Hi Angry Pig,
That dense foliage is great for rainforest.
In dry sclerophyll forest, or what I call fireforest, the eucalypts have sparse leaves. They grow fast and slender, often dropping flammable material which resists decay!
Dangerous stuff.
In relation to dropping leaves in winter, remember this is only deciduous trees. Evergreen trees with regular leaves (not just needles) are found near the equator and southern hemisphere... both rainforest and fireforest.
You may already know all this, or expect to find out when you are ready!
Richard.
