While you are thinking about the photo one, here is one that is a bit easier. There is somewhat of a relationship to the other question.
The question:
There have been some studies that show there is probably a limit to how tall a tree can get. What is this limit (ranges are OK) and what is the reason?
A combination of capillary action and the forces of cohesion/surface tension between water molecules limits the height of trees to about 350 feet, if my rememberer is working correctly. That in itself would be reason to celebrate!
My last guess...squirrels can only climb so high before reaching rarefied air. Some squirrels do have access to oxygen masks but most don't. I rather doubt that nature would allow trees to grow beyond most squirrel's limits for atmospheric sustainability.