cores

Developing an understanding of vegetation change and fluvial carbon fluxes in semi-arid environments: Soil moisture data

Abstract: 

Dryland environments are estimated to cover around 40% of the global land surface, and are home to approximately 2.4 billion people. Many of these areas have recently experienced extensive land degradation. This study focuses on semi-arid areas in the US Southwest, where degradation over the past 150 years has been characterized by the invasion of woody vegetation into areas previously dominated by grasslands. This vegetation change has been associated with increases in soil erosion and water quality problems, including the loss of key nutrients such as carbon from the soil to adjacent fluvial systems. Such loss of resources may impact heavily upon the amount of carbon that is lost as the land becomes more heavily degraded. 

Therefore, understanding these vegetation transitions is significant both for sustainable land use and global biogeochemical cycling. This study uses an ecohydrological approach to develop an understanding of the relationship between structure and function across these transitions. This is done via the monitoring of rainfall-runoff events across instrumented runoff plots with different vegetation characteristics to investigate fluvial sediment fluxes during intense summer monsoon season rainfall events.

Data set ID: 

252

Core Areas: 

Additional Project roles: 

49

Keywords: 

Methods: 

Experimental design:

Each study area consisted of a 10m wide, 30m long, downslope runoff plot, bound at the top and sides with aluminum flashing and fitted with water collecting guttering at the bottom so inputs and outputs could be quantified. The guttering fed water into a flume fixed into the ground at 4⁰ allowing water leaving the plot as runoff to be quantified.

The flumes were instrumented with a pump sampler to collect runoff samples leaving the plot and a bubbler module to measure discharge. In addition all runoff and associated sediment was collected in a covered stock tank (560 gallons for study area 1&2, 1000 gallons for study are 3). Rainfall onto the plot was measured using tipping-bucket rain gauges connected to the pump sampler. Following rainfall events all data was downloaded from the sampler using Flowlink v3.2 software.

Eroded sediment was collected from stock tank following rainfall events, coarse organic matter was removed via flotation, samples were oven dried at 60⁰C, weighed and sieved for particle size analysis using US. standard sieves at the Sevilleta LTER field station.

Setting up plots:

Plots were selected on comparable planar slopes in areas believed to be representative of endmember vegetation habitats.

Instrumentation: 

Instrument Name: Pump samplers fitted with bubbler modules

Manufacturer: ISCO

Model Number: Model 6700 pump samplers and attached model 730 bubbler modules

Instrument Name: Tipping-bucket rain gauges

Manufacturer: ISCO

Model Number: 674

Instrument Name: Flowlink software

Manufacturer: ISCO

Model Number: Version 3.2

Instrument Name: Sieve set and shaker

Manufacturer: unknown/various (from Sevilleta LTER field station)

Model Number: US. Standard: 12mm, 4mm, 2mm, 1mm, 0.5mm, 0.063mm

Additional information: 

This data was collected and analyzed by Alan Puttock as part of the PhD project: ‘Developing an understanding of vegetation change and fluvial carbon fluxes in semi-arid environments’. This project is supervised by Dr Richard Brazier, Dr Jenifer Dungait and Dr Kit Macleod. Analysis of samples/data is being carried out at the University of Exeter and North Wyke Research, United Kingdom.

This data was collected under USFWS permit number: 22522 10-026

 
Study Area 1:  
Study Area Name: Grass Endmember Plot
Study Area Location: Five Points Grass core site (exact point location of plot provided below)
Single Point:  
North Coordinate: 34.339186     
West Coordinate: -106.728303
Study Area 2:  
Study Area Name: Creosote Endmember plot
Study Area Location: Five Points Creosote core site (exact point location of plot provided below)
Single Point:  
North Coordinate: 34.338443
West Coordinate: -106.738020
Study Area 3:  
Study Area Name: Piñon-Juniper Endmember Plot
Study Area Location: Cerro Montoso core site (exact point location of plot provided below)
Single Point:  
North Coordinate: 34.231197
West Coordinate: -106.313741

Developing an Understanding of Vegetation Change and Fluvial Carbon Fluxes in Semi-Arid Environments at the Sevilleta National Wildlife Refuge, New Mexico: Characterization Data

Abstract: 

Dryland environments are estimated to cover around 40% of the global land surface, and are home to approximately 2.4 billion people. Many of these areas have recently experienced extensive land degradation. This study focuses on semi-arid areas in the US Southwest, where degradation over the past 150 years has been characterized by the invasion of woody vegetation into areas previously dominated by grasslands. This vegetation change has been associated with increases in soil erosion and water quality problems, including the loss of key nutrients such as carbon from the soil to adjacent fluvial systems. Such loss of resources may impact heavily upon the amount of carbon that is lost as the land becomes more heavily degraded.

Therefore, understanding these vegetation transitions is significant both for sustainable land use and global biogeochemical cycling. This study uses an ecohydrological approach to develop an understanding of the relationship between structure and function across these transitions. This is done via the monitoring of rainfall-runoff events across instrumented runoff plots with different vegetation characteristics to investigate fluvial sediment fluxes during intense summer monsoon season rainfall events.

Data set ID: 

251

Core Areas: 

Additional Project roles: 

48

Keywords: 

Methods: 

Experimental design: 

Each study area consisted of a 10m wide, 30m long, downslope runoff plot, bound at the top and sides with aluminum flashing and fitted with water collecting guttering at the bottom so inputs and outputs could be quantified. The guttering fed water into a flume fixed into the ground at 4⁰ allowing water leaving the plot as runoff to be quantified.

The flumes were instrumented with a pump sampler to collect runoff samples leaving the plot and a bubbler module to measure discharge. In addition all runoff and associated sediment was collected in a covered stock tank (560 gallons for study area 1&2, 1000 gallons for study are 3). Rainfall onto the plot was measured using tipping-bucket rain gauges connected to the pump sampler. Following rainfall events all data was downloaded from the sampler using Flowlink v3.2 software.

Eroded sediment was collected from stock tank following rainfall events, coarse organic matter was removed via flotation, samples were oven dried at 60⁰C, weighed and sieved for particle size analysis using US. standard sieves at the Sevilleta LTER field station.

Setting up plots: 

Plots were selected on comparable planar slopes in areas believed to be representative of endmember vegetation habitats.  

Instrumentation: 

Instrument Name: Pump samplers fitted with bubbler modules

Manufacturer: ISCO

Model Number: Model 6700 pump samplers and attached model 730 bubbler modules

Instrument Name: Tipping-bucket rain gauges

Manufacturer: ISCO

Model Number: 674

Instrument Name: Flowlink software

Manufacturer: ISCO

Model Number: Version 3.2

Instrument Name: Sieve set and shaker

Manufacturer: unknown/various (from Sevilleta LTER field station)

Model Number: US. Standard: 12mm, 4mm, 2mm, 1mm, 0.5mm, 0.063mm

Additional information: 

This data was collected and analyzed by Alan Puttock as part of the PhD project: ‘Developing an understanding of vegetation change and fluvial carbon fluxes in semi-arid environments’. This project is supervised by Dr Richard Brazier, Dr Jenifer Dungait and Dr Kit Macleod. Analysis of samples/data is being carried out at the University of Exeter and North Wyke Research, United Kingdom.

This data was collected under USFWS permit number: 22522 10-026


Study Area 1:  
Study Area Name: Grass Endmember Plot
Study Area Location: Five Points Grass core site (exact point location of plot provided below)
Single Point:  
North Coordinate: 34.339186     
West Coordinate: -106.728303
Study Area 2:  
Study Area Name: Creosote Endmember plot
Study Area Location: Five Points Creosote core site (exact point location of plot provided below)
Single Point:  
North Coordinate: 34.338443
West Coordinate: -106.738020
Study Area 3:  
Study Area Name: Piñon-Juniper Endmember Plot
Study Area Location: Cerro Montoso core site (exact point location of plot provided below)
Single Point:  
North Coordinate: 34.231197
West Coordinate: -106.313741

Developing an Understanding of Vegetation Change and Fluvial Carbon Fluxes in Semi-Arid Environments at the Sevilleta National Wildlife Refuge, New Mexico: Rainfall Runoff Events

Abstract: 

Dryland environments are estimated to cover around 40% of the global land surface, and are home to approximately 2.4 billion people. Many of these areas have recently experienced extensive land degradation. This study focuses on semi-arid areas in the US Southwest, where degradation over the past 150 years has been characterized by the invasion of woody vegetation into areas previously dominated by grasslands. This vegetation change has been associated with increases in soil erosion and water quality problems, including the loss of key nutrients such as carbon from the soil to adjacent fluvial systems. Such loss of resources may impact heavily upon the amount of carbon that is lost as the land becomes more heavily degraded.

Therefore, understanding these vegetation transitions is significant both for sustainable land use and global biogeochemical cycling. This study uses an ecohydrological approach to develop an understanding of the relationship between structure and function across these transitions. This is done via the monitoring of rainfall-runoff events across instrumented runoff plots with different vegetation characteristics to investigate fluvial sediment fluxes during intense summer monsoon season rainfall events.

Data set ID: 

247

Core Areas: 

Additional Project roles: 

47

Keywords: 

Methods: 

Experimental design: 

Each study area consisted of a 10m wide, 30m long, downslope runoff plot, bound at the top and sides with aluminum flashing and fitted with water collecting guttering at the bottom so inputs and outputs could be quantified. The guttering fed water into a flume fixed into the ground at 4⁰ allowing water leaving the plot as runoff to be quantified.

The flumes were instrumented with a pump sampler to collect runoff samples leaving the plot and a bubbler module to measure discharge. In addition all runoff and associated sediment was collected in a covered stock tank (560 gallons for study area 1&2, 1000 gallons for study are 3). Rainfall onto the plot was measured using tipping-bucket rain gauges connected to the pump sampler. Following rainfall events all data was downloaded from the sampler using Flowlink v3.2 software.

Eroded sediment was collected from stock tank following rainfall events, coarse organic matter was removed via flotation, samples were oven dried at 60⁰C, weighed and sieved for particle size analysis using US. standard sieves at the Sevilleta LTER field station.

Setting up plots: 

Plots were selected on comparable planar slopes in areas believed to be representative of endmember vegetation habitats.  

Instrumentation: 

Instrument Name: Pump samplers fitted with bubbler modules

Manufacturer: ISCO

Model Number: Model 6700 pump samplers and attached model 730 bubbler modules

Instrument Name: Tipping-bucket rain gauges

Manufacturer: ISCO

Model Number: 674

Instrument Name: Flowlink software

Manufacturer: ISCO

Model Number: Version 3.2

Instrument Name: Sieve set and shaker

Manufacturer: unknown/various (from Sevilleta LTER field station)

Model Number: US. Standard: 12mm, 4mm, 2mm, 1mm, 0.5mm, 0.063mm

Additional information: 

This data was collected and analyzed by Alan Puttock as part of the PhD project: ‘Developing an understanding of vegetation change and fluvial carbon fluxes in semi-arid environments’. This project is supervised by Dr Richard Brazier, Dr Jenifer Dungait and Dr Kit Macleod. Analysis of samples/data is being carried out at the University of Exeter and North Wyke Research, United Kingdom.

This data was collected under USFWS permit number: 22522 10-026

Study Area 1:  
Study Area Name: Grass Endmember Plot
Study Area Location: Five Points Grass core site (exact point location of plot provided below)
Single Point:  
North Coordinate: 34.339186     
West Coordinate: -106.728303
Study Area 2:  
Study Area Name: Creosote Endmember plot
Study Area Location: Five Points Creosote core site (exact point location of plot provided below)
Single Point:  
North Coordinate: 34.338443
West Coordinate: -106.738020 
Study Area 3:  
Study Area Name: Piñon-Juniper Endmember Plot
Study Area Location: Cerro Montoso core site (exact point location of plot provided below)
Single Point:  
North Coordinate: 34.231197
West Coordinate: -106.313741

Below-Ground Net Primary Production (BNPP): Root Ingrowth Donuts in Chihuahuan Desert Grassland and Creosote Shrubland at the Sevilleta National Wildlife Refuge, New Mexico (2005-present)

Abstract: 

In 2005, annually harvested root ingrowth donut structures were co-located with previously established mini-rhizotron tubes established at four sites on McKenzie Flats located on the east side of Sevilleta NWR: 10 replicate structures in both burned and unburned blue and black grama dominated grassland plots at Deep Well, 10 replicates each on nitrogen fertilization plots and respective control plots on McKenzie Flats(20 total), 10 replicates in creosote dominated shrubland at the Five Points Creosote Core site and in 2011, 13 structures were put in the Monsoon site. Roots and soil are harvested annually in late fall after the growing season, and structures are reestablished in situ for consecutive harvests each year. Each structure allows roots to be harvested at two depths (0-15 and 15-30 cm) to estimate root production, or below ground net primary productivity. In order to compare estimates of root production from two methods, root ingrowth donuts were collocated with mini-rhizotron tubes at all localities except for the burned grassland plot at Deep Well.

Core Areas: 

Data set ID: 

175

Additional Project roles: 

311
312
313
314
316

Keywords: 

Data sources: 

sev175_rootingrowth_20160127.txt

Methods: 

Experimental Design
Annually harvested root ingrowth donut structures are co-located with previously established mini-rhizotron tubes established at four sites on the McKenzie Flats on the east side of Sevilleta NWR: 10 replicate structures in both burned and unburned blue and black grama dominated grassland plots at Deep Well, 10 replicates each on nitrogen fertilization plots and respective control plots on McKenzie Flats (20 total), and 10 replicates in creosote dominated shrubland at the Five Points Creosote Core site. Methods were adapted from Milchunas et al (2005). We use a formidable 10 diameter soil core to create cylindrical holes in the ground to a depth of 30cm without disturbing soil profile at the cylinder walls. The soil core was inserted with a slide hammer and had to be removed each time with a come-along mounted on a steel-pipe tripod. Walls were subsequently lined with plastic cross-stitch craft work canvas (macram mesh) which supports cylinder walls through time but allows roots to pass through. Two pieces of 6 diameter PVC were placed in the center of the larger cylindrical hole, set in place with bags filled with sand that act as ballasts. The two pieces of PVC were beveled on opposite ends to fit together and prevent movement of the donut center. The top cylinder went to a depth of 15 cm and the bottom piece went to a depth of 30 cm, representing 0-15 and 15-30 cm in the soil profile when stacked upon one another. Finally, sifted soil from the location was used to fill the space between the plastic canvas lining the hole wall and the PVC pipe placed in the center. It is this soil which is harvested annually at two depths. A PVC cap was placed on top of the PVC to eliminate water infiltration from rain through the donut center and to keep sunlight from disintegrating the sand bag ballast. All root ingrowth donuts were GPSed.

Sample Harvest
Root donuts are harvested annually in November after the growing season. Roots are harvested by first removing the sand bags from the top cylinder and placing a bowl into the center of the cylinder. The top cylinder is then removed. Soil and roots are cut away from the cylinder wall and collected. This harvest procedure is then repeated for the lower half of the donut structure. Soil and roots collected are placed in a separate plastic bag for each depth. Once the soil and roots are harvested, the root ingrowth structure is rebuilt. After harvest, soil and root samples are stored in a chest freezer until they can be processed.

Sample Processing
The total volume of soil from each sample is measured and recorded. Soils are filtered through a series of sieves in which to harvest the roots present in the sample. The roots are then repeatedly rinsed to remove all the soil from the sample, dried at 60 degrees C, and then weighed.

Maintenance: 

23 Jan 2009All data sets (2005-2008) were combined and checked for errors in excel and exported into Navicat. From the 2007 data, I converted the dry root mass from grams to milligrams and changed depth data to be 0-15 and 15-30 cm. QA/QC'd data. I deleted data line from DWB sample 7, depth 15-30 cm with volume 2600 ml because it was a duplicate. I also changed the depth of DWB sample 12, depth 15-30 cm with volume 2000 to the depth 0-15 cm because the depth 15-30 cm was duplicated. -Changed missing data on volume and weight due to plant being dead to -888. -Changed missing data on volume and weight due to human error to -999. --A. Swann

Quality Assurance: 

Filtered data in Excel then exported it into Navicat using the import wizard.

Additional information: 

Additional Information on the personnel associated with the Data Collection / Data Processing

Sevilleta Field Crew Employee History

Chandra Tucker April 2014-present, Megan McClung, April 2013-present, Stephanie Baker, October 2010-Present, John Mulhouse, August 2009-June 2013, Amaris Swann, August 25, 2008-January 2013, Maya Kapoor, August 9, 2003-January 21, 2005 and April 2010-March 2011, Terri Koontz, February 2000-August 2003 and August 2006-August 2010, Yang Xia, January 31, 2005-April 2009, Karen Wetherill, February 7, 2000-August 2009, Michell Thomey, September 3, 2005-August 2008, Jay McLeod, January 2006-August 2006, Charity Hall, January 31, 2005-January 3, 2006, Tessa Edelen, August 15, 2004-August 15, 2005, Seth Munson, September 9, 2002-June 2004, Caleb Hickman, September 9, 2002-November 15, 2004, Heather Simpson, August 2000-August 2002, Chris Roberts, September 2001-August 2002, Mike Friggens, 1999-September 2001, Shana Penington, February 2000-August 2000.

Long-term Dynamics in Soil Field Available Nitrogen and Potentially Mineralizable Nitrogen in a Chihuahuan Desert Grassland at the Sevilleta National Wildlife Refuge, New Mexico (1989-2014)

Abstract: 

Associated with a project that was based upon the assumption that nitrogen may limit net primary plant production in desert grasslands, this project began measuring available inorganic soil N and potentially mineralizable N of soils at two desert grassland locations. Both available N and potentially mineralizable N were greatest following a drought period in 1989, declined during wetter periods that followed and remained relatively stable until another extended drought period. After drought in 1995-6, both forms of soil N increased, indicating the potential for greater NPP following drought and lower potential NPP during periods of normal precipitation.

Data set ID: 

134

Core Areas: 

Keywords: 

Purpose: 

This project began as part of a study to identify the interactions between soil inorganic nitrogen supply and El Nino-La Nina oscillations that bring wetter-than-average or drier-than-average (respectively) winter-spring precipitation to the central New Mexico region (El Nino-La Nina Fertilization Experiment). This project was known locally as "The Fertilizer Study" and was initiated by Dr. Sandra Turner. To test whether soil inorganic N was limiting aboveground net primary production, fertilizer was added to designated plots within a block of study plots. At first, the soil sampling was designed to confirm or establish the actual fertilizer contribution to each site. The amount added was the amount of inorganic N in soils from the fertilized plots minus that in the control plots. The amount in the controls plots was interpreted as being the amount of inorganic N that had not been utilized by the plant/microbial community and was "available" at that time for utilization in the future. Potentially mineralizable N measurements were performed to determine how the amount of readily mineralizable N was changed by the fertilizer addition; termed a priming effect when the addition of inorganic N results in even greater increases in mineralizable N. Early results from this study were reported at the 1990 Ecological Society of America annual meetings (White et al. 1990).

Following the first year's work, measurements of soil available N and potentially mineralizable N were continued. Except in 1990 when a computer hard-drive that contained most of that year's soil N data crashed and the data were not able to be recovered, the period from 1989 until the spring- summer of 1999 was covered by at least one collection per year.

Data sources: 

sev134_nmin_20150610.csv

Methods: 

Each 30m by 30m plot was given a number at the beginning of the study. Before each year's fertilizer application or collection, plots were chosen by selection of random numbers from a table or by using a phone book and using the last 2 digits of the phone numbers. Plots that were used in prior years were excluded from future use. The outer 2.5 m of each plot were left as a buffer strip, so the inside 25m by 25m plot constituted the actual sampling unit.

It is not known if the fertilizer was applied to the 30 x 30 m plot or only to the 25 x 25 m plot excluding the buffer. Thus, values given below are based upon application to the 30 x 30 m plot and should be used cautiously.

1989 Protocols

In 1989, fertilizer treatments were applied as NH4NO3 in 2 treatment levels with controls (low, high, and no fertilizer). Three plots received 61.8 kg N/ha, three plots received 30.9 kg N/ha, and 3 plots were not fertilized (controls). All of these plots were selected in a random manner. It turned out that plot 7 on the west side was too disturbed to be used, so plot 51 was substituted. On the east side, plot 66 was mistakenly fertilized instead of plot 56, which had been selected, so that plot 66 became the 3rd heavily fertilized plot. Hence the plots used in their respective treatments were as follows:

Treatments   East side    West side

----------       ----------    ----------

Control        16, 33, 42    16, 33, 42

Low               7, 10, 25    19, 25, 51

High              1, 26, 66     1, 26, 56

The fertilizer was applied in April on the east and west sides. Fertilizer was applied with a cyclone spreader by a person walking 5 equally spaced paths across each plot while cranking the spreader. The light treatment was applied with passes in only one direction, while passes were made in both directions across the plot for the heavy treatments.

Soil samples were collected on April 18, 1989, to verify the nitrogen additions and to measure net N mineralization and nitrification potentials. Soil cores (4.2 mm in diameter) were taken to a depth of 20 cm at 4 m intervals along a diagonal from the NE to the SW corner of the plot (starting at the edge of the 2.5 m buffer zone). These cores (15 in all) were placed in the same bag and comprised one sample. The 3 plots represented the sample units (n=3). Plot 66 was not collected until July 4th, when the mistake was identified because plot 56 had no elevated levels of nitrate or ammonium.

1990 Protocols

In 1990, it was decided that the number of treatment levels would be reduced to one fertilizer application rate and that the number of replicate treatment plots be increased to 4. Fertilizer was applied in two applications, instead of the single application in 1989, in attempts to reduce "burning" from the fertilizer. The first application was on March 1, 1990, and the second was April 4, 1990. Over an inch of rain occurred on both the east and west sides between applications. For each application, fertilizer was applied with a cyclone spreader by a person walking 3 evenly spaced passes across each plot in one direction, and then repeating the process in the perpendicular direction. The setting on the cyclone spreader was 3 1/4. The plots used were:

Treatments     East side          West side

----------      --------------      --------------

Control          24, 34, 43, 48    24, 34, 43, 48

High               3, 22, 30, 60     3, 22, 30, 60

Within each 30m by 30m plot, 3 ea. half-meter-square (1/2 or 0.5 m^2) quadrats were randomly selected for soil sampling within the northwest quarter of the plot (the 12.5 m by 12.5 m portion excluding the 2.5 m buffer). To identify the location of the 0.5 m^2 quadrats, two tape measures were run parallel to each other, one along the top of the plot and the second along the mid-line of the NW quarter. A third tape was run between the two tapes on the edges to locate the long side of the randomly selected 0.5 m^2 quadrats. Along each diagonal, 4 soil cores were taken at equal spacing starting with the corner of the quadrat and ending in the diagonal corner. Soil cores (4.2 mm diameter) were taken to a depth of 20 cm. The 4 cores from the quadrat were placed in the same bag and comprised one sample. Thus, each plot had 3 soil samples, one from each quadrat, with each treatment having 4 plots.

Protocols for 1991 through 1994

Starting in 1991 and continuing through 1994, 4 plots were sampled with 3 quadrats in each plot; however, only three soil cores were collected (2 from the opposing corners and one from the middle of the quadrat) per quadrat. As in the other years (except 1989 where only one sample was taken per plot), soils from each quadrat were analyzed separately and later averaged to get the value for the plot (3 replicate soil analyses, one per quadrat, and these values were averaged to get a plot value for each of 4 plots; n=4).

Protocols for 1995 to present: Soil Bridges and associated soil collections

In 1995, 5 soil bridges were installed about 30 m east of the Fertilizer Plots. The primary function of the soil bridge is to measure small changes in soil microtopography; erosion or deposition. At the time of soil bridge measurements, two soil cores (same dimensions, 4.2 mm diameter to a depth of 20 cm) for initial available N and potentially mineralizable N were collected from vegetated (mostly grass, 2 cores each) and unvegetated (2 cores each) areas that appeared comparable to those areas beneath the soil bridge. The two sample-types (under plants or open soils) were analyzed separately and the "average" for the bridge was determined by weighting the soil- types by their respective coverages determined beneath the bridge. For example, if vegetation cover was 35% (0.35 of area beneath the bridge had vegetation) and bare soil 65%, the N values for the soil beneath the vegetation were multiplied by 0.35 and summed with the N values for the bare soils multiplied by 0.65. This procedure gave 5 average values for soil N at each collection.+

In the summer of 1998, a study was performed to make direct comparison of the two different collection techniques (collection of soils from fertilizer plots or soils associated with the bridges) and the potential differences the collection method could have on soil nitrogen mineralization potentials.

Methods used for comparative study

Collection on fertilizer plots (fp): Four plots were randomly selected as per previous methods; 4 each 30 X 30 m plots within a 300 X 300 m study site. Within each plot, three randomly selected 0.5 m^2 quadrats within the 15 X 15 m NW quarter of the plot were selected. Within each 0.5 m^2 quadrat, a soil core (4 cm diameter by 20 cm long) was taken from the NW and SE corners of the plot. Both cores were composited to make one sample from each quadrat. This sampling method gave 3 soil samples for each of four plots, for a total of 12 samples.

Collection from the bridge sites: The 5 bridges were equally spaced along the 300 m east border of the fp study area. At each bridge, 2 soil sample cores (4 cm diameter by 20 cm long) were taken from under vegetation cover (under) and 2 from non-vegetative soil surfaces (open). The two cores were composited to give a single soil sample from under and open at each bridge.

Analyses of N mineralization potentials: After determining the water holding capacity (WHC; White and McDonnell 1988), a portion of each sample was adjusted to 50% of determined WHC and 5 subsamples were apportioned into plastic cups. Each cup contained approximately 30 g (+/- 0.05 g) dry-weight mineral soil. One subsample of each sample was immediately extracted with 100 ml 2 N KCl for NH4+-N and NO3--N analyses. The remainder of the cups were covered with plastic wrap, sealed with a rubber band and incubated in the dark at 20 degrees C. Moisture content was monitored by mass loss and replenished as needed. At days 14, 28, 35, and 42, one subsample of each sample was removed and extracted with KCl for 18 - 24 hours. The clarified KCl was filtered through a Kimwipe and analyzed on a Technicon AutoAnalyzer. 

Statistical Analysis

Fp: Extractable N at each time interval was averaged for the three soil samples from the 0.5 m^2 quadrats per plot to yield a mean value for each plot. The mean values then were used for statistical analysis (n=4).

Bridges: The relative cover for under and open was obtained from the most recent bridge measurements (made within 2 weeks of soil collections). Extractable N in each soil sample was multiplied by the respective relative cover, and N conc.-times -cover values for soils collected at each bridge were summed to give a cover-weighted value for each bridge (n=5).

The extractable N values for the four fp's were compared to the five bridges over the entire extraction period to determine differences between collection techniques (Factor 1), the effect of extraction time (Factor 2), and their interaction (Factor 1 X 2) at each time interval by analysis of variance. In addition, the variance associated with each collection method was determined and analyzed by analysis of variance to determine if the techniques significantly affected the variance associated with each technique.

Results

The two collection techniques were not significantly different for N mineralization (P = 0.47). There was no significant incubation time x collection technique interaction (P = 0.87). The bridge method did increase variance slightly, but not significantly (P = 0.114).

Net N Mineralization Potentials by different Collection Techniques:

Factor              d.f.      S.S.       M.S.   F-test    P-value
------               ----     ----        ----    ------     -------

Collection          1       0.316   0.316   0.531     0.47
Technique

Extraction/         4        330     87.5      147       0.001
Incubation time

Coll. X time       4       0.719    0.18    0.302     0.87

error                35      70.8     0.596


Net N. Mineralization Potentials for Soil Collected by Different Techniques (sum ammonium and nitrate; mg N / kg soil).

Incubation       Bridge Collections        Fertilizer Plots Collections
Time (days)     Mean       S.E.                 Mean            S.E.
-----------         ------------------             ----------------------------

   0                 1.96       0.43                  2.02            0.24
   14               5.55       0.804                 5.28            0.45
   28               7.33       0.77                   7.6             0.17
   35               8.29       0.74                   8.62           0.63
   43               9.59       1.34                  10.04           1.12


Soil Collection Methods

All soil samples were taken with a 4.2 mm diameter soil corer to a depth of 20 cm and placed into an ice chest and transported on ice to the University of New Mexico, where they were sieved (2 mm), obvious live roots removed, and stored at 5 degrees C.

Soil Analysis Methods

Soil Moisture and Organic Matter

For each collection, soil moisture content of each fresh sample was determined by mass loss upon heating at 105 degrees C for 24 hours. Organic matter was determined by loss-upon-ignition from oven-dried samples placed in a muffle furnace and brought to 500 degrees C for 2 hours.

Soil Texture and Total N and P.

At select times, texture (percent of sand, silt, and clay) was determined by the hydrometer method (Day, 1965). Total nitrogen and phosphorus were determined by Kjeldahl digestion with copper sulfate as catalyst (Schuman et al. 1973) followed by analysis of ammonium by an automated phenolate method (Technicon AutoAnalyzer Industrial Method #19-69W) and orthophosphate by an ascorbic acid method (Technicon AutoAnalyzer Industrial Method #94-70W).

Water-holding capacity

Water-holding capacity (WHC) was determine by saturating about a 50 g portion of the sieved soil contained in a funnel with DI water, allowing to saturate for 30 min., and then to drain by gravity for 30 min. The drained soil was transferred to pre-weighed soil tins and dried in an oven at 105 degrees C for 24 hours. The water lost upon drying was the water-holding capacity of the soil sample.

Field available N and N mineralization/nitrification potentials

After determining water-holding capacity (WHC), a portion of each sample was adjusted to 500f determined WHC and subsamples were apportioned into plastic cups. Each cup contained approximately 30 g dry-weight mineral soil. One subsample of each sample was immediately extracted with 100 ml 2 N KCl (with 5 ppm phenyl mercuric acetate as a preservative) for NH4+-N and NO3--N analyses. The remainder of the cups were covered with plastic wrap, sealed with a rubber band, and incubated in the dark at 20 degrees C. The plastic wrap minimized water loss during incubation, yet exchange of CO2 and O2 was sufficient to keep the subsamples aerobic during incubation. Moisture content was monitored by mass loss and replenished as needed. At approximately weekly intervals, one subsample of each sample was removed, 100 ml KCl was added and shaken with the plastic wrap coveringthe top, and allowed to settle for 18-24 h. The clarified KCl was filtered through a Kimwipe and analyzed for NH4+-N and NO3--N+NO2--N on a Technicon AutoAnalyzer (Technicon, Terrytown, NY) as described in White (1986).

This procedure gave up to three different measurements for inorganic ammonium and nitrate:

The initial extractions (time 0, wetted but not incubated) indicated field available concentrations (their sum gave total field available N);

The amount of ammonium and nitrate extracted after 35-day
incubation; and

The maximum sum of ammonium and nitrate in any extraction up to the 35-day incubation (some samples peaked prior to day 35).


Maintenance: 

File assembled 1/19/2001 JAC. File updated with data through 2005, 10/25/2005 Carl White.

File updated with data through 2008, 5/20/2009 Carl White.

Additional information: 

Additional Information on the Data Collection Period

Data collected four times per year (usually January, April, July and October). Sampled one week per season, four seasons per year.


Site Description

The fertilizer study was initiated at two locations on the Sevilleta NWR; one on the east side and one on the west side of the refuge. The east side study site was located within a 300m by 300m block on MacKenzie Flats. The vegetation was dominated by black grama and was thought to be a "typical" black grama desert-grassland. Within that area were 100 ea. 30m by 30m plots (10 plots along the side). The outer 2.5 m of the plot were left as a buffer strip, so the inside 25m by 25m plot constituted the actual sampling unit. When the fertilizer study was no longer active, the plots were sampled to continue the long-term soil record. In 1995, 5 locations along the east 300 m border of the fertilizer study area were established for future soil monitoring. Each of these new sites had soil erosion bridges installed to measure changes in soil microtopography (erosion/deposition). In the methods section are the results of a study that verified that sampling at the 5 new locations gave results comparable to those from the 4 random plots within the fertilizer study area. In 2003, the 5 new locations of 1995 were burned by prescribed fire on 19 June 2003. Additional bridge and soil sites were established within the original fertilizer study area (established in control or untreated plots) and sampled before the prescribed fire to establish similarities to continue the control or untreated soil collections at that area. These new bridge sites are numbered 7196, 7197, 7198, 7199, and 7200.

The original study also had a grassland site on the west side of the Sevilleta NWR. This site was west of the Field Station, accessed by entrance at the north gate near Bernardo and following the roadbed of the old highway alignment. This site was dominated by C-3 grasses with C-4 grasses a minor component. Shrubs were primarily 4-wing saltbush. The west side only had room for 61 each 30m by 30m plots. When the fertilizer study was ceased, no further soil collections were made on the west side for long-term study.

Method References

Day, Paul R. 1965. Particle Fractionation and Particle-size Analysis. IN: C.A. Black (ed). Methods of Soil Analysis. Part 1. American Society of Agronomy, Inc., Madison, USA.

Schuman, G.E., Stanley, M.A., and Knudsen, D. 1973. Automated total nitrogen analysis of soil and plant samples. Soil Sci. Soc. Am. Proc. 37:480-481.

Soil Characteristics Following a Lightning-Initiated Fire at MacKenzie Flats, Sevilleta National Wildlife Refuge, New Mexico (1998)

Abstract: 

We evaluated soil characteristics after a lightning-initiated fire. Following the fire in July 1998, 25 experimental plots were established on the eastern edge of MacKenzie Flats at the Sevilleta National Wildlife Refuge. Ten of these plots were located in a Bouteloua gracilis (blue grama)-dominated site, while 15 were established in another area dominated by Bouteloua eriopoda (black grama). All plots were oriented along a topographic gradient that ran in an east-west direction. At three topographic locations within each plot, soil samples were taken at two depths from an area covered by perennial grass as well as an area devoid of vegetation. Soil samples were collected in July 1998 and analyzed for moisture content and soil texture.

Data set ID: 

170

Additional Project roles: 

236
237
238
239
240
241
242
244
245
246

Core Areas: 

Keywords: 

Methods: 

Experimental Design - Following a lightning-initiated fire in July 1998, 25 experimental plots were established on the eastern edge of the MacKenzie Flats area of the Sevilleta National Wildlife Refuge. Ten of these plots were located in a Bouteloua gracilis (blue grama)-dominated site, while 15 were established in another study area, where B. eriopoda (black grama) was more abundant. In the former site, five of the 10 plots were established in burned areas, and the others were positioned in unburned grassland vegetation. In the latter study area, five plots were placed in burned areas, five were positioned in unburned grasslands, and the five remaining plots were located in an area that contained a mix of burned and unburned patches of grassland vegetation.

Sampling Design - All of the plots in the Bouteloua gracilis-dominated site were 4 m x 16 m in dimension. Of the 25 plots where B. eriopoda was more abundant, nine were 4 m x 16 m, and 16 were 4 m x 25 m. Regardless of site, all plots were oriented such that the long axis of each was parallel to a topographic gradient that ran in an east-west direction.

We established three 1.5 m x 1.5 m quadrats at the two corners and midpoint along the south side of each plot. Each quadrat was divided into four square cells of equal area. Within a southeastern cell (northeastern cell if a shrub was present in a southeastern cell), we selected three grass clumps and three interspace areas between plants. At the center of each plant and interspace, one sample was removed at each of two depths (0 - 2.5 cm and 2.5 - 10cm). The three "grass" samples at each depth were pooled to create one composite sample; similarly, the three interspace samples at each depth were also pooled into one sample (4 composite samples in total).

Field Methods - For the 0 - 2.5 cm samples, a 2.5-cm corer (6.7 cm diameter) was driven into the ground with a mallet. Over grass clumps, the corer was inserted such that the average original soil surface was flush with the top of the corer, generally at about one-half the height of the tussock. A sharpened trowel was hammered beneath the corer to cut the roots, and the core was removed. Any soil which fell onto the new surface was scraped away.

For the 2.5 - 10 cm samples, a 25-cm corer (4.5 cm diameter) was driven to a depth of 7.5 cm below the surface created by the previous sample. The corer was then twisted and gently pulled up. The average point of break for any individual core was estimated to be within 1 - 2 mm for at least 90% of the cores.  The soil was resampled if this error exceeded 3 mm.

Samples were placed into pre-labeled paper lunch bags and transferred to a cooler (without ice). They were transported to a drying shed with ambient temperature and humidity and placed on shelves within 36 hours.

Laboratory Procedures - Soil moisture was determined by the gravimetric method (Gardner 1986). Soil texture was determined by the hydrometer method (Sheldrick and Wang 1993).

Gardner, W. H. 1986. Water content. Pages 493-544 in A. Kluite (editor), Methods of soil analysis, Part 1. Physical and minerological methods, agronomy monograph no. 9, 2nd edition. American Society of Agronomy and Soil Science Society of America, Madison, WI.

Sheldrick, B.H. and C. Wang. 1993. Particle size distribution. Pages 499-557 in M.R. Carter (editor), Soil sampling and methods of analysis. Canadian Society of Soil Science, Lewis Publishers, Ann Arbor, MI.

Data sources: 

sev170_bootleg_soils_20140121.txt
Subscribe to RSS - cores