Archives -- Research Reports

Effects of Consumers and Nutrients on the Densities and Spatial Heterogeneity of Organisms in Streams

Scott D. Cooper, Department of Ecology, Evolution, and Marine Biology, UCSB

Participants: S. Roll, A. Dominguez, S. Diehl, K. Kratz, S. Wiseman, Department of Ecology, Evolution, and Marine Biology, UCSB

Over the last several years, my research group and I have conducted field experiments, and laboratory and computer analyses, dealing with the effects of consumers and nutrients on the abundances and spatial heterogeneity of stream organisms. Our work has focused on four research areas: 1) the development of population models of open (stream) systems including behaviorally flexible organisms; 2) the experimental evaluation of the effects of top carnivores (trout, stoneflies) on mean levels, variability and spatial heterogeneity of resources (benthic invertebrates and algae) at lower trophic levels (conducted in large channels and stream sections at SNARL); 3) the experimental evaluation of the effects of prey refuges, prey exchange rates, and prey resource levels on predator impacts on prey populations; and 4) experimental work on the effects of nutrient enrichment gradients and grazer immigration on the abundances of algae and grazing insects. During the summer of 1996, we concentrated on the effects of nutrient additions and grazer recruitment on the dynamics of algae and invertebrate populations in streams. As part of her Master's thesis research, Sandra Roll conducted a small-scale nutrient enrichment experiment in 24 0.2x2.4-m channels which were placed in Convict Creek at SNARL. She created a 1000-fold gradient of nutrient additions (phosphorus and nitrogen in a constant ratio which were continuously dripped into the channels) in each of two sets of 12 channels for 24 days. In one set, grazing invertebrates were allowed to colonize naturally via the drift, whereas additional drift was added to the other set (i.e., ambient vs. enhanced grazer immigration). Overstory and understory algae increased to an aymptote as nutrient inputs increased, and an enhanced abundance of large grazers (large baetids) was sufficient to suppress algal biomass and reduce temporal fluctuations in algal populations. Grazers had larger effects on overstory than understory algae and grazer impacts on overstory algae were negatively related to the level of nutrient inputs. At the end of the experiment, grazers were more abundant and emigrated less from channels with higher levels of algal biomass. These investigations were complemented by an undergraduate project conducted by Alvaro Dominquez. The goal of this project was to determine which nutrient(s) limits algal production in Convict Creek by monitoring algal colonization and growth on in situ clay pots containing agar augmented or not augmented with nutrients (treatments: no nutrients added, +P, +N, +N and P). This technique was also used to analyze the effects of different nitrogen: phosphorus ratios on algal biomass and community structure. Funding: National Science Foundation; California Alliance of Minority Projects.

Evaluation of Rangeland Stream Condition and Recovery Using Physical and Biological Assessments of Nonpoint Source Pollution

David B. Herbst, SNARL and Marine Science Institute, UCSB

Participants: E. Dinger, Department of Ecology, Evolution, and Marine Biology, UCSB

The specific aim of the project is to provide a biological basis for establishing standards and regulatory criteria for nonpoint source pollution impacts related to livestock grazing in rangeland watershed stream ecosystems. Bioassessment is a technique that uses aquatic insects and other invertebrates as indicators of pollution. Using differences in pollution tolerance and functional roles in the ecosystem, changes in the types of organisms found can be used to monitor the extent of impacts and/or habitat recovery. In order to apply the technology of bioassessment to grazing, this study will develop (1) reference stream standards, (2) a baseline for trend comparisons in invertebrate communities exposed to varied grazing management practices, and (3) a database on sediment-polluted streams that can be used to analyze invertebrate associations and establish a tolerance scoring system for indicator fauna specific to grazing-related impacts. The approach of the research supported by this grant has been to apply the technique of bioassessment to identify grazing pollution problems and compare this system with traditional monitoring methods that have relied on external stream features such as channel geomorphology and riparian vegetation. Results from the first year and a half of studies are based on (1) a pilot project comparing seasonal differences in physical habitat conditions, aquatic invertebrate communities, and fish populations among 9 stream reaches including a single ungrazed reference reach, and (2) an expanded study designed to (i) establish multiple reference stream reaches, (ii) initiate a set of sites for baseline trend monitoring, and (iii) obtain a data set from varied habitat conditions to be used for developing invertebrate indicator groups of pollution related to grazing impacts. Results suggest that bioassessment may detect short-term and local grazing impacts, but that single-season bioassessment measures are inadequate to capture the range of variation. The initial project phase has revealed differences between an ungrazed site and polluted grazed sites, and permitted contrasts and derivation of monitoring indicators, but also shown limitations due to low sample sizes and redundant measures. Sampling was expanded during the summers of 1996-97 (July-September) with samples taken from 82 stream study reaches to date. Detailed taxonomic analysis of the samples includes identification of midges (chironomidae), a group often ignored in bioassessment but found here to have nearly the same amount of taxonomic diversity as all other invertebrate groups combined. This will add great predictive power to indicator group analysis. Funding: Environmental Protection Agency.

Aquatic Habitat Formed on Owens Dry Lake by Flood Irrigation: Renewal of a Biological Community in Seasonal Habitats

David B. Herbst, SNARL and Marine Science Institute, UCSB

Dean W. Blinn, Department of Biological Sciences, Northern Arizona University

Participant: H. Kloeppel, Marine Science Institute, UCSB

Since Owens Lake dried over 60 years ago, alkali dust storms originating from the dry playa have become persistent in the Owens Valley. Among the more promising solutions to eliminating dust storms has been to temporarily flood playa dust source areas during the windy seasons. This not only reduces dust, but creates renewed aquatic habitat inhabited by many of the same creatures previously found in Owens Lake. In seeps and springs along the playa margins are refuge habitats that sustain populations of the flora and fauna (algae and invertebrates) that once lived in the lake. These organisms recolonize habitat rapidly when opportunities arise. This project provides information on the biological diversity and productivity of flooded aquatic habitat (natural and irrigated) and the water quality conditions most favorable for the renewal of food resources for migratory and breeding shorebirds and waterfowl. Algae and invertebrates form the base of the food chain for foraging water birds. Observations of ephemeral flood waters forming on the playa suggest that they are rapidly colonized from marginal spring and seep habitat refugia and become foraging sites previously unavailable to migratory shorebirds. Surveys of habitat refugia and natural flood zones around the margins of Owens Lake playa showed at least 70 species of aquatic invertebrates were present. Experimental studies of salinity effects on biological communities were conducted using field microcosms (50 liter tanks embedded in playa sediments) within which salinity and evaporation rate were controlled. Limitation of the productivity of saline aquatic habitat by biological factors at low salinity and physiological stress at high salinity supports a model for the ecology of salt lakes known as the intermediate salinity hypothesis. Laboratory studies of the development of E. hians further support this interpretation by showing that in the absence of competition or predation, survival and development of this insect are most favorable at the lowest salinities. Funding: Great Basin Air Pollution Control District.

Livestock Grazing and Rangeland Stream Ecology

David B. Herbst and Roland A. Knapp, Marine Science Institute, UCSB

Participants: M. Embury, P. Kirchner, D. R. Dawson, SNARL

Livestock grazing in the limited riparian zone of arid Great Basin streams can result in a loss of vegetative cover and erosion of stream channel habitats. Although changes in the riparian and physical environment of streams are well-documented, much less is known about the responses of aquatic communities to grazing-related impacts. For 3 years we have been monitoring the biological characteristics of stream reaches exposed to different grazing practices to both evaluate differences in the ecological attributes of grazed and ungrazed areas, and the success of management in alleviating nonpoint source pollution problems. A loss of invertebrate species diversity and shifts in indicator groups consistently occurred at some grazed sites while others were unchanged relative to reference sites. Trout abundance also was decreased at some grazed sites but not others. Results suggest that physical monitoring alone is insufficient to detect changes in aquatic ecosystem structure and function, and that bioassessment monitoring is sensitive and responsive to local and seasonal changes in rangeland stream environments. Funding: UC Water Resources Center.

Arsenic Geochemistry in Source Waters of the Los Angeles Aqueduct

Janet G. Hering, Civil and Environmental Engineering, California Institute of Technology and UC Los Angeles

Participants: J. Wilkie, V. Chiu, UC Los Angeles; P. Kneebone, T. Salmassi, Caltech; D. Sedlak, UC Berkeley

Geothermal activity is responsible for significant discharge of arsenic to Hot Creek, a tributary of the Owens River. Because of these natural inputs, water supplied to the City of Los Angeles through the Los Angeles Aqueduct contains arsenic concentrations significantly higher than in average U. S. source waters. Field studies were conducted along Hot Creek to investigate the ambient redox speciation and concentrations of arsenic in both geothermal spring and creek waters. Rapid in situ oxidation of As(III) to As(V) was observed along the creek with almost complete oxidation occurring within a 1200 meter reach. Based on assumed plug flow transport and a flow velocity of about 0.4 m/s, the pseudo first-order half-life for this reaction is approximately 0.3 hours. Conservative transport of total dissolved arsenic was observed over the reach. Pseudo first-order reaction rates determined for As(III) oxidation in batch studies with aquatic macrophytes were comparable to the in situ oxidation rate observed along Hot Creek. In batch kinetic studies, oxidation was not observed after sterile filtration or after the addition of antibiotics which strongly suggests that bacteria attached to submerged macrophytes are independently mediating the rapid As(III) oxidation reaction in this natural system. Funding: UC Water Resources Center; National Science Foundation.

Fish Community Survey in Mammoth Creek

Thomas M. Jenkins, Jr., SNARL and Marine Science Institute, UCSB

Daniel R. Dawson, SNARL and Marine Science Institute, UCSB

Participants: M. Embury, H. Kloeppel, B. Yarnell, K. Leary, UCSB

Mammoth Community Water District diverts water from Mammoth Creek for domestic use. The minimum stream flows required to maintain a healthy stream ecosystem have been a point of contention between the District and other agencies including UC. One aspect of the healthy ecosystem required by law is a healthy fishery. We surveyed fish populations at eight sites along Mammoth Creek building upon work we did last year and work performed by district consultants in the past. Fish population surveys were conducted by electrofishing. Analysis revealed that the fishery is currently "healthy" by adopted standards. Funding: Mammoth Community Water District.

Effects of Exotic Eradication on Ecosystem Structure and Function

Roland Knapp, SNARL and Marine Science Institute, UCSB

Orlando Sarnelle, Marine Science Institute, UCSB, and Michigan State University

Participants: S. Roll, W. Kuhn, A. Dominguez, UCSB

Exotic species have had large impacts on ecosystems worldwide, causing extinctions of native species and large alterations in species composition and ecosystem processes. Despite long-standing interest in exotic effects, quantitative studies of ecosystem recovery after the eradication of exotics are rare. Study of exotic eradication provides a rare opportunity to study the fundamental ecological process of community assembly in nature. Such study is essential to determine whether natural communities converge on a single configuration after perturbation. Community convergence has important implications for the conservation of biodiversity. This project examines the recovery of alpine lake systems in the Sierra Nevada after the eradication of exotic trout. Our first major objective asks whether the species composition of alpine lakes re-assembles to its pristine state after release from exotic perturbation. We are eradicating exotic trout from three lakes and comparing them to three lakes in which trout stocking will continue. We are particularly interested in how the recovery times of species that are currently extinct varies with the life history traits of those species. We will compare experimental results with an extensive survey of Sierran lakes that vary in both the duration of trout presence and in the length of time since exotic trout have died out. Our second objective examines how basic ecosystem processes respond during the recovery of experimental lakes. The goal here will be to determine how changes in species composition and biodiversity alter the relative contributions of benthic and pelagic photosynthesis to lake-wide primary production. Funding: National Science Foundation. 

Introduced Trout in the Sierra Nevada, California

Roland A. Knapp, SNARL and Marine Science Institute, UCSB

Participants: K. Matthews, V. Vredenburg, D. Court, C. Brown, U.S.D.A. Pacific Southwest Research Station; R. Jellison, T. Jenkins, P. Kirchner, L. Hammett, E. Wenk, J. Goerrison, D. Rowan, H. Kloeppel, M. Klapp, A. Martinez, J. Lester, Marine Science Institute, UCSB

This project is designed to elucidate the impacts of non-native trout on lake ecosystems in the Sierra Nevada. Historically, nearly all Sierran lakes were fishless. Starting in the 1850's and continuing to the present day, however, trout have been stocked into nearly all suitable waters. Because trout are highly-effective predators, these introductions have resulted in precipitous declines in species adapted to fishless lakes, including amphibians, zooplankton, and benthic invertebrates. In some cases (e.g., amphibians), these declines have been severe enough that some species may soon be listed under the Endangered Species Act. In order to better understand the impacts of introduced trout on lake ecosystems, we are sampling approximately 2,000 lakes and ponds over a 1,500 km² landscape in the Sierra Nevada for fish, amphibians, zooplankton, and benthic invertebrates. The information generated by this sampling effort will be used to evaluate the community-level changes caused by trout introductions, identify native species that are threatened by trout introductions, and design a series of reserves to maintain and restore viable populations of these "at risk" native species. Our study will increase our understanding of the causes underlying amphibian declines, and will have important consequences for the future management of high mountain lake ecosystems. Funding: U. S. Department of Agriculture; U. S. Forest Service.

Vertical Mixing and Resource Supply to Phytoplankton

Sally MacIntyre, Marine Science Institute, UCSB

Participants: R. Jellison, K. M. Flynn, J. R. Romero, D. Heil , B. Loose, Marine Science Institute, UCSB

My research project addresses the importance of vertical mixing to nutrient fluxes, circulation of phytoplankton, and primary productivity in lacustrine ecosystems. Using microstructure profilers which measure temperature, conductivity, and temperature-gradients on millimeter scales, we determined where the water column was mixing and the intensity of the turbulence in Mono and Convict Lakes, California. In Convict Lake, we tested whether hydrogen peroxide, which is formed photochemically in the surface waters of lakes and oceans, can be used as a natural tracer of mixing. In Mono Lake, we profiled for chlorophyll a and nutrients concurrently with the turbulence measurements. Particularly exciting is our finding that nutrient flux across the thermocline is two to three orders of magnitude higher in nearshore areas, where the thermocline intercepts the sediment-water interface, than in offshore waters. This boundary mixing led to ammonia fluxes to the chlorophyll maximum which were in excess of those required for daily primary productivity. In addition, upwelling at the top of the pycnocline led to ammonia fluxes more than twice those required for primary productivity throughout the euphotic zone. We are currently using measures of lake stability relative to surface wind forcing to determine the frequency of these upwelling and boundary mixing events. Assessing their frequency is essential for predicting the changes in Mono Lake's productivity now that the lake is again meromictic and predicted to remain so for the next 50 years. Funding: National Science Foundation. 

Monitoring of Limnology and Plankton in Mono Lake

John M. Melack, Department of Ecology, Evolution, and Marine Biology and Marine Science Institute, UCSB

Robert Jellison, SNARL and Marine Science Institute, UCSB

Participants: D.Heil, P. Kirchner, SNARL and Marine Science Institute, UCSB

Mono Lake is a large, hypersaline, highly productive alkaline lake lying just east of the Sierra Nevada. In addition to its recreational, scenic, and water resource values, it contains large populations of an endemic brine shrimp and the alkali fly which are important food sources for migrating birds. Although saline lakes are common throughout the world and provide important ecological resources for many species, they are much less studied than freshwater ecosystems. Limnological monitoring conducted from 1979-1997 represents one of the longest continuous studies of any hypersaline ecosystem and, in addition to addressing current environmental concerns in the Mono Basin, provides insight into the functioning of saline ecosystems. Funding: Los Angeles Department of Water and Power.

Responses of a Saline Lake to Environmental Change

John M. Melack, Department of Ecology, Evolution, and Marine Biology and Marine Science Institute, UCSB

Robert Jellison, SNARL and Marine Science Institute, UCSB

Participant: D. Heil, SNARL and Marine Science Institute, UCSB

Saline lakes constitute nearly half of inland waters by volume and provide ecologically important aquatic habitats in arid regions of the world. They often have high rates of algal productivity which support aquatic invertebrates and large numbers of birds. At Mono Lake, California environmental concern has focused on the impacts of higher salinity caused by the diversion of freshwater streams that used to flow into Mono Lake. In 1994, state agencies decided to gradually raise the surface elevation of Mono Lake to approximately six meters above the historic low in 1982. This action provides a unique opportunity to study the effects of environmental change on a large saline lake. Ecological studies of the lake's biota during the period of rising lake levels and decreasing salinity will complement prior laboratory studies focused on the effect of increased salinity on Mono Lake's biota. Funding: National Science Foundation.

Snow Algae Studies at SNARL

William H. Thomas, Scripps Institute of Oceanography, UC San Diego

Participants: A. M. Thomas, A. K. Thomas

We continued our studies of the effects of ultraviolet radiation on the algae/bacteria microbial ecosystem in high altitude snowfields. From earlier work we know that bacterial production is not affected by the presence of UV in natural sunlight, but algal photosynthesis is enhanced by about 25% when UV is present. We attribute this to UV-absorbing pigments acting as accessory pigments to chlorophyll in the cells so that light energy gathered in the UV is transferred to chlorophyll for an increase in the photosynthetic rate. We also have found mycosporin-amino acids in solvent extracts of the red algae snow spores. These protect the algae from UV. Thus since the bacterial production is not affected, and algal photosynthesis is enhanced by UV, the whole microbial ecosystem is highly protected from UV. In 1997 we transported green motile cells of the snow algae (from laboratory cultures at Scripps) to SNARL and incubated them for several days at the surface of snow near the Mammoth Mt. Met-site. We hypothesized that the green cells would form red spores in response to high sunlight. They did not and the cultures died. In a second experiment we reduced the sunlight over the cultures by 89%, and the green cells and their chlorophyll were preserved. Since such cells swim up to near the snow surface in summer waterlogged snow, and form red spores, we postulated that they must not swim up to the very surface if they are to survive, but must stop at light levels near 90% of sunlight intensity and form the spores there. After spore formation, the algae are then protected from high sunlight intensities and UV, can go into the soil when the snow melts, and overwinter below the dry snowpack. Then the green cells are released and this swimming process and spore formation starts all over again. Thus there is a yearly cycle of the snow algae. Funding: Scripps Institute of Oceanography, UC San Diego.

Coexistence of the Mountain Yellow-legged Frog (Rana muscosa) and Introduced Trout in Sequoia and King's Canyon National Parks

Vance T. Vredenburg, Department of Integrative Biology, UC Berkeley

Participants: Mary E. Power, Department of Integrative Biology, UC Berkeley

Mountain yellow-legged frogs (Rana muscosa) were once very common throughout the high elevation aquatic ecosystems of the Sierra Nevada mountain range in California, but have declined dramatically in recent years. Although increases in UV-B radiation and pesticide drift have been proposed as important contributing factors, much of this decline has been attributed to predation by introduced trout. At present, the distribution of introduced trout and the remaining populations of Rana muscosa are strongly allotopic, yet there are a few cases where tadpoles, adult frogs, and trout have been reported to coexist in the same habitat. I surveyed 83 lakes and ponds in a basin having many reports of coexistence and found only 8 lakes with both trout and Rana muscosa. Tadpole numbers were significantly higher in lakes that did not contain any trout. Of the 8 lakes with frogs and fish, only one had large numbers of frog larvae, and it had only a few trout and no trout reproduction. As a result of this work, I suggest that there is little if any stable co-existence between Rana muscosa and introduced trout; apparent cases probably result from transient movements of adults and subadults, or represent sink populations. The significance of these results are important to the conservation of Rana muscosa in the Sierra Nevada, and suggest that introduced trout may be one of the most important factors controlling Rana muscosa distrubutions. Funding: 1997 Gompertz Award, Museum of Vertebrate Zoology, UC Berkeley.

Detection of Predators by Rana muscosa

Vance T. Vredenburg, Department of Integrative Biology, UC Berkeley

Ph.D. Advisor: Mary Power, Department of Integrative Biology, UC Berkeley

Experiments were conducted at SNARL to see if Rana muscosa, the Mountain Yellow-Legged Frog, is able to determine the presence of fish predators from olfactory or other clues. Tadpoles were placed in large buckets with flow-through water supplies. For one sample a fish was placed in a bucket through which the water flowed before entering the tadpole bucket. Tadpole behavior was observed in the presence and absence of fish and no significant differences were noted. In another experiment, a fish was placed in a cage inside a large tank containing tadpoles. No changes in tadpole behavior were evident comparing the presence and absence of fish. However, when free-swimming fish were placed in the tank, obvious avoidance behavior was evident in the tadpole following the first predation event. Funding: UC NRS Mildred E. Mathias Graduate Student Research Grant.

Helium Isotopes in Mono Lake

Jordan Clark, Department of Geological Sciences, UCSB

Participants: G. B. Hudson, Lawrence Livermore National Laboratory; M. Trecker, UCSB

Concentrations of He-3 and He-4 in Mono Lake are greater than atmospheric equilibrium values indicating a subsurface source of helium. This assertion is supported by vertical concentration profiles which show that maximum delta-He-3 values (+70%) occur immediately below the pycnocline. The slope of the correlation between He-3 and He-4 concentrations is about 3.2 Ra (Ra = atmospheric helium isotope ratio) indicating that the subsurface source has a component of mantle helium. Helium isotope ratios of spring water collected near the lake range between 1.6 and 5.6 Ra. The most similar ratio, 2.7 Ra, was found in hydrothermal springs and gas vents from Pahoa Island which is located in the middle of Mono Lake suggesting that springs from this island contribute the majority of the subsurface helium. A helium mass balance suggests that the maximum influx of hydrothermal water into Mono Lake is1.6 x 106 m³/yr. This is equivalent to approximately a 1 cm rise in lake level each year and is less than 1% of the annual evaporation rate. This estimate of the hydrothermal water flux is a maximum value because helium may also be injected into Mono Lake by the subsurface dissolution of gas bubbles emanating from submerged gas vents. Funding: Department funds.

Spatial and Temporal Distributions of Snow Processes and Surface Energy Exchange in Alpine and Subalpine Environments

Robert E. Davis, Geophysical Sciences Division, Cold Regions Research and Engineering Laboratory (CRREL)

Participants: S. Burak, J. Fiori, B. Harrington, C. McKenzie, B. Yankielun, CRREL; K. Elder, A. Winstral, Colorado State University; G. Dana, Desert Research Institute, Reno, Nevada; J. Pape, unaffiliated; M. Colee, R. Kattelmann, T. Painter, W. Rosenthal, UCSB

This research seeks to improve understanding of the spatial and temporal distributions of snow processes and surface energy exchange in alpine and subalpine environments. We compare model predictions of snow properties with field measurements and map-based products from remote sensing. Our research improves the CRREL snow model SNTHERM, tests new techniques for measuring snow properties and develops methods to use terrain and land cover data to spatially distribute SNTHERM. Our experiments range in spatial and temporal scales from detailed physics studies at the cooperative Mammoth Mountain snow study plot over periods of a few days, to parameterized experiments over areas up to a few square kilometers lasting several weeks. This last winter we upgraded the instrumentation at the study plot to increase the number of variables we measure for model validation. Our computers automatically download a wide variety of measurements daily for processing into model input and testing formats. We will use these data to assess new formulations of turbulent transfer of latent and sensible heat exchange currently under development at the Cold Regions Research and Engineering Laboratory. We will soon complete development of a new terrain and vegetation cover data base of the Mammoth Mountain area, which will support spatially distributed modeling of snow processes in the alpine and subalpine zones. Comparison of model predictions with products from satellite and aircraft measurements will improve development of methods to segment land cover and terrain data sets, as well as our ability to specify initial conditions for model experiments. The winter and spring of 1996-1997 marked the third year of detailed measurements of snow depth, water equivalence and extent on the mountain side above the study plot. Preliminary results show that the spatial patterns of snow extent during ablation appear similar despite different amounts of total accumulation during the three years. This experiment will lead to improved parameterization of model processes below the spatial resolution of model response units. Funding: U. S. Army Corps of Engineers; ICESS, UCSB.

Hydrology, Hydrochemical Modeling, and Remote Sensing in Seasonally Snow-covered Alpine Drainage Basins

Jeff Dozier, School of Environmental Science and Management, UCSB

Participants: R. Bales, Hydrology and Water Resources Department, University of Arizona; J. M. Melack, Institute for Computational Earth System Science and Ecology, Evolution, and Marine Biology, UCSB; K. Tonnessen, National Park Service, National Biological Service; M. Williams, University of Colorado

This project is a continuation of a decade long research investigation of alpine regions. Mountainous areas, particularly in the western U. S., supply a large fraction of freshwater resources through snowmelt, and are especially sensitive to changes in climate and precipitation chemistry. Knowledge of the hydrologic cycle in alpine areas of seasonal snow and glaciers is limited by incomplete understanding of the processes that determine the cycle. Research for this investigation combines three methods to try to further understand these processes: observation in the field and laboratory; measurements from remote sensing; and models of hydrologic processes and chemical transformations. Our modeling results are helping to couple basin-wide energy-balance snowmelt models with remote sensing and flow routing. Our remote sensing work now allows us to estimate important hydrologic variables from space or aircraft. Our studies of global hydrology and hydrochemistry result in an accumulation of massive amounts of scientific data. We are addressing the need to manage these large, complex data sets. During the '96/'97 year a relational database and application were completed for ingesting, storing and retrieving meteorological data recorded by data loggers. In addition to the data itself, the database contains information about the sites from which the data were collected; the instruments used, along with their calibration information; and information about the quality of the data. The database was designed such that other types of data (eg., discharge, snow density) can be entered, stored, and retrieved, as well. Funding: N. A. S. A.

Carbon Dioxide Emissions in the Mammoth Lakes Area

Chris Farrar, U. S. Geological Survey, Carnelian Bay, California

Participants: J. Neil and J. Howle, U. S. Geological Survey

Research has continued on the carbon dioxide emissions in the Mammoth Lakes areas as part of the U. S. Geological Survey Volcanic Hazards Program. SNARL served as a base for the research aimed at identifying, quantifying, and mapping areas of anomalously high CO₂ concentrations in soil gas. Surveys have focused in a ring around Mammoth Mountain where coniferous forest has been killed by excessive gas concentration (up to 95% vol.). The source of CO₂ is either directly from degassing magma or from carbonate rocks heated by magma. Funding: U. S. Geological Survey.

¹⁸O/¹⁶O Mapping and Hydrogeology of a Short-lived, Fumarolic, Meteoric-hydrothermal Event in the Upper Part of the 0.76 Ma Bishop Tuff

Elizabeth Warner Holt, Division of Geological and Planetary Sciences, California Institute of Technology

Ph.D. Advisor: Hugh P. Taylor, Jr., Division of Geological and Planetary Sciences, California Institute of Technology

This study was initiated in order to integrate oxygen isotope systematics with mineralogical and geomorphological evidence of fumarolic activity in an ash-flow tuff outflow sheet that would be directly comparable to the Valley of Ten Thousand Smokes, which represents the only available historical analog for this phenomenon. Because of a favorable combination of scientific and logistical attributes, it became apparent that one of the best localities in the world for such a study was the outflow sheet of Bishop Tuff, which erupted at 0.76 Ma from Long Valley caldera on the east side of the Sierra Nevada, California. On the surface of this outflow sheet, which extends southeastward for about 35-40 km from Lake Crowley toward the town of Bishop, the morphology of fossil fumaroles is well-developed over wide areas, in the form of fumarolic mounds, ridges, and mineral encrustations. In addition, deep gorges have locally cut more than 150 meters down into the tuff to expose the joints, fissures, and conduits that represent the inner workings of these fumarolic mounds. On these cliff faces one can observe areas where the well-developed, typically near-vertical, columnar joints locally bend around and become shallow-dipping; such zones are invariably associated with the conduits of fossil fumaroles. The patterns of whole-rock ¹⁸O depletion in the Bishop Tuff outflow sheet display a one-to-one correlation with the area of most numerous fossil fumaroles and most intense devitrification textures in the tuff, as well as with details of the fumarole morphology. These relationships demonstrate that fumarolic activity involved vigorous, high-temperature circulation of meteoric-hydrothermal fluids through the Å 80-m-thick, partially welded upper part of this ash-flow sheet, and that the fumarolic were not dominantly composed of magmatic H₂O. The densely welded lower 2/3 of the outflow sheet is pristine and not ¹⁸O-depleted, implying that during the fumarolic activity this hot, ductile, densely welded tuff was essentially impermeable to meteoric fluids. Our observations that the Bishop Tuff fumarolic areas correlate with the regional drainage pattern, together with the large amount of water required by material-balance and time-scale arguments suggest that meteoric-fluid recharge to the fumaroles had to be enhanced by focused groundwater flow through the upper part of the tuff down along the top of the impermeable zone of densely welded tuff. This flow may have been in part from the lake that rapidly filled Long Valley caldera after the eruption of the Bishop Tuff. Our work, together with that of Gazis et. al. (1996), is the first set of studies to demonstrate that detailed mapping of isotopic stratigraphy, combined with analyses of phenocryst mineral separates, can be used to identify fossil fumarolic activity and distinguish it from the effects of other types of meteoric-hydrothermal systems. In addition, the proven influx of substantial amounts of cold meteoric water into the hot, upper portions of thick ash-flow sheets is bound to have played a significant role in the cooling and fracturing history of these ash-flow sheets. In the future, we plan to investigate whether short-lived, high-temperature fumarolic meteoric-hydrothermal activity is a general characteristic of the permeable upper zones of virtually all ash-flow tuffs that have developed significant welding. Funding: National Science Foundation. 

Sierra Nevada Hydrology

Rick Kattelmann, Institute for Computational Earth System Science (ICESS), UCSB

Participant: J. Dozier, ICESS, UCSB

Rick Kattelmann finished up work on the Sierra Nevada Ecosystem Project, spoke about the project at several conferences and workshops, and began to write articles based on pieces of the project for various publications. He continued snowpack studies at Mammoth Mountain and other sites in the Sierra Nevada. Collaborative work with the U. S. Army's Cold Regions Research and Engineering Lab continued to improve the snow research site at Mammoth Mountain. He also took advantage of the record flooding in early January 1997 to study processes of flood generation during a high-intensity rain-on-snow event. Kattelmann also participated in an effort of the State Water Resources Control Board and Mono County to determine water availability and use in the northwest corner of the Mono Basin with respect to habitat restoration plans. Funding: UC Centers for Water and Wildland Resources; N. A. S. A.

Remote Sensing of Snow Water Equivalence in Montane Watersheds

Walter Rosenthal, Institute for Computational Earth Systems Science, UCSB

Ph.D. Advisor: Jeff Dozier, Institute for Computational Earth Systems Science, UCSB

An unsupervised algorithm was developed to estimate snow-covered area at subpixel resolution from multispectral image data. Classification trees fragment the data set along boundaries of distinct land and cloud cover classes. The dimensionality and number of endmembers for each image fragment are determined from principal components analysis. Endmember spectra are converted to surface reflectance with an atmospheric radiative transfer code, and the endmembers are identified by automated search of a spectral library. The final snow cover estimate is a composite of the best mixture model per pixel, adjusted for endmember impurity. The algorithm was tested on Landsat Thematic Mapper data against high resolution aerial photographs and found to yield equivalent estimates of snow cover fractions. Estimates of snow-covered area must be combined with estimates of depth and density to yield estimates of spatially distributed snow water equivalence. Snow depth was measured with an Lband FMCW radar operating from an aerial tramway at Mammoth Mountain up to 70 meters above the ground. Snow depth, wetness, and slope varied greatly along the 2.4 km transect. Radar measurements were compared against concurrent manual depth probes, and good agreement was found between the estimates. The results suggest that deep snow packs in rugged terrain can be accurately and safely surveyed by helicopter-borne radar. Funding: N. A. S. A.; U. S. Army Corps of Engineers.

Terrestrial Botany

Resistance Induced in Wild Tobacco When Neighbors are Damaged

Richard Karban, Department of Entomology, UC Davis

Participants: I. T. Baldwin, Director, Max-Planck-Institut fur Chemische Okologie, Jena, Germany; K. Baxter, Department of Entomology, UC Davis

It is generally assumed that growing in proximity to sources of nectar will benefit plants by attracting predators and parasites that reduce herbivore loads. This research documents patterns of hornworm (Manduca quinquemaculata) abundance on wild tobacco plants (Nicotiana attenuata). Observations suggested that several plant traits were associated with hornworm eggs and larvae. Hornworms were more likely to be found on large tobacco plants. Hornworms were more likely to be found on tobacco plants with flowering Eriastrum densifolium neighbors. Experimental removal of neighboring Eriastrum densifolium flowers or whole plants reduced hornworm damage to tobacco plants in neighborhoods with E. densifolium. The effects of these manipulations were not found to increase reproductive success of neighboring tobacco plants although tobacco reproduction was reduced where M. quinquemaculata was abundant. These results suggest that close proximity to nectar resources could decrease plant fitness. Funding: U. S. D. A.

Microclimate and Plant Distribution for a Mojave Desert - Great Basin Transition Zone: Implications for Climate Change

Michael E. Loik, Department of Biology, California State University at San Bernardino

Participants: E. Miranda, Department of Biology, California State University at San Bernardino

Atmospheric levels of carbon dioxide and other greenhouse gases due to human activities are expected to double in the next century, resulting in a warming of the Earth's climate by 1.5 to 3 degrees C. Such changes in climate will cause many ecological responses, including the movement of some plant species into new regions, and extinction for certain species at the border of different ecosystems. The establishment of plants is dependent upon survival of the rigors of the environment, including seedling survival of drought and thermal extremes at the soil surface. In the face of global warming, the environment near the ground will become warmer and drier during the summer. Such changes in the climate near the soil will reduce the photosynthetic ability of seedlings and could cause damage to their cells, resulting in reduced plant vigor, and possibly the death of the young plant. This would produce a situation that would favor the establishment of some species' seedlings while precluding the establishment of others, resulting in changes in ecosystem species composition over time. Microclimate near the soil surface was measured at five field sites (two each in the Mojave and Great Basin ecosystems, and one on the border) at the transition between the northern Mojave Desert and the southern Owens Valley. Microclimate near the soil surface was characterized as air and soil temperatures, solar radiation, light levels, wind speed, and relative humidity. Measurements were made at 0.5 h intervals over 24 h at each site, and made bimonthly during 1996 and 1997. Microclimate was simultaneously measured 1 cm above the soil surface (the height of young seedlings) and at standard meteorological height (1.5 m). Also, conditions were measured for open soil as well as under adult shrubs to test for the ameliorating effect of adult plants on microclimate. Plant community structure was assessed using standard ecological techniques including line transects and computation of per cent cover and diversity indices. Little is known about the responses of Mojave Desert and Great Basin vegetation to climate change. The work at SNARL was an initial study of the processes that control vegetation distribution at the border of the Mojave Desert and Great Basin ecosystems of eastern California. The study seeks to predict changes at the ecosystem border that will occur under a warmer and drier climate. Changes in local ecosystem function will have implications for wildlife, as well as for the local grazing, recreation, and tourism industries, as well as for the hydrology that is important for water use by humans in California. Funding: California State University Professional Development Grant.

Energy Supply Limits on the Reproductive Activities of Male Ground Squirrels

Gwen Bachman, Department of Zoology, University of Oklahoma

Participants: T. Clark, R. Egan, K. Montague, E. Payne, Department of Zoology, University of Oklahoma

The project's primary goal is to assess whether and how energy supply limits the reproductive activities of male ground squirrels. We hope to determine (i) the relationship between individual variation in male reproductive behavior and daily energy expenditure, and (ii) the extent to which individual reproductive activity is limited by stored energy reserves and intake during the mating period. These questions will be examined in two species of ground squirrels with contrasting forms of intrasexual competition: the thirteen-lined ground squirrel (study site in Oklahoma) and the Belding's ground squirrel (study site at SNARL). The mating system of the 13-lined squirrel emphasizes mate searching behavior with minimal male-male combat, whereas the Belding's mating system is thought to emphasize male fighting ability. These tactics are common features of many mammalian systems. A sample of males was followed throughout the breeding period with the aid of radio transmitters mounted on collars. Location and activity of males was noted every 15 minutes for 9-10 hours each day. We also measured energy expenditure and body composition changes in males differing in activity level and experimental treatment. This year, we provided some males with access to extra food for part of each day to examine whether food availability and foraging time limited mating effort or mating success. Funding: National Science Foundation's Visiting Professorships for Women. 

Begging Energetics and Exercise Capacity in House Wren Nestlings

Mark Chappell, Department of Biology, UC Riverside

Gwen Bachman, Department of Zoology, University of Oklahoma

Our main goal is to evaluate the effectiveness of begging as an honest communication of offspring need. To do this, we combine laboratory measures of the energetic expenditures associated with begging with field observations of nestling begging and parental response. We work at the Sierra Nevada Aquatic Research Laboratory, which offers a dense house wren population in a protected habitat. In brief, we have discovered that the energetic cost of begging is significant, in that chicks of all ages (2 to 10 days) show large increases in oxygen consumption during begging activity. The increase may be as much as 2 x resting levels. However, the net energy cost of begging is very low as a fraction of daily energy consumption, since chicks beg for only a small fraction of time (perhaps 15 seconds for every 10 minutes during the day). Beg costs are also low as a function of return (i.e., food provided by parents). The cost of an average beg is much less than 1% of the energy contained in a typical food item. Begging costs also have very low impacts on growth rates. During this summer (June and July 1997) we measured the aerobic exercise capacity of house wren chicks in order to determine if begging is a maximal physiological effort. Since the net energy cost is low (in terms of daily energy intake), a maximal effort during begging might be expected if this signal is an important mechanism for soliciting or competing for food (because there is no cost to limit the escalation of signal intensity, the intensity of begging may increase until it reaches a physiological constraint). Our results show that the average metabolic rate during begging is only about half of the chicks' physiological capacity for exercise. That observation suggests that levels of competition for food are not high in house wren nests, and that average begs are not limited by physiological constraints. However, the maximum power output during begs closely approximates the maximal power output during exercise, suggesting that physiological capacity (and not some other mechanism) sets the upper limit for begging intensity. These results have implications for theoretical analyses of signal evolution. Funding: Academic Senate, UC Riverside (Chappell); National Science Foundation (Bachman). 

The Systematics, Ecology, and Biogeography of Coleoptera in the Eastern Sierra

Roger Dajoz, Museum of Natural History, Paris, France

Participants: A. Dajoz

We have visited SNARL four times, spending about 50 days each year in July and August, studying the systematics, ecology, and biogeography of the Coleoptera belonging to the dendrophagus fauna and the soil fauna. The areas that have been visited range from Sonora Pass to the north to the White Mountains in the south. The species of trees the fauna of which has been studied are Jeffrey Pine, White Fir and Red Fir. The survey that has been made gives an idea of the fauna of Coleoptera that exists in the central Sierra - a fauna which is not yet well known. We have studied the succession of insects according to the state of decay of the trees (from ailing tree to the completely decaying tree) and the succession of insects that live in the fungi on trees (Polyporaceae). These data will be compared with those collected in Arizona and in various part of Europe. The biology of some notable species has been studied (i.e. the larva of a still unknown species of Carabidae and the biometry and allometric growth of Cerambyeidae (longhorn beetles)). The soil Coleoptera have been studied in various areas, particularly in the White Mountains and near Sonora Pass. The two most important families are Carabidae and Tedrionidae. Among the data already published are the discovery of a new species of Tenebrionidae of the genus Areoskizus which lives with ants and a new species of Carabidae in the genus Callisthenes which has been found only in a restricted area near Mammoth Lakes and which is very likely a Sierra Nevada endemic species. The Coleoptera that live in riparian areas have been studied. The main species are Caribidae, Staphylinidae, Heteroceridae. Populations with notable species have been found near Fish Slough, Mono Lake, Walker Creek, and Crowley Lake. Funding: Self-funded.

Causes and Consequences of Asymmetric Soundfields in Sage Grouse

Marc Dantzker, Department of Biology, UC San Diego

Ph.D. Advisor: Jack Bradbury, Department of Biology, UC San Diego

Participants: D. Chazan, Department of Biology, UC San Diego

Researchers have been studying the Crowley basin sage grouse at SNARL since 1984. SNARL's sage grouse has become one of the most important and well studied examples of a classic lek mating system. Much is now known about the spectral and temporal cues that females use to distinguish between potential mates. However, our current study focuses on important acoustic parameters which have not yet been measured that could have substantial fitness consequences. Specifically, we suspect that the pattern of acoustic radiation might play a role in the evolution of the mating display. To study these phenomenon, we have developed a technique to measure the directionality of sound fields on free ranging birds on their natural territories. Results from the pilot study show that sage grouse vocalizations have radiation patterns unlike any previously measured. This year's studies focused on the acquisition of detailed multitrack recordings of a number of males to see if these patterns are variable across the population. In addition much of the effort was focused on the detailed acoustic calibrations which are necessary in order to interpret the biological data without environmental bias. Funding: NRS Mildred E. Mathias Graduate Student Research Grant. 

Field Studies of Sage Grouse Lek Mating Behavior in Long Valley

Robert Gibson, Department of Biology, UC Los Angeles

Participants: K. Semple, T. Clark, D. Dempsey, L. Nguyen, R. Kanda, Department of Biology, UC Los Angeles

This spring we began field work on a new multi-year project examining patterns of genetic relatedness in sage grouse, using microsatellite DNA markers. This research builds on our previous behavioral studies of a population of sage grouse in Long Valley adjacent to SNARL-VESR, which provides a base for the field work. Funding: National Science Foundation. 

The Development of Social Relationships in Belding's Ground Squirrels

Warren Holmes, Psychology Department, University of Michigan.

Jill Mateo, Psychology Department, Cornell University

Participants: S. Yang, E. Stallman, Psychology Department, University of Michigan

The long-term goal of my research on social development in Belding's ground squirrels is to explain how early social experience contributes to the emergence of kin favoritism that adult ground squirrels display in their social relationships. Favoritism shown to relatives (nepotism) is a common feature in many species of mammals, yet we know very little about how such nepotism develops in any species. At SNARL we observed juveniles (young-of-the-year) in large outdoor enclosures and recorded the identity of play partners, juveniles that routinely chased, pounced on, and wrestled with each other. In our earlier work, we had found that siblings were the most frequent play partners during the first few weeks after juveniles came aboveground from their natal burrows. In our current work, we observed juveniles in enclosures throughout the summer to determine whether their earliest above-ground relationships were maintained across the entire summer, which they were. We also found, however, that aggressive interactions increased as juveniles got older, although aggression between non-siblings increased more than it did between siblings. In another study, in which we did a detailed analysis of videotaped play bouts, we found that sibling play was more 'cooperative' than non-sibling play (e.g. play between siblings was less likely to elicit aggressive growls and squeals than non-sibling play). Thus, we were intrigued to learn from our 1996 SNARL research that social preferences to interact with siblings were maintained throughout the entire first summer of juveniles' lives and that the 'quality' of these relationships were different for siblings compared with non-siblings. Funding: Rackham School of Graduate Studies University of Michigan. 

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