Instead of blood pressure, temperature, and heart rate, the vital signs for a forest are captured in key traits such as the amount of nitrogen in a tree's leaves, the leaf area, or the density of the wood. These "functional traits" can impact how trees grow -- and therefore how forests respond to climate change. While researchers have begun trying to tease out these patterns in recent decades, incomplete data has made it difficult to understand what's happening to particular traits in any meaningful way -- especially when you get down to the level of individual trees in a forest.