What do you mean by ecological functions? Surviving and reproducing?

Well, the ocean provides examples of some. Kelp forests and corals are good examples of things that grow big and are looking for light. Both have tree like habits and growth in different ways

The design of a tree is likely to be quite convergent. E.g. trees and palm trees evolved the same basic layout.

Light trapping organisms require as much surface area exposed to the local star as they can cope with. Trees evolved by plants trying to climb over one another. It took the evolution of cellulose for them to get really tall. Alien plans might now have evolved an equivalent.

The leaf structure, on earth is a trade-off. On earth, it needs sunlight, water from the ground and CO2 from the air. It also needs to deal with damage. A lot of holes is great for CO2 absorption, but will rapidly lose water. A flat surface is great for catching the sun, but leaves all the expensive machinery exposed to damage. Balancing all of these leads to the various leaf shapes we see on both trees and smaller plants.

There’s still room for more interesting ideas, but they are unlikely to be the staples of an alien forest. E.g. if the air composition was different, balloon plants might be viable. Rather than a hard, woody stem, the top could be a hydrogen filled leaf balloon. A vine could bring water up from the roots. It would act like a lilly pad does in water.