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Goodrich, David C

Groundwater is a key driver of riparian condition on dryland rivers but is in high demand for municipal, industrial, and agricultural uses. Approaches are needed to guide decisions that balance human water needs while conserving riparian ecosystems. We developed a space-for-time substitution model that links groundwater change scenarios implemented within a Decision Support System (DSS) with proportions of floodplain vegetation types and abundances of breeding and migratory birds along the upper San Pedro River, AZ, USA. We investigated nine scenarios ranging from groundwater depletion to recharge. In groundwater decline scenarios, relative proportions of tall-canopied obligate phreatophytes (Populus/Salix, cottonwood/willow)...
1. Hydraulic redistribution may have important consequences for ecosystem water balance where plant root systems span large gradients in soil water potential. To assess seasonal patterns of hydraulic redistribution, we measured the direction and rate of sap flow in tap-roots, lateral roots and main stems of three mature Prosopis velutina Woot. trees occurring on a floodplain terrace in semiarid south-eastern Arizona, USA. Sap-flow measurements on two of the trees were initiated before the end of the winter dormancy period, prior to leaf flush. 2 Despite the absence of crown transpiration during the dormant season, sap flow was detected in lateral roots and tap-roots of P. velutina. Reverse flow (away from the stem)...
In the marginally productive rangelands of the semiarid, southwestern USA, the maintenance of organic C (OC) is essential to the stability of the ecosystem. This study was conducted to identify landscape factors responsible for the distribution of OC in watershed soils, its loss from upland areas and subsequent transport within the stream system of a large semiarid watershed (Walnut Gulch Experimental Watershed [WGEW], Tombstone, AZ). Samples were collected along transects from the surface 5 cm of each major soil mapping unit in six subwatersheds (SW). Data were recorded for slope class, landscape position, and aspect at each of the 435 sampling points. Soil analyses consisted of: total C and OC, particle-size distribution,...
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