DETERMINATION OF TROPICAL FORESTS PARAMETERS IN GROSS PRIMARY PRODUCTION CAPACITY ESTIMATION ALGORITHM IN BRAZIL

摘要

Gross primary production capacity (GPP_(capacity)) estimation algorithm was developed by Thanyapraneedkul et al. (2012) to estimate gross primary production (GPP) globally using satellite data. GPP_(capacity) is defined as low-stress GPP. The rate of photosynthesis depends on photosynthesis reduction caused by weather conditions and photosynthetic capacity. This algorithm is based on the fact photosynthetic capacity depends on chlorophyll content which can be observed by satellites. In this algorithm, GPP_(capacity) is estimated using the light-response curve of photosynthesis. A vegetation index (CI_(green)) having strong relationship with chlorophyll content is used to determine parameters in GPP_(capacity) estimation algorithm. They are determined for each vegetation type. In this study, parameters for evergreen broadleaf forests in tropical regions in Brazil were determined. It is important when we estimate global GPP_(capacity) because tropical forests in Amazon basin occupy about 9% of the forests on the earth (FAO, 2009; FAO, 2010). We used two flux data of BR-Sa1 and BR-Sa3 in Brazil and satellite reflectance data corresponding to their coordinates. Parameters for BR-Sa1 and BR-Sa3, and common parameters between both sites were determined to apply them globally. GPP_(capacity) was estimated for BR-Sal and BR-Sa3 using parameters for each site (GPP_(capacity_Site)) and common ones (GPP_(capacity_common)). The applicability of this algorithm and determined parameters were examined. Comparing GPP to GPP_(capacity) at flux level. GPP_(capacity) was regarded as a first approximation of GPP for these sites. The ratio of GPP_(capacity_common)lGPP_(capacity_Site) was 1.02 for BR-Sal and 0.95 for BR-Sa3. respectively. GPP_(capacity) could be estimated using common parameters between both sites. Comparing GPP_(capacity_common) to GPP, the ratio of GPV/GPP_(capacity_common) was 0.97 for BR-Sal and 0.98 for BR-Sa3, respectively. Though GPP_(capacity) values were slightly higher than GPP, GPP could be estimated by estimating GPP_(capacity) using determined parameters for evergreen broadleaf forests in tropical regions in Brazil.