Increasing demands on limited water resources: consequences for two endangered plants in Amargosa Valley, USA

Abstract

Recent population expansion throughout the Southwest United States has created an unprecedented demand for already limited water resources, which may have severe consequences on the persistence of some species. Two such species are the federally protected Nitrophila mohavensis (Chenopodiaceae) and Grindelia fraxino-pratensis (Asteraceae) found in Amargosa Valley, one valley east of Death Valley, California. Because both species are federally protected, no plant material could be harvested for analysis. We therefore used a chamber system to collect transpired water for isotopic analysis. After a correction for isotopic enrichment during transpiration, delta O-18 values of plant xylem water were significantly different between N. mohavensis and G. fraxino-pratensis throughout the study. Using a multisource mixing model, we found that both N. mohavensis and G. fraxino-pratensis used soil moisture near the soil surface in early spring when Surface water was present. However, during the dry summer months, G. fraxino-pratensis tracked soil moisture to deeper depths, whereas N. mohavensis continued to use soil moisture near the soil Surface. These result, indicate that pumping groundwater and Subsequently lowering the water table may directly prevent G. fraxino-pratensis from accessing water, whereas these same conditions may indirectly affect N. mohavensis by reducing surface soil moisture and thus its ability to access water.

Keywords

Amargosa Valley (USA); Asteraceae; Chenopodiaceae; desert plants; Grindelia fraxino-pratensis; groundwater; Nitrophila mohavensis; stable isotopes; water uptake patterns

Published in

American Journal of Botany
2009, Volume: 96, number: 3, pages: 620-626

UKÄ Subject classification

Botany


Publication identifier

DOI: https://doi.org/10.3732/ajb.0800181

Permanent link to this page (URI)

https://res.slu.se/id/publ/99437