Sharon Lite, Mark Dixon, Tyler Rychener, Gabrielle Katz, Jaqueline White
Basin focus:
Regional SW, San Pedro
Specific area in
basin /
field sites:
Main river= San Pedro River, southern Arizona.
Supplemental rivers = Hassayampa, Santa Cruz, Salt and Bill Williams Rivers, and Cienega Creek.
Summary/Goals: By 1) quantifing relationships between stream flow regimes, flood and fire regimes, and riparian vegetation structure, 2)defining hydrologic thresholds and trigger points for riparian change, and 3)developing models of riparian vegetation change, these studies provide a necessary ingredient for effective water management in a semi-arid basin.
Activities and outcomes during past year:
Manuscripts were published on 1) Hydrologic threshold values at which cottonwood-willow forests give way to tamarisk, 2) Factors limiting plant species richness, based on studies across lateral and longitudinal hydrologic gradients, 3) Patterns of change in channel vegetation across gradients of stream flow intermittency, and 4) Response of San Pedro riparian vegetation to seasonal rains and floods. Manuscripts were accepted for publication on 1) Comparison of various attributes between vegetation patch types of the San Pedro River, 2) A review of restoration of southwestern riparian vegetation, drawing heavily on the San Pedro as a reference river. Progess continued on 1) Assessing effects of riparian fire on riparian vegetation structure, 2) Refining models of riparian vegetation change based on drivers including flooding and groundwater, 3) Testing San Pedro ecohydrology relationships for regional robustness, and 4) Monitoring riparian vegetation change at sites on the lower San Pedro River undergoing hydrologic change, 5) Integrating the riparian vegetation models with economic valuation indices, and 6) Describing patterns of change in San Pedro river channel location. One problem arose with respect to testing of the cottonwood/tamarisk ecohydrology models (#3); #3; one of the main study rivers (Hassayampa) selected had to be discarded because of the extensive clearing of tamarisk along the river by the preserve managers.
Plans for the upcoming year:
During the next period, we will 1) finalize one manuscript on the riparian assessment condition model, 2) prepare and submit a manuscript on the riparian vegetation change model and its use in projecting vegetation changes from changes in site hydrology and climate, 3) prepare and submit two manuscripts on effects of fire on San Pedro riparian vegetation, 4) conduct field research to test the San Pedro River biohydrology models (e.g., Populus and Tamarix relative abundance) on regional rivers, 5) conduct field research to compare plant species diversity levels between the San Pedro and other regional rivers, 6)continue monitoring riparian vegetation at sites along the lower San Pedro undergoing hydrologic change, 7) integrate the riparian vegetation models with economic valuation indices.
Organization Involvement:
Determine relationships between site hydrology and structure of San Pedro riparian vegetation; develop riparian condition assessment model.
Organization Involvement:
Use coarse-scale and fine-scale vegetation change models as input for EPA-funded project to link changes in hydrology, riparian vegetation, birds, and economic value.
