This was a bug in beta(as you can see by using search)that made it through to live.
1.) You need to be a resto druid with "Master Shapeshifter" and "Improved Tree of Life"
2.) You need a warlock or a druid to banish/cyclone you while in tree form.
3.) After banish/cyclone wears off the "Tree of Life" aura will be reapplied, however, instead of increasing healing by 6%, it will be increased by much much more. It will still say "increases healing by 6%" though.
The bugged effect is lost upon shapeshifting, but the bug is NOT lost when zoning. You can bring this into BGs, and instances. However, arena seems to reset all buffs on you when you enter, so it won't work there.