Ten miles north of Flagstaff is the oldest experimental forest in the United States. It was established more than 100 years ago at a time when foresters wanted to know how to encourage ponderosa pines to grow. Now, scientists use Fort Valley to study the opposite problem: how to thin the overcrowded woods. It took decades of research to bring about that shift in thinking. KNAU’s Melissa Sevigny reports, it all started with one man and two mules.