Water attracts trees, not the other way around. Some people just don't think logically.
It would seem to me that if there were not enough water.. trees wouldn't grow.
Besides.. this was a FOUR YEAR STUDY? How freepin stupid is that? Four lousy years... don't they know how long trees live? I'm sorry, but I don't care how sophisticated your computer models are, you cannot measure/predict the impact of a forrest on a complex ecosystem in just four years.
The good Lord just doesn't work that way... or that fast.
Indeed, forest land is graded by how much rainfall it receives annually, the best forest land has the greatest rainfall, and supports the fastest forest growth.