Completed Research Projects

In this study, soil characteristics after a lightning-initiated fire were evaluated. Following the fire in July 1998, 25 experimental plots were established on the eastern edge of MacKenzie Flats at the Sevilleta National Wildlife Refuge. Ten of these plots were located in a Bouteloua gracilis (blue grama)-dominated site, while 15 were established in another area dominated by Bouteloua eriopoda (black grama).

This study measured the population dynamics of coyotes in the grasslands and creosote shrublands of McKenzie Flats, Sevilleta National Wildlife Refuge. The study was begun in January, 1992, and continued quarterly each year. Coyotes were sampled via scat counts along the roads of McKenzie Flats during winter, spring, summer, and fall of each year. The entire road transect was 21.5 miles in length.

Responses of plant communities to mammalian herbivores vary widely, due to variation in plant species composition, herbivore densities, forage preferences, soils, and climate. In this study, we evaluated simultaneous changes in 11 plant assemblages on the 100,000 ha Sevilleta National Wildlife Refuge (SNWR) in central New Mexico, USA, over a 20-yr period following removal of the major mammalian herbivores (livestock and prairie dogs) in 1972-1975.

This dataset contains weights of vegetation biomass collected in fertilizer plots from 1989 through 1992. The data were originally collected to analyze the effects of fertilization on vegetation productivity on the Sevilleta NWR.

Grazers and granivores have the potential to affect seed banks. Several studies have examined the impact of these herbivores on the aboveground vegetation, but few have looked at how they influence the seed bank. I asked whether both grazers and granivores alter the seed bank at the Sevilleta National Wildlife Refuge. Long-term experimental plots were installed in 1996 to exclude grazers and granivores from a grassland and shrubland.

Our objective was to evaluate the effects of burrowing activities by banner-tail kangaroo rats (Dipodomys spectabilis Merriam) on plant community structure and species dominance for two patch types at an ecotone between shortgrass steppe and desert grasslands in New Mexico, USA.

Maintaining high rates of water loss during times of high resource availability could allow establishing woody desert perennials to grow quickly by allowing them to take advantage of the fleeting but abundant monsoonal moisture typical of warm deserts like the Chihuahuan. However, a plant cannot endlessly increase water loss in order to grow faster --there are hydraulic constraints on rates of water loss.

This file contains daily lightning activity data for the state of New Mexico. These data were collected by a network of lightning detection stations scattered throughout the western United States. More information regarding the LLP Lightning Locating System can be found in Maier et al. (1983).

Data on soil characteristics and dominant grass and soil chemical composition gathered on active rangeland, livestock exclosures on active rangeland, and the Sevilleta NWR.

The primary objective of this study is to examine the control that substrate quality and climate have on patterns of long-term decomposition and nitrogen accumulation in above- and below-ground fine litter. Of particular interest will be to examine the degree these two factors control the formation of stable organic matter and nitrogen after extensive decay.

This study examined concentrations of organic and inorganic phosphorus in surface soils of a Bouteloua gracilis-Bouteloua eriopoda grassland and a Larrea tridentata shrubland in the northern Chihuahuan Desert, New Mexico, USA. In this desert, where grassland vegetation has a uniform spatial distribution and individual shrubs have a patchy distribution, vegetation strongly influences the locations and concentrations of soil nutrients.

The long-term goal of the decomposition study was to document the effects of climate variation on decomposition of major plant litter-types. The project began in 1989 and underwent changes of locations and litter types. The long-term litter types included black grama, Indian rice grass, juniper, and creosote.  Mass loss of the litter types can be compared to precipitation and other meteorological factors obtained at nearby locations.

 Physiological status of plants is monitored in conjunction with the sampling schedule outlined in Sevilleta Plant Demography. Several perennial life forms, including tree (Juniperus and Pinus), shrub (Larrea) and grass (Oryzopsis and Sporobolus), are being monitored at 1-3 of four sites which differ in elevation and topography as well as edaphic and annual precipitation characteristics.

This project addresses the idea that 1) structural and functional differences between shrubs and grasses are responsible for different short-term and long-term physiological and growth responses and 2) that these differences govern vegetation and hydrologic changes when grassland, shrubland and the transition (ecotone) ecosystems are subjected to climate extremes such as extended drought or prolonged periods of above-average precipitation.

 Human populations in Colorado, New Mexico and Texas depend on the Rio Grande for municipal water, agricultural irrigation, and recreation. The Rio Grande and its riparian corridor also support thousands of species of plants, invertebrates and vertebrates, some of which include over 300 species of migratory birds and the endangered Rio Grande silvery minnow and southwestern willow flycatcher.

Ant colonies possess a “societal metabolism,” acquiring, transforming, and allocating resources through a network of foragers (Moses, 2005). Ant foraging- trail networks channel foragers to known food resources and away from competing colonies (Jun et al., 2003). Computer models suggest the spread of information occurs faster in larger colonies of harvester ants, genus Pogonomyrmex (Adler and Gordon, 1992), providing a possible mechanism of differentiation. Does the ability to utilize and share information scale super-linearly with a colony’s size?

This project was designed to sample the richness and abundance of birds on the Sevilleta National Wildlife Refuge. Three types of habitat were surveyed: grassland, creosote shrubland and pinyon-juniper woodland.

This project was designed to investigate the response of plant growth and reproduction to short- and long-term variation in biotic and abiotic environmental variables. Several perennial taxa, including tree (Juniperus monsperma and Pinus edulis), shrub (Larrea tridentata) and bunch grasses (Oryzopsis hymenoides (nowAchnaterum hymenoides) and Sporobolus contractus) species, were monitored at 1-3 sites differing in elevation and topography as well as edaphic variables and annual precipitation.

The allometric ant foraging data was collected to test the allometric ant foraging model proposed by Jun et al. (2003). Key variables are the number of foragers in the colony, the time of an average foraging trip for the colony and the average distance a forager travels to collect a seed. Data on Pogonomyrmex rugosus and Pogonomyrmex maricopa were collected at the Sevilleta.

This study looks at Ocotillo (Fouqieria splendens) at the northern extent of its range in New Mexico. Gross morphological and phenological measurements are made in the field and leaves are collected for isozyme work.

Animal consumers have important roles in ecosystems, determining plant species composition and structure, regulating rates of plant production and nutrients, and altering soil structure and chemistry. The purpose of this study is to determine whether or not the activities of small mammals regulate plant community structure, plant species diversity, and spatial vegetation patterns in Chihuahuan Desert shrublands and grasslands.

Vegetation throughout the southwestern United States has changed from perennial grassland to woody shrubland over the past century. Previous studies on the development of 'islands of fertility' focused primarily on only the most limiting, plant-essential element, soil nitrogen (N).

Previous morphological work on lizards suggests that the volume of growing eggs may result in a significant decrease in lung volume during gravidity. Iguanid lizard lungs are located within continuous thoracic and abdominal cavities and are highly distensible. Because of their distensible nature and lack of a diaphragm, both naturally occurring and introduced structures within the abdominal and thoracic cavities (i.e.

This file contains hourly time-domain reflectometry (TDR) soil moisture data for 1996-2005. A key factor in a spatially explicit water-balance model is a measure of moisture in the soils over time. This metric is crucial for both calibration and validation of such a model. One of the best methods of measuring soil moisture on a continuous basis is TDR. Therefore, a network of TDR soil moisture sensors was installed at all meteorological stations on the Sevilleta National Wildlife Refuge.