ENVIRONMENTAL CONSEQUENCES in rocky mountain coniferous ...

analyses were conducted using commonly accepted techniques at the Soil Plant and
Water Laboratory, Utah State University, Logan, Utah.
Samples of the organic, or ash, surface soil horizon, and the 0-5 cm and 5-15
cm depths of mineral soil, were taken at the initiation of treatments in 1972 and
1973 and again, in 1977. A sample from each depth was taken from every quadrant of
all four units, with material from 20 or more random locations constituting each
sample. Four samples from each depth also were taken from the undisturbed forest
between Units #3 and #4 (fig. 2).
The surface organic or ash samples were analyzed for pH and total contents of
nitrogen, phosphorus, potassium, calcium, magnesium, and, in 1977 only, sodium.
Most of the mineral soil samples were analyzed for a1 1 of the above plus organic
matter content, cation exchange capacity, available phosphorus, and total extractable
(water soluble plus exchangeable) potassium, calcium, and magnesium.
In addition,
the 1977 mineral soil samples were analyzed for available sodium, boron, zinc, and
i ron.
With the use of ceramic cup extractors, the soil solution at depths of 60 and
120 cm (about 2 and 4 ft) was withdrawn under vacuum at several locations and timds
each growing season within all treatments, including the undisturbed forest, from
1972 through 1977. The sampl es were analyzed quantitatively for sodi um, potassi urn,
calcium, magnesium, nitrate, phosphate, total phenols, electrical conductivity, and
PH
RESULTS
Quantity of Debris
Harvesting and slash disposal left markedly different conditions on these
units. Gardner and Hann (1972) and Benson (1974) reported the quantities removed.
The quantity and nature of the biomass remaining is of particular interest now.
The amounts of litter and debris less than 3 cm in diameter present on the soil
surface after treatment were:
Litter weight Litter depth
Kg/ ha Cm
Undisturbed forest 35,494 2.6
Broadcast burned 34,995 1.8
Pi 1 ed-burned (under pi1 es) 31,985 1.7
Pi 1 ed-burned (between pi 1 es) 33,222 1.3
Chi pped-removed 42,213 2.4
Chi pped-returned 180,582 11.7
More than 20 samples were used to arrive at each of the tabulated values.
Within each group of 20 there was enough variation to mask any differences in
weights that may have existed among most treatments. However, one treatment, the
return of chips to the forest floor, was highly significantly different than the
others.
In a post-logging inventory of these units, Brown (1974) found that near
complete utilization produced almost as much fine debris (< 8 cm diameter) as did
conventional logging; but, on the near-complete units there was only 1/5 as much
larger diameter debris. The conventionally logged areas had 2.6 times more needles
in the debris on the forest floor than did near-complete units.