English utf8 dataset McMurdo Dry Valleys LTER http://mcmlter.org/ 2017-12-06 ISO 19115-2 Geographic Information - North American Profile Metadata - Data with Biological Extensions ISO 19115-2:2009(E) Soil Apatite Grain Weathering Metrics from Taylor Valley, Antarctica 2017-12-06 publication Ruth Heindel Kenyon College https://www.kenyon.edu/ heindel1@kenyon.edu https://www.ruthcheindel.com/ pointOfContact documentDigital Mineral apatite is the ultimate source of the essential nutrient phosphorus to the soil ecosystem. In order to assess the biogeochemical weathering of apatite grains in the dry, basic soils of the McMurdo Dry Valleys, we collected nine surface soil samples from the Fryxell and Bonney Basins of Taylor Valley. After separating more than 50 individual soil apatite grains from each sample, we used scanning electron microscopy to quantify the morphology and surface etching of apatite grains to determine the degree of weathering. We developed three metrics to quantify the degree of weathering: aspect ratio, percent crystal faces, and a qualitative pitting index. This dataset contains the raw data from analyzing the morphology of more than 600 grains using the software ImageJ. Samples were collected during January 2013. The samples from the Bonney Basin (LB) were collected 21 Jan 2013, and the samples from the Fryxell Basin (LF) were collected 18 January 2013. Samples were processed and analyzed 2014-2016. Name: W. Berry Lyons Role: associated researcher Name: Sue Welch Role: associated researcher Name: Angela Spickard Role: associated researcher Name: Ross A. Virginia Role: associated researcher Name: Renée F. Brown Role: data manager completed McMurdo Dry Valleys LTER http://mcmlter.org/ inorganic nutrients theme LTER Core Areas English This is the Taylor Valley, a subjectively approximated contour by San Gil. We use this to denote the geographical extent of studies that encompass the whole Taylor Valley. According to Wiki contributors, the Taylor Valley is the southernmost of the three large Dry Valleys in the Transantarctic Mountains, Victoria Land, located west of McMurdo Sound. The valley extends from Taylor Glacier in the west to McMurdo Sound at Explorers Cove at the northwest head of New Harbour in the east and is about 29 kilometres (18 mi) long. It was once occupied by the receding Taylor Glacier, from which it derives its name. Taylor Valley contains Lake Bonney in the west (inward), and Lake Fryxell in the east (coastward), and Lake Hoare, Lake Chad, Mummy Pond and Parera Pond close together between the two. Further east of Lake Bonney is Pearse Valley. Taylor Valley is separated from Wright Valley in the north by Asgard Range, and from Ferrar Glacier in the south by Kukri Hills. 163.624877929690 161.707763671880 -77.808487073526 -77.519802097166 ground condition 2013-01-18 2013-01-21 https://mcm.lternet.edu/sites/default/files/data/SOILS_APATITE.csv SOILS_APATITE eng; US McMurdo Dry Valleys LTER SOILS_APATITE Number of Header Lines : 1 Orientation : Column Field Delimiter : , false DATASET_CODE DATASET_CODE BASIN Identifies the region where the sample was collected; either Fryxell Basin or Bonney Basin MOISTURE_LEVEL Identifies the moisture level of the soil sample; either dry or saturated. Dry samples are from outside of stream channels, while saturated samples are from the hyporheic zone. SAMPLE_ID Unique sample identifier. LB=Lake Bonney; LF=Lake Fryxell; D=dry; W=wet LATITUDE Latitude in decimal degrees. LONGITUDE Longitude in decimal degrees. GRAIN_ID Unique grain identifier. P=phosphorus. We separated more than 50 apatite grains from each sample. PITTING_INDEX A qualitative index of how chemically altered the apatite grain was. Our pitting index ranges from 1 (grains with few to no etch pits) to 4 (grains with etch pits covering the entire grain surface). ASPECT_RATIO The length of the long axis of the grain divided by the length of the short axis, giving a measure of how elongated grains are. An aspect ratio of 1 is a perfectly round grain. PERCENT_CRYSTAL_FACES The percent of the total visible grain area that was a recognizable crystal face. DBF https://mcm.lternet.edu/sites/default/files/data/SOILS_APATITE.csv dataset We collected samples the Fryxell and Bonney Basins of Taylor Valley. In the Fryxell Basin, we collected 2 samples at low elevation near the mouth of Von Guerard Stream and 3 samples at high elevation along the southern valley wall. In the Bonney Basin, we collected 2 samples at low elevation near Wormherder Creek and 2 samples at high elevation along the southern valley wall.To isolate individual apatite grains from soil samples, we used standard sieving, heavy-liquids, and magnetic mineral separation techniques. Grains presented here are all within the 125-250 µm size fraction.To capture images of the grains for the weathering metrics presented here, we used a Hitachi TM3000 scanning electron microscope. We used the software ImageJ to analyze the images.We developed three weathering metrics that characterize grain shape and micromorphology: aspect ratio, percent crystal faces, and chemical etching (pitting index). We defined the aspect ratio as the length of the long axis of the grain divided by the length of the short axis, giving a measure of how elongated grains are. We defined the percent crystal faces metric as the percent of the total visible grain area that was a recognizable crystal face. Our pitting index ranged from 1 (grains with few to no etch pits) to 4 (grains with etch pits covering the entire grain surface). Metadata Access Constraints: none Metadata Use Constraints: none annually McMurdo Dry Valleys LTER http://mcmlter.org/ pointOfContact