PERMFILE102647

• Permit No: M1985091
• IBM Index Class Name: Permit File
• Doc Name: REGULAR 112 PERMIT APPLICATION FORM
• Media Type: D
• Archive: No

CHAFFEE-LAKE AREA, COLORADO
annual precipitation is 18.5 inches. Unfortu-
nates of precipitation are not so uniform or so
able as temperature since they are subject to
arities of wind current, convection, and other
of local variation. Although misleading when
specifically to any one local area, general data
an increase in annual precipitation rates of
4.7 inches for each 1,000 feet increase in
The effectiveness of precipitation in providing soil
oisture is dependent upon many factors other than
oral amount. At the lower elevations in this area,
umidity is low and rainfall intensities are relatively
rear. These both contribute to soil moisture losses.
n the other hand, the soil is frozen for relatively
hort periods, runoff is relatively low in the winter
nd spring, and the period of greatest activity of soil-
orming processes is much longer than at high
elevations. The higher elevations receive more total
precipitation, but much of it is snow, spring runoff is
high, slopes are very steep, and the soils are cold for
long periods of time.
In summary, the climate of the Chaffee-Lake Area
relative to soil genesis can best be characterized by its
;extremes and by its variability. Characterization at any
'one location is very difficult and dependent upon many
local factors. Other than those existing between tem-
perature and annual rates of precipitation relative
to change in elevation, reliable trends cannot be
established for local areas of the survey.
Living organisms
Living organisms that affect soil formation can be
divided on the basis of their physical size into macro
and micro groups. The macrobiological group includes
the visible plants and animals that live in or on the
soil. The microbiological group includes the extremely
small organisms, mainly bacteria, molds, and fungi,
that are visible only with the aid of a microscope. Both
groups are extremely important in the development of
the soils in the survey area.
That part of the macrobiological group consisting of
natural or man-introduced vegetation is most easily
observed and most easily understood. The Chaffee-Lake
Area is a mixed grass and timbered area that has
grasses dominating the valley floors at lowest eleva-
tions and stands of timber on the bordering mountain
slopes. The present distribution pattern between grass
and timber has apparently existed for long enough in
this area for the soils to reflect these differences in
their morphology.
The grassland soils, such as the Pierian soils, have
developed under a type of genesis that centers upon
a relatively large annual return of organic matter to
the surface soil horizons and its rapid decomposition
under well-aerated and alkaline conditions. Under the
short-grass vegetation characteristic of the survey
area, nearly as much organic matter is returned to the
soil by the death of plant roots as is returned by the
fall of above-surface plant remains. Consequently,
soil horizons enriched by humus may extend to greater
depths than would be anticipated from the density and
height of the above-ground plant growth.
s7
In the Chaffee-Lake Area, the type of soil genesis
prevalent in grassland areas produces a soil that has a
solum normally averaging 12 to 24 inches in thickness
and that is characterized by a friable, granular, humus-
enriched surface horizon of moderately light to mod-
erately dark color. The entire solum generally is
neutral to moderately alkaline in reaction and if
forming in calcareous parent materials, mature profiles
are underlain by distinct horizons of visible secondary
carbonate, as in the Manhattan series.
Minor soil differences resulting from differences in
the amount of grass are common in most landscapes.
In the more steeply sloping areas where runoff is more
rapid, there is less available soil moisture and the grass
cover is thin. In these areas genetic processes proceed
at a slower rate and decomposition of organic matter
more nearly equals the annual organic matter returns.
In consequence, soil horizons are thinner, are lighter
colored, and contain less total organic matter.
The opposite effect is noticeable in parts of the land-
scape where soil water has accumulated. Here, the
solum tends to be thicker, surface horizons are darker,
and there is more total organic matter in the soil as
seen in the soils of the Ouray series, thick surface
variant.
With increasing elevation the natural vegetative pat-
tern changes from dominantly grass to dominantly
coniferous forest. The transition does not occur
abruptly, and there are broad intermediate areas where
grassland and timberland interfinger or where stands
of trees are open and grass and shrubs constitute a
significant part of the ground cover.
In these transitional areas, soils that have some of
the characteristics of both grassland and forested soils
are present in some landscapes. These can be areas
where the two types of genetic processes themselves
are nearly in balance or where they have been alternated
over the long genetic history of the soil as the kind of
vegetation shifted. Such soils as the Pando soils, which
formed under these conditions, generally retain the
moderately thick, dark surface horizon of the grass-
land but have a thin,lightrcolored, eluvial A2 horizon
immediately above the B2t horizon.
At the higher elevations, timber stands are dense
and understory grasses and shrubs are sparse. Supplies
of soil moisture are more plentiful in these areas, and
the soils have a thicker solum than those in the grass-
lands. Needles, twigs, and bark from conifers make up
the bulk of the organic matter falling on the soil.
These decompose slowly and favor the more acid types
of decomposition.
Such soils as the Leadville soils, which formed under
these conditions, are characterized by only a very thin,
if any, dark-colored mineral surface horizon, but have
a moderately thick, very light colored, eluvial A2 hori-
zon that has lost clay, sesquioxides, and humus. Mature
profiles have B2t horizons of silicate clay illuviation.
Although they normally are only slightly acid to mildly
alkaline in reaction, most of the soils lack horizons of
visible calcium carbonate accumulation.
Typically, these kinds of soils have what appears to
be a degrading A&B horizon lying between the A2 and
B2t horizons. The genesis of this horizon has not been