Conifers have a very different lifestyle than their deciduous counterparts.
We all know that pine trees keep their needles all year, right? Wrong! Pine trees do loose their leaves, or needles, as do most other evergreens such as spruce or hemlock. But first, why these keep most of their leaves in the fall is pretty interesting. As you travel around the state and throughout the world, you'll notice that conifer trees are more dominant in places where conditions are particularly harsh.
Northern areas are covered with spruce and hemlock, and stunted trees just below the tree line on mountain tops are usually spruces. And evergreens can do surprisingly well in places that have poor soils. Why is this? Well, it takes a lot of nutrients and energy to regrow all your leaves every spring. It is much more efficient to use them year after year, so where nutrients, such as nitrogen, are scarce or conditions are tough, conifers have a "leaf-up" on deciduous trees, which shed all of their leaves every fall.
There's another advantage to keeping some needles all year. Conifers continue to photosynthesize and produce energy in the weak light of winter, however in cold weather, this process happens much more slowly. In order to conserve resources the trees drop some of their needles so there are fewer leaves to support in these lean times.
And after stressful or very dry summers, pines may lose even more needles, because the trees have not been able to build up as much stored energy in preparation for winter.
