Deborah L. Elliott-Fisk

Dating Rock Varnishes by the Cation Ratio Method with PIXE, ICP, and the Electron Microprobe

The measurement of rock varnish cation-ratios [(K+Ca)/Ti] and barium is evaluated by analyzing the same varnish scrapings with PIXE, inductively coupled plasma, neutron activation and wavelength dispersive electron microprobe. Results among these different methods are generally similar for ratios, but absolute concentrations differ in part due to uncertainties associated with weighing small samples. Barium concentrations are typically less than 1 % by weight; higher concentrations can be found in varnishes with depressions eroded into the varnish by fungi and lichens, and later infilled with aeolian detritus often including barium sulfate. Since these infilled hollows are known to produce anomalous varnish cation ratios, high barium values can, therefore, be used as an indicator that a sample is inappropriate for cation-ratio dating. The glacial chronology at Pine Creek, California, is revised in light of new data and a better understanding of variables influencing varnish chemistry.

Ecological effects of climate change on salt marsh wildlife: a case study from a highly urbanized estuary

Abstract Thorne, K.M.; Takekawa, J.Y., and Elliott-Fisk, D.L., 2012. Ecological effects of climate change on salt marsh wildlife: A case study from a highly urbanized estuary. Coastal areas are high-risk zones subject to the impacts of global climate change, with significant increases in the frequencies of extreme weather and storm events, and sea-level rise forecast by 2100. These physical processes are expected to alter estuaries, resulting in loss of intertidal wetlands and their component wildlife species. In particular, impacts to salt marshes and their wildlife will vary both temporally and spatially and may be irreversible and severe. Synergistic effects caused by combining stressors with anthropogenic land-use patterns could create areas of significant biodiversity loss and extinction, especially in urbanized estuaries that are already heavily degraded. In this paper, we discuss current ideas, challenges, and concerns regarding the maintenance of salt marshes and their resident wildlife in light of future climate conditions. We suggest that many salt marsh habitats are already impaired and are located where upslope transgression is restricted, resulting in reduction and loss of these habitats in the future. In addition, we conclude that increased inundation frequency and water depth will have negative impacts on the demography of small or isolated wildlife meta-populations as well as their community interactions. We illustrate our points with a case study on the Pacific Coast of North America at San Pablo Bay National Wildlife Refuge in California, an area that supports endangered wildlife species reliant on salt marshes for all aspects of their life histories.

GLACIAL GEOMORPHOLOGY OF THE WHITE MOUNTAINS, CALIFORNIA AND NEVADA: ESTABLISHMENT OF A GLACIAL CHRONOLOGY

The White Mountains, astride the California-Nevada stateline, are the highest and westernmost of the Great Basin ranges. This range was extensively glaciated during the Quaternary Period. Glacial landforms and scattered erratics were identified in the field using primarily morpho-and lithostratigraphic criteria, and mapped on aerial photographs and topographic maps. Topographic characteristics of the glacial deposits were analyzed using standard statistical procedures. A sequence of glacial deposits was identified in terms of six glacial stages, these glaciations named according to type site, and relative ages inferred. With the exception of perched Stage I (early) deposits along the range crest, reconstructed equilibrium-line altitudes and elevation of the glacier termini increase to the present, with glacier length and inferred size decreasing through time. Preliminary data suggest that weathering and pedogenesis are also progressive, though environmental gradients mask some of these distinctions betwee...

Foraging distribution of Pacific harbor seals (Phoca vitulina richardii) in a highly impacted estuary

Abstract Assessing the relative importance of environmental and anthropogenic influences on the distribution of wild populations is an important step in designing spatially explicit plans for their management and protection. We examined environmental variables correlated with the spatial distribution of eastern Pacific harbor seals (Phoca vitulina richardii), a marine mammal common to coastal waters, in a large, highly urbanized estuary. We assessed the relationship between prey abundance, depth, bottom relief, proximity to terrestrial haul-out sites and 3 potential sources of anthropogenic influence, and the in-water spatial distribution of seals. We identified locations of seals using satellite-linked telemetry, and used partial Mantel tests to assess which environmental variables were most strongly linked to seal foraging distribution, given spatial autocorrelation within variables. Mann–Whitney tests were used to compare environmental characteristics of locations of seals with a random distribution of locations. Because harbor seals are central-place foragers, we incorporated spatial distribution of seals relative to the central place into our analyses. High prey abundance and proximity to the haul-out site were strongly associated with the spatial distribution of seals. Harbor seals also tended to use deeper waters and areas of high bottom relief within the estuary. There was no consistent spatial relationship between the 3 anthropogenic factors and the distribution of seals, although seals tended to be found closer than expected to sites of high human activity. In highly impacted coastal areas where limited alternate suitable habitat exists, foraging seals may need to rely on disturbed (suboptimal) areas, and as a result may habituate to human presence in areas rich in food resources.

Viticultural soils of California, with special reference to the Napa valley

Abstract This paper provides an analysis of the soils and terroirs of the vineyards of the Napa Valley, CA. Following an overview of the geological history of the state and its effect on soil formation, a summary of the physical environment of the Napa Valley is given. This is followed by a survey of the different viticultural environments found in the Napa Valley, divided into four geographical regions. The paper argues that the natural physical environment exerts important controls on viticulture and that subtle soil differences can be reflected in the wines of the region.

Geography and the American Viticultural Areas Process, Including a Case Study of Lodi, California

The United States has a legal system for the formal designation of wine appellations of origin overseen by the Department of the Treasury. By regulating the labeling of wine to ascertain the area of origin of the wine for the consumer, the Department’s Alcohol and Tobacco Tax and Trade Bureau controls place names that can be used on wine labels and, indirectly then, throughout the wine trade. Approved places are known as American Viticultural Areas (AVAs) and are established (or rejected) through a formal public petition, review, comment, and sometimes, a hearing process. The geographical distinctiveness of the place drives its approval as a formal AVA. This is primarily based on physical geographic criteria such as climate, topography, soils, and geology, and also on a function of place history and name as cultural elements of the landscape. Geographers are well engaged in the AVA establishment process and through this, contribute to the education of winegrowers, the trade, the government, and the public on place-based distinctiveness of wines. Over 200 AVAs have been established in the United States since the rule-making process began in 1978, with over 100 of these AVAs in the State of California. Over the last 30 years, the federal agency has become stricter in following its criteria to delimit geographically distinctive areas with historical name recognition, less sympathetic to letting in wine-growers outside the proposed AVA boundaries without cause, and more systematic in how AVAs nest within one another. The best examples of the AVA establishment process now are also about building a sense of community and place through contestation and discourse and the give and take that shapes a community of place. The petition to divide the large Lodi, California American Viticultural Area into seven distinct AVAs is outlined as a case study in this process, where winegrowers and many other community members came together to support the establishment of finer-scale AVAs with the large Lodi AVA.

SOIL DEVELOPMENT ON LATE PLEISTOCENE MORAINES AT PINE CREEK, EAST-CENTRAL SIERRA NEVADA, CALIFORNIA

Late Pleistocene moraines at Pine Creek in the east-central Sierra Nevada Range are differentiated into three separate relative-age groups using soil morphological properties, with increasing soil development on progressively older deposits. Tiogaage soils (oxygen-isotope stage-2 equivalent) are weakly developed with A/AB/Bw/Cox profiles. Organic material extracted from Tioga-age till matrix has a conventional radiocarbon age of 19,570 ± 420 years B.P. Soils formed on Tahoe-age moraines (stage 4) show A/2BA/2Bw1/2Bwq2/2BC/2Cox horizonation with rubification to about 50 cm depth and slight clay enrichment. Organic matter from the Tahoe-age till matrix yields an infinite radiocarbon age (>38,000 years B.P.). Rovana moraines (stage 6) have moderate soil development, with A1/A2/2Bt1/2Bw2/2BC/2Cox profiles, conspicuous rubification down to about 103 cm, and significant clay accumulation in the Bt horizon. A soil-profile development index reflects the chronologic trend; however, lithologic and climatic variabil...

Tidal Marsh Susceptibility to Sea-Level Rise: Importance of Local-Scale Models

Abstract Increasing concern over sea-level rise impacts to coastal tidal marsh ecosystems has led to modeling efforts to anticipate outcomes for resource management decision making. Few studies on the Pacific coast of North America have modeled sea-level rise marsh susceptibility at a scale relevant to local wildlife populations and plant communities. Here, we use a novel approach in developing an empirical sea-level rise ecological response model that can be applied to key management questions. Calculated elevation change over 13 y for a 324-ha portion of San Pablo Bay National Wildlife Refuge, California, USA, was used to represent local accretion and subsidence processes. Next, we coupled detailed plant community and elevation surveys with measured rates of inundation frequency to model marsh state changes to 2100. By grouping plant communities into low, mid, and high marsh habitats, we were able to assess wildlife species vulnerability and to better understand outcomes for habitat resiliency. Starting...