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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

Relationships between vegetation and hydrologic measurements for 17 watersheds near Grand Junction, Colorado, were subjected to correlation analyses. Six years of vegetation measurements, four vegetation measurement methods, and 15 years of hydrologic records were used in the analyses. Highly significant correlation coefficients were found for percent bare soil and runoff, but the relationships between bare soil and sediment yields were not statistically significant. Geomorphie parameters such as angle of junction, mean slope, drainage density, relief ratio, length-width ratio, and watershed are• were more highly correlated with sediment yields than with runoff. Correlation coefficients for spring vegetation measurements and runoff were higher than for autumn measurements. First contact methods and step point vegetation measurement methods were superior to the loop method and the all contacts point method. Curves for the relationship of runoff to bare soil were strikingly different for three sets of watersheds from different precipitation zones. Bare soil measurements may provide rapid and inexpensive estimates of runoff for watersheds similar to the ones studied.

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