ENVIRONMENTAL CONSEQUENCES in rocky mountain coniferous ...

INTRODUCTION
Vegetation integrates the effects of biological and physical intrusions into an
ecosystem and provides the best indicator of response to various treatments that man
and/or nature impose on the system. Vegetation also provides both direct and indirect
benefits to man in a variety of resources ranging from timber products, to forage and
cover for wildlife, water regulation, protection of the soil mantle, and esthetics,
This is particularly apparent in the extensive 1 arch/Dougl as-fir (~arix occidentaZis/
Pseudotsuga mensCesiC) forests of the Northern Rockies where no single resource predominates
(Schmidt and others 1976).
Natural succession i n Northern Rocky Mountain forests slowly but inexorably drives
vegetation toward a greater complement of shade-to1 erant species. This is particularly
striking in larch/fir forests because of the wide range in species and shade-tolerance
levels. Vegetation classification schemes capitalize on these to1 erance differences ,
and classifications based on climax stages of the vegetation have been developed
(Daubenmi r e and Daubenmi r e 1968; Pf i s ter and others 1977). Under the cl imax concept,
nature has had sufficient time to integrate time and space variation in vegetation
development.
Natural intrusions of fire, insects, disease, wind, and other factors disrupt
succession and can either set vegetation back to year one, have little effect, or
greatly accelerate succession toward more shade-tolerant forest vegetation. However,
man's activities in the forest, particularly harvest cuttings, now create most physical ,
biological , and esthetic change. Even-aged si 1 vi cul tural sys terns--cl earcutti ng , seed
tree, and she1 terwood--coupled with site preparations that expose mineral soi 1 and
reduce vegetative competi ti on, have proved most successful in regenerati ng larch/
Doug1 as-fi r forests (Schmidt and Shearer 1973). However, changing management objec-
tives and wood-uti 1 i zation standards have made i t necessary to reevaluate some of these
silvicultural systems in terms of environmental effects. As utilization of woody
residues intensifies, the number of mi crosi tes provided by materi a1 formerly 1 e ft in
the woods decreases, the amount of fuel for prescribed burning decreases, and the
amount and form of nutrients may be changed. Some of these changes may positively
influence one resource and negatively influence others. There is no single combination
of harvest cutting, uti 1 i zation level , and subsequent cultural practice that wi 11 meet
all forest management objectives. Combinations of these practices are dictated by
economics, pub1 i c needs, protection of the basic soi 1 resource, biological and physical
practicability, forest type, landform, and a host of other factors.
One resource needing increased ernphasi s i n forest management is understory vegeta-
tion. It serves both actively and passively to increase wildlife and esthetics values,
and to protect basic soil resources. However, understory vegetation can a1 so serve as
competi ti on for tree seed1 i ngs, often del ayi ng tree regeneration for decades (Schmidt
and Shearer 1973). This paper presents prel imi nary results demonstrating the effects
of three different si lvicul tural practices combined with four different residue uti li-
zation treatments on understory vegetation in a larch/Dougl as-fir forest in Montana.
Four years of understory vegetation-response data are presented.