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<br />'q.. <br /> <br />:f '~\ <br /> <br />refinement and experimental testing of trajectories of vegetation recovery at a single site. The <br />methods used in this effort include: (1) evaluation of flood effects through on-going monitoring <br />before and after the flooding event; and (2) detailed studies at locations coordinated with <br />geomorphological studies for testing specific hypotheses relating sediment changes and <br />riparian/wetland responses to be conducted before, during and after the flood event Studies of <br />long-term recovery of riparian/wetland vegetation, as with long-term geomorphological changes, <br />will be part of a future long-term monitoring prograrn. <br /> <br />Secondary Null-hypothesis b: <br />Wetland/riparian vegetation research in the Grand Canyon has focused on variation in <br />basal area and composition across soil, moisture availability and flood-related disturbance <br />gradients in several distinct geomorphic settings (Stevens and Ayers 1m, 1993, 1994). Fluvial <br />marshes have been monitored through analysis of aerial photographs since 1965, and in the field <br />on an annual basis since 1990 (Stevens et al. in press). Monitoring should be conducted prior to <br />and after the flooding event using the following methods: <br /> <br />1) A serieS of 50 permanent 1.0 m2 georeferenced quadrats has been established at 12 <br />sandbar marshes. These quadrats will be monitored in the autumn before the high flow and in <br />the spring immediately after the high flow. Future annual monitoring, if appropriate, will be part <br />of the long-term monitoring program. Stage-related elevation, grain size, species composition, <br />basa1 area, dead stem density and reproductive output will be monitored. Comparable plots in <br />tributaries will be monitored to provide off-river controls. A series of 0.1 m2 standing crop plots <br />will be monitored before and after the flooding event and compared with previously collected <br />data to provide an assessment of standing crop changes associated with flooding. <br /> <br />2) Measurement of20 new-high-water-zone (NHWZ) marshes and four OHWZ spring <br />marshes will be continued using the GCES Map and Image Processing System (MIPS). The <br />NHWZ marshes were distributed throughout the river corridor, and were selected by Stevens and <br />Ayers (1993) on the basis of distribution within geomorphic reaches established by Schmidt and <br />Graft (1990). The four OHWZ marshes constituted a set of control sites against which to <br />determine changes in wetland vegetation not induced by darn operations. These marshes have <br />been measured on 1988, 1990, 1991, 1992 and 1993 photographs and will be remeasured on <br />aerial photographs taken before and after the flooding event <br /> <br />3) Twenty study areas have been established in Glen, Marble and Grand Canyons and <br />provide an adequate baseline under which to measure system-wide effects of planned flooding. <br />Each contains 5 m x 10 m permanent quadrats in the following geomorphic environments: <br />marsh, beach (sand bar platfonn), channel margin and debris fan habitats, as well as in the <br />OHWZ and desert zones. The low-lying quadrats will be monitored in the autumn before the <br />high flow, in the spring immediately afterwards, and in the future under the long-tenn <br />monitoring program.. Topography, particle-size distribution, ground and shrub cover, species <br />composition and basal area and dead-stem density will be monitored.. Relationships between <br />vegetation and geomorphology of those study areas lying within the GeES GIS reaches are being <br /> <br />16 <br />