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Global Distribution of Carbon Stock in Live Woody Vegetation

  • Author(s): Yu, Yifan
  • Advisor(s): Seibt, Ulrike
  • Saatchi, Sassan S
  • et al.
Abstract

The terrestrial biosphere is responsible for removing roughly one quarter of the total anthropogenic emissions of carbon dioxide from the atmosphere.

This process is dominated by the forests. The terrestrial portion of the global carbon cycle is also the most uncertain. Growing forests are a major sink of CO2 while deforestation contributes as a major source of CO2. While the locations of deforestation can be tracked with remote sensing data relatively well, the amount of carbon removed is not well known due to the lack of knowledge on the biomass density of the forests that were disturbed. Spatially explicit distribution of carbon stocks in global forests can greatly reduce this uncertainty by improving estimates of emissions from land use activities. It will also help with green house gas inventory at regional and national scales.

Increasing amounts of remote sensing based forest studies are being conducted, however, there is currently no global spatially explicit map of forest biomass/carbon. This dissertation aims to address that by producing the first global spatially explicit map of live biomass and carbon stock in forests and other living woody vegetation at ~1 km resolution for circa year 2005. A combination of remote sensing data from the Quick Scatterometer (QuikSCAT), Moderate Resolution Imaging Spectroradiometer (MODIS), and Shuttle Radar Topography Mission (SRTM) are used to provide wall-to-wall spatial information. Ground inventory and LiDAR from the Geosciences Laser Altimeter System (GLAS) onboard the Ice, Cloud, and land Elevation Satellite (ICESat) are used to create a global network of aboveground biomass (AGB) samples. Landcover map based on the GlobCover product from the European Space Agency (ESA) is used as ancillary data. These are combined in a statistical model using Maximum Entropy to create the first global map of AGB and total carbon stock (above + below ground) in living biomass. Uncertainty at the pixel level is also produced alongside the above products. The total global carbon in live woody vegetation is estimated at 337 PgC, with 311.4 PgC being in the forests (92% of total) for circa year 2005, compared with 302.8 PgC in total global live forest biomass as reported in the United Nations Food and Agriculture Organization's 2010 Forest Resources Assessment report (FRA 2010). Shrublands and savannas account for the other 25.6 PgC (8% of total) globally. National carbon stocks are calculated and reported for all the countries using several different thresholds for forest cover.

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