2006 Sevilleta Research Symposium Highlights

One day event maintains regional scope and great turnout.

The annual Sevilleta LTER Research Symposium was a big success this year despite being held to one day during the spring semester and on the heals of our Sevilleta LTER IV renewal proposal to NSF. The mid-semester date was experimental and intended to provide opportunity for undergraduates from UNM to take the day and learn about research activities at the Sevilleta NWR. We had 6 undergraduates attend, but the timing was difficult for several principal researchers who were occupied with teaching responsibilities, etc. In any case, we had at least as many participants this year as we did last, with 75 persons for lunch! Attendees included both undergraduate and graduate students from UNM Biology, Earth & Planetary Sciences and Physics Departments, as well as post doctoral fellows, research professionals and professors from UNM Biology, NM Tech & NM State, staff from the USFWS, including Regional Refuge Director Gary Montoya, and researchers from US Bureau of Reclamation, the Bosque School and the USFS Rocky Mountain Research Station
The day was primarily dedicated to talks which covered topics from the ecology of plague in Gunnison's prairie dogs to recent findings from evaoptranspiration and remote sensing along the middle Rio Grande corridor to a review of below ground fungal and nutrient dynamics at the Nitrogen fertilizer plots on the east side of Sevilleta NWR. There were 11 talks and 17 posters in all. The abstracts and titles for most are included here. Powerpoint presentations from the Symposium can be found in the Presentation section of this website.
Following our proposal submittal to NSF, we felt that only one day would be necessary for this year's event. Next year, we plan on holding the Symposium just after the end of Spring Semester, likely in early June. There will be researchers on site for their summer activities and no issues with teaching duties for researchers from California and Colorado. The 2007 Sevilleta Research Symposium will be a two day event during which we will again take the time to present current research in oral and poster presentations during the first day, followed by organizational discussions and break-out groups aimed mostly at completion of the Sevilleta LTER Synthesis Volume. Next year we may top 100 attendees with continued growing interest and participation in Sevilleta LTER activities. Stay tuned for details.
Morning Session Oral Presentations:
Welcome and overview of Sevilleta National Wildlife Refuge.
Dennis Prichard / Terry Tadano
Welcome and overview of Sevilleta LTER Project.
Scott Collins
Annual Sevilleta Climate & Weather Review.
Doug Moore
Exploring the mechanisms of plague epizootics in Gunnison’s prairie dogs.
Megan Friggens
Abstract: Plague (Yersinia pestis) continues to threaten prairie dog populations across the Southwestern United States. My dissertation research aims to define the important mechanisms of plague introduction into Gunnison’s prairie dog (Cynomys gunnisoni) colonies. Plague transmission is correlated with flea and host abundance, flea species, host susceptibility and the temperature and precipitation characteristics of the environment. I plan to test the hypothesis that weather driven rodent population changes lead to increased probability of plague epizootics. In addition, I will assess the relative importance of climate and host population variability on the flea community dynamics critical to the transmission of plague. I will use data collected from three sites in NM: The Sevilleta National Wildlife Refuge (SNWR), the Sandia Mountains in central New Mexico, and the Valles Caldera National Preserve (VCNP). At each site, small mammals are trapped, fleas and blood samples are collected, and a variety of habitat characteristics are measured. I will use this data, in addition with data on gathered from meteorlogical stations and satellite imagery to assess the relationship between weather variables, rodent and flea densities, and presence of fleas and host switching/disease transmission events at the level of the prairie dog town. I will use structural equation (SEM) models to explore the relative influence climate (direct and indirect) and host population dynamics on flea species presence and abundance. Finally, I will assess the relationship of flea community dynamics across multiple biotic, spatial, and temporal scales. The results of this research will contribute to the preservation of Gunnison’s prairie dogs, an important keystone species. In addition, this research will increase our understanding of sylvatic plague cycles and enable researchers to better predict how climate change will affect vector-borne disease dynamics in the southwestern United States.
Unwiring Ecological Research at the Sevilleta: Past, Present, and Future.
Renee Brown and Don Natvig
Abstract: Wireless network technologies have allowed for a relatively straightforward and inexpensive way to provision internet access to remote areas. The Sevilleta National Wildlife Refuge, which occupies 100,000 hectares in central New Mexico, hosts research of the Sevilleta Long Term Ecological Research Program and the University of New Mexico. In June of 2004, a 25-kilometer wireless backbone link was established across the east side of the Refuge, providing real-time data access to multiple ecological research sites. Since the inception of the Sevilleta wireless network, met stations, flux towers, wildlife cams, and other research projects have been incorporated into the network. Here, we present the history of the network, progress made in 2005, and goals for 2006. In addition, we discuss costs and mechanisms for unwiring Sevilleta research sites.
Competition between native and non-native riparian plants for nitrogen resources.
Jennifer Follstad Shaw
Overview on work at the N addition plots on Sevilleta NWR grasslands over past year.
Robert Sinsabaugh
Bottom-up regulation of plant community structure in an aridland ecosystem.
Selene Baez, Scott Collins, David Lightfoot
Abstract: We conducted a long-term rodent exclosure experiment in native grass- and shrub-dominated vegetation to evaluate the importance of top-down and bottom-up controls on plant community structure in a low productivity aridland ecosystem. We assessed how bottom-up precipitation pulses cascade through vegetation to affect rodent populations, how rodent populations affect plant community structure, and how rodents alter rates of plant community change over time. We found that bottom-up pulses cascade through the system increasing the abundances of plants and rodents, that rodents exerted no control on plant community structure and rate of change in grass-dominated vegetation, and only limited control in shrub-dominated vegetation. We discuss these results in the context of top-down effects on plant communities across broad gradients of primary productivity. We conclude that bottom-up regulation maintains this ecosystem in a state of low primary productivity that constrains the abundance of consumers such that they exert limited influence on plant community structure and dynamics.
Scaling Biophysical Parameters in Canopies along the Middle Rio Grande.
Dianne McDonnell
Bosque Ecosystem Monitoring Program (BEMP): Partnering scientific research, education, and a cast of thousands.
Kim Eichhorst and Dan Shaw
Abstract: Since 1996 the Bosque Ecosystem Monitoring Program (BEMP) has used K-12 students, teachers, UNM interns, and scientists to gather key information about both abiotic and biotic variables of the Rio Grande’s riparian forest. Data gathered from 22 sites between Ohkay Owingeh (San Juan) Pueblo and Lemitar are now used to make major land use management decisions. In fact, federal, state, regional, and local natural resource managers have come to depend upon and are now funding K-12 student-gathered data related to vegetation, groundwater, fire risk, and other parameters.
Coupling consumer dynamics to abiotic drivers and ecosystem productivity: Lizard communities in Sevilleta NWR.
Robin Warne and Blair Wolf
SinNombre virus outbreaks in the southwest: cascades and population dynamics.
Clayton Crowder, Alexis Harriis, Roberta Chavez, Ginger George, Jessica Jakubanis, Sarah Keller, Scott Knapp, Robert Parmenter
Abstract: SinNombre virus outbreaks in the southwest occur episodically in tandem with increases in small mammal densities. The trophic cascade hypothesis states that climatic changes may influence the available resources for the rodents, and thereby indirectly acting as a catalyst for these outbreaks. The NSF funded Ecology of Infectious Diseases (EDI) project has three permanent study sites in north central New Mexico to map changing rodent densities: the Valles Caldera, Placitas, and the Sevilleta National Wildlife Refuge. Hantavirus prevalence in Peromyscus species at two of the study sites (Placitas, and Valles Caldera) have increased in the past year. Hantavirus positive Peromyscus species have not yet been found on the Sevilleta. The study design at the Sevilleta allows EID to examine the population dynamics of rodents in the movement or cascades on the landscape from higher elevations to lower grassland dominated landscapes. Using datasets on rodents, ground-dwelling arthropods, and plant abundance at the Sevilleta we have examined: a) The abundance of each species in Pinon-Juniper v. Grassland; b) Total species diversity by transect; c) Abundance of Murids v. Heteromyids by transect; d) Abundance of Murids v. Heteromyids by month; e) Relative arthropod abundance and distribution changes in the use of Pinon-Juniper vs. grassland; and f) Plant biomass and change across Pinon Juniper v Grassland habitat with relation to season, transect, and precipitation.
Sevilleta and EPSCoR: Infrastructure for a hydrologic flux network.
James Cleverly and Cliff Dahm
Afternoon Poster Session:
Reproductive Biology of Larrea tridentata: A Comparison of Core and Isolated Shrubs.
Karen Wetherill, Rosemary Pendleton and Burton Pendleton
Abstract: Establishment of creosote (Larrea tridentata) into grassland sites occurs exclusively through the production of seed. We compared the reproductive biology of Larrea shrubs located in the core shrubland with isolated shrubs well-dispersed into the grasslands at McKenzie Flats. Specifically, we examined 1) the potential of individual shrubs to self-pollinate and 2) pollinator guild composition at core and grassland sites. Sampling of the bee guild suggests that there are adequate numbers of pollinators at both locations, however the community composition differs between core and grassland sites. Five of the six Larrea specialist bee species were found only at the core shrubland site. Large numbers of bees were found on isolated bushes, but their efficiency in pollinating is currently unknown. Unbagged, open-pollinated shrubs at the core site had a greater mean percentage of filled seed as compared with isolated shrubs (76% vs. 57%), which is somewhat suggestive. Isolated grassland shrubs varied greatly in the number of seeds produced in pollinator-exclusion bags, while the number of self-pollinated seeds produced by core site shrubs was more uniform. Overall, however, the difference in seed produced by bagged and unbagged branches of isolated shrubs was much less than that of core shrubs. These observed trends will be explored further in the coming year.
Quantifying the importance of seasonal resource pulses to a small mammal community and influence of these pulses on consumer population dynamics through stable isotope analysis.
Alaina Pershall and Blair Wolf
Abstract: Seasonal environmental factors of temperature, aridity and rainfall result in the temporal separation of production in C3 and C4 plants in the desert southwest. C3 plants are known to respond to the winter rain pulse and the C4 plants are known to respond to the summer monsoon rains. This project was conducted at the Five Points Larrea site at the Sevilleta National Wildlife Refuge and Long Term Ecological Research Station (NSF-LTER). This site is located on the edge of the Chihuahuan desert grassland and shrubland. Larrea tridentata (creosote bush), which constitutes a significant proportion of this shrubland, is thought to be increasingly encroaching on the desert grasslands due to climate change, thus changing the habitat structure. The Five Points site is composed of a mixture of C3 plants, including Larrea tridenta and Gutierrezia sarothrae (broom snakeweed), and C4 plants, including Bouteloua eriopoda (black grama) and Sporabolus (mesa dropseed grasses). This project links ongoing net primary productivity, arthropod, reptile and small mammal studies by demonstrating how the populations interact in a food web and how the populations respond to seasonal variations in resource production of C3 and C4 plants in a vegetative transition zone. Because C3 and C4 plants have distinct isotopic signatures of ?13C we were able to quantify the proportion of these plants in the animals’ diets through stable isotope analysis. We also analyzed ?15N to reveal the trophic postion of the animals. The results of the stable isotope analysis of rodent blood plasma indicated an increase in ?13C from June to November in genera such as Dipodomys, Onychomys and Peromyscus, indicating an increasing proportion of C4 plants in their diet as expected. In contrast, the diet of Reithrodontomys megalotis actually decreased in the proportion of C4 plants and Perognathus flavus showed little change in the composition of its diet. Analysis of ?15N showed, as expected, that the omnivorous grasshopper mouse, Onychomys arenicola, was at the highest trophic position compared to the strictly herbivorous rodent species. The three species of Dipodomys were also separated by ?15N values, which probably reflect the differences in their relative habitat and plant utilization.
Ecoregion contributions to ground-spider diversity in the Rio Grande rift valley of New Mexico.
Sandra Brantley and David Lightfoot
Abstract: We assessed the biogeographic patterns of ground-dwelling spider assemblages across a heterogeneous semi-arid region, which included 5 ecoregion boundaries. We tested the hypotheses that 1) species diversity is greater at ecotone boundaries and 2) that different vegetation communities or habitats support distinct spider assemblages at the local scale. Ground-dwelling spiders were sampled by use of pit-traps continuously year-round, for seven years, among different habitats at three study sites distributed north/south across the southern Rio Grande rift (Bandelier National Monument, Sevilleta LTER and Jornada LTER). Counts of individuals of each species were then analyzed for patterns of species richness, habitat and site community similarity, by use of cluster analysis and species accumulation curves. Most habitats within each study site supported a unique spider assemblage. In addition, our data supported the distance decay hypothesis in that spider assemblages from similar habitats across a region were dissimilar to each other. This study of 98 species of spiders over a 500 km area, demonstrates the significant influences of regional biotas on local species composition and richness. These findings also demonstrate that ecoregion transitions can be complex in areas with considerable topographic heterogeneity and multiple environmental gradients. Desertification of semi-arid landscapes at the Jornada LTER site appeared to result in lower spider diversity and abundance.
Development of Long Term Study plots for Creosotebush and Ocotillo at the Sevilleta NWR.
Joanna Redfern
Abstract: This project addresses how climate affects long-term density and demographic changes in Creosotebush (Larrea tridentata) and Ocotillo (Fouquieria splendens). We are examining how precipitation and temperature relate to shrub density, patterns of growth, seedling recruitment, and mortality of Creosotebush and Ocotillo plants at the Sevilleta National Wildlife Refuge (NWR).
Inheritance patterns of banner-tailed kangaroo rat mounds.
Andrew Edelman
Abstract: Banner-tailed kangaroo rats (Dipodomys spectabilis) are native to desert grassland ecosystems of the southwestern United States and northern Mexico. This ecosystem engineer defends exclusive territories that center around a large dirt mound containing burrows and food caches. Dispersing juveniles must establish territories by occupying a vacant mound or building a new one. New mounds, however, take several months to build and unoccupied mounds quickly collapse and become unusable. Some banner-tailed kangaroo rat females abdicate their mounds to offspring and relocate to a neighboring mound. Other juveniles inherit a mound after their mother dies. I monitored inheritance patterns of banner-tailed kangaroo rat mounds on the Sevilleta National Wildlife Refuge from March 2005-Feburary 2006. I live-trapped at active mounds each month and monitored survivorship and dispersal of kangaroo rats. Using this data I will determined whether juveniles obtained a mound through abdication, inheritance, or by dispersing. I will also examine how sex and time of birth of juveniles affects inheritance patterns of mounds.
Impact of a Mega-Drought & Bark Beetle Outbreak on Piñon-Juniper Woodland Ecosystems in the Middle Rio Grande Basin.
Paulette Ford, USDA Forest Service, Rocky Mountain Research Station,
Neil Cobb, Robert Delph, and Michael Clifford, Northern Arizona University, Merriam-Powell Center for Environmental Research,
Mike Friggens and Don Natvig, University of New Mexico, Sevilleta LTER,
Monique Rocca, Colorado State University,
Abstract: This research provides an interdisciplinary approach to assess the impact of regional drought and bark beetle infestation on ecosystem function in piñon-juniper woodlands of the Middle Rio Grande Basin. In response to drought, bark beetle populations typically explode as outbreaks. The general consensus is that drought, coupled with bark beetle infestation increases the risk of catastrophic fire in piñon-juniper woodlands in managed areas, and in property that adjoins these areas. This research will provide managers with a greater understanding of how these biotic and abiotic disturbances affect piñon-juniper woodlands ecosystems. The focus of our study is to examine the impacts of bark beetles and to address stand attributes that make certain piñon populations more susceptible to bark beetles than other populations. The overall objectives are to 1) determine the extent to which fungal spores carried by bark beetles contribute to disease symptoms associated with bark beetle infestation caused death in piñon-juniper woodland trees, 2) assess drought impacts on community structure and document the extent and severity of invasive species in drought-impacted areas, 3) quantify stand structure and fuel load changes in high mortality areas and 4) integrate data from remote sensing and other sources to assess environmental correlates of mortality.
Continental ‘Smokers’ in the Rio Grande Rift: Do you know where YOUR CO2 comes from?
Laura Crossey, Dept. of Earth & Planetary Sciences, UNM
Abstract: CO2-rich springs in extensional basins of the western U.S. are often associated with extensive Quaternary travertine and lacustrine carbonate deposits, reflecting a long-lived interaction of deeply-sourced, “endogenic” fluids with the surficial hydrologic regime. These systems can be thought of as continental analogues to the rich chemolithotrophic microbial ecosystems found in oceanic extensional tectonic settings (hydrothermal systems associated with mid-ocean ridges).
We use a combination of aqueous and gas geochemistry to understand the origin of the spring waters. Mixing models indicate only a small component of saline, radiogenic, deeply-sourced fluid is needed to produce the observed spring chemistries. Analysis of dissolved gases within the spring waters reveal a mixing trend between atmosphere/soil gas with an end-member dominated by CO2; gas compositions range to over 99 volume % CO2 in some springs. Hydrogen concentrations are consistently in the 100s of nannomolar range, and methane and hydrogen sulfide are detected in several springs. Trace gas analyses shows elevated He concentrations (low N2/He) suggestive of a deep crustal or mantle origin for the gases, linking them to magmatism and extensional tectonics. Isotopes of helium and carbon in the spring gases are consistent with a significant mantle-derived component. The CO2 richness coupled with the presence of hydrogen and a suite of redox-sensitive trace components offer a chemically rich setting for a diverse microbial community. When extensional faults serving as the conduits for endogene fluids encounter typical basin fill associated with many extensional basins (e.g., Rio Grande Rift, Basin and Range, Arizona transition zone, etc.), these fluids are mixed with the shallow hydrologic system, resulting in aquifer waters with similar geochemical character to springs. We anticipate that microbial community analysis will reveal the presence of microorganisms utilizing many of the same metabolic pathways found in oceanic hydrothermal settings. This new paradigm for continental “smokers” has important implications for establishing links between the asthenosphere, lithosphere, and biosphere.
Hydrologic Variability in Rio Grande Riparian Ecosystems, New Mexico, USA.
Jim Thibault, James Cleverly, Cliff Dahm
Astract: Water consumption by invasive vegetation and restoration of native riparian ecosystems are receiving considerable attention along the Rio Grande corridor in central New Mexico, USA. Since 2000, we have measured evapotranspiration (ET) to estimate water use at several sites composed of native and exotic vegetation. We have also monitored water table (WT) depths and flood events to help determine restoration capability. Drought conditions and below normal runoff have prevailed during this time. Annual growing season rates of ET varied from 70 to 134 cm. ET was greatest in a native cottonwood forest with a dense, exotic understory, lowest in a less dense stand of exotic saltcedar mixed with native saltgrasses, and intermediate at a dense, monospecific saltcedar stand. In 2004, after exotics had been removed from the cottonwood site, ET declined 8% from the previous three year mean, while rising 3% to 6% at the other, untreated sites. WT hydrographs ranged from relatively shallow (<1.5 m) and uniform to relatively deep (>2.5 m) and highly variable. As the drought continued, the WT at the dense saltcedar site dropped below 3 m during much of the growing season. This site was also the only location that received flooding, although it was inundated very little from 2000 to 2003. Given the physical alterations and climatic variability inherent to this riverine system, long term data from different locations targeted for restoration help capture the range of hydrological conditions and provide valuable information for water resource management and restoration planning.
Fungal community associated with roots of two closely related grasses, Bouteloua gracilis and B. eriopoda.
Andrea Porras-Alfaro, William Dvorachek, and Donald Natvig
Abstract: Studies of fungi associated with grasses have focused largely on above-ground tissues. However, fungal endophytes are also recovered from roots. This study examined fungi associated with roots of two dominant grasses, Bouteloua gracilis (blue grama) and B. eriopoda (black grama), collected from the Sevilleta National Wildlife Refuge in New Mexico. In part, this study reflects a long-term interest on the part of plant ecologists to understand the distributions of these two grass species. Plants were collected from areas where either one or the other grass was dominant, as well as from an area where the two species coexist. The diversity of fungi associated with roots was surveyed by direct PCR, cloning and sequencing of the internal transcribed spacer (ITS) of nuclear rDNA. Clones were sequenced and grouped using phylogenetic analysis. Among 140 clones sequenced, we observed more than twenty fungal species representing diverse basidiomycetes and ascomycetes. The fungi observed included several that appear to be closely related to species reported as either endophytes or plant pathogens. Most of these have not been reported previously from arid grasslands. There were no significant differences between the fungal groups associated with blue and black grama. The ecological significance of this diverse fungal assemblage is a subject ripe for additional study.
Teacher Perception and Use of Two Long- Term Monitoring Programs.
Dan Shaw
Microbial function and response to N addition in grassland soils.
Lydia Zeglin and Scott Collins
Abstract: Grassland soil microbial communities have not been often or well-characterized. In this study, extracellular enzyme assays are used to characterize the funtional microbial community in the soils of three grasslands. In addition, the response of these functional communities to experimental nitrogen (N) addition is evaluated. Grassland sites are: Sevilleta National Wildlife Refuge, New Mexico, USA (SEV); Ukulinga Research Farm, KwaZulu-Natal, South Africa (SAF); and Konza Prairie, Kansas, USA (KNZ). Between-site variation in functional microbial community is strong, and is likely related to the relative pH of the systems. These grasslands respond similarly to N addition by increasing phosphatase activity, but show no other common response. Overall, grassland soil community function seems fairly resistant to N addition. Also, grasslands respond differently than forest ecosystems to N addition, showing no resulting potential for changes in belowground C storage.
Interactions between desert seed harvester ants (Pogonomyrmex desertorum) and granivorous kangaroo rats (Dipodomys merriami) in a Sevilleta desert creosotebush (Larrea tridentata) community.
David Lightfoot
Abstract: The interactions between granivorous rodents and ants in Chihuahuan Desert ecosystems have been studied and debated for 30 years, yet no clear demonstration of competitive interactions have been presented. The Chihuahuan Desert Small Mammal Exclosure Study (SMES) was designed to test the effects of rodents on Chihuahuan Desert soils, plants, and animals across a series of study sites from the southern Chihuahuan Desert in Mexico, to the Sevilleta. This poster presents the findings of seed harvester ant (Pogonomyrmex desertorum) interactions with kangaroo rats (Dipodomys merriami) at the Sevilleta. The nests of several species of ants were counted on 1) rodent + rabbit removal plots, 2) rabbit only removal plots, and 3) control plots, all of which were replicated at both the Sevilleta grassland and creosotebush study sites. Nests were counted once each year for a period of 10 years following rodent and rabbit removals. Several Pogonomyrmex species were present at the Sevilleta grassland and creosotebush SMES study sites, but only one, P. desertorum, was common enough to assess statistically. The numbers of P. desertorum nests increased significantly 2-fold on the rodent + rabbit exclosure plots at the creosotebush study site within 3 years of rodent and rabbit exclusion. That trend increased slowly to about a 3-4-fold increase and maintained that level through the duration of the study. In contrast P. desertorum was rare at the grassland site, and there was no effect of rodent removal there on another species of ant, P. rugosus. Other ant species were not as common, and no others responded to rodent or rabbit removals. These findings demonstrate strong competitive interactions between P. desertorum and D. merriami, and similar but even more pronounced interactions were found at the Jornada SMES site too. Whether the interaction was from indirect effects of rodent herbivory on seed producing plants, or direct competition for soil surface seed resources is not known. Future studies are needed to test for direct vs. indirect competition for seed resources by granivores in these ecosystems.
Relocation of Gunnison’s Prairie Dogs to Sevilleta NWR: Conservation, Cooperation and Ecological Research.
Mike Friggens, Ana Davidson, Paula Martin, Scott Collins, Renee Robichaud, Dennis Pritchard and Terry Tadano
Abstract: We discuss the process employed during the relocation of Gunnison’s prairie dogs (Cynomys gunnisoni) from the city of Santa Fe to the Sevilleta National Wildlife Refuge during spring and summer 2004. There were 3 primary goals to this relocation project: Restoration, conservation and ecological research. The relocation process, set-up of experimental plots and current project status are discussed.
Trends of N deposition in the Northern Chihuahuan Desert: Temporal Trends and potential consequences.
Selene Baez, Joe Fargione, Doug Moore, Scott Collins and Jim Gosz
And others...

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