Decomposers: Microbiology and nutrient cycling 



Soil microbiology 



A base line study of soil microfungi was initiated during the summer of 1970 along the bio- 

 environmental gradient in ten study areas. The hot-pipe control area was studied intensively 

 while eight other sites along the bioenvironmental gradient up to and including a site at Prudhoe 

 Bay were surveyed less intensively (Fig. 1). Three control plots on site 2 at Barrow were also 

 sampled for filamentous soil microfungi and yeasts. Results from the Prudhoe and Barrow sites 

 have been reported in previous sections. All areas were studied from soil samples taken within 

 a three-week period. Estimates were made of fungal, bacterial, and yeast biomass at all site. 

 Comparative studies were made of natural and disturbed areas in Prudhoe Bay, Sagwon, Hess Creek, 

 and College. At Barrow, Eagle Summit, and College soil and litter samples were treated separately 

 so as to observe changes in species composition with change in soil depth and substrate. Soil 

 samples were taken at a depth of 5 to 15 cm. 



The numbers of filamentous fungi and yeasts were determined from dilution counts using 

 acidified potato dextrose rose bengal-streptomycin agar medium. The numbers of soil bacteria were 

 estimated using the dilution plate technique and a soil extract-cyclohexamide agar medium. In 

 the case of yeasts and bacteria only number of organisms/gram of soil was estimated. 



In the ten study sites taxonomic and ecological studies were performed on the filamentous 

 soil microfungi. A total of 5000 fungi were isolated, and from these 300 different species were 

 identified. Major species components have been identified for sites and the density and frequency 

 of each species has been determined within and between sites. In this way we were able to study 

 the distribution of taiga isolates northward and tundra isolates southward. Fungal biomass was 

 estimated by direct observation and measurement of fungal hyphae as percent of total soil organic 

 matter. Whenever possible, microenvironmental parameters were measured at the sites during 

 sample collection. These parameters included pH, depth of permafrost, soil temperature, N, P, K. 

 It was not always possible to make all these measurements in the field. Variation in frequency and 

 density of species in the different study areas was measured and assessed against the biolc^ical 

 and abiotic (including site latitude) aspects of the site. 



The sites were grouped according to the gross physic^nomy of phanerogam characteristics. 

 Accordingly, sites 4, 5, 6 and 7 in College, Hess Creek, Caribou Mt., and Wiseman were considered 

 as mixed spruce dominated upland taiga. All these sites contained Vaccinium vilis-ideae and 

 Ledum groenlandicum as undershrub. The most common moss in these sites was Hylocomium 

 splendens. The sites at Rosie Creek, Galbraith Lake and Sagwon were all wet tundra, dominated 

 by tussocks of Eriophorum vaginatum and mixed tundra sedges and grasses. Geum rossii, Poten- 

 tilla (ruiticosa and Dryas octopetala occurred in the drier parts of these study sites. The Eagle 

 Summit site was considered as an example of alpine tundra containing Betula glandulosa, Dryas 

 octopetala and dwarf Saiix sp. On cursay observation striking differences are seen in the 

 distribution and densities of major species components between selected sites. 



Table XLIII relates some microbiolc^ical measurements made at the hot-pipe study area in 

 College. There, seven sampling areas were stretched out along a 200-m transect. 



One hundred and twenty-two species of microfungi were isolated from these study areas. Forty- 

 two species occurring in the birch community were absent from the spruce comnumity in wliicli a 

 total of 80 species occurred at varying densities. Parallel to this natural area a disturbed area 

 iilso 200 m long was sampled. This area had all the trees and underbrush removed by bulldozing. 

 Reportedly, the litter present was turned into the mineral soil. 



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