Modeling forest stand structure attributes using Landsat ETM+ data: Application to mapping of aboveground biomass and stand volume

Maps of aboveground biomass (AGB) and stand volume are of interest to determine their magnitude and spatial distribution over forested areas, and required for input to forecasting carbon budgets and ecosystem productivity. Deriving estimates of AGB and volume requires information about species composition and forest stand structure. This paper introduces a method called BioSTRUCT (Biomass estimation from stand STRUCTture), which is based on georeferenced field plots to generate empirical relationships between continuous estimates of forest structure attributes and remote sensing image data represented as spectral response variables. In this study, height and crown closure attributes were modeled from Landsat ETM+ image and field plot data. These modeled attributes were then used as inputs to stand-level models of AGB and volume. The image height model had an adjusted R2 of 0.65 from ETM+ bands 3, 4, and 5. Likewise, the crown closure model had an adjusted R2 of 0.57 using ETM+ bands 3, 4, and 7. Average AGB estimates were within 4 tonnes/ha and stand volume was within 4 m3/ha of field plot values, statistically similar to a validation sample data set for both AGB (p = 0.61) and stand volume (p = 0.65), and within the range of previous published studies. Field plot distribution, error propagation, and extending models over multiple images were identified as factors requiring further investigation in order to apply BioSTRUCT over larger geographic areas.