Bodega Marine Laboratory/Reserve
February 22-24, 2008 |
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Participant Abstracts
The Ecology and Distribution of an Intertidal Macroalga: Potential Impacts of Climate Change
Jennifer Skene
Department of Integrative Biology
University of California, Berkeley
Understanding the processes that shape species distributions is a critical research question, as global
warming is altering the earth’s climate and species distributions are shifting in response. Species’ distributions are often limited by propagule dispersal, biotic interactions, and abiotic factors, which may be altered a result of climate change. This study examines factors that affect the survival of the macroalga Pelvetiopsis limitata, during two life history stages. Distributed in the upper zone of the rocky intertidal, it is exposed to air for more time than other intertidal organisms, and may be amongst the first to respond to changes in air temperature. A demographic study of adults was begun at the Bodega Marine Reserve in July 2004, to examine how growth and mortality rates vary with tidal elevation, exposure to wave
action, and season, which affect air, sea and substrate temperature, wind speed and direction, and fog cover. Results to date indicate that mortality rates of adults are highest in the winter; strong winter waves that rip algae from the rock pose a greater threat to population persistence than do desiccating high
temperatures during the summer. However, pilot experiments examining the effect of substrate
temperature, tidal elevation and shading by conspecifics on P. limitata embryo survival indicate that high temperatures may be critical in determining propagule establishment. These results indicate that warming will be detrimental to the young life history stage, while winter storms, predicted to increase in intensity as the result of climate change, will negatively impact adult populations.
Fog contributions to pedogenesis and hydrology in Pinus muricata ecosystems on
Santa Cruz Island
Julie Baker
Department of Land, Air and Water Resources
University of California, Davis
Davis
In the Mediterranean-type climates that occur over much of California, water is severely limited during the summer months. Interception of fog water can be a locally important source of plant-available water and groundwater recharge in foggy coastal areas, but the importance of fog precipitation in pedogenic mineral formation is unknown. Stable isotopes incorporated into pedogenic minerals may record water source and availability as they reflect equilibrium conditions with the soil solution at the time of formation. Soils in Pinus muricata (Bishop Pine) canopy and adjacent grassland were compared on two parent
materials, a chlorite schist and a rhyolitic tuff. Smectites dominate the fine clay (<0.2 mm) fraction in the soil formed on rhyolitic tuff, while kaolinite and halloysite dominate the fine clay fraction of the soils formed on schist. Stable 2H and 18O isotope analyses of precipitation (rain and fog) and soil solution samples indicate a depletion of the heavier isotopes in the rainwater compared to fog. Soil solution samples from surface horizons measured during precipitation events show a shift in isotope ratios to heavier values
during fog events and lighter values during rain events, but generally increase with depth as packets of water influenced by evaporation infiltrate deeper into the profile. 2H values in fine clay phyllosilicates at both pine sites also reflect this increase.
Holly Alpert
Environmental Studies Department
University of California, Santa Cruz
Although studies of treelines typically focus on high-elevation boundaries between forests and alpine ecosystems, low-elevation treelines, such as those between forests and shrubland, are also of interest in thinking about how climate change will affect species distributions. This research focuses on large-scale precipitation and small-scale microhabitat drivers of Pinus jeffreyi regeneration at a forest-shrubland
ecotone in eastern California. Germination and establishment were examined by planting P. jeffreyi seeds and seedlings into areas of altered snow depth (increased, decreased, and ambient snow depth) and microhabitat (under the potential nurse species Artemisia tridentata and Purshia tridentata and in open intershrub spaces), and monitoring survival and growth throughout two growing seasons. Soil water
availability, photosynthetically-active radiation (PAR), air temperature, and soil temperature were measured in the snow depth and microhabitat treatments. Of the 1,500 seedlings planted between the two years, only two remained alive as of October, 2007. Seedlings planted under the two shrub species predominantly died from herbivory, whereas seedlings planted in open intershrub spaces died more often from drought. There were differences in PAR between shrub canopies and intershrub spaces, but there were no
differences in soil or air temperature, soil moisture, seed germination, or seedling growth among
microhabitat or snow depth treatments. No effects of altered snow depth on seedling survival have been observed to date. Results suggest that microhabitat niches may be equally if not more important than changes in precipitation patterns for Pinus jeffreyi establishment at this ecotone.
Fire History of Jeffrey pine in the eastern Sierra Nevada, Sagehen Experimental Forest
Nicole M. Vaillant
Department of Environmental Science, Policy, and Management
University of California, Berkeley
Recently in California, and elsewhere in the western United States, there has been a movement toward
landscape level fuel treatments to reduce the potential effects of catastrophic wildland fire. Understanding the historic fire regime is important for land managers when deciding on treatment scenarios for
application today. Often times fire regimes are looked at over two time periods: pre-settlement and
post-settlement. At Sagehen Experimental Forest, the pre-settlement fire regime may have been
influenced by the Washoe tribe. The Washoe tribe was a nomadic tribe that spent summers on the
northern shores of Lake Tahoe and used higher elevation forests and meadows for hunting and gathering in the fall months. The post-settlement fire regime was most likely impacted by the Comstock Lode. In addition to the mill along Sagehen Creek, early USGS maps show the majority of lower elevation stands within Sagehen to have been culled by 1902. In addition to anthropogenic influences, climatic drivers, such as drought cycles, shape fire regimes. This study will look at both fire perimeter maps within
Sagehen (from the early 1900s to present) and fire scar samples. Forty-two samples were collected from lower elevation Jeffrey-pine and Jeffrey-pine mixed-conifer stands in five unique locations at Sagehen. Using both methods, past fire perimeters and dendrochonology, it is possible to reconstruct the fire return interval, the seasonality of fires, and test the influence of climatic drivers.
A demographic analysis of facilitation of an invasive grass by native shrubs
Alden B. Griffith
Environmental Studies Department
University of California, Santa Cruz
Much of biological invasion theory is built upon models of negative ecological interactions, but the
importance of positive interactions in specific invasions is gaining attention. This research demographically examines the role of facilitation of the invasive annual grass, Bromus tectorum, by native shrubs in the western Great Basin Desert. Plots were established under the canopies of the shrubs Artemisia tridentata and Purshia tridentata, and in intershrub spaces near Mammoth Lakes, CA (elevation 2150 m). Modeled B. tectorum population growth under shrub canopies was significantly greater than in intershrub spaces in 2005, and the reproductive potential of seedlings was significantly greater under shrub canopies in 2006. In both years, positive effects of shrub microhabitats were demonstrated by positive contributions of growth and survival rates, even when the net effect was non-significant. These results demonstrate that native shrubs can positively influence the growth of invasive populations of B. tectorum at high elevation, although the interaction is variable between shrub species and years. While much of the impact of B. tectorum is
associated with intershrub populations that promote fire continuity, shrub microhabitats may be important for boosting initial population sizes and may function as overall population seed sources.
Climate, competition, and soil type: interactions controlling endemism in serpentine grasslands
Barbara Going
Department of Environmental Science and Policy
University of California, Davis
Serpentine edaphic endemics, plant species that are specialized on serpentine soil, form a large
proportion of California’s plant diversity, yet little is known of ecological interactions contributing to their restriction to such an abiotically harsh substrate. It has been hypothesized that competition from superior competitors is the proximate cause for edaphic endemism because soil specialists are incapable of fast growth in more benign soils. In addition, endemism may vary along climate gradients, such that endemics are more specialized when climate conditions are favorable because they are less able to take advantage of an increase in resources, such as water availability. This study is designed to experimentally test the hypotheses that 1) competition from other species on benign soils is the mechanism of soil restriction and 2) soil restriction is stronger in climatically favorable environments. I am testing the effects of
competition and three levels of water availability on the performance of three serpentine endemics and three non-endemic congeners on and off serpentine soil. To further explore how climatic gradients
contribute to endemism the three serpentine endemics are being grown with or without competition at three different locations along California’s precipitation gradient. The results of this study will have broader implications for predicting the success of edaphic endemic plant species under different climate change scenarios. Current “climate envelope” models assume that species niches are primarily controlled by
climate and may not accurately predict the distribution of species whose niches may be controlled by
interactions among abiotic and biotic factors.
Developing a Mechanistic Understanding of the Species-Area Relationship from Serpentine
Habitats
Adam B. Smith
Energy and Resources Group
University of California, Berkeley
Though ecologists have known for over two centuries that the number of species rises with the size of the area sampled, we have yet to understand the relative contribution of ecological processes structuring the
species-area relationship (SAR). The leading hypotheses are that larger areas 1) sample more individuals and thus more species (the sampling hypothesis); 2) harbor more heterogeneity and thus allow niche
partitioning (the spatial heterogeneity hypothesis ); 3) diminish the probability that a population goes
extinct (the island biogeography hypothesis); 4) dilute localized biotic interactions like competition (the biotic interaction hypothesis). In 2006 I established an experiment on serpentine grasslands at UC
McLaughlin Natural Reserve to test the relative merit of these hypotheses in structuring the SAR. I demarcated 35 2×2-m plots and censused all vascular plant species within them in 2006 and 2007 (and will continue in 2008) and from this data constructed SARs for each plot. Numerical analyses of
abundances indicate that the sampling hypothesis does not fully explain the rise in species with area. To assess the other hypotheses, after the initial census, I imposed three types of manipulations and their crosses on the plots: reduction of immigration from outside plots (island biogeography), reduction of
recruitment from inside plots (island biogeography/biotic interactions), and soil homogenization (spatial heterogeneity). Preliminary analyses indicate that soil heterogeneity and recruitment have the most
pronounced effect.
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