Objectives. Desertification is hypothesized to have altered the spatial and temporal availability of resources required by the biota. Results of desertification on the Jornada include changes to shrub dominated communities and major soil changes. We hypothesize that these shifts in vegetation have changed resources temporally for many of the consumers. If grassland systems respond to rainfall without significant lags, but shrub systems do not, then consumer species should reflect these differences. In addition, shifts from grassland to shrubland results in greater structural heterogeneity of the habitats. We have hypothesized that consumer populations, diversity, and densities of some consumers will be higher in grasslands than in shrublands. Diversity and/or densities are hypothesized to be related to the NPP of the sites. Data for arthropods captured in pitfall traps on LTER III consumer plots at 2 month intervals. Data includes order, family, genus, species, and number. This data collection has been completed.
Termites are important to litter decomposition and nutrient cycling in desert grasslands. The annual feeding activity on paper baits of subterranean termites in desertified (degraded-shrub dominated ecosystems) and relatively undegraded black-grama (Bouteloua eriopoda) grasslands was measured over six years on 12 sites on the Jornada Basin. Toilet paper roll termite baits were placed on grids on each consumer plot. Data include initial bait weights and bait weights after baits had been retrieved from the field once each year. Weight loss was calculated as a measure of termite foraging activity. This study is complete.
Data for rabbits, birds, and lizards recorded from the LTER II animal transects. Data consists of species names, numbers of individuals, and distances observed from transects. Data is collected from each transect once every two weeks. See history file for exceptions.
Data for arthropods captured in pitfall traps on LTER II consumer plots. Data includes order, family, genus, species, and number.
Ammonia volatilization was measured at three sites in the Chihuahuan Desert of southern New Mexico, U.S.A. In dry soils, ammonia volatilization ranged from 9 to 11 micrograms of nitrogen per square meter per day, but rates increased to 95 micrograms of nitrogen per square meter per day in a shrubland site after an experimental addition of water. Ammonia volatilization also increased with experimental additions of NH4Cl and decreased with additions of sucrose. Competition by nitrifiers for available NH4+ had little effect on NH3 volatilization: N-Serve, added to inhibit nitrification, decreased NH3 volatilization in a grassland site and had little effect at other sites. We suggest that NH3 volatilization is controlled by the rate of mineralization of NH4+ from soil organic matter, and mineralization is stimulated by rainfall. Overall rates of NH3 volatilization from undisturbed desert ecosystems appear to be much lower than those reported for rangeland and agricultural soils.
The data set shows ammonia volatilization from grassland, cresotebush, and playa habitats in response to a variety of experimental treatments chosen to elucidate the processes controlling the volatilization under dry and post-rainfall conditions. Ammonia is collected in weak acid in scintillation vials placed inside PVC chambers in the field. The rate of ammonia volatilized per unit area ugN/m2/day) is found by mulitplying the concentration in the acid by 1250 to account for volume and area corrections.