Pumice is the major parent material for soils within Crater Lake National Park. Obviously, most of the soils are of post-Mazama age, with the exception of the soils around Union Peak, where the pumice is apparently from older eruptions (Williams, 1942:71). Bog and marsh soils form a minute portion of the soil complex. Soils of till or morainal parent materials occur in areas glaciated at the time of the caldera formation at Munson Valley from Park Headquarters to the rim, and at the heads of Sun and Kerr Valleys (Williams 1942:125-127). Observation indicates that soil formation is apparently very slow. In general, color changes due to weathering penetrate only 3 to 6 centimeters. Forest duff is thin and patchy throughout the Park. Only at lower elevations where there is a second story of ceonathus or manzanita brush is there a fairly thick layer of duff. Soils are being built up of bogs and marshes. The bog in Munson Valley south of Park Headquarters is building soil, many patches within the bog are raised above the surrounding marsh and are self-drained (Wynd 1930:,41-42). Outside the bog areas no soil is being built up, nor do there appear to be any depositional processes other than talus slides in action.
Soil conditions within the Park, are probably very similar to those studied on former Klamath Reservation lands (Anonymous 1958) and on Weyerhauser forest lands east of Lapine (Dryness 1960). The conclusions arrived at in those studies are probably valid for the whole area covered by the pumice mantle.
Crater Lake National Park soils are probably regosols of the “Western” Brown Soils Zone, and are probably similar to the Lapine, Shanahan, andi Skellock soils series. Lapine and Shanahan soils are derived from pumice fall materials, wheras the Skellock soils are derived from pumice flow materials (Anonymous 1958:.56-57; “157, 192, 200) The soils are very youthful, lacking textural development, and usually have A1, AC, C soil horizon profiles; the Lapine soils may also have a D horizon. Soil formation from the surface downward, with surprisingly high carbon-nitrogen ratios but slow organic decomposition rates; the process is likened “to that occurring under anaerobic conditions” (Dyrness 1960:224, 176-177). The downward development of the soils is significant, indicating that post-Mazama archaeological evidence is conrfined to a shallow surface zone.
Pumice deposits would appear to be good aquifer, since they are capable of holding water up to 30% of the total deposit volume (Dyrness 1960:177). Perhaps the absorption quality of the pumice mantle is the major contributor to what the writer considers an arresting feature of the regional drainage patterns. That is, in general the terrain contours resemble a mature drainage system in that the runoff channels are rounded and poorly defined, even on fairly steep slopes, until the permanent stream beds are reached where they change abruptly to youthful appearing, sharp, steep-sided channels. The dendritric patterns one would expect to find etched into the loose, gravelly surface leading to the permanent stream channels appears to be entirely lacking. It would appear that most of the precipitation is taken up by the pumice and released slowly. Surface runoff Is apparently negligible and erosion is reduced to a minimum, even in very sparsely vegetated areas. Williams (1942:68 ff) speaks of erosion altering the original pumice deposits. Undoubtedly, both wind deflation and water transport of materials, and perhaps gravitational movements have occurred. The thesis suggested here there erosional alterations are minimal, that they occurred earl in post caldera history, and that surface conditions have become very stable.
The soils possess medium to low fertility values. Nitrogen appears to be the limiting nutrient. Greenhouse experiments show little response to application of phosphorous and/or sulphur without accompanying applications of nitrogen. The presence of trace elements is also low with the parent material markedly deficient in Boron and perhaps Molydbenum (Dyrness 1960:1 7 passim) Soil Conservation Service agents at Klamath Falls (Mlessrs. Joe Cahoon, John Tribe, and Leroy de Moulin) noted that “white muscle Disease” among cattle in the Klamath area is an indicator of trace element deficiency. They also stated that bitterbrush (Pursha tridentata), a favorite deer forage, was not thrifty on pumice soils and was not heavily browsed by deer. Another factor affecting plant growth is the fact that while pumice has an enormous capacity to absorb water, up to 30% of the total volume of pumice, water does not migrate readily through the pumice. The water is thus not readily available to root systems once accessible water molecules are taken up. (Dryness 1960-162-167).