Professor
Ph.D.  University of Nebraska, Lincoln, 1982
B.S.  University of California, Davis, 1977

345 Hilgard Hall
Berkeley, California
biomet@nature.berkeley.edu
office: 510-642-2874   lab: 510-642-2874   fax:  510-642-5438

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The biosphere and atmosphere are a coupled to one another. Climatic state variables, such as temperature, insolation, humidity, wind and precipitation affect the physiological functioning of vegetation, the architecture of plant communities, and soil properties. In return, the functional type and extent of vegetation influences the state of the atmosphere. Consequently, the production, consumption and transport of atmospheric trace gases are subject to a suite of biotic and abiotic controls and pathways as they travel between the biosphere and atmosphere.

The central focus of my research is on the physical, biological, and chemical processes that control trace gas and energy exchange between vegetation and the atmosphere. Carbon dioxide, water vapor, ozone, sulfur dioxide, isoprene, monoterpenes, methane, NOx and nitrous oxide are among the trace gases that interest me. Theoretical and field studies on trace gas exchange between the bio-sphere-atmosphere interactions are being performed to understand an array of global change issues. These issues include the radiative balance and oxidative capacity of the atmosphere, the carbon, water and nutrient balances of ecosystems and the daily growth of the planetary boundary layer.

Different vegetation types have the potential to have a different impact on the biosphere-atmosphere exchange of trace gases. Important factors include a plant stand s level of heterogeneity, phenology and physiological capacity. The most important plant-related variables, that affect the state of the atmosphere, include albedo, aerodynamic roughness, leaf area, canopy height and surface resistance to trace gas exchange. Vegetation types that interest me include boreal and temperate forests, crops, orchards, chaparral, grasslands, savanna woodlands and wetlands, as they span a spectrum of plant canopy attributes.

A secondary focus of my research is on micrometeorology of plant canopies. This work involves studying the characteristics of wind, turbulence, radiation and scalar fields above and within plant stands and footprints of trace gas exchange above and within vegetation. A detailed understanding of canopy micrometeorology is needed to quantify the light, temperature, wind and humidity environment that is in contact with plants and the underlying soil, as these factors drive many trace gas exchange processes. Information on these variables used to develop and implement a hierarchy of soil-atmosphere-vegetation transfer (SVAT) models.

My research approach involves the coordinated use of theoretical models and field measurements to assess, interpret, and synthesize biometeorological data. The biosphere/atmosphere, trace gas exchange model (CANVEG) combines eco-physiological, biogeochemical and micrometeorological theory. The micrometeorological modules compute leaf and soil energy exchange, turbulent diffusion, scalar concentration profiles and radiative transfer through the canopy. Environmental variables, computed with the micrometeorological module, in turn, drive the physiological modules that compute leaf photosynthesis, stomatal conductance, transpiration and leaf, bole, and soil/root respiration. My field work revolves around the use of the eddy covariance method to measure air-surface exchange rates of trace gases. Detailed physiological and soil measurements are made in conjunction with the flux measurements to parameterize model algorithms, to diagnose the physiological capacity of the plant stand and to separate the contributions of soil and vegetation on canopy scale fluxes.

Information on carbon dioxide, water vapor and energy fluxes between land and the atmosphere is needed to quantify and understand how the state of the atmosphere is varying with time and in space. Knowing how strong terrestrial carbon sources and sinks are, how they will respond to environmental perturbations and how they vary diurnally, seasonally and inter-annually are the among the questions that remain unresolved within the carbon cycle research community. We are currently conducting a multi-year modeling and field study on the seasonal, annual and inter-annual variations of carbon dioxide, water vapor, and energy, exchange above and below an oak-grass savanna, near Ione, CA. This forest represents a system that experiences seasonal water deficits and forms an open canopy, causing it to be vertically and horizontally heterogeneous. This study is supported by the US DOE Terrestrial Carbon Project and a member of the AmeriFlux project and FLUXNET Program.

In addition to our site-specific work, we are coordinating an international group of long term carbon, water and energy measurement sites in a NSF sponsored project called FLUXNET. This project combines the efforts of regional flux networks (i.e., EUROFLUX, AmeriFlux, AsiaNet) into an integrated global network. An aspect of this research activity is to use field data to understand and synthesize how climate, soil, and plant variables affect trace gas fluxes to and from a variety of ecosystems (crops, grasslands, conifer and broadleaved forests, savanna). We endeavor to use field data to test and validate process-level trace gas flux models and develop algorithms that can be used by satellite-driven measurements to conduct global ecology calculations on net primary productivity.

A third project involves study of methane exchange of a peatland pasture. Quasi-continuous eddy covariance measurements of methane, carbon dioxide and water vapor fluxes will be made over a peatland ecosystem to study paddock-scale fluxes on daily, seasonal and interannual time scales. A new and novel Laser Absorption Spectrometer will be used to measure methane fluxes. The biophysical processes controlling methane, carbon dioxide and water exchange will be studied with periodic chamber-based measurements of carbon efflux. A suite of controlling abiotic (water table, pressure fluctuations, temperature, soil moisture, oxygen) and biotic (leaf area index, plant functional type, isotope discrimination) factors will be quantified to interpret the fluxes. The methane and carbon dioxide flux observations will be upscaled to the regional space scale and annual time scales using a combination of remote sensing data and a comprehensive geographical information system (GIS) to drive a methane emission model for the Delta region. The methane emission model will be based on empirical algorithms developed and validated at the field site.

Results from this study will contribute valuable information for ecosystem management, climate-land surface feedbacks, and air quality. The Delta peatlands of California have subsided over 10 m since being converted to farmland at the end of the nineteenth century. The levees that support the farmland are vulnerable to breaching during earthquakes and storms and by natural erosion. To stem the continued subsidence of the region, reclamation of farmland to pasture and wetlands has been proposed. Knowing what the environmental trade-offs to such land conversion on coupled fluxes of carbon and water is critical for proper environmental management. Flooding may increase carbon sequestration by serving as habitat for aquatic vegetation, but it can also promote anaerobic conditions and methane emissions. Since methane is a much stronger greenhouse gas than carbon dioxide and is a precursor for ozone production in the presence of nitrogen oxides, stimulating methane losses could have detrimental effects on the climate, atmospheric chemistry and hydrology of Central California.

Fellow, American Geophysical Union

Highly Cited Author in Agricultural Sciences, 1996-2006

Baldocchi D.D ., Liukang Xu. 2007. Evaporation from Mediterranean Oak Woodlands ¾ a Balance between the Supply and Demand for Water by Plants and the Atmosphere. Advances in Water Research. doi:10.1016/j.advwatres.2006.06.013.

Wang, Y.P., Baldocchi, D., Leuning, R., Falge, E. and V esala, T. 2007. Estimating parameters in a land surface model by applying nonlinear inversion to eddy covariance flux measurements from eight FLUXNET sites. Global Change Biology. 13, 652-670.

Miller, G. Baldocchi, DD., Law, B. and Meyers, T.P. 2007. An analysis of soil moisture dynamics using multi-year data from a network of micrometeorological observation sites Advances Water Research.30, 1065-1081.

Fisher, J.B #., Baldocchi, D.D., Misson, L, Dawson, T.E., Goldstein, A.H. 2007. What the towers don’t see at night: nocturnal sap flow in trees and shrubs at two Ameriflux sites in California. Tree Physiology, 27: 597-610.

Baldocchi, D.D ., Tang, J*. Xu, L*. 2006. How Switches and Lags in Biophysical Regulators Affect Spatio-Temporal Variation of Soil Respiration in an Oak-Grass Savanna. Journal of Geophysical Research, Biogeosciences. 111, G02008, doi:10.1029/2005JG000063.

Chen Q., Baldocchi D.D., Gong P. & Kelly M. (2006) Isolating Individual Trees in a Savanna Woodland using Small Footprint LIDAR data. Photogrammetric Engineering & Remote Sensing., 72, 923-932.

Kim, J. Guo, Q., Baldocchi, D.D., Leclerc, M Y., Xu, L, Schmid, H-P. 2006. Upscaling Fluxes from Tower to Landscape: Overlaying Flux Footprint s on High Resolution ( IKONOS ) Images of Vegetation Cover. Agricultural and Forest Meteorology . 136:132-146.