Methods for evaluating the growth potential of native timber stands are discussed. A new index curve for black walnut and general relationships of preferred timber species for eastern Kansas are presented. Forest tree growth is dependent upon a complex interaction of environmental factors--climatic, biotic, topographic, and edaphic (soils). The term site is used to express the sum total of these factors. Topography and soils affect trees in ways not readily apparent. Topography includes landform, aspect, and slope, whereas soil characteristics include texture, structure, soil moisture, and fertility. Figure 1 illustrates topographic and soil factors as they hypothetically relate to pine tree growth in the South (Zahner, 1957). Growth in height is a good indicator of the volume of timber produced in a stand. Because tree height is a function of the age of a tree and the environment in which it grows, environmental factors can be measured and related to productivity. The site-index method is the most widely accepted means of evaluating productivity in forests or woodlands. This method is easy to use and correlates well with timber yields. While index is used primarily in evaluation of native timber stands being managed for timber products, it is also valuable in estimating the potential of an area for tree planting for a number of different purposes. By definition, index is the average height (at age 50 years) of dominating trees in a fully-stocked, even-aged stand. The most commonly used techniques for estimating index are site-index curves and indirect soil-site evaluation.