Occurrence of cull in managed oak stands in Northern Illinois
For intensive management of forest properties it is essential to know the per cent of cull occurring in the various species on various sites. This study describes the technique used at Sinnissippi Forest, in northern Illinois to obtain these cull factors for well managed upland oak timber. The forest stands are described giving past history and present management policies. Soil types and their relationship to growth and volume are also mentioned. A random selection of sample trees was taken and measurements were made both before and after felling to determine form factors for a local volume table and to determine gross and net volumes within the merchantable height. The merchantable logs were taken to the mill and the actual board feet of lumber sawn was recorded. It was found in this study that cull factors based upon the percentage of total cull to calculated gross volume were 6.0 per cent, 7.5 per cent and 12.9 per cent for white oak on "good", "medium", and "poor" sites respectively. For black oak, it was determined that the cull was 10.8 per cent and 11.5 per cent for "medium" and "poor" sites, there being little or no black oak on "good" sites. Red oak on "good" and "medium" sites was found to have a cull of 7.3 per cent and 11.3 percent respectively. There was little or no red oak to be found on "poor" sites. Although the per cent of cull was also determined for site alone and for species alone, the application of these factors is not considered as accurate as applying cull factors to species by sites.