Abstract
Several 5- and 6-yr-old red pine plantations in central Wisconsin were sampled to assess the performance of crop trees and the levels of competing vegetation. A simple tree class system was devised to classify the level of brush competition on a fixed area plot surrounding each sampled crop tree. The tree class was significantly correlated with several measured and derived competition variables, and was also strongly related with three tree performance variables: height, volume, and biomass. Tree Class 1, the lowest competition level, was associated with significantly greater tree heights, volumes, and biomasses for both age groups. Logistic regression equations were developed to derive a quantitative relationship between competition, as measured by tree class, and crop tree performance. Performance was judged to be either adequate or inadequate based on an arbitrary set of standards for both volume and biomass. From the regression equations, probabilities of successful performance were calculated. For volume index and biomass, the Class 1 trees, or the trees with the lowest levels of competition, had success probabilities ranging from 76 to 89%. For the Class 4 trees, or the trees with the highest levels of competition, success probabilities ranged from 3 to 16%. North. J. Appl. For. 12(3):101-108.
Climatic Effects on Site Productivity of Red Pine Plantations