ENVIRONMENTAL CONSEQUENCES in rocky mountain coniferous ...

The stems were divided at 4 mm (0.16 inch) to provide some estimate of potential
browse on the area; observations of big-game feeding on the study area had indicated
nearly all browsing was on stems less than 4 mm (0.16 inch). Elk (~ervus canadensis)
and deer (0docoiZeus sp. ) were the primary ungulates found in the study area.
To determine biomass of small shrubs and trees less than 0.5 m (1.6 feet) tall,
and all herbaceous vegetation, vegetation on two 0.5 X 0.5-m (1.6 X 1.6-foot) quadrats
adjacent to each permanent set of quadrats was clipped, dried, and weighed.
RESULTS AND DISCUSSION
The results presented here highlight major effects or trends found in these
preliminary data. Evaluations of the vegetative response to silvicultural and residues
management treatments wi 11 be emphasized, focusing on (1) shrub response, (2) cover,
and (3) biomass. Further analyses of these data in subsequent publications will aim at
(1) refining this information, (2) identifying significant vegetation trends and their
interactions between silvicul tural and residues uti 1 i zation treatments, and (3) evaluat-
i ng individual species responses. Ultimately, long-term vegetation responses wi 11 be
determined from periodic remeasurements.
Vegetation responses usually relate closely to plant species status prior to
treatment. Because of this, we measured vegetation in the undisturbed forest immedi -
ately before treatments were imposed, and found that shrub volume averaged 31 100 m3/ha
( 16,468 yards3/acre) in the mature forest prior to harvest--equivalent in biomass to
4 687 kg/ha (4,180 poundslacre). Shrub biomass was comprised of 4 063 kg/ha (3,624
pounds/acre) of large stems, 348 kg/ha (310 pounds/acre) of small stems, and 276 kglha
(246 poundslacre) of 1 eaves. Lesser vegetation, which included herbs and small shrubs
less than 0.5 m (1.6 feet) tall , accounted for 57 percent of the surface cover, with
1 i tter and woody material accounting for most of the remaining cover. The equivalent
biomass of this 57-percent "living" cover averaged 1 184 kg/ha (1,056 pounds/acre).
Thus, total 1 ive biomass of understory vegetation (not including understory trees) in
the mature forest was 5 871 kg/ha (5,237 poundslacre). This indicates a relatively
lush understory flora, about a third more than found on nearby larch/fir forests where
spruce and subalpine fir were more in evidence (Stickney [In press]), and substantially
above the 280 kg/ha (250 pounds/acre) biomass measured on a cold, high-el evation lodge-
pole pine site in Wyoming (Schmidt and Lotan 1980).
As shown in Appendix I, 11 tree species, 21 major shrub species, and 58 herbaceous
species were found on the study area.
SILVICULTURE TREATMENT EFFECTS
Response of Major Shrubs
A1 1 harvest-cutti ng systems--she1 terwood, group selection, and cl earcut--reduced
average shrub volume to less than 25 percent of preharvest levels and as low as 10
percent on the group-selection cuttings (fig. 5). These are average values that include
a1 1 residues treatments within each silviculture treatment. Because plots were measured
2 years after harvesting, they likely show somewhat more volume than was present immedi-
ately after logging. We have no data with which to verify that assumption, but
Stickney's (In press) data indicates this is generally true.