@conference {51056, title = {A portable rainfall simulator for small paired-plot comparisons}, booktitle = {Soil Science Society of America Annual Meeting}, year = {2001}, note = {CD-ROM not available to create pdf file; no pdf number. August 1, 2001}, month = {October 15, 2001}, pages = {CD-ROM}, abstract = {We describe the design and calibration of an inexpensive rainfall simulator in which a manually operated pulley system is used to move a nozzle along a 3m track, uniformly covering an area of up to 1 x 2.5m. Nozzle heights can be set up to 3m from the ground surface. High or low intensity rainfall events can be simulated using a VeeJet and cone nozzle. The simulator, pump and 500-gallon water tank are transported in a pickup truck. Garden hoses transport water from the tank to the simulator, allowing plots to be located in remote sites. Using a VeeJet nozzle, water distribution within 0.5m2 (70.7 x 70.7cm) plots remained uniform in winds up to 40kph, as long as all sides of the simulator were protected with tarps: the average difference between the highest and lowest rates recorded by 5 gauges in each plot was just 11\% of the mean (n = 23 runs). Cone nozzles produced only slightly less uniform distributions. Nearly 80\% and 55\% of drop sizes sfell between 1 and 3mm for the VeeJet and cone nozzle, respectively. We present equilibrium infiltration rates and sediment production data from experiments designed to quantify disturbance effects based on simultaneous measurements from paired plots.}, author = {Justin Van Zee and Jeffrey E. Herrick} } @article {51309, title = {Mutual exclusion by dolichoderine ants on a rich food source}, journal = {Southwestern Naturalist}, volume = {42}, number = {2}, year = {1997}, month = {1997}, pages = {229-231}, abstract = {

Some species of ants recruit rapidly to rich food sources and may exclude other species from that food source (Holldobler and Wilson, 1990). These ant species interfere with other ant species by using chemical repellents or by physical means. For example, the dolichoderine ant Fornelius pruinosus usually displaces the formicine honeypot ants, Myrmecocystus spp., at food baits (Holldobler, 1982). Interference competition should be most intense where densities of ant colonies are high and when food reserves are limited.

}, keywords = {ant colonies, ant species, chemical repellents, food baits, food reserves, food source, formicine, Fornelius pruinosus, honeypot ants, Interference competition, Myrmecocystus spp., physical dolichoderine ant}, url = {/files/bibliography/599.pdf}, author = {Justin Van Zee and Walter G. Whitford and W. E. Smith} } @conference {51308, title = {Responses of Chihuahuan Desert annual plant communities to desertification and exposure to varying grazing stress.}, booktitle = {International Symposium and Workshop Combating Desertification: Connecting Science with Community Action}, year = {1997}, month = {May 12-16, 1997}, pages = {23}, address = {Tucson, AZ}, abstract = {

Ephemeral or annual plant communities respond to a variety of environmental factors, including rainfall, nutrients, temperature, competition, and disturbance. Stressors such as cattle grazing can alter perennial plant communities and soil properties sufficiently to change annual plant communities. We examined density and biomass of annual plant species at sites representing historically documented desertification (a degradation gradient), grazing intensity gradients, grazing exclosures and enclosures, rangeland rehabilitation efforts, and recent fires, as well as sites representing habitats unique to the Chihuahuan Desert. Traditional community vegetation parameters such as species richness and indices of species diversity do not always effectively explain patterns in annual plant communities.\ \  We emphasize examination of key species and micro habitat patterns when analyzing the effects of disturbance of ephemeral plant communities and include examples of how ephemeral plants respond to patchy environments in a wide range of habitats and landscape positions in Chihuahuan Desert rangelands.

}, author = {Justin Van Zee and A.G. de Soyza and Walter G. Whitford} }