My guess is that the raw exposure is a big deal. Trees on hillsides or mountainsides only have one side fully exposed, so there's a dominant direction they coul

My guess is that the raw exposure is a big deal. Trees on hillsides or mountainsides only have one side fully exposed, so there's a dominant direction they could brace against. They would also benefit from having other trees (and a mountain) next to them to help dissipate the energy from the wind and rain.