Satellite estimation of leaf area index across the east Siberia and the northern Japan from 1998 to 2010

Reliable monitoring of the leaf area index (LAI) is required to further understand the carbon, water, and energy cycles of forests. Kobayashi et al. VOL. 115, G01002, doi:10.1029/2009JG000939, JGR (2010) proposed a satellite-based method to estimate the overstory LAI (LAIo) separately from the understory LAI (LAIu) for larch forests covering eastern Siberia. Their method utilizes the seasonal increase in normalized difference water index (NDWI) for LAI estimation. The relationship between NDVI and LAI was calibrated by a three-dimensional radiative transfer model. The objectives of this study are (1) to extend the analysis to the whole observation period of SPOT-VEGETATION, from 1998 to 2010, and (2) to validate the LAI data sets by the ground-based overstory larch LAI measurements that were obtained at a Japanese larch (Larix kaempferi) in Kushiro watershed (43o 22'N, 144o22') in the summer of 2011. The ground-based LAI was estimated from the gap fractions along four 30-m long transects at Japanese larch. The estimated effective LAI and apparent clumping index at the site was 1.29, and 0.76, respectively. Thus, the LAI of the site was about 1.7. The ten-year's time series LAI shows interannual variations in LAI in particular in 2008 when the large-scale flooding occurred.