ENVIRONMENTAL CONSEQUENCES in rocky mountain coniferous ...

STUDY SCOPE AND METHODS
Initially our interest was to generate detailed data on woody material at
harvest study sites to serve as a basis for various cost, utilization, slash disposal,
and water and nutrient studies. The generation of detailed data remained the
primary purpose , but we began to receive repeated requests for estimates of total
residue volumes and their utilization potential. In response to these requests, our
efforts evolved into information gathering on two bases.
The first information base consisted of pre- and post-harvest data for the
various study si tes--usually several logging units formed one study site. The study
sites included mixed conifers in north Idaho, Douglas-firllarch stands in Montana,
and lodgepole pine sites in Montana, Idaho, Wyoming, and Utah. These were used to
develop a broad-based estimate of residue volumes for several of the major forest
types in the Northern Rocky Mountains. This estimate was made by using existing
forest inventory and management plan data to develop area by forest type strata to
which we applied the residue data from intensive study sites.
Because of the limited amount of residue sampling and the way various data
sources were combined, the statistical accuracy of this sampling provides a rea-
sonable first approximation of volumes and, perhaps more important, a profile of
residue characteristics that should be of value in broad-scale planning and resource
assessment.
Our data are limited to old-growth sawtimber stands where the bulk of the
harvesting - and most of the residue management problems - will occur in the future.
Our studies were limited to the six major forest types in the Northern Rockies that
usually present residue-management problems. The one major type not included is
ponderosa pine, for in most cases, harvest of old-growth does not generate large
residue volumes or pose comparable disposal problems.
For each forest type, we estimated the average volume per acre of wood 3 inches
or larger in diameter (7.6 cm), described this material in terms of utilization
potential. Additionally, we developed estimates of duff, 1 itter, and tree crowns.
Standing trees were measured using conventional survey procedures of fixed or
variable plots. Down material was measured using the planar intercept method on a
grid pattern of random direction linesV3 Crown weights were computed from formulas
based on tree species and diameter-"These components and their volumes for a
typical Douglas-firllarch stand are shown in figure 1.
3~rown, James. K. 1974. Handbook for inventorying down wcody material .
USDA For. Serv. Gen. Tech. Rep. INT-16. Intermt. For. & Range Exp. Sta.,
Ogden , Utah 84401 .
4Brown, James K., J. A. K. Snell , and D. L. Bunnel , 1977. Handbook for pre-
dicting slash weight of western conifers. USDA-FS Gen, Tech. Rep. INT-57. Intermt.
For. and Range Exp. Stn., Ogden, Utah 84401 .