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.
Creosotebush litterfall collected monthly from creosotebush zone Creosotebush litterfall collected monthly from creosotebush zone on upper bajada between College Playa and Mt. Summerford. Oven-dry weights of leave, stem, and seed fractions as well as total dry weight are recorded.
*Changes in microarthropod assemblages were monitored in six types of decomposing surface leaf-litter confined in mesh bags and set across a Chihuahuan Desert watershed for 17 months. The following hypotheses were tested: 1) microarthropod density and diversity are higher in soils with maximum surface litter accumulation, and 2) temporal patterns of density and diversity are more dependent on seasonal factors and physical disturbances than on the decompositional stage of the litter.
Soil nutrient distribution in NPP quads in the Mesquite, Grassland, Playa, Creosotebush, and Tarbush plant communities sampled at 3 spatial scales of grids. Soils were sampled from the NPP (biomass plots). Each of the five vegetation types (mesquite, grassland, playa, creosote, tarbush) had three sites (with low, medium, and high production levels). At 14 of 15 sites a grid of 70 by 70 meters was set out. Within this 49 plots of 10 by 10 meters were placed and labeled (numbered) in serpentine design. At the 15th site, Playa College, 48 plots of 10 by 10 meters were laid out in three long rows of 16 plots per row. At all sites the soil sample of 0-10 cm depth was taken 1 meter from the NE marker bar at a diagonal (heading toward the SW marker). 70m x 70m layout of NPP quads where 1 is in NE corner. 43 42 29 28 15 14 1 44 41 30 27 16 13 2 45 40 31 26 17 12 3 46 39 32 25 18 11 4 47 38 33 24 19 10 5 48 37 34 23 20 9 6 49 36 35 22 21 8 7 160m x 30m layout of P-COLL NPP quads where 1 is in NE corner. 33 32 1 34 31 2 35 30 3 36 29 4 37 28 5 38 27 6 39 26 7 40 25 8 41 24 9 42 23 10 43 22 11 44 21 12 45 20 13 46 19 14 47 18 15 48 17 16 At one of each of the five vegetation types another set of 49 soils (#101-149) was taken from within one of the 10 by 10 meter plots. Using a 7 by 7 meter grid (bounded by the southern east-west boundary line and the western north-south boundary line[#149 is in the SW corner]) soils were sampled 1 meter apart using a serpentine design. 7m x 7m layout within single 10m x 10m NPP plot. 143 142 129 128 115 114 101 144 141 130 127 116 113 102 145 140 131 126 117 112 103 146 139 132 125 118 111 104 147 138 133 124 119 110 105 148 137 134 123 120 109 106 149 136 135 122 121 108 107
Soil nutrient distribution beneath and between plant canopies in the Mesquite, Grassland, Playa, Creosotebush, and Tarbush plant communities. The LTER plant biomass plots was sampled in June 1989. A total of 750 soil samples were collected from 5 depths (0- 10, 10-20, 20-40, 40-60, 60-100 cm), 2 locations (under and between shrubs), within 5 vegetation zones (Mesquite, Grassland, Playa, Creosotebush, Tarbush), 3 sites per zone (site with low, medium, and high biomass, ranked based on FALL-89 biomass), and 5 directions per site (in buffer zone just outside of NPP plots N, S, E, W, and in the center of NPP plots C). Samples were analyzed for pH, CaCO3, NaHCO3- extractable P, KCl-extractable NH4 and NO3, total kjeldahl N, Saturation extrac cations, and DTPA-extractable micronutrients.
Plant nutrient distribution beneath and between plant canopies in the Mesquite, Grassland, Playa, Creosotebush, and Tarbush plant communities. The LTER plant biomass plots were harvested during spring, fall, 1989 and winter 1990, in 5 vegetation zones (Mesquite, Grassland, Playa, Creosotebush, Tarbush), 3 sites per zone (site with low, medium, and high biomass, ranked based on fall-89 biomass). Samples were analyzed for total Kjeldahl N, and total phosphorus. Site ranking based on Fall 1989 biomass estimates: ZONE SITES BIOMASS (using FALL-89 rank of plant) M RABB low M NORT medium M WELL high G IBPE low G SUMM medium G BASN high P TABO low P COLL medium P SMAL high C CALI low C GRAV medium C SAND high T WEST low T TAYL medium T EAST high
*We conducted a field study to test the hypothesis that creosotebush (Larrea tridentata) shrubs growing in naturally nutrient-rich sites had better quality foliage and supported greater populations of foliage arthropods than shrubs growing in nutrient-poor sites. This is data for foliage arthropods sampled from Lm LVAR creosotebush shrubs. Sampling was done in April of 1985 and 1986. Shrubs were sampled from 5 separate sites, designated A-E. 10 shrubs of 3 different selected types, random = R, high quality = H, low quality = L, were sampled at each site. Total numbers of individuals of each of the common species of foliage arthropods from each of the 30 shrubs/site are listed.
*We conducted a field study to test the hypothesis that creosotebush (Larrea tridentata) shrubs growing in naturally nutrient-rich sites had better quality foliage and supported greater populations of foliage arthropods than shrubs growing in nutrient-poor sites. This is data for foliage arthropods sampled from LVAR creosotebush shrubs. Sampling was done in April of 1985 and 1986. Shrubs were sampled from 5 separate sites designated A-E. 10 shrubs of 3 different types, R=random, H=high quality, L=low quality were sampled at each site. Total numbers of taxa and individuals of each major trophic group, herbivores, predators, omnivores, from each of the 30 shrubs/site are listed.