Harvard Forest Research Project
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Title: Attributing Regional Carbon Fluxes to Underlying Processes as part of RECCAP
Leads: Christopher A. Williams (Clark University Geography); Nicolas Gruber (ETH Zurich, Switzerland); Stephen Sitch (University of Exeter, UK); Pep Canadell (Global Carbon Project, Australia); Philippe Ciais (IPSL - LSCE – CEA – CNRS, France)
The international carbon cycle research community is undertaking its most ambitious effort ever to provide detailed regional understanding of the global carbon budget: the Regional Carbon Cycle Assessment and Processes initiative (RECCAP). The primary goals are (1) to provide higher spatial resolution to analyses of the global carbon balance with the aim of improving the quantification and understanding of its drivers, and (2) to improve capacity for quantifying and monitoring the evolution of carbon fluxes at a regional to national level. By assembling and comparing direct observations, model results, and atmospheric inversions, RECCAP is establishing the most comprehensive and detailed carbon budgets ever produced for ten land and four ocean regions all using a common framework.
Professor Williams is leading one of five high-level syntheses seeking to explain the importance of different processes contributing to each region’s carbon balance. Some of the processes being examined are enhanced plant growth from fertilization by elevated carbon dioxide and nitrogen, ozone inhibition of plant growth, effects of changes in sunlight quality and quantity, forest harvest and deforestation, and the changing climate (warming/cooling, wetting/drying).
Attribution is critically important because the future evolution of regional fluxes as well as the potential for carbon management as a climate mitigation option both depend on which mechanisms are contributing to the unexplained net carbon uptake taking place today.
Such a detailed and comprehensive attribution of the present day carbon balance has never before been attempted at a regional scale, or even globally. With its interdisciplinary approach to using a wide range of information sources, the project is expected to build confidence in regional knowledge of carbon sources and sinks and reveal inconsistencies to guide the research agenda for the next decade. To learn more visit http://www.globalcarbonproject.org/reccap
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Title: Albedo Trends Related to Land Cover Change and Disturbance: A Multi-sensor Approach
Principal Investigator: Jeffrey Masek (NASA GSFC Biospheric Sciences)
Co-Investigator: Feng Gao, Yanmin Shuai (Earth Resources Technology, Inc.)
Co-Is / Institutional PIs: Crystal Schaaf (Boston University Geography); Christopher A. Williams (Clark University Geography)
Funding Source: NASA,The Science of Terra and Aqua
Numerous papers have highlighted how land-cover change and ecosystem disturbance can alter the surface energy balance through changes in albedo, surface roughness, and evapotranspiration. In some cases, these surface changes may constitute a larger radiative forcing than those arising from related carbon emissions. Past studies on post-disturbance albedo have been limited by the resolution of available MODIS data (500m), which is significantly coarser than the characteristic scales of ecosystem disturbance and human land use. Our project addresses this issue by creating high-resolution (30m) albedo maps through the fusion of Landsat TM/ETM+ directional reflectance with MODIS BRDF/Albedo (MCD43A) data. These maps permit trends in albedo to be evaluated at the characteristic scale of vegetation change (~1 ha).
Two algorithms are proposed to retrieve Landsat-resolution albedo: a “concurrent approach” which depends on overlapping MODIS and Landsat observations from the 2000-2010 period, and an “extended approach”, which uses an a priori BRDF table to extend retrievals back to the 1980′s. These fused products will be validated using in-situ Baseline Surface Radiation Network (BSRN) data. We will then evaluate the albedo trajectories for characteristic types of land cover conversion and disturbance across the globe. Specifically, we will (i) assemble a regional library of albedo values for IGBP land cover types; (ii) assemble time series of post-disturbance albedo from a latitudinal distribution of typical forest disturbance types (fire, insect damage, harvest); (iii) evaluate decadal trends in landscape albedo for “hotspots” of vegetation change; and (iv) assess the radiative forcing associated with historical (since 1700) and future (scenario-based) global land-cover change.
The outcome of the investigation will be an improved quantification of recent and historical albedo changes associated with land cover change and forest disturbance. Such information is needed to reduce uncertainties present in the current IPCC WG1 radiative forcing budget, and to forecast the effects of land management and land cover conversion on future climate.
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Title: Impacts of Disturbance History on Carbon Fluxes and Stocks in North America
Principal Investigator: G. James Collatz (NASA GSFC, Biospheric Sciences)
Co-Principal Investigators: Jeffrey G. Masek (NASA GSFC, Biospheric Sciences), Christopher A. Williams (Clark University)
Funding Source: NASA Terrestrial Ecology
Forests of North America are thought to constitute a significant long term sink for atmospheric carbon but the relative importance of underlying mechanisms is poorly understood. This project seeks to clarify mechanisms and quantify spatial and temporal variability in forest carbon sinks. The work extends a previously NASA-funded project that involved the development of a new modeling framework characterizing carbon consequences of forest disturbance and regrowth based on Forest Inventory and Analysis (FIA) data and remote sensing (Landsat) of forest disturbances. Prior results quantify with greater certainty the regrowth carbon sink in the conterminous US, indicating that it is about half of what is generally quoted. This current research project continues to develop and advance the modeling framework by delving deeper into the mechanisms and intensity of documented disturbances using the improved NAFD products, the Monitoring Trends in Burn Severity fire data set, and forest insect damage data sets. In addition, we are engaged in a broader synthesis on the subject by integrating perspectives from flux towers, forest inventories, satellite remote sensing, ecosystem carbon modeling, and atmospheric inversions. We are exploring: (1) mechanistic attribution of forest carbon sinks to disturbance legacies versus growth enhancements; (2) spatial patterns of the continent’s process-specific sources and sinks; (3) interannual fluctuations in forest carbon sources and sinks; and (4) implications for managing forests to sequester carbon. From this new work we will provide more accurate estimates of the carbon fluxes and stocks and their implications on current and future atmospheric CO2 concentrations.
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Title: Carbon Dioxide and Water Flux Response to Extreme Weather and Climate Anomalies: A Fluxnet Syntheses
Principal Investigator: Christopher Williams
Funding Agency: National Science Foundation
In this project researchers will perform a synthesis motivated by findings at individual flux tower sites that extreme weather and climate events (e.g., droughts, floods, hurricanes, and ice-storms) lead to pronounced and protracted anomalies in key components of the measured local carbon and water budgets. The PIs will assess the degree of commonality across flux tower sites in the response of the ecosystem to extreme events, derive a coherent description of these responses, and use remote sensing data to extrapolate spatially coherent and persistent impacts on ecosystems, specifically on vegetation, that subsequently may impact carbon and water balances and climate trajectories on a larger spatial scale. The PIs will also assess the ability of land surface models spanning a wide range of complexity to simulate the observed response of terrestrial state variables and fluxes to extreme events when driven by observed meteorology. The project is composed entirely of a team of early-career scientists.
This work is supported under the NSF Carbon and Water in the Earth System solicitation, an interdisciplinary funding opportunity from the Directorate of Geosciences.