On 6 June and 25 July 2006, organic horizon soil samples (10x10x15cm in MAT, 10x10x3cm in DHT) were collected from control and N+P treatments from Moist Acidic Tundra and Dry Heath Tundra grazing plots established in 1996. We collected two subsamples from both tussock and inter-tussock areas in each MAT plot, and two subsamples per Dry Heath plot. We determined percent moisture for all soils and quantified the biomass of members of the belowground community.
Direct count slides for microbial biomass estimation were made using the methods of Bloem (1995) as adapted by Frey et al. (1999). 10ml of a soil solution diluted 1:100 (5g initial soil mass) was added to each of 5 6mm diameter wells on a slide. Bacteria slides were stained with DTAF (5-(4, 6 dichlorotriazin-2-yl) aminofluorescein) and Fungi slides were stained with calcifluor M2R fluorescence brightener. Direct counts were made using epifluoresence microscopy. Bacteria were counted, 10 images per well, 2 wells per sample. Fungal hyphal length (Lodge and Ingham 1991) was estimated using the formula of Newman (1966): R=πNA/2H where N=number of hyphae crossing transect line, A=area of well, H=total length of transects. 2 wells, each with 10 images, 3 transects per image were used.
Protozoa densities were estimated from 10 g soil samples using Most Probable Number MPN (Darbyshire et al. 1974; Ingham 1994). 10 g soil was serially diluted 10-1-10-6. Using a 24-well tissue culture plate, four replicate wells of each of the six dilutions were created by adding 0.5 ml soil solution to the wells (Rusterholz and Mallory 1994). E. coli, a bacterium food source for protozoa was added to each of the wells. Protozoa were separated into the broad categories of Amoebae, Flagellates and Ciliates.
Nematodes were isolated from 20 g of soil samples using Baermann Funnels (Hall 1996). Nematodes were preserved in formalin, counted and identified to functional group based on the morphology of the stoma and stylet (Niles 1994).
Rotifers, Tardigrades, and Enchytraeids were isolated from 5 g of soil using the methods of Peters et al. (1993).
Microarthropods were heat-extracted into 70% ethanol from soils using Tullgren funnels (Moore et al. 2000). The intact sample pairs from each plot were wrapped together in cotton cheesecloth, weighed, placed over a funnel, and heated with a 9-W
incandescent lightbulb for 5 days until dry.
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