Fig. 9.

Change rates in the PRI (a), TCARI/OSAVI (b), Macc (c), and red-edge CI (d) indices vs. the NDVI, all derived from synthetic spectra. Rates are calculated for consecutive time steps for healthy trees (triangles) and for trees in declining health progressing through five levels (dots of decreasing darkness). Panel (d) shows that in the CI vs. NDVI temporal change rate, trees in declining health were bound by two baselines and progressed between them, while healthy trees concentrated and remained at the intersection of those baselines over time. Triangles (dots) show the simulated healthy (decline) trees. Decline stages are shown in grey levels from black (low decline) to light grey (high decline). Black and grey lines indicate the boundaries that establish the baselines for healthy trees and trees in severe decline, respectively.