The Montane Ecosystem occurs at elevations between 5,600' and 9,500'. Dry, south-facing slopes of the Montane often have open stands of large ponderosa pines. Spacing of ponderosa pines is somewhat related to available soil moisture. Grasses, other herbs and shrubs may grow between the widely spaced trees on dry slopes. North-facing slopes of the Montane escape some of the sun's drying action, so their soils contain more available water. As a result, the trees grow closer together and competition for sunlight produces a tall, slender growth form. The trees may be a mixture of Douglas fir, lodgepole pine, ponderosa pine and an occasional Engelmann spruce. Montane soils with high moisture content may support groves of aspen. Along streams or the shores of lakes, look for water-loving small trees such as various willows, mountain alder and water birch.