In the latest issue of Science scientists reported that changes in water availability between 1930 and the present day drives plant species downhill with an optimum at lower elevations. The study area was about one half of California.
http://www.sciencemag.org/content/331/6015/324.abstract
I am not interested in a general global climate change discussion. I just want to ask whether you have noticed something like that during your years of being in the mountains and foothills. I could not think of a better audience to ask that question than here on SP