Lucille Mountain soils:
Soils at Lucille Mountain have formed on a blanket or veneer of gravelly, medium- to
coarse-textured morainal deposits over bedrock. From a management perspective, the
predominantly silty textures of the surface soil would lead to High hazard ratings for both
surface soil erosion and soil compaction and puddling (Ministry of Forests, 1995). The
non-calcareous metamorphic bedrock (phyllite or schist) contributes to the strongly acidic
reaction of the entire soil profile. This contrasts with the soils at the Pinkerton Mountain
and Bearpaw Ridge ESSF study areas where incorporation of local limestone bedrock has
resulted in detectable carbonates in some C horizons.
Based on examination of roadcuts and other exposures, the pedon described by Arocena
and Sanborn (1999) (Tables 1 and 2) is representative of the predominantly well-drained
soils at the Lucille Mountain study area. This pedon is classified as an Orthic HumoFerric Podzol, based on the accumulation of carbon and pyrophosphate-extractable iron
and aluminum in the B horizon (Soil Classification Working Group, 1998). At the
regional level, Humo-Ferric Podzols are the dominant soil Great Group formed on
morainal parent materials throughout Cariboo Mountains and the western slopes of the
Rocky Mountains (Agriculture Canada, 1992).
Mineralogically, the composition of the clay fractions was the simplest of 9 pedons from
central and northeastern B.C. examined by Arocena and Sanborn (1999). Mica
dominates the clays in all horizons, comprising 40-65% of these fractions, which
presumably reflects the influence of local bedrock on parent material mineralogy. In all
but the Ae horizon, chlorite is the second most-abundant clay mineral, ranging from 1020%. Expanding-type clay minerals (smectite, vermiculite) decrease progressively in
abundance from the Ae horizon (20%) to the C horizon (0%), suggesting that these have
formed by pedogenic transformation of the inherited mica and chlorite, a pattern typical
of Podzolic soils. The practical significant of this mineral assemblage is that such soils
would tend to have limited shrink-swell activity in response to wetting-drying cycles,
which would have implications for rates of recovery from soil compaction.
The highest concentrations of nitrogen, sulphur, and available phosphorus all occur in the
forest floor, underscoring the nutritional importance of conserving this material during
harvesting and site preparation. Forest floor conservation is particularly importance
given the very low sulphur concentrations in the mineral soil. The levels observed in this
pedon were similar to those at other central interior sites examined by Arocena and
Sanborn (1999), and are consistent with a broader pattern of S deficiency B.C. interior
forest soils (Kishchuk, 1998).
Forest floors were not examined in detail, but observations at other ESSF sites in the
northern wet belt indicate that mesic sites are dominated by Hemimors and Humimors
(Sanborn and Trowbridge, unpublished soil descriptions, 1999), which differ in their
relative proportions of F and H horizons (Green et al., 1993). The relatively thin forest
floors, compared to those in adjacent ICH ecosystems at lower elevation, likely reflects a
lower rate of litter input in less-productive subalpine forests.
References:
Agriculture Canada. 1992. Soil Landscapes of Canada. British Columbia – South.
Publication 5279/B.
Arocena, J. M. and P. Sanborn. 1999. Mineralogy and genesis of selected soils and their
implications for forest management in central and northeastern British Columbia. Can. J.
Soil Sci. 79: 571-592.
Green, R. N., R. L. Trowbridge, and K. Klinka. 1993. Towards a taxonomic
classification of humus forms. Forest Science Monograph 29. 49 pp.
Kishchuk, B. E. 1998. Sulphur availability on interior lodgepole pine sites. Ph. Thesis.
University of British Columbia, Vancouver. 240 pp.
Ministry of Forests. 1995. Hazard Assessment Keys for Evaluationg Site Sensitivity to
Soil Degrading Processes Guidebook. Forest Practices Code of British Columbia. 24 pp.
Soil Classification Working Group. 1998. The Canadian System of Soil Classification.
Agric. and Agri-Food Can. Publ. 1646 (Revised). 187 pp.
Table 1. Morphological description of Orthic Humo-Ferric Podzolic pedon, Lucille
Mountain.
Horizon
LFH
Depth (cm)
3-0
Ae
0-4
Bf1
4-11
Bf2
11-25
Bf3
25-60
BC
60-100
C
100-120+
Description
Dark brown (7.5YR 3/2 m); semi-decomposed and humified needle
litter and Rhododendron leaves; 2-4 cm thick; extremely acid.
Grayish brown (10YR 5/2 m); silt loam; weak, fine platy; very
friable; plentiful very fine, fine, and medium roots; 25% angular and
flat gravels and cobbles; abrupt, wavy boundary; 3-7 cm thick;
extremely acid.
Dark brown (7.5YR 3/3 m); silt loam; weak, fine and medium
subangular blocky; friable; common fine and medium roots; 25-35%
angular and flat gravels and cobbles; clear, wavy boundary; 4-8 cm
thick; extremely acid.
Dark brown (7.5YR 4/4 m); silt loam; weak medium subangular
blocky; friable; few fine and medium roots; 30-40% angular and flat
gravels and cobbles; gradual, wavy boundary; 8-18 cm thick;
extremely acid.
Yellowish brown (10YR 5/4 m); silt loam; massive; friable; few
medium roots; 30-40% angular and flat gravels and cobbles; gradual,
wavy boundary; 25-40 cm thick; extremely acid.
Olive brown (2.5Y 4/4 m); sandy loam; massive; firm; 40% angular
and flat gravels and cobbles; gradual, wavy boundary; 30-45 cm
thick; extremely acid.
Light olive brown (2.5Y 5/4 m); sandy loam; massive; firm; 40%
angular and flat gravels and cobbles; extremely acid.
Table 2. Physical and chemical properties of Orthic Humo-Ferric Podzolic pedon, Lucille Mountain (See Arocena and Sanborn,
(1999) for description of analytical methods.
g/ kg
Horizon
Depth (cm)
Sand
Clay
C
N
n.d.
n.d.
LF
3-0
515.9 18.6
Ae
0-4
388
45
9.7 0.9
Bf1
4-11
438
44
19.1 1.2
Bf2
11-25
399
41
10.2 0.9
Bf3
25-60
389
81
6.6 0.7
BC
60-100
574
45
2.7 0.4
C
100-120+
513
63
1.8 0.4
1Al & Fe = pyrophosphate-extractable Fe and Al.
p
p
2 CEC = cation exchange capacity
Alp1
Fep1 pH (H2O)
n.d.
n.d.
3.7
0.78
0.57
3.8
2.08
9.00
4.2
2.42
8.39
4.5
2.01
4.78
4.6
1.20
1.95
5.0
1.09
1.10
5.0
pH (CaCl2)
3.2
3.1
3.6
3.9
4.1
4.4
4.5
mg/ kg
Avail P
S
75.6
1711
2.5
27
8.7
108
2.3
54
3.5
54
9.5
33
21.9
13
K
2.44
0.05
0.05
0.02
0.02
0.05
0.03
Ca
9.08
0.24
0.26
0.12
0.06
0.15
0.06
cmolc/kg
Mg
5.35
0.21
0.16
0.05
0.02
0.07
0.02
Na
0.49
0.04
0.05
0.04
0.03
0.06
0.08
CEC2
20.33
3.66
3.72
1.56
0.85
0.69
0.35