Current research studies

Project Baseline
PI: Dr. Heather Schneider, UC Santa Barbara
Project Baseline is a nationwide initiative to systematically collect, preserve and archive seeds to be made available to future biologists for studies of evolutionary responses to anthropogenic and natural changes in the environment that will occur over the coming decades. Over an initial period of 3 years, seeds will be collected from multiple populations of up to 84 widely dispersed plant taxa, to represent phenotypic and genotypic variability across habitats and climates that roughly encompass each species' current geographic range, using a sampling plan designed to capture variation within and between populations. The seeds will be stored a the USDA National Center for Genetic Resources Preservation. In collaboration with experts at this facility, we will examine the critical assumption that genetic variation collected today will persist in seeds stored and grown for future experiments. Thus, in addition to providing scientists with well-characterized germplasm for use in future direct comparisons of evolutionary change (e.g., in common garden plantings), this work will contribute to the development of better methods for assessing seed quality, sampling genetic diversity, and calibrating monitoring guidelines.
 
In June 2015, Dr. Schneider and her field team worked with Jay Sexton, Molly Stephens, Chris Swarth, Daniel Toews and students to collect thousands of seeds of Bromus diandrus, Mimulus guttatus, and Rumex crispus. We set transect lines and hand-collected hundreds of seed heads from several locations in the Reserve. Duplicate voucher specimens have been accessioned into the University of Minnesota Bell Museum of Natural History Herbarium and Cheadle Center for Biodiversity and Ecological Restoration Herbarium at the University of California, Santa Barbara.
 

Diet Composition of Adult and Nestling American Kestrels During the Breeding Season

Joy McDermott (MS student, UC Merced)
 
The objective of my study is to determine the composition of prey in American Kestrel (Falco sparvarius) adult and nestling diets using stable isotopic analysis of feathers.  American Kestrels are the smallest falcon species in North America.  Although these raptors are abundant in some parts of their range, in other regions populations have declined since the 1970s (Hinnebusch et al 2010).  Kestrels are secondary cavity nesters; declines have been partly attributed to land use changes and a lack of tree nesting sites.  West Nile Virus, climate change, and increases in predatory Cooper’s Hawks have also been considered as possible contributing factors in population reductions. Due to a lack of nesting sites available to kestrels, nest box programs have been administered to ameliorate population losses.  Nest box programs present a unique opportunity to study avian species behavior, breeding habits, and diet.  The Merced Vernal Pool and Grassland Reserve currently has 10 nest boxes and approximately 20 more are expected to be built for the 2015 breeding season, providing an excellent opportunity to examine American Kestrels.  Few studies have focused on American Kestrels in the western United States regions and none have observed diets using stable isotopes.  Furthermore, there is a lack of studies analyzing kestrel diets in an arid grassland habitat like that found in the Central Valley of California where the Reserve is located.
The Merced Vernal Pool and Grassland Reserve has been experiencing a severe drought over the past three years, possibly influencing prey availability for kestrels.  American Kestrels are opportunistic predators with a diet that consists of insects, small rodents, birds, and reptiles.  In avian species, diet and resource availability are crucial during the breeding season.  Studies of Eurasian Kestrels have shown that food resources can limit brood size and nestling success.  Differences in body mass between female and male nestlings have been found in American Kestrels in controlled experiment.  Female kestrel nestlings monopolize small food resources (i.e. insects) resulting in a 63% competitive advantage over male nestlings (Anderson et. al, 1993). Identifying major prey resources during crucial periods of the American Kestrel life cycle such as the breeding season may lead to greater understanding of the driving forces behind reproductive success and population declines.  Stable isotope analyses of feathers may determine the percent of prey species in kestrel diets, thus indicating the relative importance and frequendy of prey items.  Therefore, I propose to use stable isotope analysis of carbon and nitrogen in adult and nestling kestrel feathers to determine diet composition of American Kestrels, and to distinguish variations in the diet of adult kestrels and nestlings, and between female and male nestlings.
Hypotheses: I hypothesize that overall American Kestrel diets will have a wide range of prey due to limiting resources under drought conditions.  Nestlings will feed higher on the trophic level than adults; consuming more rodents than adults do.  Female nestling diet will have a higher percentage of insects than in the diet of male nestlings.
 
Ecohydrology of Vernal Pools
Niall McCarten (PhD student, UC Davis)
 
Abstract: Vernal pool hydrological functioning is poorly understood with respect to the physical parameters of geology, soils and weather. Further, the response of plant species to the hydrological processes is also not well known. Research at sites in the Sacramento Valley measured the catchment areas and soil depth using very accurate GPS and ground-penetrating radar, respectively. Analyses of the physical environment data with weather variable determined the hydroperiod of vernal pools varies with respect to the soil depth to water-restricting layers and the quantity and seasonal timing of rainfall. The ongoing project also measured vegetation along an elevation gradient within a vernal pool depression which is correlated with hydrology and soil moisture data. The proposed work at UC Merced Vernal Pool Reserve will allow a study of these variables along a soil chronsequence and within a different regional climate regime.
 
Abstract of oral presentation at the American Geophysical Union meeting, San Francisco; December 2014
Teasing Apart the Effects of Atmospheric Nitrogen Deposition from Grazing and Drought in Vernal Pool Wetlands and Adjacent Grassland
Marilyn Fogel, David Araiza, Bobby Nakamoto, Maria Vega, Daniel Toews, Christina Bradley, and Christopher Swarth (UC Merced)

The remaining vernal pools flanking California’s Central Valley may be protected from development, but they are not pristine environments. At UC Merced’s Vernal Pools and Grassland Reserve, dairy cattle grazing is a fact of life, needed to keep non-native grasses from encroaching on and dominating these low lying, ephemeral pools. In addition to grazing, atmospheric deposition of nitrogen from adjacent agricultural farms and dairies has affected the biogeochemical cycling here, in particular because the area has never been ploughed and is essentially a terminal, interior catchment with almost no outputs. For the past two years, the region has been subjected to extreme drought resulting in altered patterns in vernal pool development and nutrient exchange. We are using stable nitrogen, carbon, and hydrogen isotopes in organic and inorganic reservoirs to understand which of the three stressors (e.g. N loading, grazing, or drought) affects the ecosystem functioning the most. Simple measurements of residual dry matter (the rancher’s standard) coupled with soil analyses and plant distribution, isotopic composition, and productivity will be presented at a landscape scale. Atmospheric deposition, as rain in winter and early spring and as dust in summer and fall, delivers substantial ammonium and nitrate to the Reserve and could be traced back to nearby hotspots, as well as from major storm systems. Concentrations and compositions of N in precipitation were highly variable depending on when the last storm event had occurred. Ammonia/ammonium in rainwater ranged from δ15N= -24 to +7‰, probably explaining the large range in the δ15N of plant tissues collected in winter/spring (-4.3 to +10.9‰,) and that of extractable ammonium from surface soils (δ15N = -7 to +13‰). Interior grassland and vernal pool ecosystems, with substantial inputs and little to no outputs, host biogeochemical processes that amplify heterogeneity on relative small scales.

Abstract of study presented at the Ecological Society of America meeting, Sacramento; August 2014
Biogeochemistry and Elemental Cycling in a Vernal Pool and Grassland Reserve
David N. Araiza, Christopher W. Swarth, Liying Zhao, Bobby Nakamoto, and Marilyn L. Fogel
(UC Merced)
 
Most California vernal pools have been destroyed by agricultural and urban development. Remaining pools are threatened by aggressive non-native grasses and excessive N loading from atmospheric deposition. Cattle grazing is recognized as an important management tool for maintaining the pool hydroperiod by controlling the surrounding grasses; this also reduces competition with native, rare vernal pool plants.  Cattle graze the entire 2590 ha Reserve. However, grazing, combined with over fertilization of pools from nearby agricultural fields, could cause changes to this ecosystem in ways not yet understood. Soil types and their elemental compositions are other factors that may influence plant growth in these ecosystems. Therefore, we investigated ecosystem biogeochemistry by measuring residual dry matter (RDM); major, minor and trace elements; and stable isotope composition in plants and 12 soil types in the Merced Vernal Pool and Grassland Reserve. Inorganic nitrogen concentrations in surface soils were high in every soil type and throughout the reserve (mean 74.2 ppm; n=50). Heavy metals, Ni, Zn, Cu, Cr, Mn, and Ba, were in relatively low concentrations and not likely influencing the distribution of aquatic animals in pools. V, B, Pb, and Ba were in higher concentrations in pool soils than in grasslands within RbA and CkB soils. In KaB and ReB soils, Cu and Pb were in lower concentrations in pool soils than grasslands. Pb levels throughout the Reserve were well within acceptable limits. Metal concentrations in cattle stock ponds were the lowest of all soils. RDM, measured after the growing season, provides a measure of grazing intensity and possibly nutrient availability. RDM of ungrazed areas outside the Reserve was 4050 kg/ha, four times greater than within the Reserve. Lightly grazed areas, the majority of the Reserve, had a mean RDM of 1012 kg/ha. In vernal pools, mean RDM was 560 kg/ha, most likely because grass density was low there. The RDM of over-utilized areas was 553, nearly half the RDM measured on most of the Reserve. RDM grasses were all C3, annual grasses (δ13C=-27.2±0.86‰; δ15N=0.8±1.3‰), whereas living plants collected in summer included several C4 species, including Swamp Timothy along with native C3 plants (δ13C=-25.9‰; δ15N=5.3±3.7‰). Isotopic compositions of winter-growing grasses were different from those of summer plants indicating that plants used different nitrogen sources seasonally. Soils were uniform in δ13C=-28.1±0.4‰, but variable in δ15N=3.5±2.5‰. Soil organic matter is derived principally from C3 annual grasses, rather than native species that dominate in summer.
 
Conservation genomics of endangered California Tiger Salamanders
PrincipaI Investigator: Bradley Shaffer, UCLA
 
Dr. Shaffer and his students focuses their research on the federally and state listed California tiger salamander, Ambystoma californiense. The species has declined across its limited range in central California, and our work has provided the scientific backing both for listing the species, and for delimiting species boundaries, understanding patterns of gene flow, and quantifying the ways that salamanders live in the harsh ecological landscape of the Great Central Valley. Much of our recent work has focused on an amazing case of hybridization between non-native, introduced Barred tiger salamanders and native California tiger salamanders. It’s a story that has as much to say about mechanisms of speciation as it does about conservation biology, and we continue to explore the system from a variety of genetic, genomic, and ecological perspectives. Other projects in my lab have developed the red-legged frogs Rana aurora/draytonii as another system where genetic, and ultimately genomic data should provide tremendous insights into conservation and management of the endangered California red-legged frog. Our work on the California Tiger Salamander recently received a major boost from the National Science Foundation with a new $684,000 award to the Shaffer lab. The project uses cutting-edge genomic tools to characterize historical and contemporary salamander populations, and to track the spread of thousands of non-native genes as they invaded the native range of the California tiger salamander over the last quarter century.
 
Structure of the small mammal community at the Vernal Pools-Grassland Natural Reserve
PI: Jessica Blois, UC Merced

Dr. Blois aims to document the taxonomic and population genetic structure of the small mammal community within the UC Vernal Pools-Grassland Natural Reserve (VPGNR) and to understand how the living small mammal community differs from the ‘dead’ small mammal community documented through remains contained in raptor pellets and carnivore scats.  This project provides an opportunity to generate a comprehensive baseline of the small mammal community on the VPGNR, understand whether fine-scale population genetic structure exists within species across space and through time (via comparison of animal and bone tissues), and understand which small mammals are likely to be present in fossil deposits in the region. This project represents the initial steps in a long-term live-dead analysis, and through this work we will be able to compare the structure and function of both the living and dead mammal communities in this grassland ecosystem to similar communities in other grassland systems around the world. We will also collect voucher specimens for each species at each locality that we sample. All collected individuals will be curated into the UC Berkeley Museum of Vertebrate Zoology (MVZ), where they will be accessible to the scientific community.  State collecting and trapping permits are being processed as of July 2014.

Ecosystem mapping and natural resources using unmanned aerial vehicles
PI: Yang Quan Chen and Brandon Stark, UC Merced
This project studies and maps the Merced Vernal Pools and Grassland Reserve by means of unobtrusive photography and videography through the use of multi-spectral and RGB cameras affixed to small unmanned aerial vehicles (sUAV). We hope to create higher resolution Vernal Pool density maps both spatially and temporally. Furthermore, we hope to develop, solidify and validate some correlations between the surrounding wildlife and habitats through the use of imagery and post processing.
 
Grazing impacts and forage vegetation assessment
PIs: Marilyn Fogel and Chris Swarth, UC Merced
The measurement of Residual Dry Matter (RDM) is a widespread, basic method of assessing cattle grazing pressure on grasslands by the clipping and weighing samples of dried grass. RDM describes the dried grass that remains standing in summer after the cattle have been moved off a grazing area. RDM becomes a rough estimate of the forage that remains and it indicates the potential for erosion in the fall. RDM is therefore a measure of grazing intensity. Too little RDM may indicated that too many cattle might be grazing too long in one area. In 2013, 2014 and 2015 we collected about 75 triplicate samples of RDM each fall season from across the Reserve for analysis in the Fogel lab on campus. RDM values were somewhat low to acceptable across the Reserve. A standard of 800 lbs RDM per acre is the benchmark that we aim for with the current grazing system. RDM values below this standard were recorded in areas where the dairy cows congregate along fence lines and gates, and in the vicinity of stock ponds. The area near the barn is heavily utilized because the rancher often moblizes the cows here using the corrals and cattle shutes.
 
American Kestrel breeding productivity
PI: Chris Swarth and Steve Simmons, UC Merced
The objective of this study was to determine the breeding productivity of American Kestrels on the Reserve and to expand the population of these small falons in eastern Merced County. UC Merced undergraduate students assisted with all aspects of the project. As a result, this study provided a unique opportunity for UC Merced students to participate in a wildlife conservation project that enhanced their undergraduate experience by letting them participate in active field research. This project also helps fulfill the US Fish and Wildlife Service mandate which requires UC Merced to practice enhanced conservation on the campus Reserve. The Peregrine Fund, a leading non-profit organization advancing research and conservation of birds of prey worldwide, launched the American Kestrel Partnership in 2012 to further conservation efforts such as this one at UC Merced. There is widespread support for this types of projects. The relevance of this study is that it aids a wildlife species that requires some level of human intervention to increase and expand natural populations. In spring 2014 a total of 10 wooden nesting boxes were erected in the Reserve. At the end of the nesting season, 6 of 10 boxes were occupied and a total of 15 Kestrel chicks had fledged. This high level of nest box occupancy suggests that Reserve lands provide important nesting and foraging habitat for American Kestrels.
In spring 2015, 20 more Kestrel boxes were erected. These were monitored for productivity in spring and summer.