influence of competition on individual white pine thinning response

A model predicting white pine (Pinusstrobus L.) diameter growth after thinning included competition, initial diameter, and crown class as independent variables. Model coefficients indicated a decrease in percent 8-year diameter growth with increasing crown suppression, crown competition, or tree size class. Variables selected were superior to age, percent live crown, and prethinning growth. Equations predicting basal area and volume growth were similar in form to diameter growth. Height growth, however, was more closely correlated with crown characteristics and unaffected by competition. Annual growth patterns were similar to periodic growth patterns, revealing decreased growth with increasing competition or crown suppression. Trees having little competition and dominant crowns utilized their growing season longer, with earlier initial growth and faster growth than trees having greater competition or crown suppression. Within a crown class, diameter growth decreased as competition increased. Individual tree competition was seen as the most important factor influencing tree growth that a forester can control.