Data set ID:
The purpose of this study is to quantify vegetation dynamics in response to lagomorph and shrub exclusion. Data consist of vertical line intercept measures of the perennial grasses, suffretescents and shrubs. Sixteen plots at each of 3 sites (Gravelly Ridges, Dona Ana exclosure, and Parker Tank) were established in 1938-39 by Ken Valentine. Plots were 21.3 x 21.3 m in 4 rows of 4 plots with a 7.6 m buffer zone. All plots were sampled before treatments. Plots were divided into east and west halves and 14 randomly located 10.65 m transects were located in each half plot. Vegetation (black grama, dropseeds, bush muhly, fluff grass, other grasses, creosotebush, honey mesquite, tarbush, mariola, and other shrubs) was measured using vertical line point intercepts. Plots have been re-read in 1947, 1956, 1960, 1967, 1989, 1995, and 2001 for Gravelly Ridges and 1939, 1947, 1960, 1967, and 2001 for Dona Ana and Parker Tank using the same methods. Treatments were applied factorially yielding a control plot, single factor plots, and plots with varying degrees of combinations of factors. The factors were lagomorph exclusion (using wire fencing), shrub removal (hand grubbing at the ground surface), furrowing (shallow, hand raked furrows to trap surface water), and seeding (broadcast applications of seeds of native perennials). Seeding and furrowing treatments were only applied in 1939. Lagomorph exclusion has persisted since establishment, and shrub removal treatments have been reapplied immediately following all years of vegetation sampling. This study is complete.
For more information, refer to:
Havstad, K.M., R.P. Gibbens, C.A. Knorr, and L.W. Murray. 1999. Long-term influences of shrub removal and lagomorph exclusion on Chihuhuan Desert vegetation dynamics. Journal of Arid Environments 42: 155-166.
-field data sheets were used
Data from the 16 21.3x21.3 m plots within this study were collected in 1938, 1947, 1956, 1960, 1967, 1989, 1995, and 2001. Data consist of vertical line intercept measures of the perennial grasses, suffretescents and shrubs. Prior to 1989 all measures were in tenths of inches. Beginning in 1989 all units are cm. All data in files have been converted to centimeters. Plots were divided into east and west halves. 14 10.65m lines were randomly positioned (from north to south) for intercept measures in each half for a total of 28 10.65 cm lines in each plot. The 28 transects are not marked; they are randomly relocated for each remeasurement. Exclosure fences are 4 foot high barbed wire fences with wooden posts and wooden brace posts. This fence is lined on the outside with two stacked layers of 2' high, 1" mesh poultry netting that was buried 6-10" and wired to the barbed wire fence. Thus, a lagomorph fence approximately 3.5' high is maintained around these exclosures. Grasses were measured for basal cover, and all other species were measured for canopy cover. Data in files for analysis include the four main grasses (Bouteloua eriopoda, Muhlenbergia porteri, Dasyochloa pulchella, and Sporobolus contractus), miscellaneous grasses (recorded by species in original data file), the four main shrubs (Larrea tridentata, Prosopis glandulosa, Flourensia cernua, and Parthenium incanum) and miscellaneous shrubs/suffrutescents (also recorded by species in the original data file).
SAS program will be used to analyze data. The focus for the analysis of these data in 1995-96 is to examine the change in cover, by species, over the length of the study in response to the presence of shrubs (the "C" treatment). The seeding ("S") and furrowing ("F") treatments can be ignored in the analysis given that they were nonsignificant in prior years. Data in text file (combline.txt) is labeled according to sas data file "lagmorph.sas". Note that on occassion the four letter acronym ERPU may appear in files. This genus of grass has been renamed Dasychloa and the correct acronym is now DAPU.
USDA-ARS Gravelly Ridges Exclosure, SE corner. The exclusion study is located on the outside of the southeast corner of the Gravelly Ridges major exclosure (259 hectares) built in 1935 and located in Pasture 20B of the USDA Jornada Experimental Range. Dona Ana Enclosure and Parker Tank exclosure.
Time of sampling varied (see abstract and methods). This study is complete.