BACKGROUND: The Ashland Resource Area completed the BUNCOM Landscape Project Environmental Analyses (EA). The proposed action included reducing the fire hazard by construction Defensible Fuel Profile Zones (DFZ) along some of the major ridges in the Sterling Creek drainage. One Project Design Feature was to target the DFZ for a 40 percent canopy closure. The operational prescription for obtaining the ID team's objectives, including the 40 percent canopy closure, was to retain 80-120 square feet of basal area per acre of the largest diameter class trees. These stands were reserve marked by a local forest consultant.
Superior Lumber Company was the purchaser of this sale and the DFZ units were harvested by a combination of different logging systems (tractor, cable, & helicopter). After harvest, members of the ID Team reviewed portions of the DFZ to see if canopy objective was met. It was decided to let a canopy closure contract out to determine: 1) any difference between canopy closure data from two different instruments, the moosehorn and spherical densiometer, 2) what the canopy closure is for the DFZ.
FINDINGS: In comparing paired observations of the moosehorn and the densiometer, it is clear that the densiometer averaged higher overall in average canopy closure. 1,436 moosehorn readings and 560 densiometer readings were taken. This study included portions of five units for a total of 73 acres. The average canopy closure of 32.2 percent for the moosehorn and an average canopy closure of 39.4 percent for the densiometer. All unit canopy closures averaged between 25 and 50 percent (more typically between 30 and 40) at basal areas averaging around 100 square feet per acre.
The contractor, Marty Main, tried to establish correlation between basal area and associated canopy closure from the data collect. No correlation was detected. Comparing basal areas and canopy closures across a wider range of existing stand densities might to be a useful research undertaking.
APPLICATIONS: It is important to remember that these canopy closure readings are two dimensional measurements and cannot reflect the inherent differences in vertical structure of forest canopies, either pre-harvest or post-harvest. Using these measurements to predict the appropriateness of canopies for certain resource values (i.e. wildlife habitat values, etc.) should be done with caution. The information learned enables us to be aware of the variability within a range when implementing an absolute project design feature for canopy cover.
SUBMITTED BY: Kenny McDaniel and Bill Yocum, Ashland RA, BLM. Phone McDaniel at 770-2315 <kmcdanie@or.blm.gov>.