Current Research Projects

Shrub encroachment is a global phenomenon. Both the causes and consequences of shrub encroachment vary regionally and globally. In the southwestern US a common native C3 shrub species, creosotebush, has invaded millions of hectares of arid and semi-arid C4-dominated grassland. At the Sevilleta LTER site, it appears that the grassland-shrubland ecotone is relatively stable, but infill by creosotebush continues to occur.  The consequences of shrub encroachment have been and continue to be carefully documented, but the ecological drivers of shrub encroachment in the southwestern US are not well known.

The Sevilleta LTER and University of New Mexico have received a five year grant from the National Science Foundation for the project entitled, "Grassland sensitivity to climate change at local to regional scales: assessing the roles of ecosystem attributes versus environmental context." The overarching goal of this research is to determine the consequences of chronic drought on biodiversity and ecosystem services in grasslands across precipitation and temperature gradients.

The distribution, structure and function of mesic savanna grasslands are strongly driven by fire regimes, grazing by large herbivores, and their interactions. There is evidence to suggest, however, that fire and grazing influence savanna grassland structure and function differently in South Africa (SA) compared to North America (NA). These differences have been attributed to the contingent factors of greater biome age, longer evolutionary history with fire and grazing, reduced soil fertility, and greater diversity of plants and large herbivores in SA.

The varied topography and large elevation gradients that characterize the arid and semi-arid Southwest create a wide range of climatic conditions - and associated biomes - within relatively short distances. This creates an ideal experimental system in which to study the effects of climate on ecosystems. Such studies are critical givien that the Southwestern U.S. has already experienced changes in climate that have altered precipitation patterns (Mote et al. 2005), and stands to experience dramatic climate change in the coming decades (Seager et al. 2007; Ting et al. 2007).

This data base contains taxonomic and ecological information for the plant species on the Sevilleta National Wildlife Refuge.

The purpose of this study is to monitor the fruit production of three woody tree species that occur on the Sevilleta National Wildlife Refuge (NWR). Two monoecious species, Pinus edulis and Quercus turbinella, are assessed, as is a dioecious species, Juniperus monosperma. In August, fruit production is estimated for the three species at five sites within the Sevilleta NWR.

The germination rate of creosote (Larrea tridentata) on the Sevilleta appears to be very low. During the early years of the LTER project it was attempted to quantify such germination through the use of seedling plots which were monitored on a bi-annual basis (spring and fall). During the period from 1989 through 1992 there were no creosote seedling that germinated on the monitoring plots.

Plant phenology or life-history pattern changes seasonally as plants grow, mature, flower, and produce fruit and seeds. Plant phenology follows seasonal patterns, yet annual variation may occur due to annual differences in the timing of rainfall and ambient temperature shifts. Foliage growth and fruit and seed production are important aspects of plant population dynamics and food resource availability for animals.

This data set includes precipitation chemisty from 20 funnel collectors on the Sevilleta National Wildlife Refuge (NWR). Variables measured include volume, NO3-N, NH4-N, SO4, Cl, Na, K, Ca, Mg, and PO4. The sample interval depends on the frequency of significant precipitations events. Field collection of precipitation chemistry samples occurred as soon after a significant precipitation event as possible (usually within a week after the event).

Most research on microbial soil crusts has been concentrated in the cold desert grasslands of the Colorado Plateau and the Basin and Range region of the western United States.  Relatively little is known about the microbial communities of soils of the warm, semi-arid grassland region of the southwestern United States.

Most recent studies of microbial processes and microbial ecology at the Sevilleta National Wildlife Refuge (SNWR) have focused on the semiarid grassland biome. These studies can be broadly classified into process, phylogenetic and modeling categories.

This project was designed to examine the long-term response of semi-arid vegetation communities to the removal of dominant species.  One dominant species representing each of the three major biomes occurring at the Sevilleta National Wildlife Refuge was selected for removal from the sampled plots.  These species included: Bouteloua gracilis (blue grama), the characteristic dominant grass of shortgrass steppe, Bouteloua eriopoda (black grama), a dominant grass of Chihuahuan D

In 2005, root ingrowth donuts were established on the Sevilleta NWR to monitor below ground biomass under different conditions and to compare estimates of root production between root ingrowth donut and mini-rhizonton tube methods at four sites on the east side of the refuge. Soil and roots are collected from the "donuts" annually in late fall after the growing season, and structures are then re-established in situ for consecutive harvests for the following years. Each structure allows roots to be harvested at two depths (0-15 and 15-30cm) to estimate root production, or "below ground net primary productivity".

This project was initiated to evaluate temporal and spatial dynamics across vegetation transition zones.  Current research includes an investigation into how the extent of Bouteloua eriopoda (black grama) and B. gracilis (blue grama) cover changes over time in relation to meterological conditions.  Likewise, the dynamics of the forb community in relation to shifting climatic conditions is being explored. 

This study originated with the objective of parameterizing riparian evapotranspiration (ET) in the water budget of the Middle Rio Grande.  We hypothesized that flooding and invasions of non-native species would strongly impact ecosystem water use.  Our objectives were to measure and compare water use of native (Rio Grande cottonwood, Populus deltoides ssp.

Fire is a common agent of disturbance in grassland ecosystems.  The removal of cattle from the Sevilleta National Wildlife Refuge (SNWR) after 1973 resulted in an increased number of lightning-initiated wildfires which left a mosaic of burned patches across the landscape.  Prior to 2002, lightning-initiated wildfires were actively suppressed, but have since been allowed to burn.  The effects of fire on post-grazing vegetation have been addressed in several studies.  Fire effects have also bee

The late Dr. Clifford S. Crawford established the Sevilleta’s Schoolyard LTER Program which funds an educational outreach program known locally as the Bosque Ecosystem Monitoring Program (BEMP).  The major focus of the program is to monitor key indicators of structural and functional change in the Middle Rio Grande riparian cottonwood forest ('bosque') corridor through central New Mexico, including the Sevilleta National Wildlife Refuge.

Two of the most pervasive human impacts on ecosystems are alteration of global nutrient budgets and changes in the abundance and identity of consumers. Fossil fuel combustion and agricultural fertilization have doubled and quintupled, respectively, global pools of nitrogen and phosphorus relative to pre-industrial levels. In spite of the global impacts of these human activities, there have been no globally coordinated experiments to quantify the general impacts on ecological systems.

Humans are creating significant global environmental change, including shifts in climate, increased nitrogen (N) deposition, and the facilitation of species invasions. A multi-factorial field experiment is being performed in an arid grassland within the Sevilleta National Wildlife Refuge (NWR) to simulate increased nighttime temperature, higher N deposition, and heightened El Niño frequency (which increases winter precipitation by an average of 50%).

The Small Mammal Population Study (Sev008) is a baseline SevLTER dataset initiated in 1989 with the inception of the project in order to examine the spatial and temporal distribution of populations. This research is coupled with measures of primary productivity, and climate to ascertain: 1) the influence of climate on population dynamics; and 2) the role of animals as trophic drivers regulating vegetation dynamics.

The Sevilleta Gunnison’s Prairie Dog (Cynomys gunnisoni) Restoration project examines keystone consumer (herbivore) effects on grasslands in concert with ecological restoration of a “species of greatest conservation need in New Mexico” (NMG&F Comprehensive Wildlife Conservation Strategy, 2007). SevLTER partners directly with US Fish & Wildlife on the Sevilleta National Wildlife Refuge and non-profit Prairie Dog Pals on this ambitious effort to re-establish Gunnison’s prairie dogs to blue grama-dominated (Bouteloua gracilis) Great Plains grassland at the foothills of the Los Pinos Mountains on Sevilleta.

Net primary production (NPP) is a fundamental ecological variable describing rates of carbon consumption and fixation.  Estimates of NPP are important in understanding the spatial and temporal responses of communities to a wide range of ecological processes including decomposition, fertility, and producer-consumer dynamics.  Net primary production is influenced by many factors, including temperature, soil nutrient content, soil texture, pollination, herbivory, and granivory.

Increased atmospheric CO2 concentrations caused by fossil fuel consumption are affecting global climate, increasing temperatures and precipitation variability in many regions. Such changes in climate can exceed the physiological tolerances of existing long-lived plant species or, alternatively, make conditions more favorable, increasing species productivity and abundance.

The Sevilleta’s climate is characterized by an intriguing combination of abundant sunshine, low humidity, and high variability for most meteorological factors. The site exists at the boundary between several major air mass zones that contribute to the dynamics of the local climate.

The Monsoon Rainfall Manipulation Experiment (MRME) enables the quantification of changes in the structure and function of a semiarid grassland ecosystem that have been caused by increased rainfall variability.  Variability in precipitation affects the timing and duration of the pulses of soil moisture that drive primary productivity, community composition, and ecosystem processes in semiarid grasslands.