Sunlight is the source of energy for plants, which create food through photosynthesis. Photosynthesis occurs in the foliage, or the green leaves or needles, of a plant. The amount of food a plant can produce is partly dependent on the amount of its leaf or needle surface area. The scientist in this study wanted to test her hypothesis that pines growing at higher elevations adapt to these harsher environmental conditions by growing needles that live for more years than needles growing at lower el Topics: Active Forest Management, Adaptation, Biomass, Climate, Elevation, Graphing data, Lodgepole Pine, Photosynthesis.