HR: 1340h
AN: B23A-1033    [Abstracts]
TI: Tamarix Abundance in Arid River Basins of Arizona (USA) Reflects Prevailing Hydrology
AU: * Stromberg, J C
EM: jstrom@asu.edu
AF: Arizona State University School of Life Sciences, BOX 874501, Tempe, AZ 85287-4501 United States
AB: Flow regimes are strong determinants of riparian vegetation structure. Flow regimes vary among rivers of the American Southwest because of intrinsic hydrogeomorphic differences and because of differing degrees and types of human influence. This study reports on a survey of river reaches in the Gila and Bill Williams drainage basins of Arizona. that varied in flow permanence (perennial, intermittent, ephemeral), presence or absence of an upstream flow-regulating dam, and presence or absence of municipal effluent as a water source. The study focused on abundance patterns of Tamarix ramosissima, a species introduced to North America, relative to those of Populus fremontii and Salix gooddingii, which historically were common pioneer trees in the region. Analysis indicated that Tamarix was significantly more abundant than Populus-Salix at sites with intermittent flow (and thus where groundwater seasonally declined below rooting zones of shallow-rooted phreatophytes) and at sites below flow-regulating dams. Populus-Salix, in contrast, was the dominant forest type along free-flowing, perennial rivers. In reaches with ephemeral flow, including those below diversion dams, all forest types were sparse or absent and xeric shrublands predominated. Riparian ecosystem restoration projects are underway along several rivers in the American Southwest, most of which have a goal of increasing the abundance of Populus-Salix forests. These data affirm the importance of flow regime restoration for re-establishing Populus-Salix as the dominant pioneer forest type.
DE: 1808 Dams
DE: 1820 Floodplain dynamics
DE: 1829 Groundwater hydrology
DE: 1860 Streamflow
SC: Biogeosciences [B]
MN: Fall Meeting 2005