In January 2001, we surveyed streams and ponds above 300 m asl in Taylor Valley, South Victoria Land, Antarctica. One pond was examined in detail. Organic materials covered nearly 100% of the adjacent soil to 5-20 m from the shore, with intermittent patches to 80 m. Organic matter averaged 257 gC/m2, and totaled 1388 kg organic C on the soil around the pond. Soil moisture content (0.56 to 12.41%) decreased with distance from shore, whereas pH (7.8 to 10.8) increased with distance. Electrical conductivity was lowest in the soils less than 10 m from the pond (416 +- 94 uS/cm). Mineral soil organic C and total N concentrations were greatest between 10-30 m from the edgeof the pond (1.21 +- 0.37 and 0.13 +- 0.05 mg/g soil, respectively). Soil invertebrates were present in only 50% of samples and included tardigrades, rotifers and two nematodes, Scottnema lindsayae and Plectus antarcticus. A non-parametric, discriminant function analysis based on soil moisture, soil organic carbon and electrical conductivitycorrectly predicted 87.0% of sites that had invertebrates and 70.8% of sites for which invertebrates were absent. Tardigrades, rotifers and Plectus were found only in the wettest soils nearest the pond whereas Scottnema was restricted to drier soils farther from shore. Other ponds and streams also showed substantial accumulations of organic matter, suggesting that upland wetlands serve as resource islands in these polar deserts that provide a source of organic matter to nearby soils.
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.
Log: This file was created by Rebecca Lavier. Data were entered by Rebecca Lavier on 12 February 2001.
These data were proofed by Pilar Tillberg and Rebecca Lavier on 14 February 2001. [Pilar Tillberg 14 Feb 01]
Calculations for # nematodes per kg soil were done by Rebecca Lavier on 15 February 2001. [Rebecca Lavier 15 Feb 01].
Soil Moisture calculated as the (g of water/ g dry soil) *100 by M L Haddix 9/26/14
Data were collected from the Upper Pond site in Antarctica. Data were collected on 22 January 2001. Nematodes were extracted on 24 January 2001. Samples were counted by Dorota Porazinska on 25 January and 26 January 2001. [Rebecca Lavier 12 Feb. 01].