Improving Forest Biomass Estimation Methodology in Estonia Using Spaceborne SAR Imagery
Olesk, Aire¹; Voormansik, Kaupo²; Zalite, Karlis³; Reinart, Anu⁴; Noorma, Mart³; Desnos, Yves-Louis^5
1ESA/Regio, ESTONIA; ²Regio, ESTONIA; ³University of Tartu, ESTONIA; ⁴Tartu Observatory, ESTONIA; ⁵ESA, ITALY

In order to efficiently monitor the environment and to understand the global carbon cycle, it is crucial to work out methodologies for successful integration of remote sensing and forest inventory data. In Estonia, where forests cover more than half of the land, a satellite and in situ data processing methodology was developed to reduce the uncertainties in the carbon balance of the terrestrial ecosystems. This study presents how Synthetic Aperature Radar (SAR) imagery, optical satellite data and forest inventory data from Estonian Forest Register were successfully combined to map the spatial distribution of forests and above-ground biomass. A country-specific data processing methodology allows producing up-to-date biomass maps that can be used to assist the national inventory reporting under the UNFCCC (Intergovernmental Negotiating Committee for a Framework Convention on Climate Change) and the Kyoto Protocol. By applying Earth Observation (EO) techniques and combining satellite and in situ data from various sources, valuable information for a complete analysis of CO2 sink and Estonian landscape specific Emission Factors (EFs) can be provided.

The goal of this research was to demonstrate a cost- and time-effective method to assist the future national greenhouse gas inventory reporting by integrating remote sensing and forest inventory data. The complete study consisted of several tasks, including: 1) Modeling Estonian landscapes CO2 emission and absorption using meteorological and Earth Observation (EO) data with a Gross Primary Productivity (GPP) model, 2) Estimating Estonian forest carbon stocks based on ALOS PALSAR satellite imagery, 3) Calculating Estonian land use map according to IPCC standard based on DMC multispectral satellite imagery and 4) Measuring GHG fluxes in situ in Estonian forests and wetlands.

Research results were published through a web-based map application (http://regio.space.ee/pecs/), that provides an overview of latest land use map (according to Intergovernmental Panel on Climate Change (IPCC) requirements) and first countrywide forest biomass map of Estonia. Web map application was developed for raising public awareness of the climate change issues and providing continuous forest monitoring updates to enable a more sophisticated calculation of carbon stock that in turn allows Estonia to report at a higher IPCC tier methodology when providing annual country-specific GHG inventory data.