Prevalence of multiple forest disturbances and impact on vegetation regrowth from interannual Landsat time series (1985-2015)

Given long time series of satellite imagery, multiple disturbances can be detected for a particular location at different points in time. We assessed multiple disturbances for the 650 Mha of Canada's forested ecosystems using annual change information derived from Landsat time series imagery (1985-2015). Changes were typed by agent (fire, harvest, and non-stand replacing). Spectral change rate and time between successive disturbances were used to characterize disturbance-type combination differences. Short-term spectral recovery following the last disturbance was compared to a reference sample of pixels disturbed only once. Results indicated that of the 97.6 Mha disturbed, 13.5 Mha have had two or more disturbances, with low magnitude non-stand replacing disturbances involved in the majority of occurrences (77.2%). The total area disturbed represents 18.27% of forest ecosystems, with 2.53% having multiple disturbances and 0.54% having multiple stand-replacing disturbances. Systematic time series-based investigation of multiple disturbance events and agents provides insights on forest disturbance dynamics and recovery processes.