2017

Juan Camacho

Juan’s 2017 REU project was, “The Reproductive Response of Forbs to Seasonal Fire.”

This study is to show how forbs respond reproductively to seasonal burning. Forbs were monitored in the McKenzie Flats of the Sevilleta National Wildlife Refuge in New Mexico. Forbs were studied in 15 0.24 hectare plots that consist of five control plots, five plots burned in the fall 2016 and five plots burned in the spring of 2017.The number of flowers and fruits were compared with approximate volume to see if there are intraspecific differences between forbs in different treatments. Soil samples were also collected from the plots to determine if there are significant differences in percent nitrogen and moisture content in the soil that may be contributing to forb recovery. I expected there to be a difference in reproductive growth between burned and unburned plots. I also anticipated the burned plots to have higher percent nitrogen levels and moisture content in the soil. Some species showed increased reproductive ratios in burned plots. One species was reproductive at a smaller size in the burn plots in comparison to the control. Another species struggled to reestablish in burn plots. In conclusion, seasonal fires do have impacts on the reproductive response of forbs, but these differences are most likely caused by decreased competition, not by changes in soil properties.

 

Lela Culpepper

Lela’s 2017 REU project was, “An ambiguous relationship uncoupled: The effects of maternal fruit traits and environment on seedling morphology of Brassica tournefortii.”

The environment experienced by maternal plants can affect embryonic, fruit, and seedling size. This can result into fruit or seed traits becoming correlated with seedling traits such as leaf size and leaf number. In the field, these phenotypic associations between maternal reproductive traits and seedling morphology can be complicated by environmental gradients. In this study, I will conduct a common laboratory experiment using seeds from 21 sites in the Mojave Desert to tease out these potential relationships. First, I sought to determine whether phenotypic variation in reproductive and seedling traits of Brassica tournefortii, an invasive species in the southwestern United States, vary across elevation gradient(s) in the Mojave Desert. The second objective of this project is to examine possible correlations of seedling life history traits with maternal reproductive traits (i.e. seed number per fruit and fruit weight), and their relationship with elevation in the introduced range of B. tournefortii. Incidentally, I can also test if the type of habitat landscape affects variation in traits, specifically leaf margin morphology. By conducting this experiment, we can show if seedling vigor of Mojave Desert populations of B. tournefortii is affected by maternal fruit traits and elevation. By determining possible effects of elevation on these trade-offs, we can indirectly assess evolutionary potential of this invasive species at the landscape scale. This information can be critical for managing their invasiveness in southwestern U.S.

Kaija Gahm

Kaija and Alex’s 2017 REU project was, “The Gray Areas: Mapping Gray Vireo (Vireo vicinior ) territories at the Sevilleta National Wildlife Refuge.”

The Gray Vireo (Vireo vicinior) is a small songbird listed as ‘Threatened’ by the state of New Mexico, where it inhabits juniper savannahs. Though nesting males are known to defend a territory around their nest through singing, information on these territories remains limited. Working at several sites in the Sevilleta National Wildlife Refuge in central New Mexico, we sought to 1) determine the size of Gray Vireo territories in Sevilleta, 2) investigate what factors influence the size of these territories, and 3) explore the changes in territory size and shape over the course of the nesting process. Using color bands for identification, we followed nesting males through their territory, marking every tree that they sang from. With both the minimum convex polygon (MCP) and kernel utilization distribution (KUD) methods of territory generation, we constructed song territories for each pair of vireos, finding the average territory size to be 4.13 ha for MCP’s and 2.87 ha for KUD’s. MCP territory size was significantly greater with lower juniper coverage, potentially because of a higher availability of nesting sites. Territories were most commonly located on northwest facing slopes and least commonly on east-facing slopes, which may be due to differences in vegetation structure. Factors such as slope, roughness, and proximity to other vireo territories did not appear to have a significant effect on territory size. Future work could refine our methods of constructing territories and explore what constitutes ideal Gray Vireo breeding habitat to aid in conservation of the species.

Jennifer Holguin

Jennifer’s 2017 REU project was, “Soil and Belowground Productivity Response to Chronic Drought and Shifted Monsoon in an Arid Grassland.”

Climate change models predict aridlands will experience chronic droughts, with increasing variability in precipitation events, and a shift in monsoon season timing. This elevation in stress is anticipated to not only decrease vegetation productivity, but may also show to negatively impact soil microbial community function, as they are highly responsive to water availability. To evaluate effects of extreme and prolonged drought on desert ecosystem processes, we assessed soil and below-ground productivity in a long-term severe drought experiment established in 2012 on a Southwestern North American arid grassland. Two grasslands dominated by Bouteloua gracilis (blue grama grass) and Bouteloua eriopoda (black grama grass), were constructed to include 10 replicates of ambient control plots, and treatments that imposed significant reduction in growing season precipitation (-66% of ambient), and reduction in number of events¬– delayed rainfall treatment. Factors focused on were: pH, soil organic matter (SOM), and percent root standing crop biomass. In June and July of 2017 soil cores and standing crop root samples were taken from each plot at a depth of 13cm and 15cm respectively. In both sites, we saw a slight (non-significant) increase of soil alkalinity in chronic drought treatments with a slight decrease or no change in delayed monsoon treatments. Soil organic matter in the blue grama site was seen to significantly decrease under the chronic drought treatment with a non-significant decrease in SOM in the delayed monsoon treatment. In the black grama site we saw a significant increase in SOM under delayed monsoon treatment with a slight non-significant decrease in SOM in the black grama chronic drought treatment. Root biomass was shown to slightly decrease in both sites with both treatments. Soil organic matter decrease or increase may be due to soil conditions differing in extent of vitality where vegetation in blue grama chronic drought plots have already been almost completely diminished, and in the black grama site vegetation is still plentiful but nonetheless dying off therefore inputting more SOM. It is imperative that we study the impacts of projected climate conditions on aridland soils and vegetation as they are key components to success and survival of many other aridland organisms.

Mary Lloyd

Mary’s 2017 REU project was, “Inventory Amphibian Abundance and Vocal Behavior in the Middle Rio Grande Valley.”

In any type of ecosystem it remains essential to understand how the presence and vocalizations of an invasive species may affect the vocal and territorial behavior of native species. This experiment seeks to reveal whether the presence of the invasive American bullfrog, Lithobates catesbeiana, affects the abundance and diversity of native amphibians in the Middle Rio Grande Valley. Understanding such relations may guide management strategies to prevent the disappearance of ecologically fundamental species, such as the Northern Leopard frog, Rana pipiens, which was historically present in this area but has recently vanished. By using both automated acoustic recorders and visual and auditory surveys, I collected sufficient inventory of amphibian species relative abundance and analyzed the effects of bullfrog acoustics on native frog species. Furthermore, I observed how the relationship between biotic and abiotic environmental factors played a role in native frog distribution. Using t-tests I compared both call densities and abundance of all frog species at various sites. Trends linking four environmental characteristics of the sites to findings of species were also implied. Results showed that sites containing particular characteristics, such as water body width and vegetation, attracted certain species over the others. A significant number of bullfrogs occupied most sites with little but important native frog activity. Vocalizations from bullfrogs seemed to deter the native frogs from calling. Unexpected visual and auditory appearances of the Northern Leopard frog were confirmed.

Tom Merchant

Tom’s 2017 REU project was, “Aquatic Invertebrate Communities Across the Sevilleta NWR.”

In this study, we attempt to understand of the invertebrate community composition in the artificial and natural springs of the Sevilleta National Wildlife Refuge. Additionally, we are concerned with the factors that may influence this composition. We asked whether community composition was driven by geography and environmental factors, such as water quality, surrounding environment, and spring structure. To answer our questions, we sampled macroinvertebrates from the springs across the Sevilleta NWR. We then compared the similarity of these springs with factors such as location, surrounding vegetation, substrate, dissolved oxygen, salinity, pH, and water temperature. Our study showed the relative importance of these components in shaping the composition of the invertebrate community. Location, substrate, pH level, disturbance, and vegetation all played a role in determining community structure. This show that invertebrate communities are responding to diverse set of factors. We also suspect that site location was so important because of the invertebrates’ poor ability to disperse across the landscape. As we expected other factors were either relatively stable across the sites or to have a minor impact on the community structure.

 Adam Nash

Adam’s 2017 REU project was, “Harvester Ants: Density and Granule and Seed Preference.”

Despite the high interest in fossils and gems brought back to the mound by harvester ants, little work has been done in determining ant preference of granules and substrate. Harvester ant seed preference may also play a role in determining how dominant vegetation will change as vegetation zones begin to shift. We surveyed several locations based on differences in dominant substrate and found ant mound density within the site. Samples were taken from mounds at each site, and sieved and sorted by rock type. A Bagnold’s plot was used to find size distribution, and an NMDS plot was used to find relationships between sites in terms of rock type. Preweighed seeds of three different types of dominant vegetation were placed in each type of dominant vegetation, to determine if ants were selecting one type of seed over another. Ant mound density was not dependent on dominant substrate or dominant vegetation. Harvester ants chose rocks below 3.0 mm at a similar rate across all sites. In terms of rock type, mounds were more similar to the controls than to other mounds, indicating that harvester ants are selecting mostly opportunistically. However, general trends in the NMDS plot show that ants were selecting for quartz and against sandstone and ironstone concretions. Both species of harvester ants ignored creosote and juniper seeds, while Pogonomyrmex rugosus selected for blue grama and Novomessor cockerelli ignored blue grama. Selection of rocks may be based on thermoregulation purposes. Finding niche differences can help further define each species role in the ecosystem.

Thomas Thompson

Thomas’s 2017 REU project was, “Monsoon Rainfall Variability Changes Plant Communities.”

Monsoon Rainfall Manipulation Experiment (MRME), initiated in 2007, is part of the Sevilleta LTER located in Sevilleta National Wildlife Refuge (SNWR), New Mexico. Summer monsoon rainfall is manipulated by spraying 60 mm of water in addition to the ambient rainfall of experimental sites, in three separate treatments: 12 events of 5 mm and 3 events of 20 mm, along with a control treatment that receives no added water. These treatments (many small events or a few huge events) are related to trends in real monsoon precipitation recorded at the Sevilleta LTER. In this desert grassland ecosystem, water is the primary limiting factor for plant growth. We examined biological responses to the aforementioned monsoon rainfall types using previous data collected at MRME along with observations of both aboveground net primary productivity (ANPP) and soil organic carbon content. Our research focused on identifying signatures of a feedback loop where rainfall variability changes plant communities; the plant community changes affect organic carbon deposition to soil, and organic carbon content of soil causes further changes to plant communities. We observed multiple shifts of plant communities in response to 5 and 20 mm treatments: a decrease of species richness in both small and large treatments compared to control treatment, less variability of ANPP in the 20 mm treatment, an increase in the 20 mm treatment’s proportion of grasses compared to the control and 5 mm treatments. We observed no differences between mean soil organic carbon content of the control, 5 and 20 mm rainfall treatments.

Alex Wells

Alex and Kaija’s 2017 REU project was, “The Gray Areas: Mapping Gray Vireo (Vireo vicinior) territories at the Sevilleta National Wildlife Refuge.”

The Gray Vireo (Vireo vicinior) is a small songbird listed as ‘Threatened’ by the state of New Mexico, where it inhabits juniper savannahs. Though nesting males are known to defend a territory around their nest through singing, information on these territories remains limited. Working at several sites in the Sevilleta National Wildlife Refuge in central New Mexico, we sought to 1) determine the size of Gray Vireo territories in Sevilleta, 2) investigate what factors influence the size of these territories, and 3) explore the changes in territory size and shape over the course of the nesting process. Using color bands for identification, we followed nesting males through their territory, marking every tree that they sang from. With both the minimum convex polygon (MCP) and kernel utilization distribution (KUD) methods of territory generation, we constructed song territories for each pair of vireos, finding the average territory size to be 4.13 ha for MCP’s and 2.87 ha for KUD’s. MCP territory size was significantly greater with lower juniper coverage, potentially because of a higher availability of nesting sites. Territories were most commonly located on northwest facing slopes and least commonly on east-facing slopes, which may be due to differences in vegetation structure. Factors such as slope, roughness, and proximity to other vireo territories did not appear to have a significant effect on territory size. Future work could refine our methods of constructing territories and explore what constitutes ideal Gray Vireo breeding habitat to aid in conservation of the species.