Model effects on GLAS-based regional estimates of forest biomass and carbon

Ice, Cloud, and land Elevation Satellite (ICESat) / Geosciences Laser Altimeter System (GLAS) waveform data are used to estimate biomass and carbon on a 1.27 × 106 km2 study area in the Province of Québec, Canada, below the tree line. The same input datasets and sampling design are used in conjunction with four different predictive models to estimate total aboveground dry forest biomass and forest carbon. The four models include non-stratified and stratified versions of a multiple linear model where either biomass or (biomass)0.5 serves as the dependent variable. The use of different models in Québec introduces differences in Provincial dry biomass estimates of up to 0.35 G, with a range of 4.94 ± 0.28 Gt to 5.29 ± 0.36 Gt. The differences among model estimates are statistically non-significant, however, and the results demonstrate the degree to which carbon estimates vary strictly as a function of the model used to estimate regional biomass. Results also indicate that GLAS measurements become problematic with respect to height and biomass retrievals in the boreal forest when biomass values fall below 20 t ha−1 and when GLAS 75th percentile heights fall below 7 m.