Blurs

Trees are usually associated with moderate climates: sufficient rainfall, tolerable temperatures, fertile soil and a reasonably long growing season. Yet trees grow in places that seem to violate almost every rule. Some survive where winter temperatures plunge far below freezing. Others cling to mountainsides where the growing season is measured in weeks. Some endure intense drought, salt spray, volcanic soils or repeated fire. There are forests close to the Arctic Circle, trees growing on isolated volcanic islands and individual trees that have survived for thousands of years. They aren't anomalies in the sense of being impossible. They are examples of just how far evolution can push a plant's ability to survive. What Makes a Place Too Harsh for a Tree? Trees have several fundamental requirements. They need water, but too much water can be just as problematic as too little. They need carbon dioxide and sunlight for photosynthesis. They require nutrients and a stable enough grow...