2022

Hillary Bohm

The River is a Mirror

The Rio Grande has been and continues to be a cultural and ecological life-sustaining entity. The existence of so many ecosystems and livelihoods depends on the existence of the river. The Rio Grande and the life surrounding it illustrates how intricately woven together people and the environment are and shows us that human connection with the environment can be beautiful and beneficial and has been happening since humans were around. I collaborated with NWR visitor center managers to make a triptych that focuses on the Rio Grande. The three paintings explore connections among the three sister refuges in the area: Valle de Oro National Wildlife Refuge, Sevilleta National Wildlife Refuge, and Bosque del Apache Refuge and will be displayed in their visitor centers. I researched what the river meant to people who had both ancestral, traditional, and contemporary connections to it with a focus on articles and sources that worked from an environmental justice framework. Conversations and collaboration with National Wildlife Visitor center managers, refuge managers, and my biologist and artist peers were highly influential, cherished, and one of my favorite parts of the process when creating this body of work. While creating a zine and using found trash and discarded research objects to make 3D elements, I explored themes of transformation, divergence, and moving forward. Through the summer, I thought of the river as an entity that could teach me many things. Rivers create physical and social landscapes with water as their medium. Through the process of creating this project, I was able to see myself and the world around me reflected in the river. I want to leave the viewers with the questions: what is the river telling them here and now, how are they connected to it and the life around it, and what do they see in its reflection?

Priscilla Castañeda

Effects of Precipitation on Biogeochemical Cycling in Semi-arid Ecosystems

Global change is expected to alter rainfall patterns in arid ecosystems which is likely to have notable impacts on biogeochemistry. Arid regions are driven by pulsed rain events that trigger biological activity and drive many soil nutrient processes. Regional climate data predicts that rain events will become more frequent, smaller in size and also increase in variability, but other climate models predict for less frequent, larger, and more intense rain events. We examined the effects of changing rainfall frequency and size, as well as interactions between rainfall and fertilization, on soil nutrient cycling in a dryland ecosystem. We conducted our study using the Monsoon Rainfall Manipulation Experiment (MRME),a long-term ecological study site that manipulates rainfall events according to climate model predictions, with rainfall treatments including many small, few large, or natural rainfall (control) events, all with equal inputs of precipitation. Rainfall manipulations are crossed with a fertilization treatment. We assessed effects of rainfall size and frequency on soil nutrient availability at three time points surrounding the plant growing season (pre-monsoon, peak growing season, and post-monsoon). We found few effects of rainfall size and frequency on soil available nutrients, while the effects of fertilization were much stronger, and all effects were dependent on season. Prior to the monsoon (and application of treatments), fertilized plots had a lower pH than control plots, although this effect disappeared after the monsoon, and there were no effects of precipitation treatments. Only in samplings after seasonal fertilizer application, soil nitrate and ammonium were both higher in fertilized than control plots, and there was no interaction between fertilization and precipitation manipulations. There was a marginal effect of precipitation size and timing on nitrate in the post-monsoon sampling as control plots had higher nitrate than those with large infrequent rainfall events, which were higher than plots with small frequent rainfall events. We found no effects of either fertilization or precipitation on phosphate. In conclusion, we found few effects of rainfall event size and frequency on soil nutrients, suggesting rainfall frequency does not affect microbial processing of nutrients, or that limiting nutrients are immediately taken up by the plant or microbial community. Further analyses on soil microbial biomass and nutrient processing will shed light on mechanisms driving nutrient availability in these dryland ecosystems.

Karin Ebey

Analysis of dietary niche overlap of turtles in the Middle Rio Grande Basin using stable isotopes

Sympatric species are thought to coexist through niche partitioning which reduces competition. Invasive species can negatively impact ecosystems through competition for limited resources and disrupting niche partitioning. In this study, dietary niche partitioning in the freshwater turtle community in the Middle Rio Grande Basin, consisting of the native Painted Turtle (Chrysemys picta) and Spiny Softshell (Apalone spinifera), the presumed invasive Common Snapping Turtle (Chelydra serpentina), and the invasive Red-eared Slider (Trachemys scripta), was explored. Turtles were caught at the Rio Grande Nature Center State Park and Sevilleta National Wildlife Refuge using baited hoop net traps and tail tips were collected for stable isotope analysis. The turtle community differs greatly between the sites, most notably in the abundance of Red-eared sliderswhich is higher in the more urban Rio Grande Nature Center State Park. At the Rio Grande Nature Center State Park, C. picta overlapped in isotopic space with both T. scripta and C. serpentina, but to a greater degree with T. scripta. At Sevilleta National Wildlife Refuge, C. picta, C. serpentina, and A. spinifera do not overlap in isotopic space, but the one T. scripta sampled was within the C. picta isotopic niche space. Thus there is a high potential for competition between T. scripta and C. picta, because of a high degree of isotopic niche overlap. These results have implications for invasive species management in the Middle Rio Grande Basin. This study provides a valuable baseline of turtle communities affected by urbanization, invasive species, and climate change.

Sophie Epps

Off to the races: soil organic matter hastens seed germination

Soil nutrient and soil moisture content have been known to vary spatially across semi-arid woodlands. Soil nutrient heterogeneity can influence the growth and survival of seedlings. Within New Mexico, two semi-arid woody species, Pinus edulis and Juniperus monosperma, have different growth and drought response mechanisms. It is important to understand spatial heterogeneity within an ecosystem, as microenvironmental characteristics can differ between canopy patches and contribute to drought responses of these woody species. At the Sevilleta National Wildlife Refuge (SNWR), New Mexico, little is known about how soil properties affect the ability of piñon and juniper species to respond to drought events. To investigate the impact of microenvironmental characteristics on piñon seedling regeneration, we sampled 20 soil sites across a 1 ha plot within piñon-juniper woodlands of SNWR. Further, to determine germination rates of P. edulis seedlings, seedlings were established in one of the 20 soil samples and monitored in growth chambers. Across our 1 ha plot, we found soil organic matter, moisture content, and NPK nutrients were greater under a closed canopy. Our greenhouse study revealed seedlings grown in soil with higher organic matter had an earlier day of emergence. Our results indicate soil nutrient heterogeneity influences P. edulis seedling survival. These results provide an understanding of the distribution and abundance of nutrients across a landscape that impacts the population dynamics of woody species. Focusing on microenvironmental characteristics allows us to better understand the relationship between the environment and P. edulis seedling survivorship. Investigating spatial heterogeneity across a semi-arid landscape suggests resource availability in relation to anthropogenic climate change.

Jodhan Fine

Bell’s Vireo (Vireo bellii): an Understudied Songbird in New Mexico

At the Sevilleta National Wildlife Refuge (NWR), Bell’s Vireo (Vireo bellii) breed at the northern edge of their New Mexico range. Sevilleta is located in the convergence zone of the eastern Bell’s Vireo (Vireo bellii bellii/medius) and the southwestern Bell’s Vireo (Vireo bellii arizonae), but the exact subspecies classification at Sevilleta is unknown. Bell’s Vireo have exhibited recent range expansion in New Mexico following the Rio Grande Riparian corridor north. The New Mexico Department of Game and Fish lists Bell’s Vireo as a state threatened species due in part to habitat loss and extensive brood parasitism by the Brown-headed Cowbird.  Because Bell’s Vireo are both a common host of Brown-headed Cowbird parasitism and a conspicuous species with easy to find nests, they are a perfect bird to center a parasitism study on. Over the last three years we’ve examined the parasitism rate and the breeding success of Bell’s Vireos. Additionally, we’ve explored how nest height and density of surrounding vegetation correlate with parasitism. Our study—researching the productivity and success of Bell’s Vireo nests—provides insight regarding the status of these vulnerable birds. Furthermore, broadly studying how vegetation relates to parasitism could be useful for future riparian management efforts along the Rio Grande. The results of this study may also prove helpful for two riparian reliant federally listed species: Yellow-billed Cuckoo (Coccyzus americanus) and Southwestern Willow Flycatcher (Empidonax traillii extimus).

Kyle Gallant

Drought sensitivity of grass and shrub species in contrasting Chihuahuan Desert sites with contrasting climate, and physical characteristics

Precipitation in arid regions has a significant impact on net primary production (NPP) of plant communities. Many dryland plant species are sensitive to slight variations in precipitation, and regional variation in plant community sensitivity to climate and aridity has been observed. Regional variations in sensitivity may be a result of site-specific climate, topographic, or vegetation characteristics, or of differences in soil properties across sites, even within the same biome. Data has been collected at two Long Term Ecological Research (LTER) sites in New Mexico (Sevilleta and Jornada) for several decades, allowing for comparison of climate and NPP data at sites that have Larrea tridentata and Bouteloua eriopoda at both locations. These long-term data sets allow for similar analyses at different sites with variation in vegetation, climate, soil, and topography, and may help in understanding drought sensitivity in the same plant species under different conditions.  We found that the grassland sites seem to be the most sensitive to climate variations, with the Sevilleta site being the most sensitive. A differentiation in soil texture between the two different ecotypes can be seen. As well, landscape slope and aspect seems to not be significant in controlling the sensitivity of each plant species, although the data are sparse. A biomass percentage sensitivity was also discovered, hinting that outside the mean SPEI there might be a shifting relationship between the dominant species that exist at the community level.

Gaby Harrold

Biocrust Thresholds Across a Nitrogen Gradient

Biological soil crusts, or biocrusts, are interconnected communities of organisms which perform key biological processes, including nitrogen fixation and photosynthesis. The role of biocrust microbes in the geochemical cycles of nitrogen and carbon influence soil fertility, soil stability, water dynamics, and plant community composition. Atmospheric nitrogen deposition has increased due to climate change, and affects these interconnected processes of the biocrust communities. This study aims to determine the critical threshold of inorganic nitrogen deposition into the dryland biocrust community, as well as determine a timeline of changes to the key biological processes following a one-time nitrogen addition. A diverse set of measurements will be taken from each plot, so as to gain an understanding of the effects of additional nitrogen on the cyanobacteria, ascomycete fungi, and grasses which make up the target biocrust community. Overall health of the biocrust in each treatment plot will be determined by percent cover analysis. Pigment counts of scytonemin and chlorophyll α will serve as proxy data for nitrogen fixation and photosynthetic activity by biocrust cyanobacteria. Root samples of the black grama(Bouteloua eriopoda) grass will be used to take hyphal counts of mycorrhizal fungi colonization which will serve to demonstrate the health of the ascomycete fungi in the biocrust community. Quantitative and qualitative measures of health of the focal black grama grass in each plot, along with percent cover analysis of the grass vegetation, will demonstrate the bottom-up effects of any impacts to the biocrust community. The results of this study will help to build understanding of the effects and critical thresholds of climate change factors on a key component of dryland ecology

Katie Jansson

Correlation of arid soil properties and vegetative cover on stand and ecotonal scales

Ecotones are transition zones between ecological systems, and are commonly delineated by plant community composition (Hufkens et al., 2009). However, the underlying controls of ecotones and their boundaries are often not clear. The Sevilleta National Wildlife Refuge in central New Mexico contains the convergence of three different ecotones, each with varying vegetation, but surface observations alone do not explain the interaction and distribution of their ecotonal ranges- or why these plants grow where they do. However, these vegetation differences and ecotone boundaries may correspond to soil variations. This project will explore how surface hydraulic conductivity and hydraulic proxies at depth such as texture, color, stickiness, plasticity, and gravel percentage are correlated to ecotones. In the study area, B. eriopoda (black grama) and L. tridentata (creosotebush) interact with soil variations both on a broader, ecotonal scale of kilometers and on a local scale of meters. Saturated hydraulic conductivity, or K_sat, is controlled by vegetation on a small scale, and because of this control, K_sat varies across ecotones on a broad scale depending on the dominant vegetation type. Topsoil properties were found to be consistent regardless of vegetation or ecotone, but on a small and large scale vegetation is correlated with water retention properties deeper in the soil profile. As shrub encroachment into grasslands continues to affect many areas of the Southwest United States, knowing the areas of highest potential for shrub encroachment could aid in conservation efforts and studies on rangeland health.

Esteban Mendez

Arthropod Communities Across Topographically Distinct Microhabitats

Arroyos are ephemeral stream beds that exist in arid ecosystems (Antevs 1952). A variety of desert songbirds are known to nest and forage more frequently within arroyos compared to uplands. Within the juniper savannah there are many insectivorous desert songbirds that frequently nest in trees and contend with the pressures of extreme heat and lack of water that is inherent in said ecosystem. There are several proposed explanations for why desert songbirds prefer to nest in arroyos within the context of the extreme pressures they face, such as: higher soil moisture, and greater vegetation abundance (Kozma & Mathews 1997). Arthropod community characteristics have been shown to be important in other studies of songbirds in arid regions where the delivery rate of food items to nestlings positively correlated to survival rate and was thus vital to nest success along with the ability to increase delivery rate/food item size and access to a diversity of prey items (Browning, et al. 2012). In this light, the role arthropod populations may play in the breeding patterns of many songbirds is underexamined. Here it is shown that the relative abundance, richness and evenness are comparable between arroyos and uplands while biomass and to a greater extent community composition of arthropod populations show differences between arroyos and uplands. Using a variety of collection techniques was critical in creating arthropod assemblages representing arroyo and upland microhabitats. Collecting a greater sample size will yield a more accurate picture of the diversity present in arroyos and uplands.

Nika Povelikin

An exploration of lizard community composition and niche partitioning

Desert habitats are thought to have limited species richness across many taxa, with lizards being a notable exception. Elucidating patterns of niche overlap in desert lizard communities might help explain mechanisms which allow lizard species to coexist in semi-arid environments and overcome interspecific competition. I examined niche partitioning along microhabitat and dietary axes of niche diversity within the lizard community found in the disturbed landscape around the Sevilleta National Wildlife Refuge field station. Capture mark recapture and Visual Encounter Surveys were used to obtain data on lizard movement, community composition, and substrate use. Additionally, tissue samples were taken from captured lizards to investigate dietary niche through stable isotope analysis. The lizard community in the disturbed field station habitat was distinct from the lizard communities in other habitats at the refuge. Significant partitioning of dietary niche and differential use of substrates revealed potential mechanisms by which species in the field station community might reduce competition and facilitate coexistence.

Ben Simmons

Characterizing dietary niche of two exotic ungulates in central New Mexico

Exotic species are an impactful aspect of many contemporary ecosystems. On the Sevilleta National Wildlife Refuge in central New Mexico, African oryx (Oryx gazella) and feral horses (Equus ferus caballus) represent two exotic ungulate species. Ungulate herds can have intense impacts on plant composition and diversity. However, these species’ diets, their niche overlap with native ungulates, and their broader impacts on the ecosystems in the southwestern United States remains largely uncharacterized. Here, we used fecal DNA metabarcoding and stable isotope analysis to produce high resolution categorization of these species’ dietary niches. Fecal samples were collected before and after the monsoon season began to assess the impact of seasonal changes in forage availability on dietary niche breadth and overlap among these two introduced species.  In the context of a nutrient stressed ecosystem, we predicted dietary niche may be more restricted during the dry season.  Fecal DNA metabarcoding revealed the diet of O. gazella commonly consisted of plants in the Chenopodiaceae family while E. caballus ferus primarily consumed plants in the Poaceae family. Stable isotope analysis affirmed these findings, categorizing African oryx as mostly browsers and feral horses as grazers. These results indicate African oryx to have very little overlap with native ungulate species. In fact, they may be fulfilling a niche that has been left dormant by many of the large mammal herbivores that went extinct in this area approximately fourteen thousand years ago. However, our results indicate feral horses on this landscape may present a dietary niche overlap detrimental to pronghorn antelope and other native grazing ungulates.

MC Vigilante

RIFT: After Objectivity

RIFT,
an interactive VR world with an accompanying zine, investigates the limits of objectivity. Both works are derived from a large set of “scientific” images captured at the Sevilleta NWR. I gathered data from the PhenoCam ecosystem monitoring program, drinker trailcams, and 3D models of animal skeletons. Using a variety of computational tools, I abstracted these images to emphasize faults in their supposedly objective origins.

Glitches
demonstrate how queer uses of digital space enable new ways of knowing and being. Like a glitch, the desert is a manifestation of refusal, a persistent assertion of survival against all odds. In the Rio Grande rift valley, layers of sediment expose deep time
against the limitations of shallow space. By nature, digital images are ideal for exploring this kind of planetary gestalt. I’m most interested in using sound to create visual glitches. With some finagling, any digital image can be heard and edited as an audio file. When reconverted to an image, each sonic manipulation manifests as a distinct style of glitch. In the innate formlessness of binary data, I see great potential for reclaiming embodied connections to the land.

I
created the architecture for my virtual world using structure from motion (SFM), a photogrammetry process employed by many geoscientists. Behind the scenes, SFM algorithms produce a plethora of strange image files. Texture maps, lightmaps, confidence plots, and wireframes are a window into the inner workings of opaque technologies. These images aren’t meant to be perceived by human eyes. Many textures in RIFT are derived from this “secret” database.

By
presenting such unnerving digital images, I hope to draw attention to issues of visibility and distortion. While digital imaging enhances our ability to observe the physical world – especially as scientists – I subvert this expectation by emphasizing illegibility.
By exploiting the presumed authority of computation, RIFT breathes truth into futurist, nonobjective visions of landscape.

Gavin Wagner

Rebar, Weather Stations, and Plants: a climate-focused revival of 40-year- old transects

Dryland ecosystems face intersecting challenges as global climate patterns shift. In the past, iterative surveys of vegetation transects in the Sevilleta National Wildlife Refuge (SNWR) have documented changes in community structure within the context of various environmental stimuli. However, prior transect studies in this region have focused on smaller spatial and temporal scales. While it is widely accepted that climate is a crucial driver of long-term vegetation dynamics, narrow-scale studies do not account for the spatial and temporal climate variation that characterizes ecoregions. This study explores vegetation changes through the lens of long-term climate data in ecoregions representative of the Southwestern United States. 30 line transects within and adjacent to the SNWR in central New Mexico, USA, were established in 1976 by the Bureau of Land Management and were resampled in 1986, 1996, 2006, and 2016. Statistical and spatial correlations between changes in vegetation and various climate parameters were observed over this 40-year period. These results reinforce the notion that vegetation cover has changed over time within and among the transects, that climate is an important driver of these changes, and that interspecific competition may play an additional role.