I am not aware of any common image analysis method that can differentiate hardwood trees from softwood shrubs under all circumstances. You will want to search the scientific literature on this subject to see if anyone has developed appropriate algorithms that account for conditions in your study area. Success with any method will require consistent spectral differences between hardwood trees and softwood shrubs that are detectable in the wavelength interval measured by the image data. So it may be helpful to start by collecting spectra from the different materials that you hope to distinguish, and looking for consistent spectral differences in the two groups of materials. Regards, Peg Shippert Exelis VIS