• Lab Group
  • Dennis Baldocchi
  • Personnel
  • Visiting Scientists
  • Contact Info
• News
  • 2008
  • 2007
  • 2006
  • 2005
  • 2004
  • 2003
  • 2002
  • 2001
• Research
  • Projects
  • Field Site Descriptions
  • Field Site Pictures
  • Research Opportunities
  • Data
• Publications
  • Peer Reviewed Papers
  • Research Highlights
  • Book Chapters
  • Publications (PDF Password Protected)
• Education
  • ESPM 129 Biometeorology
  • ESPM 228 Adv Topics in Biometeorology & Micrometeorology
  • Education Tools
• Weblinks
  • National & International Research Project & Programs
  • Journals
  • Biometeorologists at Other Universities
  • Weather & Climate
  • Instruments
  • Jazz on the Internet

Research Projects

To develop a mechanistic understanding on the biophysical controls on ecosystem carbon budget and to develop the next generation of coupled climate-carbon cycle models, we need to understand how trends and inter-annual variations in climate affect carbon and water exchange between terrestrial ecosystems and the atmosphere on a decadal time scale. We propose a study that will investigate and quantify the dynamics of net carbon dioxide exchange between the biosphere and atmosphere, which are triggered by such critical features as switches, pulses, lags, and acclimation. The study will be conducted over two ecosystems that are representative of the Mediterranean climate zone and are model systems for studying how ecosystems respond to environmental perturbations. One site is an oak savanna woodland and the other is an annual grassland. They are separated by 2 km, are exposed to identical weather. We will investigate the biotic and abiotic factors contributing to interannual variability in CO 2 exchange by extending a data set we are collecting to nine years. The interpretation of these data and their dynamics will involve a comprehensive suite of biophysical, ecophysiological and ecological measurements. Net canopy-atmosphere carbon fluxes will be measured with the eddy covariance method and these fluxes will be partitioned into their constituent components, canopy photosynthesis and ecosystem respiration. This will be accomplished by making overstory and understory eddy covariance measurements and by measuring soil respiration with a flux-gradient system, developed by this team. Interpretation of the temporal variations of these fluxes will be based on the CANOAK and MAESTRO models and measurements of meteorological conditions (solar radiation, wind, temperature, rain, humidity), soil microenvironment (CO 2, moisture and temperature), soil physical and chemical properties (bulk density, texture, hydraulic conductivity, C and N), plant functional (photosynthetic capacity, stomatal and mesophyll conductance, transpiration) and structural (canopy height, leaf area index, diameter of breast height and three dimensional crown tructure) characteristics. We will upscale the fluxes in space and time with remote sensing and regional weather data. Upscaling will be accomplished in the following manner. First, periodic measurements of high resolution spectral reflectance will be made with a spectral radiometer and continuous measurements of vegetation indices (NDVI and PRI) will be made with an LED spectrometer developed in our lab. Second, relationships between vegetation indices and carbon fluxes will be derived from the field observations. And third, we will apply these algorithms to vegetation indices obtained from MODIS and produce ecosystem-scale estimates of carbon assimilation. We will add a new component to our project that will compare long term eddy flux measurements against changes in stand biomass and soil carbon. These will be based on a sequence of LIDAR measurements and biometry field sampling.

Our research site meets the criteria to be designated as an AmeriFlux super-site. First, we are making measurements that represent components of a larger landscape and region that is an appreciable carbon sink. Second, we are ranked as a Tier 1 AmeriFlux site, based on the breadth of measurements, the type of instrumentation, compliance with calibration procedures, the regular submission, quality and documentation of data, and length of data record. And third, our site is in a climate zone and ecosystem that is among the most under represented in the AmeriFlux network, according to the bioclimate zone analysis of Hargrove (2003) .


2. Understanding the Coupling of Greenhouse Gases (Methane, Carbon Dioxide, Water Vapor) and Energy Fluxes and Scaling them across a Spectrum of Time and Space over a Vulnerable Ecosystem and a Biological Hot Spot: the Sacramento-San Joaquin Delta Peatland. Sept 2006 through Sept 2010.

Dennis Baldocchi, PI, co-Is, Whendee Silver and Nina Maggie Kelly. National Science Foundation, Carbon and Water in the Earth System

Project Summary

Intellectual Merit: An experimental and modeling approach is used to determine the biophysical processes that control coupled fluxes of carbon dioxide, water and methane in temperate peatlands. This project work will quantify the land- atmosphere exchange of carbon and water, will integrate these fluxes across a spectrum of time and space, and provide a framework for scaling our results to other sites and future scenarios. Temperate peatlands are hotspots of soil carbon storage and biological diversity, and are extremely vulnerable to management decisions that alter water levels. They provide key economic (grazing, peat production) and ecosystem (filters for upslope pollutants and nitrogen, carbon sequestration) services. They are also potentially important sinks of carbon dioxide or sources of carbon dioxide or methane. So interactions between terrestrial biogeochemistry and the hydrological cycle are likely determinants of their role in global warming. 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.

Broader Impacts: 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. Only through a coupled study of carbon, water and methane exchange will these goals be achieved. The proposed research will also contribute to undergraduate, graduate, and post graduate training. Outreach activities will include environmental education and extension in the region.

3. Fluxnet, A global network of carbon, water, and energy flux measurement sites.

D. Baldocchi, PI, co-Is, Beverly Law, Robert Cook, Niall Hanan, Alex Knohl, Ray Leuning, Hank Margolis, Yoshikazu Otahni, GuiRu Yu, Ricarrdo Valentini. ILEAPS Project.

Project Summary

FLUXNET is a new ILEAPS project that constitutes a global network of carbon dioxide, water vapor and energy flux measurement sites. In this global configuration it expands the diversity of biomes, climate regions, disturbance and land use treatment that are associated with its constituent regional networks. Specific aims of FLUXNET are to quantify spatial/temporal variations of the physical and biological processes controlling carbon dioxide, water vapor and energy exchange between terrestrial ecosystems and the atmosphere. As a global network, the project will be responsible for recruiting, sharing and exchanging of newly acquired and extant data among collaborators and with the scientific community, in associated fields like atmospheric chemistry, remote sensing, biogeography, ecohydrology, ecosystem ecology and biogeochemistry. The scientific team will collaborate with the FLUXNET Data Information System (DIS) at Oak Ridge National Lab, and provide scientific guidance and computational software to produce value-added data products, like gap-filled datasets and daily and annual integrated fluxes. We will also provide software and guidance to FLUXNET DIS to create new and expanded datasets that partition net ecosystem carbon fluxes into photosynthetic and respiratory components. The FLUXNET will serve its constituent community, scientifically, by catalyzing, leading and conducting network-scale data synthesis analyzes. Examples include: 1) assessing the biophysical factors causing interannual variability of net carbon dioxide exchange for a selection of major biomes and climate zones; 2) examining the roles of disturbance, climate and plant functional type on carbon and water fluxes; 3) examining the biophysical controls of carbon fluxes from the expanded cohort of FLUXNET sites; 4) performing geostatistical analyzes across a regional array of study sites to quantify scales of coherent spatial patterns in carbon, water and energy fluxes; and 5) quantifying micrometeorological and turbulence characteristics across a spectrum of canopy structure, land surface complexity and atmospheric stability. This project will serve the international community by convening international workshops, hosting visiting scientists, and supporting a project scientist. Finally, FLUXNET aims to be instrumental in training the next generation of biogeoscientists from developed and under-developed countries by hosting a young scientist forum.

4. Controls of Canopy Photosynthetic Activity on Roots and Soil Carbon Dynamics in Ponderosa Pine and Oak/Savanna Ecosystems
Allen Goldstein, PI, co-Is W. Cheng and .D. Baldocchi, PI. Kearney Foundation of Soil Science. Jan 2004-Dec. 2006.

Summary : The first objective of this research is to make the link between the seasonality of fine root dynamics and the carbon balance of the ecosystem. The second objective of this research is to improve our understanding of how canopy photosynthesis influences fine root initiation, growth and mortality. In order to reach these objectives, we combined CO 2 flux measurements (at ecosystem, soil, and leaf level) with aboveground (shoot, needle, stem) and belowground (fine root) growth dynamics. The first part of this research was conducted in a young Ponderosa pine plantation at the Blodgett Forest Ameriflux site located at 1315 m above sea level in the Sierra Nevada Mountains of California. One of our hypotheses was that fine root development at our site is a high priority and is tightly coupled to canopy photosynthesis and available soil water. This hypothesis is partially confirmed and mainly holds for the first part of the vegetation period when a tight coupling between photosynthesis and root growth was observed. We found that the seasonal window for optimal root growth is extremely reduced at our site, partially due to low soil temperature during the winter and partially due to soil water stress during summer. However, large rates of photosynthesis were observed following summer rains during the second part of the vegetation period while temperature was optimal, but root growth did not resume and mortality rates did not decrease. The second hypothesis was that fine roots exert a major control over the seasonal patterns of soil respiration; and that such control is most apparent when roots are actively growing. This hypothesis is also partially confirmed because increases in soil and ecosystem respiration corrected for temperature variations were observed during the actively growing period. However, the increase in respiration during root growth was limited in magnitude. The largest variation in soil respiration at our site occurred due to an increase in heterotrophic respiration during unusual rain pulse events in the second part of the vegetation period (summer). However, the activity of these heterotrophs was highly dependent on the earlier input of fresh soil labile carbon by the roots.