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 & PolicyCalifornia State University, Monterey Bay

Seaside, California 93955lars_pierce@csumb.edu

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 reducethe impacts of land use change on water resources?

CO2ET PS

H2O C N

N

RH Nloss Ndep

Plant

Soil

PPT

Material Flux Constraint

C

CL Nup

Root

Leaf

Root

Leaf

RO

RA

NL

LAI

Tf

Schematic flowchart of the BIOME-BGC Ecosystem Model.

BGC ModelIntegrated 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, RunoffCarbon: Photosynthesis, Growth, Respiration, TurnoverNitrogen: Uptake, Allocation,Turnover, Loss

0

200

400

600

800

1000

1200

0 200 400 600 800 1000 1200

Measured Biomass (g m-2 yr-1)

Sim

ulat

ed B

iom

ass

(g m

-2 y

r-1)

Figure 2. Measured above-ground biomass compared to the above-groundbiomass simulated using BIOME-BGC for the water x CO2 experiment inthe Jasper Ridge CO2 project (Field et al., 1997).

Photo courtesy of Fred Watson

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.

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100

200

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600

60 90 120 150 180 210 240 270 300 330

day of the year

pla

nt

dry

wt

(g/m

2) 1xCO2

2xCO2

1xCO2+T

2xCO2+T

Lettuce Yield

Not much effect on total yield; significant impact on timing of harvest+2.5C (harvest 5 days earlier)

2xCO2 (harvest 10-15 days earlier)

growth growthprep fallow

-1800

-1600

-1400

-1200

-1000

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-400

-200

0

200

Agriculture Oak WoodlandN

et R

echar

ge

(mm

H2O

/yr)

Ambient T T+CO2 T+CO2+PPT T+CO2+PPT+N

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

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

Photo courtesy of Fred Watson

LULC vs. GEC at the watershed-scale

Land Use / Land CoverGabilan Ck Watershed (94 km2)Derived from 1995 Landsat TM

Crops (8%)

Urban (1%)

Oak Woodland (26%)Grassland (51%)Chaparral (14%)

Gabilan Ck Simulations4 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.

Leaf Area Index vs. Satellite Reflectance

-0.1

0

0.1

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0 2 4 6 8 10 12Ground-measured LAI

Landsat TM

NDVI

Natural sites (AccuPAR LAI)

Agricultural sites (Destructive LAI)

Fitted curve

Courtesy of Fred Watson, CSUMB

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500

Present Past

Net

Rec

har

ge

(mm

/yr)

Ambient

T+CO2

Gabilan Ck WatershedLULC vs. Climate Change @ Watershed-scale

+41mm -44mm

Land Use / Land Cover(Net Recharge = Runoff-Irrigation)

Conclusions

• Plot scale• LULC >> Temperature, CO2 Changes

• Watershed scale • LULC ~ Temperature, CO2 changes

• 10% Ag/Urban Land Use

Simulated Effects of ENSO on Soil Moistureand Evaporation,1997 - 1998,Chualar Creek

Oak Woodland & Chaparral

Agriculture

Movie Link

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

MacaqueBGC

VSIM

Monterey County Land Use, 2000

Map created by Wendi Newman, CSUMB

Parameter Source Derived Inputs Models Outputs

Climate NWSCIMIS

TemperaturePrecipitation

Topography USGSElevation

Slope, Aspect

Land CoverTM

AVHRRVegetation

Type, Amount

Soils NRCS Soil Texture

Land Use AMBAG ZoningDensity

MTCLIM

BGC

Macaque

Microclimate

RunoffWater Use

Water Stress

Productivity

Leaching

NWS - National Weather ServiceUSGS - US Geological SurveyNRCS - USDA Natural Resources Conservation ServiceAMBAG - Assoc. of Monterey Bay Area Govts.TM - LANDSAT Thematic MapperAVHRR - NOAA Adv. Very High Resolution Radiometer

MTCLIM - climate interpolation modelBGC - ecosystem process model

Regional Hydro-Ecological Simulation System (RHESSys)

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1xCO2 2xCO2 1xCO2+T 2xCO2+T

Irri

ga

tio

n (

mm

/yr)

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)