The mass and extent of organic matter cover on soils adjacent to Higland Pond were examined with line transects extending from the approximate center of the pond to a distance of 90 m beyond the shoreline. Eight line transects were established, approximately oriented in N, NE, E, SE, S, SW, W, and NW directions. An estimate of organic matter cover on soil surfaces was determined as the fraction of the distance over which organic material intercepted each line. Organic matter samples were collected at intervals along each transect at ca. 50 cm intervals within continuous cover and where present within areas of patchy cover. Collections were made with a 0.83 cm diameter steel corer, thrust through the organic layer into the underlying mineral soil. Organic matter samples were returned to the Crary Laboratory facility, McMurdo Station, Antarctica for mass determinations. Samples were placed in a drying oven at 60degC for 24 hours. Dry weights were recorded and samples then were placed in a muffle furnace for 6 hours at a maximum temperature of 500degC. Ash weights were recorded and ash-free dry weights calculated for all samples. These data then were used to estimate the amount of organic matter on soil surfaces associated with upland wetlands. All estimates of ash-free dry mass were converted to units of organic carbon, assuming a content of 50% carbon by weight.

Mineral soil samples (n = 48) were collected around Highland Pond along transects established in each of the 4 off-cardinal directions. Samples were collected in 4 zones classified by extent of surface organic mat cover and appearance (foliar or granular mats). Zone 1 consisted of soils with foliar mats covering 100% of the surface and extended to 10 m from the edge of the pond. Zone 2 had granular mats covering greater than 30% of the soil surface and extended about 10-30 m from the edge of the pond. Zone 3 had intermittent mats covering less than 20% of the soil surface and extended 20-80 m from the pond. Zone 4 had no visible mats and extended greater than 80 m from the edge of the pond. Each sample consisted of approximately 1 kg of soil collected from the top 10 cm of the mineral soil profile with pre-sterilized Nasco trowels. Three samples were collected from each zone along each of the 4 transects, for a total of 48 samples. Sampling excluded surface organic material. Samples were sealed in Whirl-Pak polyethylene bags and transported to Crary Laboratory at McMurdo Station for analyses.

At Crary Laboratory, mineral soils were sieved to remove rock fragments greater than 2 mm. Subsamples were oven-dried at 50degC for 48 h to determine gravimetric soil moisture content. Invertebrates were extracted from approximately 100 g soil using the modified sugar centrifugation technique described by Freckman and Virginia (1993). Extraction of invertebrates was completed within 48 h of collection. Species identification and life stage were determined and enumerated using light microscopy. Soil salinity was determined from the electrical conductivity of a 1:5 soil solution of sieved soil in de-ionized water. Electrical conductivity was measured using a Corning 311 conductivity meter, temperature-calibrated with a 0.01 M KCl solution. Soil pH was determined from a saturated paste (1:2 soil in de-ionized water) with an Orion model 720A pH meter. A subsample of each soil sample was ground in a ball mill and acidified with 50% HCl to remove carbonates. Approximately 75 mg of both the acidified and un-acidified soil were analyzed with a Carlo Erba 1500 elemental analyzer (Milan, Italy) to determine total carbon and nitrogen, and organic carbon content. Carbonate content of the soil was calculated as the difference between total carbon and organic carbon by comparing results from the acidified and un-acidified samples.