Photos can capture a wealth of detail about woodland structure and, if a photo is taken from the same spot and in the same direction after a gap of a few years, a surprising amount of change may be observed.
Select points that can be relocated and points that will illustrate anticipated change. If a suitable existing, durable feature (e.g. a conspicuous boulder) is not available, mark the spot with a stob. Record location, date and direction of view. A hand-held GPS receiver is very useful for recording a location and finding it again a few years later.
Aim to revisit the points after about five years, sooner if rapid change is expected. Do not establish too many points; a few well chosen points are more likely to be revisited and thus more likely to be of use.