After testing how well arborist trees would grow on a desert hill and then moving the arborist elsewhere and culling the trees, one or two years later I suddenly see a lot of Red Pine trees appearing in the same area previously populated by various immature fruit trees.
Previously nothing grew there as the dead trees indicate and the next pine trees are rather far away, beyond the southeast houses in the screenshot. I never planted any decoration trees either, so while the trees growing there is nice, it is very unusual behaviour.