Current research studies
Diet Composition of Adult and Nestling American Kestrels During the Breeding Season
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.
David N. Araiza, Christopher W. Swarth, Liying Zhao, Bobby Nakamoto, and Marilyn L. Fogel (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.
Several studies conducted in the Reserve have been published.