An ecological study of three sub-alpine streams in Alberta
A preliminary investigation of the ecology of three subalpine streams, Twin Creek, Cabin Creek and Middle Fork Creek, situated on the eastern slopes of the Rocky Mountains, Alberta was carried out during the period June 1974-March 1976. · The annual (1975) average number of invertebrates per square metre was 3,003 and 1,459 in Twin Creek and Cabin Creek respectively . The annual (1975) average standing crop (wet weight) of invertebrates was 9.17 g m- 2 and 3.01 g m-2 in Twin Creek and Cabin Creek respectively. There was a greater diversity (H') of invertebrates in Twin Creek than in Cabin Creek. Oreogeton sp. (Diptera: Empididae) was the most abundant organism in Cabin Creek, whereas Nemoura columbiana (Plecoptera: Filipalpia) was the most abundant invertebrate in Twin Creek. Harvesting of 50% of the for est in Cabin Creek watershed in September 1974 had no obvious effect on the benthic invertebrate community of Cabin Creek. In 1975 adults of 24 species of Plecoptera, 15 species of Trichoptera and 6 species of Ephemeroptera were coll ected within the Ma n~ot Basin watershed. The Plecoptera exhibited a di stinct seasonal succession of emergence from February to October, the Trichoptera were found flying from May to October, while the Ephemeroptera emerged during the months July to October . During the fall and winter of 1975, the breakdown of willow leaves (Salix gZauca x myrtiZZifoZia) in Twin Creek and Cabin Creek was investigated. The fall/winter decay coefficient (k/day-1 ) was 0.0216 and 0.0036 in Twin Creek and Cabin Creek respectively. Both microbial decomposition and invertebrate feeding on the leaves was significantly greater in Twin Creek than in Cabin Creek. It was estimated that invertebrate feeding accounted for 45% of the dry weight lost from the leaves in Twin Creek and nymphs of the stonefly Nemoura coZumbiana played a major role in the breakdown of leaf material in this creek. The low concentration of dissolved orthophosphate may be a factor limiting the decomposition process in Cabin Creek. From August 1975 to October 1976 the periphyton biomass in Twin Creek, Middle Fork Creek and Cabin Creek was determined using the chlorophyll 'a' technique. The mean annual biomass of chlorophyll 'a' was 0.033 g ~-2 ,o~023 g m:2 and 0.007gm-2 in Twin Creek, Middle Fork Creek and Cabin Creek respectively. In Twin Creek and Middle Fork Creek the biomass of chlorophyll 'a' exhibited distinct maxima in June and November/December. Experiments indicated that the calcareous substrate of Cabin Creek may , in part, be responsible for the low p 0 - i phyton biomass in this creek.
Bibliography: p. 154-164.
Mutch, R. A. (1977). An ecological study of three sub-alpine streams in Alberta (Unpublished master's thesis). University of Calgary, Calgary, AB. doi:10.11575/PRISM/23522