Early effects of thinning pure ponderosa pine in Western Montana /

Just as the gardener thins his carrots and the farmer thins sugar beets' to give those remaining greater space for development, so does the forester often need to thin forest stands to harvest trees which would ordinarily die and to increase rate of growth on the trees he selects to leave, thus enhancing the value of the stand.An indication of what may be ex- pected after thinning young ponderosa pine in western Montana is given by data obtained from the fifth-year examination of nine experimental thinning plots in the Lolo National Forest near Missoula.In these plots, established during the summer of 1935, treatment had a measurable effect during the 5-yea period.All thinnings were from below, i.e., removing the overtopped trees of small crowns and poor form first and working upward in consecutive order through the fair to better crown trees, increasing the number removed with increase in intensity of thinning (see plate 1).The plots, ranging in area from 0.1 to 0.4 acre, consist of two groups.One group, including four plots, is on a site of fair quality (site quality class IV) and the other, including five plots, is on a poor quality site (site quality VI).Treatment of each plot within these groups was as follows: Group I , Fair Quality Site Lightly thinned Moderately thinned Heavily thinned Unthinned check