Effects of subsoiling on woody roots of Jeffrey pines on two different soil types
This study was initiated to determine the long term effects of subsoiling to alleviate soil compaction due to use of mechanized harvesting equipment in forest stands. Two stands having a predominance of 90 to 110 year old Jeffrey pines (Pinus jeffreyi Grev. & Balf.) were selected for this investigation. Each stand was located on the Milford Ranger District of the Plumas National Forest on the eastern slope of the Sierra Nevada mountains of northeastern California. One stand has a volcanically derived soil and the other stand has a granitic soil. In 1992, prior to precommercial thinning by mechanical shearing equipment, 12 permanent 1.0 ha plots were established in each stand. Four treatments performed after thinning were assigned at random to each plot. The treatments were: 1) subsoil the entire plot to a depth of 70cm; 2) subsoil skid trails only; 3) no subsoiling; and 4) no thinning, no subsoiling treatment.Each treatment was replicated three times in each stand and all plots in both sites were subjected to a controlled burn during the spring of 1993.