For the first time, scientists have discovered how tree roots in the mountains may play an important role in controlling long-term global temperatures. Researchers have found that temperatures affect the thickness of the leaf litter and organic soil layers, as well as the rate at which the tree roots grow. In a warmer world, this means that tree roots are more likely to grow into the mineral layer of the soil, breaking down rock into component parts which will eventually combine with carbon dioxide. This process, called weathering, draws carbon dioxide out of the atmosphere and cools the planet. The theory suggests that mountainous ecosystems have acted like Earth's thermostat, addressing the risk of 'catastrophic' overheating or cooling over millions of years.
http://www.sciencedaily.com/releases/2014/02/140205210436.htm