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San Rafael, CA, United States

Chase D.A.,San Francisco State University | Chase D.A.,WRA Inc. | Todgham A.E.,University of California at Davis
Transactions of the American Fisheries Society | Year: 2016

We investigated the physiological response of the endangered Tidewater Goby Eucyclogobius newberryi to the presence of Threespine Sticklebacks Gasterosteus aculeatus (native to California) and Rainwater Killifish Lucania parva (nonnative). A fully factorial experimental design was used to examine species assemblage effects on juvenile fish over a 28-d period. Growth characteristics (weight, SL, and relative condition factor [Kn]) and stress hormone levels (cortisol) were assessed under ample food conditions and at a salinity of 15‰. Weight and SL of Tidewater Goby increased throughout the experiment; growth did not differ in relation to fish assemblage treatment, but significant differences in growth were observed between sampling dates within the experiment. Rainwater Killifish exhibited marginal increases in weight, SL, and Kn, but these increases were not different among assemblage treatments or over time. For Threespine Sticklebacks, weight and SL increased during the final 2 weeks of the experiment, resulting in significant differences over the entire experimental period; however, growth characteristics of this species did not differ among assemblage treatments. Cortisol levels in all three species were not significantly affected by assemblage treatment. The present results indicate that juvenile Tidewater Goby are not adversely affected by native Threespine Sticklebacks or nonnative Rainwater Killifish under stable abiotic conditions in the absence of food limitation. Received March 6, 2015; accepted September 24, 2015 © 2016, American Fisheries Society 2016. Source


Breen A.N.,University of California at Davis | Breen A.N.,WRA Inc. | Richards J.H.,University of California at Davis
Western North American Naturalist | Year: 2010

Natural establishment of seedlings in desert playas with temporally variable precipitation hinges on many factors, including seed production, seed dispersal, seed entrapment, seed germination, and seedling survival. We investigated natural seed dispersal patterns and the effects of surface texture, wind barriers, resource availability (water and nutrients), and protection from herbivory on seedling establishment in a desert playa. We hypothesized that the seed rain would be consistent throughout the year and that seedling establishment would improve in resource-amended plots with barriers to wind dispersal. Contrary to our hypotheses, seed flux peaked seasonally during the winter, and fertilization had no consistent effect on seedling establishment. Seed availability for dispersal correlated with precipitation in the previous water year, whereas seedling recruitment was greatest when current-year precipitation during the spring germination and summer seedling growth periods was high. Gravel and barrier surface treatments contained more surviving seedlings than other surface treatments. Comparison with plots located outside of herbivore exclosures, however, showed that greater seedling presence in gravel plots may be due somewhat to protection from herbivory provided by the gravel, rather than simply to the greater seed-trapping quality of the gravel. With abundant seed availability, application of surface treatments, like coarse gravel, combined with increased seasonal water availability could lead to improved shrub establishment from seed in desert playas. © 2010. Source


Harris T.B.,WRA Inc. | Rajakaruna N.,College of the Atlantic | Nelson S.J.,University of Maine, United States | Vaux P.D.,University of Maine, United States
Journal of the Torrey Botanical Society | Year: 2012

Acadia National Park is a center of plant diversity in northeastern North America. The Park's varied habitats and flora are sensitive to a number of natural and anthropogenic perturbations. Stressors such as invasive plants, pest and pathogens, ozone, acidic fog and sulfur deposition, nitrogen deposition, heavy metals, fire and fire suppression, over-browsing, visitor use, hurricanes, and climate change have all had effects on the Park's habitats and plant species at some point and it is unclear how many of these stressors are currently affecting the flora of Acadia National Park. We discuss the botanical diversity of Acadia, assess the natural and anthropogenic stressors and threats affecting the Park's flora, and summarize critical information gaps to better assess the known stressors and threats to the flora. Understanding these stressors and threats is critical to making informed management decisions to preserve the botanical diversity of Acadia and other regional parks. © 2012 Torrey Botanical Club. Source


Ciccotelli B.,College of the Atlantic | Harris T.B.,University of Massachusetts Amherst | Harris T.B.,WRA Inc. | Connery B.,Acadia National Park | And 2 more authors.
Rhodora | Year: 2011

We conducted a preliminary floristic study of six vernal pools in Acadia National Park on Mount Desert Island, Maine. Plant species were recorded on three sampling dates from April to October, 2008. Sixty-five vascular plant species from 26 families were recorded. Of these, 27 are considered occasional or uncommon in Acadia National Park. Thirteen species are new reports for vernal pools in the northeastern United States. This represents the first published study of the vernal pool flora of Acadia National Park. © 2011 New England Botanical Club. Source


Gurney C.M.,University of California at Berkeley | Gurney C.M.,WRA Inc. | Prugh L.R.,University of Alaska Fairbanks | Brashares J.S.,University of California at Berkeley
Rangeland Ecology and Management | Year: 2015

Granivory and soil disturbance are two modes by which burrowing rodents may limit the success of native plant restoration in rangelands. This guild of animals has prolific effects on plant community composition and structure, yet surprisingly little research has quantified the impact of rodents on plant restoration efforts. In this study, we examined the effects of seed removal and soil disturbance by the giant kangaroo rat (Dipodomys ingens) on native plant restoration in a California rangeland. Using experimental exclosures and stratifying restoration plots on and off rodent-disturbed soil, we assessed the individual and combined effects of seed removal and soil disturbance on seedling establishment of four native plant species. Across all species, biotic soil disturbance by kangaroo rats reduced seedling establishment by 19.5% (range = 1-43%), whereas seed removal reduced seedling establishment by only 6.7% (range = 4-12%). Rates of seed removal across species weakly paralleled kangaroo rat dietary preferences. These results indicate the indirect effects of burrowing rodents such as kangaroo rats on native seedling establishment via changes in soil properties may rival or exceed the direct effects of seed removal. © 2015 Society for Range Management. Published by Elsevier Inc. All rights reserved. Source

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