Increases your armor contribution from items while in Tree of Life Form by X%, and increases your healing spell power by Y% of your spirit while in Tree of Life Form.
Improved Tree of Life is a talent in the DruidRestoration tree, requiring you to spend 44 points in Restoration to max it. The talent Tree of Life is a prerequisite. Improved Tree of Life form increases your armor contribution from items by up to 200% and increases your healing spell power by up to 15% of your spirit, but only while in Tree of Life Form. This spell power increase applies only to healing spells, not damage, although this matters little as you cannot cast any damaging spells aside from Thorns and Nature's Grasp while in Tree of Life form.
If you have this talent, it's important to take into account that spirit on items will now slightly benefit your spell power, which is worth it to keep in mind when comparing potential item upgrades, especially considering the many slight differences between gear choices in WotLKendgame.
This talent works very well with Living Spirit, which will further increase your spirit, and thus your healing spell power.
Improved Tree of Life increases your armor contribution from items, but since patch 3.0.8, bonus armor beyond the base armor of an item will no longer be multiplied by any talents. This means that armor on rings, amulets, trinkets and additional armor on cloth and leather items (marked with green text in the game) do not gain the bonus from this talent.
Unlike the Tree of Life talent, which reduces the cost of your heal over time spells both in and out of Tree of Life form, Improved Tree of Life provides no benefit while you are not in Tree of Life form.