My research project looks at the distribution of forest floor plants in relation to canopy coverage and moisture, with nearby trees serving as a proxy. I suspect that zonation is occurring with regards to canopy coverage and moisture availability. Canopy coverage represents light levels, but also disturbances so those two concepts will be somewhat entangled. If zonation is occurring it suggests niche partitioning is going on, and that some plants may be better at colonizing disturbed areas than others. It may be possible that a sort of climax community is formed in areas that go undisturbed enough.
Casual makes it quite clear that some form of zonation is going on in some contexts. There are areas that are primarily Oregon grape associated with red cedar, for example. These areas tend to be dry. My study didn’t measure this, but the areas tend to have mature trees second growth trees. What ivy is present is either very new growth or in poor health. In other areas invasive ivy and holy are extremely common.
I’d been concerned that the ivy might take over the whole forest, but noticed it wasn’t climbing on sword ferns and was entirely absent from some locations. Ivy on trees is often cut by humans but it is too common to be removed from the forest floor so it must have limits on its fundamental or realized niches. The ivy, along with other invasives such as Daphne (spurge laurel) may be good at colonizing disturbances but outcompeted in the long run by native plants in some contexts. The dominance of Oregon grape and sword ferns in some areas makes me wonder if certain areas will ultimately create a sort of climax community, for example dry red cedar groves will have one sort of ground cover community that remains stable while the trees live and there aren’t disturbances.
You have very good observations of your study site which will help with your discussion and a good start to the theoretical perspectives for your introduction.