“Based on the images captured by NASA's Moderate Resolution Imaging Spectroradiometer (MODIS), it was revealed that 1.6 percent of the total land surface of China became heavily forested in a span of only ten years from 2000 to 2010.”
So trees don't change the 0 sum aspect behind cloud seeding: if the rain falls in one place, it can't rain in some other place. The primary reason why plants (read: anything photosynthetic) have a role to play in where it rains is the same principle behind cloud seeding. Plants, when they don't have sufficient nutrients to run photosynthesis and make new plant material, release unused photosynthesis as short chained hydrocarbons, usually ethane and some derivatives. Idea here is that it gives them a place to land the electrons from photosynthesis without tearing themselves apart when nutrients aren't readily available. These short chained hydrocarbons go on to play the same role as the silver compound used by China; they form the 'seeds' for droplet formation.
Neither method does anything to address the fact that there is only so much water in the atmosphere (although that is changing with a changing climate).
http://www.natureworldnews.com/articles/20305/20160321/china...
“Based on the images captured by NASA's Moderate Resolution Imaging Spectroradiometer (MODIS), it was revealed that 1.6 percent of the total land surface of China became heavily forested in a span of only ten years from 2000 to 2010.”
http://rspb.royalsocietypublishing.org/content/284/1854/2016...
“China is investing immense resources for planting trees, totalling more than US$ 100 billion in the past decade alone”