Vegetation communities are usually regulated by soil type & depth, altitude, rainfall and aspect. You could look at the image below and think all the forest is the same but that is far from the truth. Plants have evolved for specific niches within any landscape. Some species are highly adaptable and robust while others have very specific requirements and can't grow outside of their perfered habitat.
The boundaries between some plant communities can be blurred with species from each community interchanging with the other. Conversely, some plant communities have boundaries that are obvious and conspicuous because of the regulating factors being so prominent. Inevitably, high plant diversity means high animal diversity so some boundaries offer animals many more opportunites then they would have living in just one community type.
The image below is taken from the Coral Sea looking across Thornton Beach around the slopes of Table Mountain (Mt Emment) through the Noah Creek Valley up to Thornton Peak, which is in cloud. The inserts show what the plant communities would look like at that specific location and are based on the Wet Tropics Vegetation Maps.
1a Complex mesophyll vine forest (on deep fertile soils).Very wet and wet lowlands and foothills mainly on basalts and alluvium.
64a Coastal Beach Complex Variable open to closed shrubland, grassland and low to medium woodland and forest complex
14a Simple microphyll vine-fern forest. Moist to very wet (± cloud) highlands on granites, metamorphics and rhyolites.
17a Simple microphyll vine-fern thicket. Very wet (± cloud) highlands on granites.
10a Simple notophyll vine forest. Moist to very wet uplands and highlands on metamorphics, granites and
2a Mesophyll vine forest. Very wet to moist lowlands to uplands on a variety of geologies.
2 d Mesophyll vine forest characterised by Barringtonia racemosa +- Hibiscus tiliaceus +- Heritiera littoralis +- Archontophoenix alexandrae Licuala ramsayi prominent in the sub-canopy
Wet Tropics Managemnt Authority Vegetation Maps
Thornton Sheet - Showing transect as per photo.