Grazing in grasslands creates changes in plant community structure. The magnitude of these changes depends on the productivity and the intensity of grazing. Low productivity grasslands coupled with high grazing intensity may lead to shrub encroachment in some aridland ecosystems. We examined the effects of cattle grazing in arid grassland at the Sevilleta LTER site in central New Mexico USA where cattle were removed in 1973 and an area just north of the Sevilleta LTER where grazing by cattle still occurs. At each site we measured plant species composition and cover in permanent plots in the spring and fall from 2004 to 2007. Quadrats were clipped annually to quantify aboveground standing crop to answer the following questions: 1) Does cattle grazing affect plant species composition and standing crop? 2) Does grazing alter community response to inter-annual climate variability? and 3) How does grazing impact the abundance of native grasses?
There were three replicates of each treatment: currently grazed by cattle, grazing exclosures erected in 1993 to prevent cattle grazing, and ungrazed (since 1973) grassland on the Sevilleta NWR.
Each replicate plot was 300x300-m, containing a standard Sevilleta mammal trapping web (see small mammal metadata). Trapping webs contained 12 transects radiating from a central point at a uniform angle (Parmenter et al. 2003 Ecol. Monogr.) where there were located 12 numbered stakes for a total of 144 sample points per web. Stakes were numbered starting from a central point outward such that points along transect 1, for example, were numbered 1 through 12. Vegetation was sampled in permanently located 50x50-cm quadrats at four evenly spaced points along each radius of each grid transect (48 permanent quadrats per replicate). Sampling started at the outer most numbered stake (e.g., stake 12, 24, 36, etc). Each transect had four permanently located quadrat positions moving inward toward the center point. Thus, sample points on transect one were number 12, 10, 8, 6. One corner of each 50x50-cm quadrat was placed over the sampling stake with the diagonal of the quadrat pointing toward the center of the mammal trapping web.
Quadrat frames were gridded in 10x10-cm sections to facilitate cover estimates. Cover of plant species rooted in the quadrat was visually estimated in 1% intervals to 10% (e.g., 1, 2, 3%) and then in 5% intervals (e.g., 15, 20, 25%) thereafter. If a species had a cover less 1%, the cover was recorded as 0.1%. Only annual plant species were measured in the spring (April or May), whereas in the fall (September) both annual and perennial species were measured.
/logFile created on 2/28/2006 based on metadata and data supplied by Scott Collins. --KLV, 2/28/2006 Data from 2004 to 2007 was QA/QC for mistakes in data entry. TLK 13 January 2009 Data from 2004 was checked row by row for errors. tlk 3 February 2009 Online data updated on 13 February 2009 along revised metadata. TLK Plot S1 for 2006 and 2007 was renamed S1a. Metadata was updated 10 April 2009 tlk
Data were checked against field data sheets after entering in an excel spreadsheet. Beginning in 2007, data were entered on a palmtop computer in the field. These data were transferred to a desktop computer and stored on the network drive. They were visually assessed for obvious mistakes in cover and species codes along with checking if all sample units had been measured.
Coordinates of the Center of the trapping webs.
NAD83_LAT1 NAD83_LON1 PROJECT_AREA PLOT_NUM
34.41072006 106.60885539 Weldon McKinley Ranch X1
34.41612323 106.60873476 Weldon McKinley Ranch G1
34.41058896 106.59906840 Weldon McKinley Ranch G2
34.41597776 106.59894444 Weldon McKinley Ranch X2
34.41051363 106.59251318 Weldon McKinley Ranch G3
34.41587466 106.59238861 Weldon McKinley Ranch X3
34.40613630 106.60895894 Sevilleta National Wildlife Refuge S1 (Old plot)
34.40497234 106.60012129 Sevilleta National Wildlife Refuge S2
34.40405039 106.59568944 Sevilleta National Wildlife Refuge S3
In 2006, plot S1 was moved to a new location and given a different layout from the above mentioned plots because the original S1 plot was being grazed by a small colony of prairie dogs. The new S1 plot is in a grid format using the same stake numbers as the trapping web replicates. This new plot was labeled S1a. There are no vegetation measurements for either S1 or S1a during the Spring 2006 field season. Also, exclosure plots (X1-X3) on Weldon McKinley Ranch were not measured in Fall of 2006 or Spring and Fall of 2007.
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.