Accomplishing Forest Restoration with Biomass Harvesting Methods

Eagle Lake Ranger District
Lassen National Forest

Fire Affects

Some people have questioned the effectiveness of utilizing biomass harvest thinning operations in conjunction with prescribed fire for the development of DFPZs. During the fall of 2002, this concept was put to the test with the Cone Fire in Blacks Experimental Forest.

CF1

The photograph above illustrates the stark difference in the effects of the Cone Fire between the thinned and unthinned portions of the stand. The fire burned most intensely in the unthinned portion of the stand, creating over 90% mortality in the trees. As the fire hit the edge of the thinned portion of the stand, the intensity and mortality decreased dramatically. The fire became a slow burning ground fire within 200 feet of the thinned stand's edge and had a negligible impact on the residual conifers.

CF2

This photograph represents the stand structure and mortality in the unthinned portion of the Cone Fire. Notice that the most of the trees per acre are in the smaller size classes which contributed to the fire intensity and mortality. Stand structure prior to the fire consisted of 987 trees per acre, 147 square feet of basal area and 108% (overlap) crown closure. Ninety-four percent of the trees in the stand received 100% crown scorch.

CF3

This stand was mechanically thinned in 1996 and treated with prescribed fire in the fall of 1997. The smaller trees in the unthinned portion of the fire created a continous fuel ladder from the ground to the crown of the larger trees. Since the thinning removed the smaller trees, the intensity of the fire decreased significantly once it entered the thinned stand. The fire had no effect or impact on the remainder of the unit beyond 200 feet of the unit's edge. Stand structure consists of 83 trees per acre, 110 square feet of basal area, and 42% crown closure. Note the scale difference between the trees per acre for the thinned and unthinned trees per acre in the next photo.

CF4 - Combined Data

This photograph represents the difference between the trees per acre by diameter group between the thinned and unthinned portions of the Cone Fire. The gray bars represent the trees per acre in the unthinned portion and the orange bars represent the trees per acre in the thinned portion of the fire.