Fraction of Photosynthetically Active Radiation Absorbed by Amazon Tropical Forest: A Comparison Among Estimates Based on in situ Measurements, Modeling and Remote Sensing.
Mônica
Carneiro Alves
Senna, Universidade Federal de Viçosa, monica@vicosa.ufv.br
(Presenting)
Marcos
Heil
Costa, Universidade Federal de Viçosa, mhcosta@ufv.br
(Presenting)
In this work we compare three different estimates of the fraction of absorbed photosynthetically active radiation (FAPAR) by an Amazonian tropical rain forest. The estimates are based on in situ measurements, modeling and remote sensing. The field measurements were taken in the Tapajós National Forest, Santarém, State of Pará, Brazil. The model used is IBIS, which simulates the fluxes in the soil-vegetation-atmosphere system considering two vegetation layers. The monthly FAPAR product of MODIS, from Boston University, is used.
FAPAR based on field observations is calculated from incoming and reflected PAR measurements taken above the canopy, and downward PAR at 15 m height, and is corrected to be representative of the entire canopy. The annual mean value obtained from these field measurements is 0.91. FAPAR simulated by IBIS has an average value of 0.76. The average FAPAR estimated by MODIS is 0.85. The in situ measurements are consistent with the literature. The values obtained by IBIS, although smaller than the other two, agree with the results of another similar model, the Common Land Model.