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?
Total standing crop was sampled each year in September or October during peak biomass. All aboveground vegetation in a 20 X 50-cm area was clipped, placed in paper bags, dried at 60 degrees C for 48 hours and weighed. Clipping quadrats were located just off the trapping web transects near odd numbered stakes (e.g., 11, 9, 7, 5) for a total of 48 samples of total aboveground standing crop (current year's live plus current year's dead plus previous year's dead).
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.
Metadata created. 5 April 2009 tlkPlot S1 for 2006 and 2007 was renamed S1a. Metadata was updated 10 April 2009 tlk
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 than other 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. This new plot was labeled S1a. Also, exclosure plots (X1-X3) on Weldon McKinley Ranch were not measured in 2006 or 2007.