Evaluation of the importance of nonlinear spectral mixing in coniferous forests

We developed a simple technique to evaluate the importance of non-linear mixing in coniferous forests with different overstory structural characteristics and different backgrounds. The methodology consists on using a hybrid forest reflectance model for reflectance simulation, and on using factor analysis and target testing for unmixing the forest reflectance into three components: a forest canopy component (free of background effects), a background component (free of canopy effects) and a background-and-canopy dependent component. This third component is considered responsible for non-linearities since it depends simultaneously on the background reflectance and on the canopy transmittance. After running the model, the contribution of the third (non-linear) component to the total forest reflectance was evaluated and compared over different forest scenarios parameterized with data collected on maritime pine stands in Central Portugal.