Research on Remote Sensing Model for FPAR Absorbed by Chlorophyll

The Fraction of Absorbed Photosynthetically Active Radiation(FPAR) has been recognized as one of the important variables in carbon cycle research of terrestrial ecosystem.According to the physical meaning of FPAR,the concept of effective FPAR,which is FPAR absorbed by chlorophyll within the leaf,is introduced in this article.We developed the effective FPAR remote sensing model using simulated data,and analyzed the feasibility of estimating effective FPAR based on chlorophyll content,which was expected to introduce a way to estimate NPP/GPP using effective FPAR.The results showed:(1) the difference between FPAR absorbed by leaf(FPAR_(leaf)) and FPAR absorbed by chlorophyll(FPAR_(chl)) cannot be neglected.FPAR_(chl) is not more than 50% of FPAR_(leaf) basically.The correlation between FPAR_(chl) and FPAR_(leaf) is nonlinear.(2) A strong correlation was found between chlorophyll content and FPAR_(leaf),but the correlation between chlorophyll content and FPAR_(chl) is much stronger.So FPAR_(leaf) and FPAR_(chl) can be accurately estimated based on chlorophyll content,and the estimation average errors are 2.90% and 6.6% respectively.(3) the estimation accuracy of FPAR_(leaf) and FPAR_(chl) models is higher when chlorophyll content is not less than 20μg/cm~2.For 60 samples that chlorophyll content is not less than 20μg/cm~2,the average errors of estimated FPAR_(leaf) and FPAR_(chl) are 1.79% and 5.07% respectively.