1. Estimating leaf area index (LAI) and fraction of absorbed PPFD (fAPAR) based on forest inventory data and satellite images
We are developing LAI and fAPAR maps for Finland for the purposes of using them in broad scale forest carbon modeling. LAI and fAPAR are based on models of specific leaf area and estimates of leaf biomass for each inventory plot. To estimate leaf biomass for plots, we adopted the methodology from Tuominen et al. (2010). In that approach standard NFI10 tree level measurements were complemented with multivariate linear mixed-effects model with species-specific parameters designed for the multi-response NFI data (Eerikäinen 2009). Application of this multivariate linear mixed-effect model enabled calibrated estimates of tree height and crown base heigth for each individual tree, based on DBH (diameter at breast height). Biomasses of foliage, branches, stem, bark, stump and roots were estimated by biomass models Repola (2008, 2009).
The k nearest neighbour (k-nn) method (e.g. Kilkki and Päivinen 1987, Muinonen and Tokola 1990, Tomppo 1990) was applied for producing estimates of biomass variables in the form of thematic maps covering the area of intrest. The k-NN imputations may also be done using yaImpute package in the R Statistics (Crookston et al. 2007).
See example maps for biomass for Central-Finland (click the pictures to enlarge):