To get your trees to survive their early life and not get eaten by animals (tasty green branches and roots without nasty bark) or die from deer massage (they scratch themselves on the bark and can damage trees to the point of decades old trees dieing), you need people actually maintaining the cultivated area until it becomes a quality mixed forest - otherwise, only the fast growing trees will survive like spruce and beech.
Spruce acidify the ground and cover it with needles, nothing else grows there - so not good for biodiversity. Beech are low-density wood and don't bind much carbon.
Setting up the development of an old-growth forest is lots of work.
(Edit: if someone plants a tree, odds are it'll get eaten - you will not get a tree for 5USD, you'll likely feed the local fauna)