Project Ideas
A major objective of the REU Program is to give undergraduate students an opportunity to conduct independent research. Mentors for the REU Program have expertise in a broad range of ecological disciplines, and could advise on a range of topics related to the ecology of Chihuahuan desert shrubland, desert grassland, and arid land river and riparian ecosystems. Mentors were invited to describe specific projects that would be available to students participating in the REU program.
Aquatic Ecology
Unlike the Rio Grande, ditches that are adjacent to the river are permanent water sources and a potential source of flying invertebrate fauna to the river. In this project, the student would conduct a comparison of aquatic fauna from ditches and the Rio Grande main channel at the Sevilleta NWR. Comparisons can be made between the different habitats: is there a different invertebrate community? Is there different vegetation? What about the substrate? (Mentor: Ayesha Burdett)
The Rio Grande has an extremely variable flow regime, from extremely low flows to huge floods that spill out over the banks. There are several areas adjacent to the river that are inundated during large floods but remain dry for most of the year. Evidence from other locations indicates that there is a ‘bank’ of dehiscent invertebrates in the soil that are able to respond rapidly to flooding. Is there a similar ‘bank’ at the Sevilleta? Are different organisms found in areas with different flooding frequencies? (Mentor: Ayesha Burdett)
Species distribution patterns are the fundamental part of the biogeography and species evolution. In aridland systems, springs serve as isolated refuges for aquatic species with potentially limited distributions. This project will examine the temporal and spatial patterns of algae in these extreme desert springs habitats, predicating differences related to isolation and/or water chemistry in these aquatic areas. The work will be done at the Sevilleta National Wildlife Refuge, 60 miles south of Albuquerque, New Mexico. There are more than 30 isolated springs with high conductivities and salinities; preliminary work examining diatom communities show great differences among the springs likely related to water chemistry. This summer, I would like to expand the sampling regime to include additional springs in the region. (Mentor: Becky Bixby)
Water is a rare resource in aridland ecosystems like those found in the Northern Chihuauan Desert. However, there are over 40 know artesian springs in the refuge each of which would harbor an interesting insect fauna. A biogeographic comparison of insect (or algae) dynamics of stream insect communities in artesian springs compared to wildlife watering areas would help us document the kinds of insects in the region and the importance of these water sources to their long-term survival. (Mentor: Scott Collins)
The Sevilleta NWR is home to about 40 small springs spread across the landscape. Some remain in a natural condition and others have been modified to become watering points for animals. These springs are vital water sources for aquatic organisms, and represent different types of microhabitats with different environmental niches. However, there have been limited surveys of organisms in these springs. This project would involve collecting invertebrates to gain an understanding of distributions of different taxa in relation to the different microhabitats. (Mentor: Ayesha Burdett)
Fungal Communities:
Characterization of coprophilic fungi at Sevilleta National Wildlife Refuge. We are studying endophytic fungal communities at the SNWR. A preliminary assessment of blue grama (Bouteloua gracilis), one of the most important forage grasses in North America, indicate that the roots of this grass harbor large quantities of dark septate fungi and several of the most common species are also known coprophiles, species that specialize at living on/in dung. The REU student will study the fungal community inhabiting dung of common granivores (Dipodomys spectabilis, D. merriami, and Neotoma albigula) and herbivores (Sylvilagus auduboni, Lepus californicus, Antilocapra and Odocoileus hemionus). The student will collect and process dung samples using traditional and molecular techniques in search of coprophilic species also found as endophytes within different tissues of blue grama. Prospecting for fungal species present within the dung of several mammals in the study site will yield important clues about the life-cycle of some of the most common root- and seed-inhabiting endophytes. (mentor: Bob Sinsabaugh)
Invertebrate Communities:
Obligate pollination mutualism between yuccas and yucca moths has been studied in many systems and represent a classic example of pollination/seed predation mutualism. While yucca moths provide the plants with pollen, moth larvae feed on a portion of the developing yucca seeds. Although banana yucca, Yucca baccata, is common in the grasslands of the Sevilleta, the interaction between the plant and its pollinators has not been well studied in this system. This project will investigate the relationship between Y. baccata and its pollinator moths within the context of the SNWR. (Mentors: Beth Haley and Jennifer Rudgers)
Very little is know about the microbial flora of invertebrates, but species with limited distributions and diets often harbor unique assemblage of diverse microorganisms. The meloid beetle, Epicauta longicolus is a diurnally-active species that feeds only on the toxic plant Silverleaf Nightshade (Solanum elaeagnifolium, Solanaceae) and is active for only 3-4 weeks between late May and mid-July. Because E. longicolus is the only signficant herbivore of this plant, we suspect that it must possess a microbial flora uniquely adapted to the digestion of the plant's toxic flowers. The student on this project will characterize microbial endosympionts associated with E. longicolus using a combination of molecular and culture-dependent techniques. (mentor: Takacs-Vesbach/Toolson)
This summer’s project will combine forays into the fields of insect behavioral ecology, plant evolutionary ecology, and plant-herbivore interactions. We will study a system involving a toxic plant, Silverleaf Nightshade (Solanum elaeagnifolium, Solanaceae), and its only significant herbivore, the meloid beetle, Epicauta longicolus. S. elaeagnifolium is a perennial species that is only able to colonize and thrive in disturbed habitats such as those found along roads on the Sevilleta NWR. E. longicola is a diurnally-active species that feeds only on S. elaeagnifolium, and is active for only 3-4 weeks between late May and mid-July. Our work last summer showed that the beetles prefer to feed on the petals and pistils of the flowers. (mentor: Eric Toolson)
Plant Community Ecology:
Although much is known about the composition and dynamics of the aboveground parts of grassland plant communities, very little is known about what goes on belowground. One potential project for this summer would be to measure how much plant biomass occurs in the shallow soils in desert grasslands at the Sevilleta. There are several experimental areas at the Sevilleta where studies of below ground production could be conducted. These include comparisons or burned and unburned areas, or grazed and ungrazed areas, or areas with and without added nitrogen fertilizer. Thus, a variety of interesting projects and comparisons are possible. (Mentor: Scott Collins)
Willows propagate via seeds or clonal reproduction, and these propagules may be dispersed by wind, water, or animals, thereby making these plants prolific dispersers. Like other endemic sandbar willows, Salix exigua populations commonly exhibit invasiveness in riparian ecosystems. As a result, these willow-invaded habitats are overcrowded and have obstructed stream flow. In this project, the student will be responsible for leaf tissue sampling along the Rio Grande and genotyping using neutral genetic markers. The results will be used to determine population structure and dispersal patterns of Salix exigua along portions of the river and its tributaries. This project is suitable for students interested in seed dispersal, riparian forest ecosystems, and plant population genetics. (Mentor: Brian Alfaro)
Plant community changes following prescribed fire at the Sevilleta National Wildlife Refuge. We are conducting experimental burning treatments in different seasons to determine the impact of fire seasonality on community and ecosystem processes. An experimental burn was conducted in November 2007 and additional fires are scheduled for March and June 2008. These plots are large enough for studying insect responses (pitfall traps), plant population and community studies, and ecosystem processes, such as soil C and N dynamics. (Mentor: Scott Collins)
Several vegetation transition zones occur within SNWR. Transition zones are ideal locations for studying species interactions and helping us understand how plant communities change across the landscape. One transition zone is between the Chihuahuan Desert grassland (dominated by black grama grass, Bouteloua eriopoda) and Short Grass Stepp (dominated by blue grama grass, Bouteloua gracilis). A series of photographs have been taken through time at the black-blue grama transition zone. The student would identify and map plants in the images to measure changes through time. Changes in plant cover would be compared to environmental factors, including past precipitation, temperature or burn status, to help us understand how these dominant grasses may interact under future changing climate. (Mentor: Laura Ladwig)
Biological soil crusts are microbial communities that are found on the surface of almost all arid and semiarid ecosystems. They play ecologically important roles in nutrient and water cycling, which has been shown to benefit individual plant growth. This project will investigate the role of soil crusts in structuring plant communities across a range of different biomes at the Sevilleta. Students who have an interest in plant or soil microbial ecology will likely be a good fit for this project. (Mentor: Anny Chung)
A study of below ground biomass production during the summer monsoon season. This would including digging sifting, drying and weighing root samples at the start and the end (sort of) of the monsoon season. Installing root in-growth bags (not donuts) etc. The question would be focused on which plant community type has the highest root abundance and dynamics in the top 20 CM of soil. ( Mentor: Scott Collins)
Older individuals of blue grama grass exhibit ‘ring’ (or doughnut) morphology, in which the center of the plant dies back, and the edges continue to expand. This growth habit is common among clonal plants in arid ecosystems, but surprisingly, well supported explanations for it have remained elusive. A recent model showed that negative plant-microbe interactions can produce rings, but this idea has not yet been experimentally validated. We are left wondering can negative feedbacks between plants and soil organisms explain the mysteries of ring formation in clonal plants? We will use a combination of field observation, field experiments, and a greenhouse experiment to test whether a build-up of negative interactions with soil microbes can explain ‘ring formation’ in a dominant Sevilleta plant, blue grama grass (Mentors: Anny Chung, Jennifer Rudgers, and Scott Collins).
One reason for invasiveness is phenotypic plasticity of functional and reproductive traits, which allows introduced plants to overcome initial pressures of bottleneck and founder effects. The student will investigate phenotypic plasticity in Sahara mustard (Brassica tournefortii Gouan), an invasive plant that has recently expanded in the roadsides, agricultural fields, and desert habitats of southwestern United States. The project involves greenhouse work, common garden field experiments, and molecular work. This project is suitable for students interested in invasive plant biology and evolutionary ecology. (Mentor: Brian Alfaro)
We know very little about the larger scale patterns of vegetation and soils at the Sevilleta National Wildlife Refuge. The landscape offers interesting environmental gradients along the N and S ends of the Los Pinos Mountains. These gradients serve as an interesting environmental template for analysis of variation in plant and animal communities at the Sevilleta National Wildlife Refuge. (Mentor: Scott Collins)
Dominant plants are the most abundant species in the community and have a large influence on ecosystem functioning. Several years ago dominant plants were experimentally removed from two communities; creosote shrubs (Larrea tridentata) was removed from shrublands and black grama (Bouteloua eriopoda) removed from grasslands. The student would remeasure the vegetation and soils within the removal plots to determine how sites have responded several years after dominant plant removal. Did the plant communities recover or were communities drastically changed by the removal of the dominant species? (Mentor: Laura Ladwig)
Water is a very important driver in arid grassland ecosystems. During the growing season precipitation comes in distinct rainfall events that set the stage for plant production and growth. In general, rainfall is scattered in time and space such that soils often dry out after a particular storm event. What is the impact of continuous, frequent moisture on arid grassland plant communities? Does more water lead to more or fewer species of plants during the growing season? Several other hypotheses could be tested as well. (Mentor: Scott Collins)
Plant Physiology/Ecology:
Given that rainfall is the key resource driving net primary production, it is vital to develop a clear understanding of how many common plant species respond to changing patterns of summer rainfall. Our rainfall manipulation experiments provide an ideal setting to study the ecophysiological responses of dominant and subordinate grasses to altered patterns of monsoon rainfall under relatively controlled experimental conditions. (mentor: Scott Collins)
A challenging question in arid land ecosystems is to understand how patterns of rainfall affect fluxes in soil moisture and how those fluxes affect availability of other key limiting nutrients, especially nitrogen. Field measurements on nitrogen fluxes could be made in our summer monsoon experiment and this work could be combined with simple lab incubations of soil under different watering schemes to assess soil N availability under different rainfall scenarios. (mentor: Scott Collins)
Pulsed precipitation is a defining feature of semiarid ecosystems, these wetting and drying cycles promote different plant physiological responses to precipitation. When it rains, plants decide if its worth investing energy to take advantage of a particular precipitation pulse (e.g. by producing new roots or synthesizing new enzymes for photosynthesis) with the extent of response being highly dependent on the level of stress attained during dry inter-pulse periods and the plant functional type composition. Investigating the relative importance of these adaptations is of primary interest to understand the functioning of Piñon and Juniper woodlands, an extensive ecosystem type in the semiarid North American Southwest. Physiological responses to precipitation pulses can be gauged with measurements of photosynthesis and transpiration along with simple models of plant function. Within the context of a large-scale rainfall manipulative experiment in a PJ woodland at the Sevilleta LTER, we provide the opportunity to develop experiments based on these gas exchange and modeling techniques to asses the physiological response of trees to wetting and drying cycles. (mentor: Will Pockman)
Understanding water dynamics in the rhizosphere is key to developing ecological theory on how plants adapt and survive harsh conditions. Due to the scarcity of water in semiarid ecosystems, gradients of soil water availability develop in space and time. Investigating the strategies that plants develop to optimize the use of available water in the soil is a very active topic of research in ecology. We invite students to develop experiments to characterize some of the belowground processes that Piñon and Juniper trees display to cope with water scarcity and how such strategies affect water dynamics in the rhizosphere. Measurements of root hydraulic conductivity, root sap flow, and plant water potential among other techniques will be available to formulate such ecohydrological experiments within the framework of a large-scale experimental setting at the Sevilleta LTER. (mentor: Will Pockman)
Determination of Pinon-Juniper Foliage Biomass on the Sevilleta. Quantification of annual aboveground net primary production among trees in Pinon-Juniper (PJ) habitats is challenging Our past methods for annual foliage production as well as wood increment addition on both Pinon (Pinus edulis) and Juniper (Juniperus monosperma) lack the precision necessary for detecting inter-annual variation. . Most recently, dendrometers (bole growth measuring devices) have been installed on a number of individual trees at a Sevilleta PJ site that will allow a better measurement of annual gross growth. However, we now need a method of relating such bole growth to annual foliage production for both species. This proposed project would involve developing methods for this and testing their efficiency under field conditions. (Mentor: Doug Moore/E. Muldavin)
Earth&Planetary Sciences:
How are the basic composition of plant community on landscapes of the Sevilleta National Wildlife Refuge influenced by of soil development geomorphological processes? ( Mentor: Les McFadden/McFadden Lab)
How does the orientation of a hillslope affect the types of soils forming on those slopes? How is this linked to the types of vegetation growing on those slopes and the geological processes that shape hillslopes? (Mentor: Les McFadden/McFadden Lab)
How do soils in the landscapes of this area reflect the different ages of different parts of the landscape, such as fluvial terraces and alluvial fans? (Mentor: Les McFadden/McFadden Lab)
Vertebrates:
Research by members of the Wolf lab this summer will include work on trophic interactions between reptiles, small mammals and invertebrates and how animals use specific resource pools. This work will provide opportunities for REUs to conduct both field and lab based research. We are a ecological physiology lab and often use stables isotope approaches to describe and quantify interactions between animals and their environments. (Mentor: Blair Wolf)
Reintroduction of the Gunnison’s prairie dog on Sevilleta National Wildlife Refuge has taken place since 2005. The overall goal is to restore a stable population of Gunnison’s prairie dogs to a semi-arid grassland ecosystem where the species was historically located on the Sevilleta NWR. Prairie dogs are ‘ecosystem engineers’ and reintroducing this species will improve the health and diversity of the grasslands on the refuge. Two new relocation sites were established in 2010 and there have been three seasons of releases on these sites. This reintroduction project provides many interesting research opportunities. Studies on population success, impacts of the reintroduction on plant and animal communities, as well as studies of prairie dog behavior could be conducted this summer. (Mentor: Jon Erz)
Little is known about the population densities and effects of brood parasitism on the Gray Vireo in New Mexico. The Gray Vireo is a Species of Conservation Concern (USFWS 2002), listed as Threatened in the State of New Mexico (New Mexico Game and Fish 2008), and their nests are frequently parasitized by the Brown-Headed Cowbird. This projects occurs at two study sites in Los Pinos mountains. The students will determine the population density in the two areas, find nesting vireos, monitor nests, and determine the effects of brood parasitism. (Mentor: Kathy Granillo)
Native prairie dogs, K-rats and non-native (cattle) herbivores may have a considerable impact on plant community structure by altering the composition and pattern of vegetation across the landscape. Many studies of plant and animal community structure could be conducted in our long term cattle and small mammal exclosure experiments. (Mentor: Scott Collins)
Describe and compare plant species richness and abundance across 8 study sites in the various grasslands on the east side of the refuge. These 8 sites are used in the winter to survey for wintering grassland birds, principally Sprauge's Pipit. We would also like to use these sites to survey breeding grassland birds. We need to understand the plant community on each site and how they differ between sites. Two sites are in predominantly blue gramma sites, two are in mixed blue and black gramma, two are in an intergrade area between short grass prairie and Chihuahuan grassland, and two are in Chihuahuan grassland. (Mentor: Kathy Granillo)
