organic matter

Small Mammal Exclosure Study (SMES) Leaf Litter Study in the Chihuahuan Desert Grassland and Shrubland at the Sevilleta National Wildlife Refuge, New Mexico

Abstract: 

The purpose of this study is to determine whether or not the activities of small mammals regulate plant community structure, plant species diversity, and spatial vegetation patterns in Chihuahuan Desert shrublands and grasslands. What role if any do indigenous small mammal consumers have in maintaining desertified landscapes in the Chihuahuan Desert? Additionally, how do the effects of small mammals interact with changing climate to affect vegetation patterns over time?

This is data for cover of dead plant leaf litter accumulations on soil surfaces measured on each of the SMES study plots. Leaf litter cover was measured from each of the 36 one-meter2 quadrats twice each year when vegetation was measured.

Core Areas: 

Data set ID: 

96

Additional Project roles: 

122
124

Keywords: 

Data sources: 

sev096_smeslitter_20160308.csv

Methods: 

Experimental Design:

There are 2 study sites, the Five Points grassland site, and the Rio Salado creosotebush site. Each study site is 1 km by 0.5 km in area. Three rodent trapping webs and four replicate experimental blocks of plots are randomly located at each study site to measure vegetation responses to the exclusion of small mammals. Each block of plots is 96 meters on each side. Each block of plots consists of 4 experimental study plots, each occupying 1/4 of each block. The blocks of study plots are all oriented on a site in a X/Y coordinate system, with the top to the north. Treatments within each block include one unfenced control plot (Treatment: C), one plot fenced with hardware cloth and poultry wire to exclude rodents and rabbits (Treatment: R), and one plot fenced only with poultry wire to exclude rabbits (Treatment: L). The three treatments were randomly assigned to each of the four possible plots in each block independently, and their arrangements differ from block to block. Each of the three plots in a replicate block are separated by 20 meters.

Each experimental measurement plot measures 36 meters by 36 meters. A grid of 36 sampling points are positioned at 5.8-meter intervals on a systematically located 6 by 6 point grid within each plot. A permanent one-meter by one-meter vegetation measurement quadrat is located at each of the 36 points. The 36 quadrats are numbered 1-36, starting with number 1 in the top left corner (north-west) of each plot (top being north), and running left (west) to right (east), then down (south) one row, and then right (east) to left (west), and so on Quadrat/rebar number one is in the northwest corner of each plot, and numbers 1-6 are across the north side of the plot west to east, then quadrat/rebar number 7 is just south of quadrat/rebar number 6, and rebar numbers increase 7-12 east to west, and so on. 3-inch nails were originally placed in the top left(north-west) corner of each quadrat. These may be difficult to see. A 3-meter wide buffer area is situated between the grid of 36 points and the perimeter of each plot.

While measuring vegetation on each quad, the total amount of leaf litter cover on the soil surface that was seen on each quadrat was measured. "Leaf litter cover(n)" for the cover of leaf litter on the soil surface of the quadrat was stated in terms of the 10 cm squares. For cover values less than 5, increments of 1.0 were used. For cover values greater than 5, increments of 5.0 were used. Leaf litter included all detached dead plant material on the soil surface, including woody branches. Only leaf litter cover that is in the open was measured, not within clumps of grass, etc. Some leaf litter cover had distinctive margins and was easy to define and measure. However, much leaf litter consisted of many diffuse small patches that are separated by bare soil, and distributed throughout the quadrat. For such diffuse cover, the actual cover in one typical 10 by 10 cm square (e.g., 0.3) was determined, the number of squares with diffuse cover (e.g., 5) was counted, then the number of squares was multiplied by the actual cover for a typical square (e.g., 0.3 X 5 = 1.5, then round to 1.0 or 2.0, or if the value had been greater than 5, round to the nearest increment of 5.0) for the total litter cover. All litter cover was pooled into one observation, and no height was measured.

Maintenance: 

SEVILLETA SMES LEAF LITTER DATA 1998 log Updat03/09/06 Status DONE 01/31/06 - Checked data for missing data points, doubles, and errors. Missing data points were recorded using -999 (Human Error) or -888 (-888), duplicates of data points were removed, and errors were corrected. If a data point contained a measurement and a measurement with a count, the zero observation was removed. - Removed Species, and Per fields. Tape field was changed to ID# and observations made in the Per field were moved to the new ID# field. No observations were made in the tape field. EC field was added and NA was recorded in this field for this year. Date MM/DD/YY field was changed to just DATE. Other changes in the fields include PLT to PLOT, BLK to BLOCK, and SPECICOV to COVER. - Any empty cells were filled in with -999 (or -888) for missing data or an NA for not applicable. - Yang Xia 02/24/06 - Checked data for missing data points, doubles, and errors. Missing data points were recorded using -999 (Human Error) or -888 (-888), duplicates of data points were removed, and errors were corrected. If a data point contained a measurement and a measurement with a count, the zero observation was removed. - Removed Species, Comments, and Per fields. Tape field was changed to ID# and observations made in the Per field were moved to the new ID# field. No observations were made in the tape field. EC field was added and NA was recorded in this field for this year. Date MM/DD/YY field was changed to just DATE. Other changes in the fields include PLT to PLOT, BLK to BLOCK, and SPECIcOV to COver. - In the spring, Missing all Plots for Block 1 at the Grassland site. There are missing data in Site G Block 2 Plot 3 Treatment C, Site G Block 3 Plot 3 Treatment R, and Site G Block 4 Plot 2 Treatment C. - For the fall, All plots are presented, but with several data points missing. - Any empty cells were filled in with -999 (or -888) for missing data or an NA for not applicable. - Yang Xia 03/03/06 - Changed data to fit parameters. For example if a measurement was 6 it was rounded to the closest appropriate value, which in this case is 5. See 'Variable Descriptions' Variable 7. Also, if a measurement was less than 0.5 it was rounded to 1 to indicate that an occurence was present. - Yang Xia 03/06/06 - Quads 21-24 were originally classified as Trt C in the spring at the Grass site for Blk 4 Plt 3, Changed to Trt L. - Quads 10-17 were originally classified as TRT C in the spring at the Creosote Site for BLOCK 2 PLOT 2, changed the TRT to TRT L. - Quads 11-14 were originally classified as TRT C in the spring at the Creosote Site for BLOCK 3 PLOT 4, changed TRT to TRT L. 03/08/06 - Modified metadata to correct format. - Yang Xia 03/09/06 - changed EC variable data to "1" with the comments, and "0" for no comments. NA for not applicable. 03/09/06 - changed start date from september 1995 to May 1995 in the research Hypotheses, since the data collection was starting on 05/02/95. doc

Additional information: 

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

Sevilleta Field Crew Employee History

Megan McClung, April 2013-present, Stephanie Baker, October 2010-Present, John Mulhouse, August 2009-Present, 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.

Livestock Exclosure Nutrient Study from a Chihuahuan Desert Grassland at the Sevilleta National Wildlife Refuge, New Mexico (2003)

Abstract: 

Data on soil characteristics and dominant grass and soil chemical composition gathered on active rangeland, livestock exclosures on active rangeland, and the Sevilleta NWR.

Data set ID: 

159

Core Areas: 

Keywords: 

Data sources: 

sev159_exclosnutrient_09212005.txt

Methods: 

Experimental Design

This study compares grazed grassland (treatment G), grassland within livestock exclosures (treatment X) and undisturbed (by livestock) grassland (treatment S - for Sevilleta). During the winter of 1992/1993, three 300m x 300m plots were delineated for each of these three treatments. Plots are referred to as G1, G2, G3, X1, X2, X3, S1, S2, and S3 (number increasing from west to east). Each of these nine plots are separated by at least 300 m. Exclosure plots are surrounded by wire fencing, and the Sevilleta plots are located within the NWR boundary. A rodent trapping web is centered within each plot. Within the framework of this mammal trapping web, twelve 3x4 m quadrats were randomly placed. Corners of plots are marked by aluminum fence posts and locations were recorded with GPS. Centers and lines of mammal trapping webs are marked by 1m high (centers and end of lines) and .25m high (lines) rebar and aluminum numbered tags. Corners of quadrats are marked by short rebar. The location of mammal trapping webs and quadrats is the same within each plot.

For this particular study a subsample of four quadrats, chosen randomly for each plot, within each plot was sampled. Data collected include soil texture, field water content, 50% water holding capacity, organic matter content, percent C, percent N, percent P, and dominant grass (usually Bouteloua eriopoda) percent C, percent N, and percent P. Soil samples were collected as cores to 10cm depth, with 5-10 cores taken along a diagonal from one corner of the quadrat to the other corner, then pooled in a plastic bag as one sample from each quadrat. Grass samples of green above-ground tissue (growth from summer/fall 03) include tissue from 5-10 individual plants within the quadrat. All analyses were conducted for each quadrat excepting soil texture, for which equal weights of soil from each quadrat were pooled into one sample per plot. Soil samples were collected on 8/10/03 and plant samples were collected on 10/18/03, before and after the most significant rains of the season.

Soil texture was analyzed using the hydrometer method, and data are recorded as sand, silt, and clay. Soil field water content was measured as the difference in weight before and after the drying of a subsample of soil. Soil organic matter was measured as the difference in weight before and after combustion of a subsample of dry soil. Soil 50% water holding capacity was measured using standard Sevilleta techniques (after White). Soil and plant percent C and N were measured using a Carlo Erba AutoAnalyzer. Soil and plant percent P was measured as extractable P, converted to PO4-P, using a Technicon AutoAnalyzer.

Additional information: 

Additional field crew member: Ben Zimmerman

Additional Study Area Information

Study Area Name: Pino Gate

Study Area Location: The study site was located near the base of the Los Pinos mountains and directly adjacent to the nothern fencline of the SNWR at Pino Gate

Elevation: 1600 m

Vegetation: Burrograss (Scleropogon brevifolius), sand dropseed (Sporobolus ryptandrus), and black grama (Bouteloua eriopoda) were the dominant vegetation.

Soils: Deep clayey loam soils

Geology: On an upper bajada slope, in a broad swale

Climate: Long-term mean annual precipitation is 243 mm, about 60% of which occurs during the summer. Long-term mean monthly temperatures for January and July are 1.5°C and 25.1°C, respectively.

Site history: Historically, prairie dogs were common throughout the area, but were exterminated by the early 1970’s (John Ford, United States Department of Agriculture Wildlife Services, personal communication). Gunnison’s prairie dogs began to re-colonize the study site from adjacent private land in 1998. During our study, the colony occurred within a 5 ha area, near the base of the Los Piños Mountains in an area with deep clayey loam soils. The site has been long inhabited by kangaroo rats, and represents typical northern Chihuahuan Desert grassland.

North Coordinate:34.406954
South Coordinate:34.406954
East Coordinate:-106.606269
West Coordinate:-106.606269

Additional Metadata

Animal grazers affect grassland disturbance patterns via changes in plant community composition and structure, nutrient cycling, and soil structure. Human-managed livestock grazing is a significant grassland disturbance worldwide.

Research Questions/Hypotheses:

a. Is livestock grazing related to changes in arid grassland soil structure and chemical composition or plant nutrient composition? If so, how?

(hypothesis) Grazed rangeland will have more compact soil (lower water holding capacity), lower levels of nutrients (C, N, P) and lower organic matter content than grassland unaffected by livestock grazing. Grazed rangeland will produce grasses of lower nutritional quality (i.e. higher C:N and C:P ratios) than grassland unaffected by livestock grazing.

b. When livestock are exclosed from a rangeland, does soil structure and chemical composition or plant nutrient composition `recover', exhibit resilience, align more closely with values characteristic of grassland unaffected by livestock grazing?

(hypothesis) Within livestock exclosures (free of livestock for 9 years) soil water holding capacity will be higher, levels of nutrients (C, N, P) and organic matter content will be higher, and plant nutritional quality will be higher (C:N and C:P ratios will be lower) than on grazed rangeland. These structural and chemical characteristics will be intermediate between those of grazed rangeland and grassland unaffected by livestock grazing.

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