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In many places along the lower Colorado River, saltcedar (Tamarix spp) has replaced the native shrubs and trees, including arrowweed, mesquite, cottonwood and willows. Some have advocated that by removing saltcedar, we could save water and create environments more favourable to these native species. To test these assumptions we compared sap flux measurements of water used by native species in contrast to saltcedar, and compared soil salinity, ground water depth and soil moisture across a gradient of 200?1500 m from the river's edge on a floodplain terrace at Cibola National Wildlife Refuge (CNWR). We found that the fraction of land covered (fc) with vegetation in 2005?2007 was similar to that occupied by native...
Tamarix spp. removal has been proposed to salvage water and allow native vegetation to recolonize western U.S. riparian corridors. We conducted wide-area studies on the Lower Colorado River to answer some of the scientific questions about Tamarix water use and the consequences of removal, combining ground surveys with remote sensing methods. Tamarix stands had moderate rates of evapotranspiration (ET), based on remote sensing estimates, averaging 1.1 m/yr, similar to rates determined for other locations on the river and other rivers. Leaf area index values were also moderate, and stands were relatively open, with areas of bare soil interspersed within stands. At three Tamarix sites in the Cibola National Wildlife...
Soil evaporation, a critical ecohydrological process in drylands, can exhibit substantial spatio-temporal variation. Spatially, ecohydrological controls of soil evaporation may generally depend on a hierarchical structure spanning from the presence or absence of litter, through canopy patches of woody plants and intercanopy patches separating them, up to the overall vegetation mosaic characterized by density of woody plant cover in the landscape, although assessment of these factors in concert is generally lacking. Temporally, ecohydrological controls can be further complicated by not only seasonal climate, but also phenology, particularly in seasonally deciduous drylands. We experimentally assessed the interactive...
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This metadata references a comma-delimited file describing 492 digitized prints of large-format photographs from 160 viewpoints. The photographic images themselves are referenced in a separate metadata file entitled "Photographs Showing Change in Riparian Vegetation in the Grand Canyon, 1889-2012". The viewpoints were first photographed by Stanton in 1889-1890, and then re-photographed in about 1989-1992 and 2010-2012. This set of photos focuses on change in riparian vegetation and partially overlaps a larger set of Stanton viewpoints re-photographed by Webb and others and available at http://wwwpaztcn.wr.usgs.gov/fscc/stanton-repeat-photography/index.php. The file of descriptive information gives viewpoint stake...
Recent trends of increasing woody vegetation in arid and semiarid ecosystems may contribute substantially to the North American C sink. There is considerable uncertainty, however, in the extent to which woody encroachment alters dryland soil organic carbon (SOC) and total nitrogen (TN) pools. To date, studies assessing SOC and TN response to woody plant proliferation have not explicitly assessed the variability caused by shrub age or size and subcanopy spatial gradients. These factors were quantified via spatially intensive soil sampling around Prosopis velutina shrubs in a semidesert grassland, using shrub size as a proxy for age. We found that bulk density increased with distance from the bole (P < 0.005) and...
We use a spatially explicit landscape model to investigate the potential role of rainfall on shrub?grass transitions in the Jornada Basin of southern New Mexico during the past century. In long-term simulations (1915?1998) along a 2700 m transect running from a dry lake bed to the foothills of a small mountain, we test two hypotheses: (i) that wetter winters and drier summers may have facilitated shrub encroachment in grasslands, and (ii) that increases in large precipitation events may have increased soil water recharge at deeper layers, thus favoring shrub establishment and growth. Our model simulations generally support the hypothesis that wetter winters and drier summers may have played a key role, but we are...
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The viewpoints were first photographed by Stanton in 1889, and then re-photographed in about 1991, 2010 and sometimes other years. This set of photos focuses on change in riparian vegetation and partially overlaps a larger set of Stanton viewpoints re-photographed by Webb and others and available at http://wwwpaztcn.wr.usgs.gov/fscc/stanton-repeat-photography/index.php. The file of descriptive information gives viewpoint stake number, name, and river mile, and documents occurrence of the exotic shrub Tamarix ramosissima, changes in cover of native and invasive woody riparian vegetation, occurrence of Diorhabda spp., the beetle introduced to control Tamarix, reductions in cover of native Prosopis glandulosa, changes...
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The dataset includes 492 digitized prints of large-format photographs from 160 viewpoints. A separate metadata file "Photographs Showing Change in Riparian Vegetation in the Grand Canyon, 1889-2012" describes a comma-delimited file of descriptive information. The viewpoints were first photographed by Stanton in 1889, and then re-photographed in about 1991, 2010 and sometimes other years. This set of photos focuses on change in riparian vegetation and partially overlaps a larger set of Stanton viewpoints re-photographed by Webb and others and available at http://wwwpaztcn.wr.usgs.gov/fscc/stanton-repeat-photography/index.php. The file of descriptive information gives viewpoint stake number, name, and river mile,...
    map background search result map search result map Photographs Showing Change in Riparian Vegetation in the Grand Canyon, 1889, 1991, 2010 and other years Catalogue of Photographs Showing Change in Riparian Vegetation in the Grand Canyon, 1889-2012 Photographs Showing Change in Riparian Vegetation in the Grand Canyon, 1889-2012 Photographs Showing Change in Riparian Vegetation in the Grand Canyon, 1889, 1991, 2010 and other years Catalogue of Photographs Showing Change in Riparian Vegetation in the Grand Canyon, 1889-2012 Photographs Showing Change in Riparian Vegetation in the Grand Canyon, 1889-2012