| Data Tables, Images, and Other Entities: |
| Data Table: | Units_and_Column_Descriptions
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Short Name: | LTM |
| Data Set Owner(s): |
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Individual: | Diana Wall |
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| NREL, |
| Colorado State University, |
| Fort Collins, CO 80523 USA |
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Individual: | Ross Virginia |
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| Environmental Studies Program, |
| Dartmouth College, |
| Hanover, NH 03755 USA |
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| Metadata Provider(s): |
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Organization: | McMurdo Dry Valleys LTER |
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Address: |
| Byrd Polar Research Center , |
| 108 Scott Hall, |
| 1090 Carmack Rd, |
| Columbus, OH 43210-1002 USA |
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| Abstract: |
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A long-term soil manipulation experiment has been conducted
as part of the McMurdo Dry Valleys Long Term Ecological Research (LTER) project.
The response of soil organisms (nematodes, rotifers and tardigrades) to the
treatments is monitored by sampling soil on an annual basis.
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| Keywords: |
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- nematodes
(theme)
- rotifers
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- tartigrades
(theme)
- McMurdo
(theme)
- Antarctica
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- LTER
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| Additional Information: |
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| Citations |
| Notes |
Data contained in these files has been subjected to quality control standards
imposed by the investigator. The user of this data should be aware that, while efforts have
been taken to ensure that these data are of the highest quality, there is no guarantee of
perfection for the data contained herein and the possibility of errors exists. If you
encounter questionable data, please contact the MCM LTER data manager corrected or qualified.
Thus, these data may be modified and future data will be appended.
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| License and Usage Rights: |
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| MCM LTER data may be used freely with the following restrictions: |
The Principal Investigator be sent a notice stating reasons for acquiring any
data and a description of the publication intentions.
The Principal Investigator of the data set be sent a copy of the report or
manuscript prior to submission and be adequately cited in any resultant
publications.
A copy of any resultant publications should be sent to the McMurdo data
manager and principal investigator.
The end-user follow the guidelines set forth in the LTER Network Data Access
Policy, Data Access Requirements, and General Data Use Agreement found at
http://www.mcmlter.org/data_guidelines.htm
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| Geographic Coverage: |
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Geographic Description: | Study site is on the south side of Lake Hoare, Taylor Valley, Antarctica (77deg37'59" S, 162deg52'57" E). |
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Bounding Coordinates:
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| West: | 162.8825 degrees
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| East: | 162.8825 degrees
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| North: | -77.63305556 degrees
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| South: | -77.63305556 degrees
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Mimimum Altitude: | 0 meter |
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Maximum Altitude: | 1000 meter |
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| Temporal Coverage: |
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Begin:
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End:
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| Maintenance: |
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Description:
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This file contains archived data pulled from nemadisk and off of the field season directories by Jeb Barrett.
The data page contains the raw data for nematode abundance in # of animals per kg oven dry weight equivalent.
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Frequency:
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| Contact: |
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Organization: | McMurdo Dry Valleys LTER |
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Position: | Data Manager |
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Address: |
| Byrd Polar Research Center , |
| 108 Scott Hall, |
| 1090 Carmack Rd, |
| Columbus, OH 43210-1002 USA |
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| Publisher: |
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Organization: | McMurdo Dry Valleys LTER |
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Address: |
| Byrd Polar Research Center , |
| 108 Scott Hall, |
| 1090 Carmack Rd, |
| Columbus, OH 43210-1002 USA |
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| Methods Info: |
| Step 1: |
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Description:
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The experimental design is a randomized block, with 8 replicates per treatment. Within each block are 8 plots measuring approximately 1m x 1m, with a central circular area of 85 cm diameter (approx 0.57 m2) used for treatments and sampling. The treatments are as follows:
(C) control plots (no manipulations),
(T) enhanced soil temperature using ITEX conical open-top chambers made of solar fiberglass,
(W) Nanopure water added to field capacity to 10 cm depth (5.6 L/plot) once per season,
(TW) temperature enhancement and water addition,
(WS) sucrose added in solution (15.82 g sucrose in 5.6 L water per plot) once per season,
(WM) mannitol added in solution (17.01 g mannitol in 5.6 L water per plot) once per season,
(TWS) temperature enhancement plus sucrose addition,
(TWM) temperature enhancement plus mannitol addition.
Soil samples were taken for organism enumeration and moisture content analysis as follows: Sampling bags were prepared with one sterile 'Whirlpak' bag and clean plastic scoop per sample. Samples were taken from within the 85 cm diameter circular area of each plot. The location of the sampling was recorded each year so that areas were not re-sampled. Using the plastic scoop, soil was collected to 10 cm depth. Very large rocks (>20 mm diameter) were excluded from the sample. The soil was shoveled into the 'Whirlpak' bag until three quarters full (about 1.5 kg soil). The soil was mixed well in the bag, then the bag was closed tightly, expelling as much air as possible. The soil samples were stored in a cooler for transportation. On return to the laboratory (within 8 hours of sampling), the soils were stored at +5°C until further processing.
In the laboratory, soil samples were handled in a laminar flow hood to prevent contamination. The Whirlpak bags of soil were mixed thoroughly prior to opening. Approximately 200 cm3 of soil was placed in a pre-weighed 800 mL plastic beaker. Rocks greater than 3-4 mm in diameter were removed from the sample. A sub-sample of approximately 50g was removed and placed in a pre-weighed aluminum dish, and weighed on a balance accurate to 0.01g. This sample was dried at 105C for 24 hours. The sample was removed, placed in desiccator to cool down, and re-weighed. These data were used to calculate water content of the soil and to express data as numbers of soil organisms per unit dry weight of soil.
The remaining soil in the plastic beaker was weighed. Cold tap water was added up to 650 mL. The soil suspension was stirred carefully (star stir or figure of 8) for 30 seconds, using a spatula. Immediately the liquid was poured in to wet screens - a stack of 40 mesh on top of a 400 mesh. The screens were rinsed gently with ice cold tap water (from a wash bottle) through the top of the stack, keeping the screens at an angle as the water filtered through. The water was kept on ice at all times. The top screen was removed, and the lower screen rinsed top down, never directly on top of the soil, but at the top of the screen and from behind. The water was allowed to cascade down and carry the particles into the bottom wedge of the angled screen. The side of the screen was tapped gently to filter all the water through. The suspension was rinsed from the front and the back, keeping the screen at an angle and not allowing the water to overflow the edge of the screen. The soil particles were back washed into a 50 mL plastic centrifuge tube, tipping the screen into the funnel above the tube and rinsing the funnel gently. The suspension was centrifuged for five minutes at 1744 RPM. The liquid was decanted, leaving a few mL on top of the soil part icles. The tube was filled with sucrose solution (454g sucrose per liter of tap water, kept refrigerated) up to 45 mL. This was stirred gently with a spatula until the pellet was broken up and suspended. The suspension was centrifuged for one minute at 1744 RPM, decanted into a wet 500 mesh screen, rinsed well with ice cold tap water and back washed into a centrifuge tube. Samples were refrigerated at 5C until counted.
Samples were washed in to a counting dish and examined under a microscope at x10 or x20 magnification. Rotifers and tardigrades were identified and counted. Nematodes were identified to species and sex, and counted. Total numbers in each sample were recorded on data sheets. All species of nematode, and all rotifers and tardigrades found in the sample were recorded. Data were entered in to Excel files, printed, and checked for errors
For measurements of pH, 40 of DI water was added to 20 g of soil in a clean, DI- rinsed glass beaker (coarse fragments >2 mm were removed). The samples were stirred until thoroughly mixed (about 5-10 sec). After sitting to equilibrate for 10 minutes the samples were stirred again and a reading was taken with a Beckman 0265 pH meter. For measurements of electrical conductivity, an additional 60 ml of DI water was then added (totaling 100 ml water). The samples were stirred until thoroughly mixed (about 5-10 sec). After sitting to equilibrate for 10 minutes the samples were stirred again and a reading was taken with a YSI 30 conductivity meter. Extraction of chlorophyll from the soil. All procedures were carried out in the dark or very low irradiance to avoid degradation of the chlorophyll. The soil samples were mixed thoroughly in the vials, and a sample of approximately 5 g was weighed out in to a 50 mL plastic centrifuge tube with a screw-top cap. 10 mL of a 50:50 DMSO/90% acetone solution was added to each sample and they were mixed thoroughly on a bench-top Vortex mixer for about 5 seconds. The vials were placed in a -4°C constant temperature room, in the dark, and left for 12-18 hours. Determination of chlorophyll a concentration - This was determined fluorometrically using a Turner model 111 fluorometer. A calibration using a known concentration of chlorophyll was carried out prior to sample analysis. The machine was blanked using a 50:50 DMSO/90% acetone solution. Each vial was mixed thoroughly, then centrifuged for 5 minutes at about 1800 RPM. A sample of approximately 4mL of the DMSO/acetone solution was taken from the top of the sample with a pipette, being careful not to get any soil particles in the solution. The sample was placed in a cuvette, in to the fluorometer and the fluorescence was recorded. This was done fairly quickly in order to prevent light from breaking down the chlorophyll. This measurement is called Fo, the initial fluorescence. After taking this reading, 0.1 mL of 1N HCl was added directly to the cuvette and the cuvette was gently agitated. After 20 s, the fluorescence was re-measured. (During this step, the acid converts the chlorophyll to phaeophytin by releasing a magnesium ion in an acidic environment). This measurement is called Fa, the fluorescence after acidification. The solution was discarded in to a waste container, and the cuvette rinsed 3 times with DMSO/90% acetone solution before proceeding with the next sample.
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