A study was conducted at the West Virginia University Forest, U. S. A. on the effect of thinning on growth and yield of red pine during Spring, 1986. It was done by comparing two different stands, one thinned and the other unthinned. The thinned plantations received three commercial crown thinnings.

The sawtimber volumes in each stand were estimated through a cruise. Sawtimber volume estimates per hectare in the thinned stand were found slightly lower than in the unthinned stand. Volumes for both the stands were then projected for next 10 years. Future sawtimber volumes were also predicted and found to be slightly higher in the thinned stand than in the unthinned one. These results were believed to have occurred because the thinning intensities were too light to prompt a better growth response at the early stage.

Data obtained from increment cores of 40 trees in each stand were analysed by a paired t-test. It was found that the growth rate in the thinned stand was significantly higher than in the unthinned stand. It means, the thinned stand would show better growth performance if both were left for another 10 years.