There is currently no credo for what I like, growing trees. So this is my suggestion. Possibly needing gardener, or maybe just farmer as the pre-requisite credo.
Specific benefits I would like to see:
1. A tripling of the biome expansion rate for trees planted by a forester: Currently a tree planted and let to grow in grassland might give 2-4 tiles of wald. Bringing this up to 6-12 would allow me to only plant quality trees, rather than needing to plant a bunch of q10's, wait, then cut them down and start planting what I really want to grow.
2. A similar reduction in soil/water requirements to the gardener's for garden pots.
3. A wooden treeplanter's box, instead of the clay pot(Yes I know this is a bit of an insane request, given how it would affect quality, but i do hate the treeplanter's pot limitations.) Have it require heartwood leaves like bone clay requires pit clay to ensure difficulty in making and limit quality increase, its even thematic with the leaves/forest.
4. An increase in the frequency of products being regenerated on planted trees(Can the decay system be sped up or more likely to happen on a given object?), alternatively, just a larger quantity of products generated from a tree, 25%? 50%?
5. Some sort of minor tree speed growth increase, 10% or whatever.
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As someone who likes growing trees and would also like to cultivate multiple forest biomes in a single area, these are the effects that would make managing trees more enjoyable, and enable me to seriously consider moving specific forest biomes multiple tiles to get it into a good living location.
Additionally, since most of what I do is carpentry/farming capped(Not counting the treeplanter's pot), I don't really feel it needs any stat/skill increases are needed.