Changes in plant composition have the potential to cause disturbances in both structure and function throughout the ecosystem. One element of the ecosystem that can be affected is bird diversity and behavior. Certain species of birds depend more, or entirely, on habitats containing specific functional groups or species of vegetation. Habitat preferences in birds develop because of factors such as availability of food, nesting and perching locations, and cover. Certain species of birds may be generalists while others use a small variety of plants due to strict habitat requirements. In this study we examine how different growth types of plants affect bird abundance, bird species diversity, and bird activity on the Jornada Basin. The experiment took place on the Biodiversity plots (25m X 25m)at the New Mexico State University Chihuahuan Desert Rangeland Research Center from June through August 1997. The site contained 6 blocks, each containing 8 treatments, including: control, perennial grass removal, reduced Larrea cover, reduced Prosopis cover, shrub removal, only a single dominant species of each growth form remaining, subshrubs removal, and succulents removal. The following data were recorded in each plot: species type, time spent in plot, type of vegetation utilized, presence of a pair or family group, and behavior. Behaviors recorded included perching, singing, calling, foraging on the ground, foraging in the vegetation, nesting , and preening. Birds were observed in each plot for periods of 35 minutes with a 10 minute acclimation period prior to the start of the observation period. The replications were done according to a predetermined schedule which was developed in such a manner so as to reduce sampling error as much as possible. 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.
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.