter LAI was added to the standing LAI to form a corrected LAI for each layer.
Individual sawgrass plants vary considerably in size; larger, older plants have much more variable culm and leaf widths than smaller, younger plants. Additionally, sawgrass culms are primarily circular in shape, whereas the leaves are flattened. In this study, LAI provides a measure of the maximum area of plant material resisting flow through a 1-meter block. The detailed measurements reported herein were considered necessary to provide maximum flexibility in correlating plant characteristics with roughness coefficients.
The sorted and measured plant material, the periphyton, and the dead litter were dried at 105 °C for 8 to 12 hours and then weighed. Biomass was expressed as grams dry weight per square meter (gdw/m2). Quadrats were sorted into vegetative communities based on species composition. Plant communities were further subdivided into density classes based on total biomass minus periphyton: sparse = 0-500 gdw/m2; medium = 500-1000 gdw/m2; dense = 1000-2000 gdw/m2; and very dense = >2000 gdw/m2.
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