|Scott, Russell - Russ|
Submitted to: American Geophysical Union
Publication Type: Abstract Only
Publication Acceptance Date: 10/1/2003
Publication Date: 12/8/2003
Citation: Scott, R.L., Hultine, K., Ferre, P. 2003. The ecohydrological interactions between mesquite and its water sources [abstract]. American Geophysical Union 84(86). Supplemental Abstract B51A-06. Interpretive Summary: Mesquite has increased in abundance across many of the rangelands and floodplains of the American Southwest. Because mesquite has a deep taproot it can access deeper groundwater sources when available. This scientific presentation highlights the interactions that were found to occur between mesquite and its water sources at a site along the San Pedro River in southern Arizona. As a result of these interactions, many inter-related ecological and hydrological consequences were found.
Technical Abstract: Velvet mesquite, a native woody plant to southern Arizona, USA and Sonora, Mexico, has successfully expanded its range and encroached into both upland and riparian grasslands during the 20th century. In this study, we examined the interactions between mesquite and its water sources in order to determine how the trees responded to moisture availability. This study took place in a riparian area and because the trees had access to both deep groundwater and surface water, these interactions resulted in important hydrological and ecological consequences. Surprisingly, we found that the mesquite responded to and even manipulated both surface and deep soil moisture even though they apparently had access to a stable groundwater source throughout the growing season. During dry season nights, observations of root sap flow showed that the trees moved moisture upwards in the taproot and out into the surface soils in lateral roots. As a consequence of this "hydraulic lift", diurnal soil respiration measurements showed that the soil microbes were stimulated following the nocturnal release of moisture into the near-surface regions. During rainy season nights, there was sap flow movement toward the tree in the surface lateral roots and downwards in the taproot indicating "hydraulic descent". Borehole GPR measurements of the deeper, 2 - 10 m, vadose zone moisture content increased apparently as a result of this tree-facilitated water movement. Also, hydraulic descent influenced water table elevations indicating direct groundwater recharge via plant pathways.