ENVIRONMENTAL CONSEQUENCES in rocky mountain coniferous ...

This reflects our finding that residue in mature stands is generated
from insects, blowdown, disease, and other factors that occur at
infrequent and irregular intervals .
4, We were able to predict with some success the amount of residues
generated in different uti 1 iration standards of 1 oggi ng given basic
data for a specific stand.
Volume of Wood in Undisturbed Stands
The total volume of wood in mature sawtimber stands averages from 3,000
ft3/acre (21 0 m3/ha) in dry-site Douglas-fir stands to 8,000 ft3/acre (560 m3/ha)
in grand fir stands (table 1). On the average only about half this volume is green,
merchantable material (figure 2). A high proportion of moist-site western larch and
grand fir is rotten material. Some of this rotten material is crumbly and could not
be harvested with conventional equipment; some is solid rot--usually a sound core
surrounded by sapwood rot.
There is substantial volume of sound dead material in lodgepole pine and in
spruce-alpine fir types, averaging 60 to 70 percent of all dead material in the
stand. This volume probably reflects fairly dry, cool summer conditions that
inhibit decay.
One notable feature in all stands is the relatively small potential for
util izing additional green material--tops and small stems. Other than merchantable
material, much of the green volume is cull material, which in part is suited for
fiber products but is too rotten or poor form for roundwood products, such as
saw1 ogs or pol es .
The large amount of sound-dead material in mature lodgepole pine stands
ref1 ects recent bark beet1 e epidemics. In southwestern Idaho, a mountain pine
beetle epidemic has killed up to 90 percent of the cubic volume in some stands.
trees remain standing and initially are sound; then the roots decay, the tree fa1 1 s,
and rot sets in. Frequently, the trees become jack strawed and remain several feet
off the ground (figure 3). In these instances the wood remains essentially intact
except for drying checks. Much of this material can be utilized but, in its current
condition, presents a fire hazard, is difficult for large animals to move through,
and usually inhibits regeneration.
In other forest types, the typical pattern seems to be a more gradual decay
that creates residues in stages of deterioration from new, sound dead to partially
rotted, to a shell of crumbly, rotted material.
The