Climate Change and Its Potential Effect on Vernal Pool Ecosystems: Example of Oregon & California Hardpan Vernal Pools Presented by Niall McCarten
Overview Vernal Pool Wetlands brief overview Climate atmospheric water balance Current Climate and Vernal Pool Functions Vernal Pool Hydrological Functioning Vernal Pool Ecological Functioning Example of Plants Predictions of Regional Climate Change in Areas of Vernal Pools in Oregon and California Potential changes to hydrological and ecological functioning in vernal pool ecosystems
Vernal Pool Landscapes Vernal pool ecosystems vary based on geology, soil, topography, climate, and vegetation and the integration of the structure and function of these components. Hydrological types of vernal pools following Rheinhardt & Hollands (2008) Agate Desert, OR Hardpan Table Mtn, CA Basal Flow Laguna formation, CA hardpan
Vernal Pool Wetland Biodiversity High level of species diversity High level of endemism 90 or more species of rare plants in Oregon & California)
Climate Amount of rainfall (cm) Climate Distribution of rainfall (amount over time) Evapotranspiration (cm) Fn (Temp, Humidity, Wind, Cloud Cover) Water Balance of the Atmosphere Inputs- Precipitation (PPT) Outputs- Evapotranspiration (ET) Input (PPT) Output (ET) = Water Balance In vernal pool ecosystems in Oregon & California s Mediterranean climate there is more water loss due to higher ET than PPT. The annual difference in water balance is variable due to annual differences in PPT & ET.
Rainfall & Evapotranspiraton (mm) Rainfall & Evapotranspiraton (mm) Rainfall & Evapotranspiraton (mm) 1400 Atmospheric Water Balance Rainfall & Evapotranspiration 1400 1200 1000 PPT ET Water Balance = - 835 mm Average Year 1200 1000 PPT ET Water Balance = - 173 mm El Nino Year 800 800 600 600 400 400 200 200 0 9/12/1998 11/1/1998 12/21/1998 2/9/1999 3/31/1999 5/20/1999 7/9/1999 8/28/1999 10/17/1999 12/6/1999 1400 0 8/8/1997 9/27/1997 11/16/1997 1/5/1998 2/24/1998 4/15/1998 6/4/1998 7/24/1998 9/12/1998 11/1/1998 1200 1000 800 600 ET PPT Water Balance = - 957 mm Drought Year Cumulative Rainfall and Evapotranspiration Example: Sacramento, CA 400 200 0 8/21/2006 10/10/2006 11/29/2006 1/18/2007 3/9/2007 4/28/2007 6/17/2007 8/6/2007 9/25/2007 11/14/2007 Data CIMIS Station 131
Vernal Pool Ecohydrology Research at the University of California, Davis Hydrology Seasonal, variably saturated hydrology of a perched aquifer associated with hardpan vernal pool watershed, Spatial and temporal multi-scale field measurements of groundwater and soil moisture, Variably saturated hydrological modeling, Soils Biogeochemical processes, and Plant Ecology Fidelity and biological feedback to wetland physical functioning.
What Environmental Factors Control Vernal Pool Hydrological Functions? Example of Hardpan Vernal Pool Watershed Climate Soils & Geology Surface Topography and slope Area of watershed (surface and subsurface) Soil porosity and texture hydraulic conductivity Depth to water restricting layer (hardpan) = volume of water Slope of hardpan Shape of the pool basin Soil chemistry and conductivity Vegetation Transpiration
Study Site Sacramento County, CA. Hardpan vernal pool = perched aquifer Photo of site during early season ponding in a vernal pool depression Photo of study site following dry-down Research site studied by Dr. Mark Cable Rains identified perched aquifer and subsurface hydrologic connectivity (2006, 2008)
Vernal Pool Watershed Hydrological Research Piezometers & Leveloggers P = Pools S = Swale U = Upland D = Discharge M = Soil Moisture
Watershed and Topography Sacramento County, California Elevation: 43 to 46 m above mean sea level Watershed 89,376 m 2 Soils: Red Bluff- Redding gravely loam 0-3 percent slope Depth to aquitard: 0.5 to 1.5 m
Stratigraphic Variation in Soil Horizons Ground Penetrating Radar View
Upland Subsurface Vernal Pool Ponding & Subsurface Drainage Subsurface
Surface & Subsurface Saturation & Rainfall
Volumetric Soil Moisture (cm 3 ) & PPT (cm) Soil Moisture Response to Rainfall Soil Moisture a Key Component of Vernal Pool Wetland Hydrology Soil Moisture Profile S1 0.600 0.500 0.400 Depth 55 cm Depth 40 cm Depth 25 cm Depth 15 cm PPT 0.300 0.200 0.100 0.000 11/14/2007 12:00 AM 1/3/2008 12:00 AM 2/22/2008 12:00 AM 4/12/2008 12:00 AM 6/1/2008 12:00 AM 7/21/2008 12:00 AM
Vernal Pool Ecological Functioning Example: Response of Plants to Variably Saturated Subsurface Hydrology, Surface Expression of Water Table, & Soil Moisture Other Ecological Functions Invertebrate community structure Amphibian species breeding habitats Bird seasonal habitat Overall biodiversity Biogeochemical processing Water quality benefit from perched aquifer (Rains et al. 2006)
Plant Elevation Relationships Annual native species Perennial native species Perennial native species Annual non-native species
Days of Ponding Species and Ponding Period 120 100 80 60 LOMU NALE LAFR ERVA POMO PLST PSBR ELMA CRSC Plant Species Codes
Plant Physiological Adaptations Life in a Carbon-Limited Environment Adaptations to Longer Hydroperiods Floating and submerged leaf morphologies Dark carbon fixation (Crassulacean Acid Metabolism), Carbon uptake from soil Oxygen pumping (aerenchyma) Floating seed
Predicted Climate Change in the Agate Desert, Oregon & Central Valley, California In general, increase in temperature (probable increase in evapotranspiration), Increase in rainfall, Increased variability in rainfall and temperature.
Change per decade Medford, OR 0.25 to 0.4 degrees 1.2 to 2.0 inches Sacramento Valley, CA 0.1 to 0.25 degrees F 1.2 to 2 inches rainfall San Joaquin Valley, CA 0.25 to 0.4 degrees F 0.6 to 1.2 inches SOURCE: Progress on Incorporating Climate Change into Planning And Management of California s Water Resources Technical Memorandum Report July 2006 Department of Water Resources
Rainfall (mm) Annual Average Rainfall for Medford, Oregon 1914-2007 3500 3000 17% increase 1914-2007 2500 2000 1500 1000 182% 1983-1985 500 0 1900 1920 1940 1960 1980 2000 2020
Climate Related Changes to Vernal Pool Ecosystems (watershed evaluation) Changes in the Vernal Pool Water Balance Is there a net loss or gain in the water balance? Current Vernal Pool Water Loss = Precipitation Watershed (P0) Evapotranspiration (E0) Future Vernal Pool Water Loss = Precipitation Watershed (P1) Evapotranspiration (E1) Vernal Pool Water Loss Ratio (W) = Vernal Pool Water Loss/Precipitation Relative Change = P1 (1 W) x E1 (from Davis, Laveau, & Gerla 2005) W
Project VP_6-1-08-4PM Initial Conditions, Pressure Head Hydrological Modeling HYDRUS 2-D (Simunek and van Genuchten, 2007) Finite Element Mesh, variably saturated soil analysis Van Genuchten - Soil Hydraulic Model Initial Conditions Volumetric Soil Moisture profile Soil texture Soil hydraulic conductivity Boundary Conditions Time variable for PPT, ET Atmospheric surface No flow subsurface Drainage out as seepage Z Z X X -3.811-3.464-3.118-2.771-2.425-2.079-1.732-1.386-1.039-0.693-0.346 0.000 Project VP_6-1-08-4PM Boundary Conditions, Water Flow Pressure Head - h[m], Min=-3.811, Max=0.000
Scenarios for Climate Change Effects to Vernal Pool Ecosystems No Change (PPT & ET proportional) Higher PPT relative to ET Longer hydroperiod- change to plant community structure (Barbour et al. 2006) Later season expression of plants with less than 100 days of ponding, Potential loss of Lolium and other generally upland weedy species, Increase in annual plants adapted to longer inundation including rare species (Orcuttia, Tuctoria, Neostapfia), and common species (Isoetes, Pilularia), Some shallower vernal pool basins on hardpans may have experience higher coverage of perennial plants (Eleocharis). Higher ET relative to PPT Reduction or loss of perennial and longer hydroperiod species, Potential higher invasion of non-native plants from upland margins, Reduction or loss of rare plants with higher hydroperiods and specialized aquatic physiological and morphological adaptations. Climate effect on California vernal pool invertebrates see Christopher Pyke publications using a surface basin hydrological model.
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