But before trying to make sense of this complicated state of affairs, let's take a walk in the woods. Go out and read this under a single large tree. A mature tree can take 10-15 degrees off the temperature on a hot summer day and cut the cold wind in the winter. The tree's trunk, branches and leaves break the wind and cast a shadow that slows the evaporation rate from the ground and plants around you, increasing the humidity that plants thrive in. They slow the erosion of the soil by breaking up the size and speed of the raindrops, allowing the water to soak in more and run off less.
Leaves breathe in carbon dioxide and breathe out oxygen.
The decomposing leaves and roots increase the organic matter above and below the ground, all the while making nutrients available to other forms of life. Not that grasses don't do the same thing, trees just do it more dramatically. Trees not only shelter you from the extremes of the climate, they make you more aware of it at the same time. The effects of that single tree are amplified in a stand of trees, and it is this cumulative effect that makes a forest. As in a native prairie, the native woodlands reveal a wealth of information about the planet in this locale.