# Decision-making in tree limb growth?

Sorry if this is a naive question, but it occurred to me as I was walking across campus today; How does a tree decide which limb is allocated the most resources, and thus grows the largest? My first thought is the first branch to deviate from the base receives the most energy investment, and so on, but I don't have the time (or will) to actually test that. Does it have more to do with efficacy of the limb for photosynthesis? Or is it largely due to chance/unknown variables? Thanks in advance, I feel this is something I learned back in botany and just forgot completely.