Soil Ecology and Research Group

last update January 31, 2002


Death Valley

Amargosa Niterwort ( Nitrophila mohavensis)

James L. Reveal and the United States Department of Agriculture,

Natural Resources Conservation Service

Soil Ecology and Restoration Group personnel will conduct a study of the hydrologic and biologic parameters of the two target species, the endangered Amargosa niterwort (Nitrophila mohavensis) and the threatened Ash Meadows gumplant (Grindeliafraxino-pratensis), located in the Lower Carson Slough area of Death Valley. The study will include: the determination of water usage by both plant species, i.e., ground water versus overland water flow; a survey of potential habitat for both target species and other potential special status plant species; the mapping of the perimeters of each such occurrence using a Global Positioning System (GPS); the forming a complete list of all vascular plants occupying the areas of occurrence of each special status plant species; the assessment of the physiological tolerance of the target species to desiccation; and the development of both guidelines for the propagation and transplantation of nursery stock and long term management practices regarding the two target species.

To determine the source of water used by both the Amargosa niterwort and the Ashy Meadows gumplant, two methods will be used to provide conclusive evidence. First, we will evaluate the water potentials of the target species and compare them with other surrounding species using a pressure chamber. Initial water potential measurements will be taken on several occasions during the winter of 2001-2002 (bi-monthly starting in December or January, depending on rainfall) to provide baseline data. Water potentials will then be measured beginning in spring (April or May) and continue through the summer on a bi-monthly basis. If the target species maintain high (less negative) water potentials into the dry summer season, it can be postulated that deep ground water is being utilized.

The second method that will be used, to provide conclusive evidence, is the comparison of both hydrogen (D:H) and oxygen (16O:18O) isotopic signatures (Dawson & Ehleringer, 1998; Dawson & Pate, 1996; Meinzer, et al., 1999). Sources of water used by vegetation can be determined by comparing these stable isotopes in the plant xylem sap with the signatures of potential sources, such as rain, surface flow, ground water or soil water. We will collect samples of rainfall during any precipitation event, ground water samples from the installed wells in the study area, and soil water samples through deep cores placed near selected target species plants. We will then collect several stem samples from randomly selected target plants and analyze the isotopic signatures for all samples at the University of New Mexico Ecology Analytical Laboratory. This will provide us conclusive evidence as to the source of water used by the two target species, Amargosa niterwort and the Ashy Meadows gumplant.

To accomplish this research, it will be necessary for SERG to have permission to sample the monitoring wells currently located in the project area and to receive "take" permits for both the Amargosa niterwort and the Ashy Meadows gumplant. Stems from each plant species are needed to conduct the isotopic analysis, though the overall impact, due to the small numbers of stems required (3-4) would be minimal.

The survey of potential habitats for the two target species and other potential special status plant species will be conducted in two steps. First, SERG personnel will review all pertinent information such as aerial photographs, previously known collections and reports and other pertinent information uncovered during the literature search, to determine what areas are potential habitat areas for the two target species and possibly other special status plant species. Once this has been accomplished, two two-man survey teams will conduct the surveys, using a directed search method, by walking all selected areas beginning in late winter-early spring and continuing on into the early summer months. The survey teams will visit the project site for a five-day period once a quarter beginning in January and finishing in July. All occurrences of target species and other special status species will be mapped using GPS. If possible, a complete census will be conducted for each special status plant species or, if an estimate of numbers will be made if numbers are too great to count. Plant estimates will be conducted through the use of a modified California Native Plant Society protocol, using both transects and quadrats (McClenaghan et. al., 1997). Additionall, all vascular plants located in the areas of each special status species will also be listed and correlated with adjacent special status species.

The development of guidelines for the propagation of and transplantation of Amargosa niterwort and the Ashy Meadows gumplant will be accomplished initially in the SERG greenhouse located at San Diego State University. If seeds are currently available, SERG greenhouse personnel will begin conducting propagation tests during the 2001-2002 winter months. Tests will include, but not be limited to, testing pre-germination methods such as hot and cold stratification, physical scarification and acid and hot water baths. Different germination mediums will be tested based on the various soils found in the areas where current populations exist. Seedlings that germinate will then be placed in various sizes of plant propagation containers such as 2"x2"x8" plant bands, 3"x3"x12" plant bands, one gallon pots and "half-high" containers (4" diameter by 16" PVC pipes) to determine root requirements.

Seedlings would then be kept under observation at the SERG greenhouse facility, outside in open sun, to determine water requirements during the summer months. At the end of the one year study, we should have not only have a set of guidelines for the propagation and maintenance of both the Amargosa niterwort and the Ashy Meadows gumplant, but a number of plants available for actual transplanting into the Lower Carson Slough area, or another suitable area of choice, the following spring (2003).

If seed is currently not available, this part of the project would have to be delayed until the following year and a permit to collect seed during the summer/early fall of 2002 provided SERG personnel. Once seed has been collected, the propagation and transplantation aspect of the project can begin as outlined above.

SERG will provide a report outlining all results and conclusions, including recommended management practices for the conservation of the targeted species and other related special status plant species located in the project area.

Final Report (February 27, 2004)