We humans, capable of reasoning but inclined toward mysticism, tend to think of our species as the pinnacle of evolution (if not created outright). Though we do possess superior brain power, we are inferior to other species in many respects, including a life span that is significantly shorter than some plants and animals; of course, many if not most humans anticipate an afterlife that will extend their existence through eternity.
Trees, far more vital to Earth's ecosystems than are humans, tend to have long lifespans, often exceeding a hundred and, in some cases, even thousands of years. Following death, they may remain intact for many years, their upright or fallen structures providing shelter and/or nutrients for a wide variety of life forms. They, like all wild plants and animals, are gradually recycled by natural forces and their chemical components fuel future generations of life.
Many humans, on the other hand, choose to be walled-off from nature after death, preferring to occupy a small parcel of land within a quilted box (see Coffins: The Final Insult); self-described children of God, they believe cremation or a "green burial" is undignified and do not contribute to nature's web of life. Trees know better.