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Land Use and Environmental Change Impact on Watershed-scale Processes

This research investigates the influence of land use and global environmental changes on water and carbon cycling in the Salinas Valley. The study examines the effectiveness of management policies in mitigating the impacts of land use change on water resources. The BGC model is used to simulate the interactions between land use, climate, CO2, and water and carbon cycles.

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Land Use and Environmental Change Impact on Watershed-scale Processes

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  1. Interactions of Land Use and Global Environmental Change on Watershed-scale Processes Lars Pierce, Fred Watson, Melinda Mulitsch, Wendi Newman, Adrian Rocha, Jodiah Nelson, Mark Fain, and others Institute of Earth Systems Science & Policy California State University, Monterey Bay Seaside, California 93955 lars_pierce@csumb.edu

  2. Water Resource Issues in the Salinas Valley: How do LULC and global-scale environmental changes (climate, CO2, etc.) influence water and carbon cycling? How do the impacts of LULCC vs. GEC compare? How effective are management policies designed to reduce the impacts of land use change on water resources?

  3. BGC Model • Integrated Water, C, N cycles • (Running et al. models) • Timestep: Daily • Spatial Scale: • Homogeneous plot (~30m) • 1 vegetation, 1 soil layer • Driving Variables: • Daily climate (T, ppt) • Vegetation / Land Cover • Leaf Area Index • Soil text, depth, C, N • Key Processes: • Water: Rain/Snow, Interception, • Soil Moisture, ET, Runoff • Carbon: Photosynthesis, Growth, Respiration, Turnover • Nitrogen: Uptake, Allocation, • Turnover, Loss CO2 PPT ET PS RA Plant LAI Leaf Leaf C N Root Root Tf CL NL Nup Soil N H2O C RO RH Nloss Ndep Material Flux Constraint Schematic flowchart of the BIOME-BGC Ecosystem Model.

  4. Simulated Biomass (g m-2 yr-1) Measured Biomass (g m-2 yr-1) Figure 2. Measured above-ground biomass compared to the above-ground biomass simulated using BIOME-BGC for the water x CO2 experiment in the Jasper Ridge CO2 project (Field et al., 1997).

  5. Photo courtesy of Fred Watson

  6. Salinas Valley of the Future? • Atmospheric CO2: 700 ppmv • Temperature: +3.5 ± 2 oC • Precipitation: +25%, Seasonality? • Nitrogen Deposition • Land Use: Oak, Agriculture • Separate vs. Combined Responses to Change • 1994 - 96 Daily Climate for Salinas, California • Equilibrium Fluxes and Pools for NPP, Water Use • Agriculture: No N, Water Limitations; 3 crops/yr.

  7. Lettuce Yield growth prep growth fallow Not much effect on total yield; significant impact on timing of harvest +2.5C (harvest 5 days earlier) 2xCO2 (harvest 10-15 days earlier)

  8. LULC vs. Environmental Change (Net Recharge = Runoff-Irrigation)

  9. Plot-level Conclusions • Oak Woodland • Responsive to changes in CO2, T, PPT, N (10-30%) • Large Interactions (5-15%) • Agriculture • Responsive to changes in CO2, T only (5-20%) • Small Interactions (< 5%) • Land Cover Change > Environmental Change

  10. LULC vs. GEC at the watershed-scale Photo courtesy of Fred Watson

  11. Oak Woodland (26%) Grassland (51%) Chaparral (14%) Crops (8%) Land Use / Land Cover Gabilan Ck Watershed (94 km2) Derived from 1995 Landsat TM Urban (1%)

  12. Gabilan Ck Simulations 4 Simulations: LULC vs. Climate Change • 1995 LULC (Present): • Ambient & 2xCO2 Climate • ~1800 LULC (Past, Ag/Urban -> Grassland): • Ambient & 2xCO2 Climate • Separate vs. Combined Responses to Change • 1996 - 98 Daily Climate for Salinas, California • Agriculture: No N, Water Limitations; 2-3 crops/yr.

  13. Leaf Area Index vs. Satellite Reflectance Courtesy of Fred Watson, CSUMB

  14. LULC vs. Climate Change @ Watershed-scale Gabilan Ck Watershed +41mm -44mm Land Use / Land Cover (Net Recharge = Runoff-Irrigation)

  15. Conclusions • Plot scale • LULC >> Temperature, CO2 Changes • Watershed scale • LULC ~ Temperature, CO2 changes • 10% Ag/Urban Land Use

  16. Simulated Effects of ENSO on Soil Moisture and Evaporation, 1997 - 1998, Chualar Creek Oak Woodland & Chaparral Agriculture Movie Link

  17. Fred Watson’s Tarsier: http://science.csumb.edu/~tarsier/ MacaqueBGC

  18. VSIM

  19. Monterey County Land Use, 2000 Map created by Wendi Newman, CSUMB

  20. Regional Hydro-Ecological Simulation System (RHESSys) Models Parameter Source Derived Inputs Outputs Temperature Precipitation NWS CIMIS Climate Microclimate Runoff Water Use Water Stress Productivity Leaching MTCLIM BGC Macaque Elevation Slope, Aspect Topography USGS TM AVHRR Vegetation Type, Amount Land Cover Soils NRCS Soil Texture Zoning Density Land Use AMBAG MTCLIM - climate interpolation model BGC - ecosystem process model NWS - National Weather Service USGS - US Geological Survey NRCS - USDA Natural Resources Conservation Service AMBAG - Assoc. of Monterey Bay Area Govts. TM - LANDSAT Thematic Mapper AVHRR - NOAA Adv. Very High Resolution Radiometer

  21. Irrigation Water Use +T - not much impact on irrigation water use (due to shorter crop rotation) 2xCO2 - 14% reduction in irrigation water use (1 less event)

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