polygon

Polygon Study: Variability in soil biogeochemistry and biodiversity

Abstract: 

In the Antarctic Dry Valleys, soil polygons are prominent features of the landscape and may be key units for scaling local ecological information to the greater region. We examined polygon soils in each of the 3 basins of Taylor Valley, Antarctica. Our objectives were to characterize variability in soil biogeochemistry and biodiversity at local to regional scales, and to test the influence of soil properties upon invertebrate communities. We found that soil biogeochemical properties and biodiversity vary over multiple spatial scales from fine (less than 10 m) to broad (greater than 10 km) scales. Differences in biogeochemistry were most pronounced at broad scales among the major lake basins of Taylor Valley corresponding to differences in geology and microclimate, while variation in invertebrate biodiversity and abundance occurred at landscape scales of 10-500 m, and within individual soil polygons. Variation in biogeochemistry and invertebrate communities across these scales reflects the influence of physical processes and landscape development over ecosystem structure in the dry valleys. The development of soil polygons influences the spatial patterning of soil properties such as soil organic matter, salinity, moisture, and invertebrate habitat suitability. Nematode abundance and life history data indicate that polygon interiors are more suitable habitats than soils in the troughs at the edges of polygons. These data suggest that physical processes (i.e. polygon development) and biogeochemistry are an important influence on the spatial variability of biotic communities in dry valley soil ecosystems.

Data set ID: 

4006

Core Areas: 

Additional Project roles: 

244
245
246
247

Short name: 

Poly

Methods: 

       During the 1994-1995 season, two polygons (1 and 2) were sampled at each location. Each "set" consisted of three polygons and the three linear cracks which separated them. Samples were taken from three intersecting cracks (labelled A0, B0, or C0) outwards towards the middle of the three nested polygons. The middles were labelled AB, BC, and AC. Transect lines were labelled A, B, and C according to the label of the crack crossed. Transect samples were taken at 0.2, 0.4,0.6, 0.8, 1.0, 2.0, 4.0, and 8.0 m on either side of the crack. Positive (+) values were to the right of the crack. Negative (-) values were to the left of the crack. Transect lines were sometimes too short to take an 8.0 m sample.
       
       During the 1995-1996 season, four contingent polygons were selected as P1, P2, P3 and P4 in a clockwise direction. The middle of the south facing crack was selected as the "0" point and soil samples were taken at 0, 0.2, 0.5, 2, and 5 m along a transect towards the middle of the polygon (in a south to north direction).
       
       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 (greater than20 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 +5degC 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 200cm3 of soil was placed in a pre-weighed 800mL plastic beaker. Rocks greater than 3-4mm 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 105degC 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 into 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 backwashed into a 50mL 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 particles. The tube was filled with sucrose solution (454g sucrose per liter of tap water, kept refrigerated) up to 45mL. 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 backwashed into a centrifuge tube. Samples were refrigerated at 5degC until counted.
       
       Samples were washed into a counting dish and examined under a microscope at x 10 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.
       
       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 -4C 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 seconds, 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. Data were entered in to Excel files, printed, and checked for errors.
       
       Soil chemistry. We estimated soil salinity by measuring the conductivity of a 1:5 soil solution of the less than2 mm soil fraction in de-ionized water using a Corning 311 conductivity meter calibrated with a 0.01 M KCl solution. We measured the pH of the less than2 mm soil fraction in a saturated paste (1:2 soil in de-ionized water) with an Orion model 720A pH meter. Each soil was air-dried, and ground in a ball mill prior to elemental analysis of acidified and un-acidified soils on a Carlo Erba 1500 elemental analyzer to determine total C and N, and organic C content. Soil inorganic C content was estimated by the difference between total and organic carbon.
      

1994-1995

Field Notes Lake Bonney

Comments. These samples were taken on 8 December 1994 at the Lake Bonney polygon experiment site.  Scottnema, Eudorylaimus, Plectus, Tardigrades and dead unidentifiable nematodes were found at the site. Sample A8.0(+) spilled and wasn't calculated.  [Ed Kuhn, 17 April 1997]. A comments column was deleted and it's contents were used to create the "other" columns  in order to separate species.  All nematodes included in these columns were dead when identified and those not identifiable were included into the unknown column.[Ed Kuhn, 28 July 1997]

File log. The initial iteration of this log was created on 17 April 1997 by Ed Kuhn. The original data was in the Excel file LBpoly.worms.Dec94.raw. The file was checked against the hard-copy forms by Ed Kuhn and Pella Brinkman on 6 March 1997. The file was reformatted to a common format. Number of organisms per kg dry soil was calculated on 18 March 1997 by Ed Kuhn. The new file was named LBpoly.worms.Dec94.calc. The file log and the "comments" text box were added to this Excel file on 17 April 1997 by Ed kuhn. [Ed Kuhn,17 April 1997]. No value was recorded for polygon 2, sample A 8.0(+) soil "mass". The default "#Value" was replaced with our standard "." for no data available [MS 9 Oct 1998].

This file was sent as an example of our data to Denise Steigerwald, the MCM LTER data manager at the University of Colorado. She suggested several changes which were incorporated by Dan Bumbarger on 29 July 1997. These changes were:

1. Addition of a 'Date Sampled' column

2. The format of the 'Date Counted' column was changed so that the year was apparent.

3. The first 'Soil wt.' label was changed to 'fresh weight of soil used for extraction (g)'.

4. The labels 'L' and 'D' were replaced with 'living' and 'dead'.

5. The label 'juvs' was replaced with 'juveniles'.

6. The label 'Scott' was replaced with 'Scottnema' and italicised.

7. The label 'nema' was replaced with 'nematodes'.

8. The label '(# in extraction)' was added to the column headings for the counts of organisms in the sample.

9. The subtitle 'unclassified nematodes', which implies nematodes which could not be sexed or placed in an age class, were added under the other group heading.

10. An additional label 'Other organisms (# in extraction)' was added above the columns with counts for non-nematode organisms and unclassified nematodes.

11. the label 'trdgrds' was changed to 'tardigrades'.

12. New labels were added for the columns used to determine the water content of the soil. Both columns were headed with 'Soil sample used to determine water content', the first column was changed to 'Fresh weight of soil (g)' and the second was re-labelled 'Dry weight of soil (g)'.  [Dan Bumbarger 29 July 1997].   Added columns and changed column headings to fit a new common format.  The comments and file log were combined into a single text box.[Dan Bumbarger, 3 March 1998]

Soil Moisture calculated as the (g of water/ g dry soil) *100 by M L Haddix 8/15/14

Numbers per kg dry soil calculated by M L Haddix using formula 1000*(#individuals/(extraction mass*(mass of dry soil/mass of soil used for moisture calc))) 8/15/14

Field Notes Lake Fryxell

Comments.  These samples were taken on 2 December 1994 at the Lake Fryxell polygon experiment site. Scottnema and Eudorylaimus were found in these samples.[Ed Kuhn, 17 April 1997]

File log.  This log was created on 17 April 1997 by Ed Kuhn. The original data are in Excel file LFpoly.worms.Dec94.raw. The file was checked against the hard-copy sheets on 3 March 1997 by Ed Kuhn and Drew Hall. The file was reformatted to a common format and number/kg dry soil was calculated on 20 March 1997 by Ed Kuhn. The new file was named LFpoly.worms.Dec94.calc. The file log and the" comments" text boxes were added to this file on 17 April 1997 by Ed Kuhn. 

This file was sent as an example of our data to Denise Steigerwald, the MCM LTER data manager at the University of Colorado. She suggested several changes which were incorporated by Dan Bumbarger on 29 July 1997. These changes were:

1. Addition of a 'Date Sampled' column

2. The format of the 'Date Counted' column was changed so that the year was apparent.

3. The first 'Soil wt.' label was changed to 'fresh weight of soil used for extraction (g)'.

4. The labels 'L' and 'D' were replaced with 'living' and 'dead'.

5. The label 'juvs' was replaced with 'juveniles'.

6. The label 'Scott' was replaced with 'Scottnema' and italicised.

7. The label 'nema' was replaced with 'nematodes'.

8. The label '(# in extraction)' was added to the column headings for the counts of organisms in the sample.

10. An additional label 'Other organisms (# in extraction)' was added above the columns with counts for non-nematode organisms and unclassified nematodes.

11. the label 'trdgrds' was changed to 'tardigrades'.

12. New labels were added for the columns used to determine the water content of the soil. Both columns were headed with 'Soil sample used to determine water content', the first column was changed to 'Fresh weight of soil (g)' and the second was re-labelled 'Dry weight of soil (g)'.  [Dan Bumbarger 29 July 1997].

The comments box and log file were combined into a single textbox. columns were added to make the file conform to a new common format.  [Dan Bumbarger, 3 MARCH 98]

The last row of "0" were not entered for plectus, rotifers, tardigrades and Unknowns (Excel row 107). These were entered [MS 12 Oct 1998]

Soil Moisture calculated as the (g of water/ g dry soil) *100 by M L Haddix 8/15/14

Numbers per kg dry soil calculated by M L Haddix using formula 1000*(#individuals/(extraction mass*(mass of dry soil/mass of soil used for moisture calc))) 8/15/14

Field Notes Lake Hoare

Comments.  These samples were taken on 29 November1994 at the Lake Hoare polygon experiment site. Scottnema and Eudorylaimus were found in these samples.[Ed Kuhn, 21 April 1997] On July 29, 1997 the 'comments' column was removed.  The two entries were as follows: Sample A 0.8(+):'Dropped sieve in sink- may have splashed' and A0:'Sampled about 10cm from center.' [Dan Bumbarger, 29 July 1997].

File log.  This log was created on 21 April 1997 by Ed Kuhn. The original data are in Excel file LHpoly.worms.Dec94.raw. The file was checked against the hard-copy sheets on 3 March 1997 by Ed Kuhn and Drew Hall. The file was reformatted to a common format and number/kg dry soil was calculated on 19 March 1997 by Ed Kuhn. The new file was named LHpoly.worms.Dec94.calc. The file log and the" comments" text boxes were added to this file on 21 April 1997 by Ed Kuhn. 

This file was sent as an example of our data to Denise Steigerwald, the MCM LTER data manager at the University of Colorado. She suggested several changes which were incorporated by Dan Bumbarger on 29 July 1997. These changes were:

1. Addition of a 'Date Sampled' column

2. The format of the 'Date Counted' column was changed so that the year was apparent.

3. The first 'Soil wt.' label was changed to 'fresh weight of soil used for extraction (g)'.

4. The labels 'L' and 'D' were replaced with 'living' and 'dead'.

5. The label 'juvs' was replaced with 'juveniles'.

6. The label 'Scott' was replaced with 'Scottnema' and italicised.

7. The label 'nema' was replaced with 'nematodes'.

8. The label '(# in extraction)' was added to the column headings for the counts of organisms in the sample.

9. An additional label 'Other organisms (# in extraction)' was added above the columns with counts for non-nematode organisms and unclassified nematodes.

10. the label 'trdgrds' was changed to 'tardigrades'.

11. New labels were added for the columns used to determine the water content of the soil. Both columns were headed with 'Soil sample used to determine water content', the first column was changed to 'Fresh weight of soil (g)' and the second was re-labelled 'Dry weight of soil (g)'.  [Dan Bumbarger 29 July 1997].

Columns were added to make the file confor  a new common format. [Dan Bumbarger, 3 March 98]

Soil Moisture calculated as the (g of water/ g dry soil) *100 by M L Haddix 8/15/14

Numbers per kg dry soil calculated by M L Haddix using formula 1000*(#individuals/(extraction mass*(mass of dry soil/mass of soil used for moisture calc))) 8/15/14

Data sources: 

SOILS_POLYGON

Maintenance: 

This file contains data compiled by Ed Khun, Andy Parsons and Jeb Barrett. The final data QA/QC and analysis were performed by Jeb Barrett.

Data and metadata was moved into DEIMS in 2015 (Inigo San Gil), revised by Michelle L.Haddix, and latest versions sent into the clearinghouses in 2016

Additional information: 

 Some data columns names are coded. The FIRST letter may represent the nematode species, and the following letters represent the life stage/sex/sum type.  The nematode  species codes are:
      
      S: Scottnema lindsayae 
      E: Eudorylaimus spp. 
      P: Plectus spp.  
      
      For example, in the attribute table,  "(code)ML" has the description "The total number of living male (species) adult nematodes extracted from the soil sample in number of organisms per kg soil oven dry weight equivalent. In this case, a column name  called "SML" would be  "The total number of living male Scottnema lindsayae adult nematodes..."

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