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Carbon & Water Exchange of California Rangelands: A n Oak-Grass Savanna, Annual Grassland and Peatland Pasture Ecosystem. Dennis Baldocchi Biometeorology Lab, ESPM University of California, Berkeley. Scientific and Management Questions.

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Dennis baldocchi biometeorology lab espm university of california berkeley

Carbon & Water Exchange of California Rangelands:An Oak-Grass Savanna, Annual Grassland and Peatland Pasture Ecosystem

Dennis Baldocchi

Biometeorology Lab, ESPM

University of California, Berkeley


Scientific and management questions

Scientific and Management Questions

  • What are the magnitudes and temporal variability of the exchanges of energy, CO2 and water vapor in terrestrial ecosystems?

    • Is my rangeland a Carbon Sink?

    • If, not, How can I manage it to become one?

  • How does climate, vegetation type, physiological conditions phenology, changes in land use, management and disturbance history modulate the exchange of energy, carbon and water; and vice versa?

    • Can my rangeland off-set global warming?

    • Can it conserve water for the watershed and reservoir?


Take home messages

Take Home Messages

  • Oak Woodlands are modest Carbon Sinks, Grasslands are Carbon Neutral, & Peatlandpastures are Carbon Sources

  • Year-to-year variability in Carbon Uptake is due to length of the wet season.

    • Oaks are risk adverse and experience less inter-annual variability in NEE than grasslands

  • Savanna woodlands use/need more water than annual grasslands

    • Trees tap ground-water to sustain themselves during the summer

  • Oak woodlands are darker and warmer than annual grasslands


Dennis baldocchi biometeorology lab espm university of california berkeley

Oak-Savanna

TonziRanch Flux Tower


Dennis baldocchi biometeorology lab espm university of california berkeley

Annual Grassland

VairaRanch


Oak grass savanna a two layer system

Oak-Grass Savanna: A Two Layer System

Winter:

Trees deciduous; grass green

Summer:

Trees green; grass dead

Spring:

Trees green;grass green


Oak grass savanna are model systems for studying ecosystem ecology

Oak-Grass Savanna are Model Systems for Studying Ecosystem Ecology

  • Structure/Function

    • Oak and grasses provide contrasting life forms, woody/herbaceous, perennial/annual

    • The Canopy is open and heterogeneous

      • gives us a opportunity to test the applicability of ecosystem and biogeophysical models, developed for ideal and closed canopies

  • Environmental Biology

    • The Mediterranean climate provides distinct wet/ cool and dry/hot seasons to examine the ecosystem response (photosynthesis, transpiration, respiration, stomatal conductance) to a spectrum of soil moisture and temperature conditions

  • Global Change

    • The Mediterranean climate experiences great extremes in inter-annual variability in rainfall; we experience a wider range in precipitation over a few years than long-term predicted changes.


Dennis baldocchi biometeorology lab espm university of california berkeley

Sherman Island Peatland Pasture


Dennis baldocchi biometeorology lab espm university of california berkeley

Peatland Pastures are a Model for studying Land Subsidence and Carbon Management in the Delta


Dennis baldocchi biometeorology lab espm university of california berkeley

Background Conditions

http://www.carolsatriani.com/img0005.html


Annual precipitation 500 700 mm y mean annual temperature 14 16 c

Annual Precipitation ~500 - 700 mm/yMean Annual Temperature ~ 14-16 C


Dennis baldocchi biometeorology lab espm university of california berkeley

Cool Wet, Winters...Hot, Dry Summers

Camp Pardee, CA


Climate trends pardee ca

Climate Trends: Pardee, CA

Temperature Increased by about 1.25 C over 50 Years;

Precipitation Trend is Flat, but with High Inter-annual Variation


Dennis baldocchi biometeorology lab espm university of california berkeley

Environmental Conditions

Ma et al, in prep


Experimental methods

Experimental Methods

  • Eddy Covariance

    • above the stand (20 m tower)

    • below the stand (2 m tower)

  • Micrometeorology

  • Sap flow (heat pulse)

  • Soil respiration chambers

  • Leaf Physiology (A-Ci curves)


Eddy covariance

Eddy Covariance


Results and discussion

Results and Discussion

http://www.terrysteinke.com/pixpages/etchingpages/valleyoak.html


Dennis baldocchi biometeorology lab espm university of california berkeley

‘Breathing of the Ecosystem’


Dennis baldocchi biometeorology lab espm university of california berkeley

Pasture is a Carbon Source

mowing

NEE = +27 gC m-2 y-1, 2008

NEE = +82 gC m-2 y-1, April, 2007-April ,2008


Dennis baldocchi biometeorology lab espm university of california berkeley

Oak Woodlands are Carbon Sinks, -92 +/- 43 gC m-2 y-1

Annual Grasslands are Carbon Neutral, 30 +/- 116 gC m-2 y-1

Oak Woodlands are Risk Adverse, they Experience less inter-annual variation in NEE than Grasslands


Dennis baldocchi biometeorology lab espm university of california berkeley

Perspective

16.86 sheets of 8 ½ by 11 inch paper is 1 m2 in area and equals 76 g


Dennis baldocchi biometeorology lab espm university of california berkeley

Carbon Fluxes Scales with Spring Rainfall

Ma et al, 2007 AgForMet


Dennis baldocchi biometeorology lab espm university of california berkeley

Net Primary Productivity

John Battle's biometric NPP = 235 gC m-2 y-1.

NPP = GPPtree - Ra_tree - Rh = 299 gC m-2 y-1

NPP=NEP+Rh=97+186=283 gC m-2 y-1.


Dennis baldocchi biometeorology lab espm university of california berkeley

Dry Matter Production, Grasslands


Dennis baldocchi biometeorology lab espm university of california berkeley

Interannual Variability in

GPP and Reco scale with one

another


Dennis baldocchi biometeorology lab espm university of california berkeley

Sustained and Elevated Rates of Respiration after Fall Rain


Impacts of photosynthesis and rain pulse on ecosystem respiration of the oak woodland

Impacts of Photosynthesis and rain pulse on ecosystem respiration of the Oak Woodland

Baldocchi et al, JGR, Biogeosciences, 2006


Dennis baldocchi biometeorology lab espm university of california berkeley

Remote Sensing of Canopy Structure and NPP


Ikonos 1 m resolution in b w 4 m res in color

IKONOS: 1 m resolution in b/w; 4 m res. in color


Lidar measurement of tree height

LIDAR Measurement of Tree Height


Dennis baldocchi biometeorology lab espm university of california berkeley

Canopy Photosynthesis Follows changes in Canopy Structure


Dennis baldocchi biometeorology lab espm university of california berkeley

Upscale GPP and NEE to the Biome Scale

area-averaged fluxes of NEE and GPP were -150 and 932 gC m-2 y-1

net and gross carbon fluxes equal -8.6 and 53.8 TgC y-1

Jingfeng Xiao and D Baldocchi


Dennis baldocchi biometeorology lab espm university of california berkeley

Water, Energy and Evaporation

http://www.carolsatriani.com/2019.html


Dennis baldocchi biometeorology lab espm university of california berkeley

Evaporation from Irrigated Pasture


Dennis baldocchi biometeorology lab espm university of california berkeley

Inter-annual Variation in Rain and Evaporation

On Average, Woodland Uses 410 mm of Water on 540 mm of Rain


Dennis baldocchi biometeorology lab espm university of california berkeley

Oak Trees Tap Ground Water, and Must to Survive

G. Miller, Y. Rubin, D. Baldocchi unpublished data


Dennis baldocchi biometeorology lab espm university of california berkeley

Oak Trees Access a Significant Fraction of Water from Water Table

G. Miller, Y. Rubin, S. Ma, D. Baldocchi unpublished data


Dennis baldocchi biometeorology lab espm university of california berkeley

Role of Land Management on

Water and Energy Exchange and Climate

Case Study:

Savanna Woodland vs Grassland


Dennis baldocchi biometeorology lab espm university of california berkeley

Oak Woodlands are Warmer than Grasslands

Mean Potential Temperature difference Equals 0.84 C;

grass: 290.72 K vs savanna: 291.56 K


Dennis baldocchi biometeorology lab espm university of california berkeley

Available Energy Drives Heat Exchange and Evaporation

  • Savanna absorbs much more Radiation (3.18 GJ m-2 y-1) than

  • the Grassland (2.28 GJ m-2 y-1) ; DRn: 28.4 W m-2


Dennis baldocchi biometeorology lab espm university of california berkeley

Savanna injects more Sensible Heat into the atmosphere because it has more Available Energy and it is Aerodynamically Rougher

Tall and Rougher Savanna Promotes Turbulent mixing over Short, SmootherGrassland


Dennis baldocchi biometeorology lab espm university of california berkeley

Landscape Differences on Short Time Scales:

Grass ET > Forest ET


Dennis baldocchi biometeorology lab espm university of california berkeley

Role of Land Use on ET on Annual Time Scales:

Annual Oak ET (400 +/-35 mm/y) > Grass ET (322 +/-48 mm/y)


Dennis baldocchi biometeorology lab espm university of california berkeley

Synthesis/Conclusions


Conclusions

Conclusions

  • Oak Woodlands are Carbon Sinks, Grasslands are Carbon Neutral

  • Year to year variability in Carbon Uptake is due to length of wet season.

    • Oaks are risk adverse and experience less inter-annual variability in NEE than grasslands

  • Photosynthesis and Respiration are tightly linked

    • Oaks need high N levels to attain sufficient rates of carbon assimilation for the short growing season

  • Savanna woodlands need about 80 mm more water to function than nearby grasslands

    • Trees tap ground-water to sustain themselves during the summer

  • Oaks are darker and warmer than grasslands


Biometeorology team

Biometeorology Team

Funding: US DOE/TCP; NASA;

WESTGEC; Kearney; Ca Ag Expt Station


Questions

Questions

  • How would you use these data to make land mgt Decisions?

    • Are you compelled to cut-trees for grass, to save water and cool the climate?

      • What about Topography and the role of trees to maintain soils and serve as habitat

    • Encourage trees on grasslands to sequester carbon?

      • Do you have enough rain?

    • Should Delta Peatland Pastures revert back to tules and wetlands?

      • What about methane emissions (20x CO2), mosquitoes and water quality?


Annual et and interannual variation

Annual ET and Interannual Variation

Savanna Soil Stores about 80 mm water and uses that much extra to sustain a sparse woodland, over a grassland


Canopy structure laser altimeter data

Canopy Structure:Laser Altimeter Data


Goals of research

Goals of Research

  • Quantify the Biophysical Controls on Ecosystem Metabolism (carbon gains and losses) and Water Balance of Oak Woodlands and Peatland Pastures

  • Quantify and understand mechanisms controlling net annual budgets and inter-annual variability of carbon, water and energy exchange of oak woodland and annual grassland and Peatland Pastures

  • Produce predictive and mechanistic ability to quantify future conditions, e.g. global warming, elevated CO2 and ozone, perturbed water supply, and land use change, land subsidence, methane emissions and in order to manage rangelands

  • Upscale fluxes to the region for management decisions

Kueppers et al 2005 PNAS


Ikonos grassland

IKONOS:Grassland


Dennis baldocchi biometeorology lab espm university of california berkeley

Sherman Island Peatland Pasture


Dennis baldocchi biometeorology lab espm university of california berkeley

Evidence of Trees Tapping Ground Water

G. Miller 2009, PhD Dissertation


Dennis baldocchi biometeorology lab espm university of california berkeley

ET and Soil Water Deficits:

Root-Weighted Soil Moisture

Baldocchi et al., 2004 AgForMet


Dynamics of grassland canopy structure

Dynamics of Grassland Canopy Structure


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