Various classifications of change in forest ecosystems have been proposed. Aldrich (1975)
approached the variability in forest cover from a thematic angle, enumerating nine general forest
disturbance classes:
no disturbance
harvesting (areas subjected to timber removal operations)
silvicultural treatments (e.g., thinning)
land clearing (vegetation removal and site preparation)
insect and disease damage (epidemic conditions)
fire (prescribed burning and wildfire)
flooding (man-caused and natural)
regeneration (artificial or natural)
other (not fitting any of the above categories).