ENVIRONMENTAL CONSEQUENCES in rocky mountain coniferous ...

SUMMARY
The results presented in this paper briefly summarize the major effects of silvi-
culture and residues treatments on understory vegetation in a 1 arch/Dougl'as-fi r forest.
Subsequent reports will analyze complex species trends and interactions to illustrate
some of the more basic aspects of the study. A1 though the data reported here cover
only the first 4 years after harvesting, some immediate treatment effects and trends
are apparent.
All of the harvest cuttings drastically reduced total shrub volume and
biomass, but 4 years after harvesti ng a1 1 treatments had regai ned one-fourth
or more of their shrub volume and one-third to two-thirds of their preharvest
biomass. Clearcuts recouped their logging-caused shrub losses most effec-
tively. She1 terwood cuttings reduced shrub volume somewhat less than did the
clearcuts and group selections, but the recovery of shrubs was slower on the
shel terwood sites .
Residues treatments affected shrubs more than si 1 vi cul ture treatments for the
first 4 years. The understory-protected treatment stood out as being dramat-
ical ly different than the other three residues treatments. It resulted in a
much smaller loss of major shrubs during logging, and its 4-year recovery of
both shrub volume and biomass far exceeded that of the other three treatments
This effect was particularly apparent in the shel terwood cuttings where the
residual stand of trees afforded some protection of the understory during
1 oggi ng .
Burni ng , coup1 ed wi th e4 ther i ntermedi ate- or conventional -wood-resi dues-
util ization standards, consistently reduced major shrub vegetation more than
ei ther the understory-protected or a1 1 -residues-removed treatments. However,
even on the burned areas, shrubs recovered substantially within 4 years after
harvesting .
The relative importance of different shrub species in terms of volume and
biomass varied substantially--some positively, some negatively, some showing
1 i t tle change--i n response to the different combinations of si 1 vi cul ture-
residue treatments.
Lesser vegetation, comprised of herbs and small shrubs, responded rapidly and
differentially to the various combinations of treatments. Before harvesting ,
herbs and small shrubs provided cover on 57 percent of the soil surface in
the mature forest, and litter and woody material accounted for most of the
remainder. Four years after treatment, cover on a1 1 treatments averaged 67
percent. Most of this increase was in herbaceous material . Removing a1 1 the
residues on the group selections increased herbaceous cover the most. At the
other end of the scale, herbaceous cover decreased slightly on the shelter-
woods where the understory trees and shrubs had been protected during harvest-
i ng,
Of the total live understory biomass (not including trees) in the uncut
mature forest, major shrubs accounted for 80 percent, and herbs and small
shrubs the remainder of the understory vegetation. Four years after treat-
ments, an average of all treatment combination.responses shows that herbs and
small shrubs now account for over half the total biomass. Collectively,
shrubs and herbs returned to 56 percent of their preharvest biomass at 2
years and 75 percent at 4 years, but a far larger proportion was now in the
lesser shrubs and herbaceous material.