Soil water and vegetation responses to precipitation and changes in depth to ground water in Owens Valley, California

Abstract

Gl Introduction Gl Purpose and scope G2 Background G2 Description of study area G3 Plant communities G3 Study design G5 Methods G9 Evaluation of drawdown G10 Site K G10 Site D G12 Site H G12 Site B G12 Soil water responses G12 Site K G15 Site D GL7 Site H G19 Site B G20 Vegetation responses G20 Vegetative cover G20 Response to precipitation G21 Response to changes in depth to ground water G24 Xylem pressure potential G25 Seasonal variation G28 Variation in predawn xylem pressure potential with changes in soil water content G29 Variation between transects G30 Plant growth G32 Response to precipitation G32 Response to changes in depth to ground water G33 Phenological stages G34 Summary and conclusions G34 References cited G36 FRONTISPIECE Perspective and oblique view of Owens Valley, California, showing the dramatic change in topographic relief between the valley and surrounding mountains. FIGURES 1. Map showing location of study area and water-table drawdown sites G4 2. Photograph showing view looking southeast across southern Owens Valley G5 3. Photographs showing major plant communities in Owens Valley G6 4. Diagrams showing location of pump-equipped and monitoring wells for water-table drawdown sites G8 5. Photograph showing use of point-frame apparatus G9 6-18. Graphs showing: 6. Groundwater levels at water-table drawdown sites Gil 7. Idealized soil matric potential profile in soil with water-table depth of 3.5 meters near end of summer G13 Contents 8. Soil water content and soil matric potential in soil profile at transect Dl, October 1986 G15 9. Soil matric potential profiles at transects K1-K5 G16 10. Soil matric potential profiles at transects D1-D6 G18 11. Soil water content and soil matric potential at transect HI, March 1986 G19 12. Soil matric potential profiles at transect HI G20 13. Soil matric potential profiles at transect B1 G20 14. Combined measurements of cover repetition for all sites and species measured in September, 1983-86 G21 15. Normalized cover repetition for phreatophytic shrubs at each transect G22 16. Seasonal precipitation at Bishop and Independence during each growing season, 1982-86 G24 17. Cover repetition measured in September, 1984-86, for phreatophytic shrubs and grasses at sites H and B G26 18. Normalized cover repetition for individual species at site B measured in September 1985 and 1986 G30 19-22. Schematic plots showing: 19. Midday xylem pressure potential by month for Nevada saltbush, rabbitbrush, greasewood, sagebrush, and shadscale G41 20. Predawn xylem pressure potential by month for Nevada saltbush, rabbitbrush, greasewood, sagebrush, and shadscale G42 21. Midday xylem pressure potential at all vegetation transects G43 22. Predawn xylem pressure potential at all vegetation transects G46 23-28. Graphs showing: 23. Plant growth in relation to precipitation at sites K and D

Seasonal variations in plant nitrogen relations and photosynthesis along a grassland to shrubland gradient in Owens Valley, California

“…Most studies of species distribution in the region have focused almost exclusively on the role of water availability in influencing the abundance of shrubs versus grasses (Elmore et al 2003(Elmore et al , 2006Griepentrog and Groeneveld 1981;Groeneveld and Or 1994;Groeneveld et al 1994;Naumburg et al 2005;Sorenson et al 1991). However, within a given watertable depth, community composition can be extremely variable, suggesting that other factors such as soil nutrients may play a critical role in plant function and distribution.…”

“…In a study involving Great Basin shrub species, the deep rooted Ericameria nauseosa (formerly Chrysothamnus nauseosus) was the only species to have an increased growth response to a summer precipitation event (Snyder et al 2004). Studies within Owens Valley have documented interannual variability in plant productivity and cover coinciding with interannual variability in precipitation patterns, even when plants have adequate access to groundwater Sorenson et al 1991). While these results have not been explicitly linked to N availability, they suggest that there may be an ecologically important relationship between shallow soil water, soil N availability, and plant growth.…”

Evapotranspiration of mixed shrub communities in phreatophytic zones of the Great Basin region of Nevada (USA)

“…water loss through ET approaches precipitation rates). However, in basins that have a shallow and reliable groundwater source, ET and plant growth will not be constrained by limitations associated with low precipitation; here, ET rates may exceed precipitation rates because plants (facultative and obligate phreatophytes) are able to access the groundwater (Meinzer, 1927;Sorenson et al, 1991;Scott et al, 2004;Elmore et al, 2006;Butler et al, 2007).…”

Groundwater-dependent ecosystems: the where, what and why of GDEs

“…Use of groundwater by phreatophytes is highest during the driest season of the year when alternative water sources become depleted and transpirational demand is highest. It is also suggested that phreatophytes are susceptible to the rate as well as season of drawdown (Mahoney and Rood 1992;Stromberg and Patten 1992;Tyree et al 1994;Scott et al 1999Scott et al , 2000Groom et al 2000;Shatfroth et al 2000;Horton et al 2001;Eamus et al 2006a) by having a higher rate of water-table decline than fine-root elongation rate, and/or lowering the water table during a time other than the root growth season (Sorenson et al 1991). Low magnitude and rates of change in groundwater levels as opposed to rapid drawdown, may allow intra-and inter-generational adaptation and persistence of phreatophytes (Scott et al 1999;Shatfroth et al 2000).…”