Research Projects

(1)Analysis of Desert Shrubs Along First-order Channels on Desert Piedmonts: Possible Indicators of Ecosystem Health and Historic Variation

(2)Basic Research Linkages Among the Soil-Hydrologic-Biologic Systems Common to the Desert Piedmonts, U.S. Army Yuma Proving Grounds

PI: Eric McDonald

Collaborators: Dr. Erik Hamerlynck (Rutgers University), Dr. Joseph McAuliffe (Desert Botanical Garden)

Funded by: (1) SERDP SEED Project #CS1153 (2) DoD EPSCoR Project 40983-EV-DPS

Right: Oblique aerial view of a desert piedmont and ephemeral drainage networks

Keywords: desert shrubs, Desert Piedmonts

Project Description

The objectives of these projects are to develop critical knowledge about the relation between key soil processes, soil and surface water hydrology, and plant ecological dynamics common to desert piedmonts at the U.S. Army Yuma Proving Ground (YPG). Objectives are being met using a multidisciplinary approach, combining key aspects of the soil-water balance, historic background mortality of plants, ecophysiological measurements of living plants that are marginal to areas of plant mortality, and a the development of the basic soil-hydrological foundation connecting zones of mortality and living plants. The projects have five main objectives:

1. Characterize fundamental physiochemical and hydrological processes of key desert soil areas critical to YPG
2. Apply knowledge of soil processes to determine important linkages among soils, soil hydrology, and ecological dynamics.
3. Evaluate if changes in soil and surface hydrology, due to both military activities and natural environmental variation, can be shown to predominantly account for changes in ecosystem health, especially the historic contraction of vegetation along the margins of alluvial fan surfaces.
4. Determine historic range in variation of key desert vegetation common to alluvial fan surfaces and first-order rills.
5. Provide recommendations that can be used to further develop and test methods or procedures that can be used to monitor ecosystem status and identify impacts related to natural disturbance relative to military activities

Much of the ephemeral water available for desert ecology appears to be derived from episodic surface runoff from alluvial surfaces; therefore, any change in surface runoff will directly correspond to changes in vegetation vitality along active washes. Vegetation along first-order drainages is likely to be impacted first by any natural or anthropogenic changes in the flux of surface runoff because these drainages are directly linked to surface runoff. Higher order channels may not be as sensitive to environmental change because as channel order increases, an increasingly larger contributing area and greater number of contributing channels supply runoff. An increase in likelihood of ephemeral runoff may result in a decrease in sensitivity to environmental change. If this hypothesis is true, then monitoring the ecology of selected first-order channels across both impacted and non-impacted drainage basins may provide an environmental “heads-up” about potential impact to downstream ecosystems due to a change in the supply of water from upland areas.

Below: Oblique aerial view of a typical desert piedmont and complex ephemeral drainage networks in the lower Colorado River region of the Sonoran Desert.

Below: Roads across drainages directly impact vegetation health (a). Upstream side of drainage has abundant vegetation and good biodiversity (b). By comparison, down stream side of road has lost all major trees and most shrubs (c).

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