"2. What sort of soil is predominant in this place? What "soil series" is it?"
This was a tougher question for me than the water question, because the Helena area is quite diverse in its soils and geological history...And to be honest, soils is an area of which I am pretty ignorant, other than the real basic stuff. So I took this as a real opportunity to learn something new about my home valley.
The best online resource for a general view of the soils in the valley and surrounding mountains was at http://soildatamart.nrcs.usda.gov/Manuscripts/MT631/0/HelenaNF.pdf
Below is a screen shot of the map of the soils of the Helena National Forest, which includes the forested hills and mountains around the valley. Note that it does not cover the Helena intermontane valley itself (the central area in white).
The forest area nearest the part of Helena where I currently live is classified as "L. Soils Underlain by Limestone":
The landscape is characterized by mountain
slopes and ridges, dip slopes, and structural
breaklands. Dominant slope gradients are 0 to
40 percent on dip slopes, 25 to 60 percent on
mountain slopes, and 60 to 90 percent on structural
breaklands. Soils have medium to moderately fine
textures and calcareous substrata. This map unit is at
4,000 to 7,000 feet elevation. Vegetation is
dominantly lower, mixed or upper, mixed forest. There
are minor amounts of mountain grassland or
shrubland and upper subalpine forest. This map unit
occupies about 11 percent of the survey area. It is
about 30 percent Typic Cryochrepts, 15 percent
Calcic Cryoborolls, 15 percent Mollic Cryoboralfs,
15 percent Typic Ustochrepts, 10 percent Lithic
Ustochrepts, and 15 percent rock outcrop and minor
soils.
Typic Cryochrepts, Calcic Cryoborolls, and Mollic
Cryoboralfs are on higher-elevation mountain slopes,
dip slopes, and structural breaklands. Vegetation is
mainly upper, mixed forest with some mountain
grassland or shrubland. Typic Cryochrepts have lightcolored
surface layers; Calcic Cryoborolls have thick,
dark-colored surface layers; and Mollic Cryoboralfs
have thin, dark-colored surface layers.
Typic Ustochrepts and Lithic Ustochrepts are on
lower-elevation mountain slopes, dip slopes, and
breaklands. Vegetation is mainly lower, mixed forest.
Typic Ustochrepts are 20 to 60 inches or more deep
over bedrock. Lithic Ustochrepts are 4 to 20 inches
deep over bedrock.
Rock outcrop is on structural breaklands and
mountain slopes. Typic Calciborolls are included on
lower-elevation dip slopes.
Timber productivity is low on lower-elevation
mountain slopes, dip slopes, and breaklands.
Moisture stress limits forest regeneration. Timber
productivity is moderate on higher-elevation mountain
slopes, dip slopes, and structural breaklands. Grass
competition frequently limits forest regeneration.
Forest understories frequently have moderate forage
productivity. Grasslands and shrublands have high
forage productivity. Steep slopes limit tractor
operation and livestock access to forage on mountain
slopes and structural breaklands. Erosion hazards
are slight to moderate for logging and slight for roads.
Structural breaklands are on the lower flanks of
mountains and frequently form canyons with scenic
limestone outcrops.
(pp. 12-13)
These are soil types. But what are they exactly? For that, I have to do more reading and get back to you!
The above report only covers the areas within the Helena National Forest, the boundaries of which are about a mile away from where I currently live. It does not cover the Helena Valley floor itself.
The Rodney Street area where I live is on an alluvial/colluvial fan very near the area described above, so the soils are mixed from the above types, intermixed with complex anthropogenic layers, as a result of mining, construction, residential yards and gardens, etc. built up over about 150 years of human activity. Down in Last Chance Gulch there was so much placer gold mining that some say there is over 25 feet of mixed fill down there.
Further out in the valley, out by where I grew up, the soils are much more compact clays, and the organic layers are quite thin, sometimes only a few inches. Lousy gardening, I can tell you, until you add enough amendments like manure and compost.
I found more detailed maps for specific areas at http://www.mt.nrcs.usda.gov/soils/ but didn't have the time or inclination to wade through a fairly sophisticated GIS-oriented system. Sometimes too much info is as bad as not enough! But it's good to know about in case I have specific questions about a specific area later.
I am heading down to the Library later today and I'll see what else I might find on the soils here.
ADDED LATER: Didn't make it to the library after all today; did some cleaning instead.
The best online resource for a general view of the soils in the valley and surrounding mountains was at http://soildatamart.nrcs.usda.gov/Manuscripts/MT631/0/HelenaNF.pdf
Below is a screen shot of the map of the soils of the Helena National Forest, which includes the forested hills and mountains around the valley. Note that it does not cover the Helena intermontane valley itself (the central area in white).
The forest area nearest the part of Helena where I currently live is classified as "L. Soils Underlain by Limestone":
The landscape is characterized by mountain
slopes and ridges, dip slopes, and structural
breaklands. Dominant slope gradients are 0 to
40 percent on dip slopes, 25 to 60 percent on
mountain slopes, and 60 to 90 percent on structural
breaklands. Soils have medium to moderately fine
textures and calcareous substrata. This map unit is at
4,000 to 7,000 feet elevation. Vegetation is
dominantly lower, mixed or upper, mixed forest. There
are minor amounts of mountain grassland or
shrubland and upper subalpine forest. This map unit
occupies about 11 percent of the survey area. It is
about 30 percent Typic Cryochrepts, 15 percent
Calcic Cryoborolls, 15 percent Mollic Cryoboralfs,
15 percent Typic Ustochrepts, 10 percent Lithic
Ustochrepts, and 15 percent rock outcrop and minor
soils.
Typic Cryochrepts, Calcic Cryoborolls, and Mollic
Cryoboralfs are on higher-elevation mountain slopes,
dip slopes, and structural breaklands. Vegetation is
mainly upper, mixed forest with some mountain
grassland or shrubland. Typic Cryochrepts have lightcolored
surface layers; Calcic Cryoborolls have thick,
dark-colored surface layers; and Mollic Cryoboralfs
have thin, dark-colored surface layers.
Typic Ustochrepts and Lithic Ustochrepts are on
lower-elevation mountain slopes, dip slopes, and
breaklands. Vegetation is mainly lower, mixed forest.
Typic Ustochrepts are 20 to 60 inches or more deep
over bedrock. Lithic Ustochrepts are 4 to 20 inches
deep over bedrock.
Rock outcrop is on structural breaklands and
mountain slopes. Typic Calciborolls are included on
lower-elevation dip slopes.
Timber productivity is low on lower-elevation
mountain slopes, dip slopes, and breaklands.
Moisture stress limits forest regeneration. Timber
productivity is moderate on higher-elevation mountain
slopes, dip slopes, and structural breaklands. Grass
competition frequently limits forest regeneration.
Forest understories frequently have moderate forage
productivity. Grasslands and shrublands have high
forage productivity. Steep slopes limit tractor
operation and livestock access to forage on mountain
slopes and structural breaklands. Erosion hazards
are slight to moderate for logging and slight for roads.
Structural breaklands are on the lower flanks of
mountains and frequently form canyons with scenic
limestone outcrops.
(pp. 12-13)
These are soil types. But what are they exactly? For that, I have to do more reading and get back to you!
The above report only covers the areas within the Helena National Forest, the boundaries of which are about a mile away from where I currently live. It does not cover the Helena Valley floor itself.
The Rodney Street area where I live is on an alluvial/colluvial fan very near the area described above, so the soils are mixed from the above types, intermixed with complex anthropogenic layers, as a result of mining, construction, residential yards and gardens, etc. built up over about 150 years of human activity. Down in Last Chance Gulch there was so much placer gold mining that some say there is over 25 feet of mixed fill down there.
Further out in the valley, out by where I grew up, the soils are much more compact clays, and the organic layers are quite thin, sometimes only a few inches. Lousy gardening, I can tell you, until you add enough amendments like manure and compost.
I found more detailed maps for specific areas at http://www.mt.nrcs.usda.gov/soils/ but didn't have the time or inclination to wade through a fairly sophisticated GIS-oriented system. Sometimes too much info is as bad as not enough! But it's good to know about in case I have specific questions about a specific area later.
I am heading down to the Library later today and I'll see what else I might find on the soils here.
ADDED LATER: Didn't make it to the library after all today; did some cleaning instead.