Once there are plants, from tiny worms to large beasts, they will naturally migrate over on their own.
On a newly built planet, the soil's organic matter content is zero, so many plants don't take well. What the Plant Department's Blue Catalpa, Black Rice, Woodberry, and Pueraria need to do is cultivate all kinds of shrub and arbor saplings, transplant them to designated areas, spread chemical fertilizer, give them special care, protect them through their fragile juvenile phase, and enrich the variety of plants.
Once the plants are rich enough, the animals will naturally become rich as well.
When the variety of flora and fauna is rich, the ecosystem will tend toward stability.
In this colossal project of transforming a planet, there's no need to waste time and energy worrying about the state of any particular tree or any particular patch of forest.
