nitrate

Stoichiometry Experiment

Abstract: 

Soil communities in the McMurdo Dry Valleys are subject to many limitations, including resource limitations. However, the nutrients that are predominantly limiting to growth and diversity of soil biota are not known. Additionally, landscape history (N deposition, P weathering) and native N and P content (glacial till provenance) may influence the ability of soil communities to respond to nutrient additions or changes in nutrient availability associated with environmental change. Long-term experiments in the Bonney and Fryxell basins have been established with yearly application of aqueous nutrient additions: C, N, P, CN, and CP. Multiple nutrients additions were made at the Redfield Ratio of 106:16:1 (C:N:P). Responses of soil chemistry, CO2 flux, and biota are reported.

Core Areas: 

Data set ID: 

4013

Additional Project roles: 

316
317
318
319
320
321
322
323
324
325

Short name: 

SE_CHEM

Methods: 

Three sites were chosen on generally flat areas of moderately patterned soil. Plots were laid out in an identical design at each site. There are 7 treatments replicated 8 times in blocks. Treatments were randomly assigned to the plots within each block. Each plot measures 1 m x 1 m (with a 0.83 m diameter area within used for experimental treatments and analyses). Plots are delineated by nails inserted in the soil, and the margins of each site are marked by PVC stakes approximately 60 cm high. 
 
Water and aqueous nutrient treatments were applied annually at a rate of 5.6 L per plot, with 15 g C m-2 as mannitol, 2.5 g N m-2 as NH4NO3, and/or 0.75 g P m-2 as Na3PO4 (see Treatment Codes under Additional Information). Soil samples were taken for soil chemistry, 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 0.83 m diameter circular area within 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 than 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 gently mixed 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 Crary laboratory in McMurdo (within 8 h 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 limit contamination. The Whirlpak bags of soil were again mixed by gentle tumbling prior to opening. A subsample of approximately 50 g was removed and placed in a pre-weighed aluminum dish, and weighed on a balance accurate to 0.01 g. This sample was dried at 105°C for 24 hours. The sample was removed, placed in desiccator to cool, and re-weighed. These data were used to calculate gravimetric water content of the soil (g water g-1 dry soil) and to express data as value per unit dry weight of soil. Invertebrate soil extractions follow the methods of Freckman and Virginia (1993). 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 leaving approximately 100 g soil, and the weight of the soil was recorded. 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 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 particles. The tube was filled with sucrose solution (454 g 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 backwashed into a centrifuge tube. Samples were refrigerated at 5°C 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. A subsample of the soil was gradually stepped down and frozen at -20°C and shipped to Dartmouth College for soil chemistry analysis. All soils were sieved to less than 2 mm. For measurements of pH, 40 ml DI water was added to 20 g of soil in a clean, DI-rinsed glass beaker. The samples were stirred until thoroughly mixed (about 5-10 sec). After sitting to equilibrate for 10 min., the samples were stirred again and a reading was taken with a VWR 8015 pH meter. For measurements of electrical conductivity, an additional 60 ml 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 min., the samples were stirred again and a reading was taken with an Orion 160 conductivity meter. 
 
For mineral N content, a 20 g subsample was extracted in 50 ml 2M KCl for 1 h and filtered through Whatman #42 filter paper. Extracts were frozen prior to analysis for NH4-N and NO2+NO3-N on a Lachat Quikchem 8500 (Lachat Instruments, Loveland, CO). Ortho-phosphate content was measured by extracting a 10 g subsample in 50 ml 0.5M NaHCO3 for 1 h and filtering through Whatman #40 filter paper. 30 ml of the extracts were then brought to pH ~ 2 with 6N HCl and allowed to degas for 2 hours. Samples were frozen prior to analysis on a Lachat. For total C and N, a subsample of soil was hand-ground using a sapphire mortar and pestle, from which a 250 mg subsample was run on a Carlo Erba NA 1500 N Elemental Analyzer (Carlo Erba Instruments, Milan, Italy). For organic C, 1 mg of ground soil was acidified with 1 ml 6 N HCl and dried at 95°C for 48 h. A 250 mg subsample was run on a Carlo Erba, and the value was corrected for the change in weight associated with acidification. 
 
Microbial C, N, and P were measured using the chloroform fumigation extraction technique. Approximately 20 g of soil from each sample was extracted in 50 ml of 0.5 M K2SO4. Extracts were shaken at 240 rpm for 45 minutes, then centrifuged at 15,000 rpm for 15 min. Half of the supernatant was brought to pH ~ 2 with 3N H2SO4. A duplicate 30-g subsample was placed in a vacuum desiccator and fumigated with ethanol-free chloroform for 120 h. After fumigation, 10 g were removed and extracted in NaHCO3 as above for ortho-PO43- content. The remaining 20 g were extracted in K2SO4 as described above. All extracts were frozen prior to analysis. 
 
Acidified K2SO4 samples were run on a Shimadzu TOC-5000A (Shimadzu Corporation, Columbia, MD) for TOC. 
 
Unacidified samples underwent a Kjeldahl digestion and analyzed for N on a Lachat.
      

2006-2007

Field Notes Bonney

LOG: This file created by Jeb Barrett on January 15 2007.

Soil was sampled on January 15th by Jeb Barrett, Ross Virginia, Diana Wall, Byron Adams and Breana Simmons. Treatments were applied on January 19th, 2007 by Breana Simmons, Jeb Barrett and Byron Adams.

Worms were extracted using sugar floatation on 15 Jan 2007

Worms were preserved 20 Jan 2007

Samples were counted by Ed Ayres and Dorota Porazinska on 16-17 Jan

Data entered on 19 Jan 2007 by Ed Ayres

Data proofed on 26 Jan 2007 by Dorota Porazinska

Invertebrates per kg dry weight equivalent calculations made by Jeb Barrett.

Numbers per kg dry soil changed by M L Haddix using formula 1000*(#individuals/(extraction mass*(mass of dry soil/mass of soil used for moisture calc))) 7/03/13

Related files: BR_soils.xls, F6_soils.xls, F6_worms.xls, RECON_worms.xls, SE-BR070127.xls, SEfryx070122.xls

Field Notes Fryxell

LOG: This file created by Jeb Barrett

Soil was sampled on January 11th by Jeb Barrett, Ross Virginia, Diana Wall, Byron Adams and Breana Simmons. Treatments were applied by Breana Simmons, Ed Ayers and Byron Adams on January 17th, 2007.

Worms were extracted using sugar floatation on 12 Jan 2007

Samples were counted by Byron Adams, Diana Wall and Breana Simmons on 12 Jan

Data was entered by Breana Simmons on 13 Jan 2007

Data proofed on 26 Jan 2007 by Dorota Porazinska

Worms preserved 14 Jan 2007 by Breana Simmons.

Invertebrates per kg dry weight equivalent calculations made by Jeb Barrett.

Numbers per kg dry soil changed by M L Haddix using formula 1000*(#individuals/(extraction mass*(mass of dry soil/mass of soil used for moisture calc))) 7/03/13

Related files: BR_soils.xls, BR_worms.xls, F6_soils.xls, RECON_worms.xls, SE-BR070127.xls, SEfryx070122.xls

2007-2008

Field Notes Bonney

LOG: This file created by Breana Simmons on January 3, 2008

Data entered by Breana Simmons/Ed Ayres

Data checked by ??

Sampling

'Plots were sampled on January 2, 2008 by Diana Wall and Byron Adams, with direction from Breana Simmons. Solar chambers from the OTC plots were used as a guide for sampling. To ensure sampling under the treated area, the cone was centered in the plot and the sample was taken from the exact middle. Future samples should be taken in a "clockwise" formation. A stake was driven in at the 12:00 position (south) in all plots by Ed Ayres and Byron Adams, so that in the future, chambers can be set up against it as a guide for both sampling and treating. In blocks 5 -8 stakes were put in at at the 6:00 position due to plot logistics (you cannot walk BETWEEN plots 5 and 6 or 7 and 8 - paths are on the outside - see map).

Treating

Plots were treated by Byron Adams and Breana Simmons. Diana Wall and Ed Ayres filled containers. To reduce the number of pour jugs, two C, N and P jugs were used, for a total of 6 jugs. DI was applied first, then C, P, CP (from the P jug), CN (from the C jug) and N. This is not as confusing as it sounds. Chambers were placed again, over the center, against the nail, as a guide for pouring. Any solution containing C became hard to pour and jugs were shaken rigorously over plots.

Processing

Fresh soil was weighed by Ed Ayres into soil cans and placed in a 105C oven for 24 hours. Diana Wall and Breana Simmons were on screens. Byron "Skua Boy" Adams centrifuged and played paper towel wad basketball. Dry soil was weighed by ??. Nematodes were counted by ??.

Invertebrates per kg dry weight equivalent calculations made by Uffe N. Nielsen on Juy 22 2009.

using the formula:

Numbers per kg dry soil changed by M L Haddix using formula 1000*(#individuals/(extraction mass*(mass of dry soil/mass of soil used for moisture calc))) 7/03/13

Field Notes Fryxell

LOG: This file created by Breana Simmons on January 3, 2008

Data entered by Breana Simmons/Ed Ayres

Data checked by ??

Sampling

'Plots were sampled on January 2, 2008 by Diana Wall and Byron Adams, with direction from Breana Simmons. Solar chambers from the OTC plots were used as a guide for sampling. To ensure sampling under the treated area, the cone was centered in the plot and the sample was taken from the exact middle. Future samples should be taken in a "clockwise" formation. A stake was driven in at the 12:00 position (south) in all plots by Ed Ayres and Byron Adams, so that in the future, chambers can be set up against it as a guide for both sampling and treating. In blocks 5 -8 stakes were put in at at the 6:00 position due to plot logistics (you cannot walk BETWEEN plots 5 and 6 or 7 and 8 - paths are on the outside - see map).

Treating

Plots were treated by Byron Adams and Breana Simmons. Diana Wall and Ed Ayres filled containers. To reduce the number of pour jugs, two C, N and P jugs were used, for a total of 6 jugs. DI was applied first, then C, P, CP (from the P jug), CN (from the C jug) and N. This is not as confusing as it sounds. Chambers were placed again, over the center, against the nail, as a guide for pouring. Any solution containing C became hard to pour and jugs were shaken rigorously over plots.

Processing

Fresh soil was weighed by Ed Ayres into soil cans and placed in a 105C oven for 24 hours. Diana Wall and Breana Simmons were on screens. Byron "Skua Boy" Adams centrifuged and played paper towel wad basketball. Dry soil was weighed by ??. Nematodes were counted by ??.

Invertebrates per kg dry weight equivalent calculations made by Uffe N. Nielsen on July 22 2009.

using the formula:

Numbers per kg dry soil changed by M L Haddix using formula 1000*(#individuals/(extraction mass*(mass of dry soil/mass of soil used for moisture calc))) 7/03/13

2009-2010

Field Notes Bonney

LOG: This file created on 1/18/10 by Zachary Sylvain.

Data entered by Zachary Sylvain.

Data checked by Zachary Sylvain.

Calculations by Zachary Sylvain using the formula: (# individuals / dry soil) * 1000

Samples collected at 12:00 (upslope, away from Lake Bonney)

2N taken from 11:00 due to rock at 12:00

3P taken closer to center but still at 12:00 (rock)

Samples taken by Zachary Sylvain and Byron Adams and plots treated by Zachary Sylvain and Byron Adams

Numbers per kg dry soil changed by M L Haddix using formula 1000*(#individuals/(extraction mass*(mass of dry soil/mass of soil used for moisture calc))) 7/18/13

Field Notes Fryxell

LOG: This file created on 01/08/10 by Bishwo Adhikari

Data entered by Bishwo Adhikari

Data checked by Zachary Sylvain.

Calculations by Zachary Sylvain using the formula: (# individuals / dry soil) * 1000

Soil samples collected on 01/05/10 by Dr. Becky Ball

Extraction done on 01/06/10

Plot treatment by Zach Sylvain, Bishwo Adhikari and Dr. Becky Ball

Solutions formed "slush" in caps when refilling carboys

Numbers per kg dry soil changed by M L Haddix using formula 1000*(#individuals/(extraction mass*(mass of dry soil/mass of soil used for moisture calc))) 7/18/13

Data sources: 

SOILS_SE_CHEM

Maintenance: 

Jan, 2010 - Sue Welch created this metadata and accompanying Oracle data table from metadata info and an Excel spreadsheet from Becky Ball . 2014, Data and metadata moved into DEIMS, Inigo San Gil.

Additional information: 

 Since the attribute table for this dataset is very large, the user must construct the actual column name.  The FIRST letter represents the species, and the following letters represent the life stage/sex/sum type.  The nermatode 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..."
       
     TREATMENT Codes
     
      In the attribute table, the treatment is the manipulation for a given plot from which the soil was collected. The treatments are: (C) carbon additions as mannitol, (N) nitrogen additions as NH4NO3, (P) phosphorus additions as Na3PO4, (CN) carbon and nitrogen additions, (CP) carbon and phosphorus additions, (W) water-only additions, and (U) un-amended plots.
    

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