A New Approach to Tree Grading for Northern Hardwoods

The application of a practical tree-grading system has been deterred by the lack of basic information that relates tree characteristics to product yields and values. These relationships are very complex, and, because of the infinite combinations, analysis was impossible until the advent of high-speed computers. Past attempts usually were based on log grading in the tree and considered only a few factors affecting wood quality. Most approaches were empirical, and the results were generally unsatisfactory. This paper covers the techniques and interim results of an investigation to devise a reliable, accurate, and practical tree-grading system for sugar maple (Acer saccharum Marsh.) in the Lake States. The main objectives was to develop equations (using multiple regression analyses) for estimating the value of standing trees by relating stem characteristics, such as defect indicators, tree form, and growth factors, to product yields. The results so far indicate that accurate predictions of product grade yields such as lumber or a given clear-cutting size distribution are possible. Such a tree-grading technique in timber appraisal work will make equitable sales transactions possible. Other uses will be to help determine the best product use before cutting and to evaluate the effects of stand treatment upon the quality of the growing stock left after cutting.

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