Climate Change and Its Potential Effect on Vernal Pool Ecosystems: Example of Oregon & California Hardpan Vernal Pools

Transcription

1 Climate Change and Its Potential Effect on Vernal Pool Ecosystems: Example of Oregon & California Hardpan Vernal Pools Presented by Niall McCarten

2 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

3 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

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5 Vernal Pool Wetland Biodiversity High level of species diversity High level of endemism 90 or more species of rare plants in Oregon & California)

6 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.

7 Rainfall & Evapotranspiraton (mm) Rainfall & Evapotranspiraton (mm) Rainfall & Evapotranspiraton (mm) 1400 Atmospheric Water Balance Rainfall & Evapotranspiration PPT ET Water Balance = mm Average Year PPT ET Water Balance = mm El Nino Year /12/ /1/ /21/1998 2/9/1999 3/31/1999 5/20/1999 7/9/1999 8/28/ /17/ /6/ /8/1997 9/27/ /16/1997 1/5/1998 2/24/1998 4/15/1998 6/4/1998 7/24/1998 9/12/ /1/ ET PPT Water Balance = mm Drought Year Cumulative Rainfall and Evapotranspiration Example: Sacramento, CA /21/ /10/ /29/2006 1/18/2007 3/9/2007 4/28/2007 6/17/2007 8/6/2007 9/25/ /14/2007 Data CIMIS Station 131

8 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.

9 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

10 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)

11 Vernal Pool Watershed Hydrological Research Piezometers & Leveloggers P = Pools S = Swale U = Upland D = Discharge M = Soil Moisture

12 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

13 Stratigraphic Variation in Soil Horizons Ground Penetrating Radar View

14 Upland Subsurface Vernal Pool Ponding & Subsurface Drainage Subsurface

15 Surface & Subsurface Saturation & Rainfall

16 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 S Depth 55 cm Depth 40 cm Depth 25 cm Depth 15 cm PPT /14/ :00 AM 1/3/ :00 AM 2/22/ :00 AM 4/12/ :00 AM 6/1/ :00 AM 7/21/ :00 AM

17 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)

18 Plant Elevation Relationships Annual native species Perennial native species Perennial native species Annual non-native species

19 Days of Ponding Species and Ponding Period LOMU NALE LAFR ERVA POMO PLST PSBR ELMA CRSC Plant Species Codes

20 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

21 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.

22 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

23 Rainfall (mm) Annual Average Rainfall for Medford, Oregon % increase %

24 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

25 Project VP_ PM 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 Project VP_ PM Boundary Conditions, Water Flow Pressure Head - h[m], Min=-3.811, Max=0.000

26 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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