Intern Project Ideas For 2006

The following is a list of some of the researchers at Cedar Creek and their ideas for independent intern projects. These projects are currently in different stages. Some of the projects have been completed. Others have had certain components studied. The rest have not been pursued. This list is to give you a general idea of what types of projects are being done as well as a background for brainstorming for your own projects.

Jeff Corney
Associate Director, Cedar Creek Natural History Area
***Intern Project Ideas (in conjunction with John Haarstad):***

• CCNHA Interpretive Nature Trail Guide Book Project: Through an agreement with the City of East Bethel, Cedar Creek is allowing the City to put in a public-access trail system around Fish Lake complete with a visitor kiosk and interpretive nature trail loop for K-12 and other interested groups to enjoy and learn about nature.  We would like to create a nature guide unique to Cedar Creek that helps interpret the environment around the Lake, and ultimately throughout Cedar Creek, that is easily accessible to a variety of audiences.  This project would entail going out in the field and learning the various flora, fauna and geology of the area, then researching both scientific and cultural information about the various natural features and writing concise interpretations coupled with digital photos and other useful graphics to be compiled into a nature guide book.

Tali Lee
Post-doctoral Researcher
Assistant Professor, University of Wisconsin Eau Claire
Symposium Topic:Variation in species response to species richness, CO2, and N: the role of unique functional attributes.  Models suggest a fluctuating cycle in the species dynamics of communities, but it remains unclear what role the individual physiology and nutrition of species with unique functional attributes may have in diverse mixtures compared to monocultures under elevated CO2 and altered N conditions. The objective of this study is to evaluate the response of species from different functional groups to intra- vs. interspecific competition, atmospheric CO2 and increased soil N in terms of biomass, leaf-level photosynthesis and related traits. Both B. inermis and A. millefolium are showing lower rates of leaf photosynthesis in 16-spp mixtures compared to monocultures, and this response is consistent across all years of the study. However, the responses of L. perennis and A. gerardii in 16-species plots compared to monocultures are changing over time suggesting that their unique functional attributes (N2 fixation and C4 photosynthesis) may modulate responses over time.
Research Interests:I am engaged in research that involves investigating how elevated CO2 concentrations and increased soil N interact to affect leaf-level physiological processes across the BioCON species and to examine if these responses to elevated CO2 and N remain similar across the growing seasons.  Our evaluation is done at the leaf level in order to identify potential physiological mechanisms underlying community responses to these global changes.  Generally we are asking the following questions: 1. to what extent do field-grown prairie species acclimate leaf photosynthesis to elevated CO2 concentrations and is this response moculated by soil N supply? and 2. do functional groupings help explain the variations in species responses to elevated CO2 and increased soil N?  My research also involves using 15N analysis to estimate N2 fixation by the legume species, the relative N contribution from this process among the legume species, and finally, the implications of these N inputs across richness, CO2 and N levels.

Nicole Miller
Graduate Student, Washington University in St. Louis
Symposium Topic:  Environmental Change and Pollination Ecology in a common legume, Trifolium repens.
Project Background:  Environmental changes are known to cause many dramatic and often detrimental changes to our natural habitats, including a decrease in plant survivorship (Morse and Bazzaz 1994), a reduction in species diversity (Zavaleta et.al. 2003), and a decrease in herbivory (Hamilton et.al. 2004). Atmospheric CO2 is also known to change plant physiology and, thus, could influence plant-pollinator interactions. Many studies have shown that vegetative characteristics responds positively to elevated CO2 in that they increase biomass (Lee et.al. 2003), allocate more carbon to root growth (Norby et.al.2004), and produce more carbon-based defense compounds that deter herbivores (Lincoln et.al. 1993). However, CO2 has been shown to cause earlier flowering (Farnsworth and Bazzaz 1995), increase the total number of flowers (Jablonski et al. 2002), flower size (Garbutt and Bazzaz 1984), flower longevity (Garbutt and Bazzaz 1984), and the quantity of nectar and alter the quality of nectar (Lake and Hughes 1999). All of these floral traits are known to influence pollinator foraging behavior (Ashman and Morgan 2004, Fenster et al. 2004).  In addition, enhanced N input is known to affect floral traits of plants such as increasing the number of flowers produced (Wagner et.al. 2001), enhancing floral display (Ernhardt and Rusterholz 1998), and altering the quantity of nectar (Campbell and Halama 1993). Moreover, environmental change could also influence another important plant-animal interaction that could have dramatic effects on plant-pollinator interactions, that of a plant and its florivores, animals that consume floral parts. While the response of vegetative herbivores to environmental change has been explored, the effects on florivores are not well understood.  In addition, the impacts of this interaction on plant-pollinator interactions is virtually ignored in light of global climate change.
***Intern Project Ideas:*** 

• In order to assess the influence of environmental change factors on florivory, the amount of florivory will be quantified via digital photography and incidence data, and the culprits will be qualified for each by insect collection and identification. The influence of florivory on plant-pollinator interactions will be quantified by pollinator observations, which will include both the direct and indirect impacts of florivores on their host’s pollinators.  It is important to note, however, that the best species for this project, lupine, is almost finished flowering, so we would need to get started right away!

Ray Dybzinski
Graduate Student, University of Minnesota, Department of Ecology, Evolution, and Behavior
Symposium Topic:  The effects of plant species diversity, seed predators, and their interaction on undispersed seeds.
Research Interests: I am broadly interested in plant community ecology.  What mechanisms promote/limit plant diversity?  How do plant species coexist locally given that most plants need the exact same suite of resources?  I am particularly interested in the effects of enemies (disease, herbivores, etc.), the mechanisms and importance of recruitment limitation, and how resource competition interacts with enemy effects and recruitment limitation to affect plant community structure.
***Intern Project Ideas (in conjunction with John Haarstad):***

• How symmetric or asymmetric is seedling-adult competition? 

A seedling sowing experiment…still figuring this one out…

• Does biodiversity reduce pathogen or insect damage I?

Pick a single plant species or a suite of species and quantify leaf damage by pathogens (identified if possible) or insects across the diversity gradient.  If abundant populations (e.g. species in monoculture) are more damaged by enemies than rare populations (e.g. species in 16-species plots), then this suggests a possible mechanism of plant species coexistence (the Janzen-Connell Effect) and of the productivity-diversity relationship.

• Does biodiversity reduce pathogen or insect damage II?

Pick a single plant species or a suite of species (that are assigned to grow in the biodiversity plots) and grow seedlings in pots that are physically located in the biodiversity plots.  Inoculate each pot with soil from the plot it’s growing in.  Somehow maintain the pot at the canopy height (so that it’s not light-limited).  If individuals are more damaged by enemies in monoculture (especially conspecifics) than in polycultures, then this suggests a possible mechanism of plant species coexistence (the Janzen-Connell Effect) and of the productivity-diversity relationship.  This experiment could be greatly improved by growing some pots with or without inoculant and with or without insecticide.

• Does oomycete removal affect community or population biomass production?

Establish ten or so paired plots in a single field (or in multiple fields).  Treat one of each pair with an oomyceticide for a season and measure community and population biomass at the end of the season and seedling emergence and survivorship during the season.  Oomycetes are the pathogens that cause damping off, downy mildews, water molds, and other important plant diseases.  Do these pathogens have an important effect on prairie communities?  If so, are the effects different for different species?

Peter Tiffin
Assistant Professor, University of Minnesota, Department of Plant Biology
Symposium Topic (tentative):  Evolutionary impact of elevated CO2.
Research Interests:I am interested in understanding the evolutionary processes of natural populations.  I am currently involved in two major projects.  One project uses molecular population genetics and molecular evolutionary analyses to understand the long-term evolution of plant genes involved in defense against herbivores and pathogens.  Specifically, we are examining intraspecific diversity and interspecific divergence for >15 defense genes.  The focal species for this research are two wild relatives of maize, the teosintes Zea mays spp. Parviglumis and Z. diploperennis.  The second project examines the effect of atmospheric CO2 concentrations have on patterns of selection and the genetic basis of phenotypic variation.  This work is utilizing quantitative genetic and QTL approaches with the model plant A. thaliana.

Jeannine Cavender-Bares
Assistant Professor, University of Minnesota, Department of Ecology, Evolution, and Behavior
Symposium Topic:  The role of evolutionary history in the assembly of plant communities.
Research Interests:  I am interested in the evolution of plant form and function and the physiological mechanisms that plants use to survive in their environment.  How flexible are plants in their ability to respond to changing environments over different time scales either through genetic change or phenotypic plasticity?  Recently, I have been investigating the phylogenetic structure of oak dominated communities in order to gain insight into to the mechanisms that allow closely related species to coexist.  This research speaks to the question of how diversity is maintained.  One aspect of this work involves the use of non-parametric statistical techniques that require null models, tools which I find increasingly important.  Much of my research takes a comparative approach to understanding physiological properties of plants (including hydraulic architecture, gas exchange, nutrient use, and chlorophyll fluorescence) across environmental gradients allowing me to examine intra- and interspecific variation in plant function.  I am also interested in plant-mycorrhizal interactions and am currently examining the ectomycorrhizal communities of oak seedlings grown under contrasting soil moisture regimes.  Projects I am involved in take me from the lab bench to the greenhouse and to oak dominated forests in the southeastern U.S., Central America, and Mediterranean regions of Europe.  I integrate a range of techniques from molecular methods to soil analysis and forest canopy research.  My research program addresses fundamental questions in ecology and evolution but is directly relevant to conservation issues and global change.

Brian Pelc
Research Assistant, University of Minnesota, Department of Forest Resources
Symposium Topic:Drivers of shrub expansion and consequential impacts on ecosystem understories.
Research Interests:Across the various burn treatments in Cedar Creek’s oak savanna ecosystem, Corylus Americana, or American Hazel, shows varied growth patterns and densities.  My research explores the relationship between C. Americana resprout vigor at divergent disturbance frequencies (i.e., clipping) in oak savanna and oak woodlands as well as the relationship between hazel and other plants in both ecosystems.
***Intern Project Ideas:***

• There is existing data on herbaceous diversity and biomass at numerous savanna plots.  I will be analyzing this data with regard to responses by herb spp to various of both corylus as well as canopy density.  An intern could help me by adding new plots and collecting data that represent combinations of conditions not already observed.
• Do other shrub spp have similar impacts on their community?  Do other shrub spp have similar responses to disturbance?  An intern could replicate either the observation study or the clipping study with prunus, rhus, oak grubs, etc.
• I am collecting data on corylus regrowth at several disturbance frequency intervals on the individual level.  However, I am also performing some of the same treatments as “maintenance” in my plot level experiment.  An intern is welcome to test whether plot-level responses mimic individual responses to two-week clipping.
• I intentionally picked “individual” shrubs for the clipping experiment that are somewhat isolated from others so we can test our hypothesis more accurately.  An intern is welcome to look at herbaceous responses within these patches and compare them to herb responses in the competition experiment to see if there are potential state factor differences that may explain why the corylus is isolated.

Orna Reisman Berman
Visiting Scholar, University of Minnesota
Symposium Topic:  A shrubland, an open savanna or woodland: the shaping forces of fire, grazing and clear-cutting around the globe and in Burn Unit 113.
Research Interests:  Vegetation ecology, landscape ecology, climatic conditions, the ecology of open areas, ecophysiology.

Martha Phillips
Professor, College of St. Catherine
Symposium Topic:Long-term trends in the abundance of the invasive species Phalaris arundinacea in undisturbed wetlands at the Cedar Creek Natural History Area, Minnesota.
Research Interests:  Wetland ecology, plant community ecology, plant competition, physiological ecology of plants, and restoration ecology.

Mikhail Blinnikov
Faculty, St. Cloud State University
Symposium Topic:Modern phytolith assemblages on E120 Biodiversity experimental plots.
Research Interests:My research focuses on studying microscopic silica remains of plants in soils on selected plots of the E120 Biodiversity experiment.  The main goal is to assess how plant cover, biomass, and composition on these plots influenced silica records in modern soils over a 10-year period.  This is a modern analog study that will be useful for future paleoecology work with silica phytoliths.  It is frequently assumed that phytoliths provide a reliable modern signal of vegetation composition, but this has not been sufficiently tested.  Preliminary results indicate a reasonably strong correlation between phytoliths in soil and plants on the plots, but only 30 out of 60 samples have been processed so far.

David Tilman
Director, Cedar Creek Natural History Area
Regents’ Professor, University of Minnesota, Department of Ecology, Evolution, and Behavior
Symposium Topic:Biofuels Part One: Biodiversity, biofuels, and ecosystem services - Lessons of a long-term experiment.  The Cedar Creek experiments have shown that biological diversity causes ecosystems to be more productive, more stable, to store more carbon in soil, and to be less invasible by exotic species.  These traits also make the restoration of prairie to be an excellent way to produce biomass for biofuels while, at the same time, supplying valuable ecosystem services such as greatly reduced carbon dioxide emissions and cleaner groundwater.
Research Interests:Ecological effects of human domination of the earth, including effects on ecosystem services of value to society; the ecological mechanisms controlling speciation, community assembly, species invasions and the evolution and maintenance of biodiversity; population ecology and theory of community dynamics and biodiversity; role of resource competition; biodiversity and ecosystem functioning; effects of habitat destruction.

Clarence Lehman
Adjunct Professor, University of Minnesota, Department of Ecology, Evolution, and Behavior
Symposium Topic:Biofuels Part Two: Prairie biofuel: From pure science to practical applications.
Research Interests:Theoretical ecology and computation in biology; biodiversity and ecosystem functioning; habitat restoration.

Carol Adair
Research Associate, University of Minnesota, Department of Forest Resources
Symposium Topic:  Effects of CO2, N, and diversity on soil carbon fluxes - is there also a role for water?
***Intern Project Ideas:***

• Is the CO2 effect on soil carbon flux a result of the effect of CO2 on soil water content?

Introduction:
Influencing the inputs, distribution, and turnover of carbon (C) in belowground pools are important ways in which changes in water, diversity, N, and atmospheric CO2 can influence ecosystem processes, with potentially large consequences for plant and soil C storage.  Soil carbon flux (SCF) is a major pathway of C loss from ecosystems, and determining the controls on rates of SCF is crucial for predicting if ecosystems will act as sources or sinks for CO2 in the face of global change.  In BioCON, SCF increases with elevated CO2 and N (with N increasing the effect of CO2), but the mechanisms responsible for this increase are not yet fully understood. 
Rates of soil carbon flux (SCF) are often linked to soil temperature, soil moisture, and rates of plant allocation of C belowground (or periods of high plant activity; REFS).  In BioCON, average temperature and SCF for sampling periods across a year are somewhat positively correlated (R2 = 0.58 for 1999-2004), but on small or daily time scales SCF and temperature are weakly and negatively correlated (R2 = 0.018; Craine and Wedin 2002, Craine et al. 2001GCB, unpublished data).  Craine and Wedin (2002) hypothesized that this negative relationship was driven by photosynthetic activity:  plots with high leaf area (and thus more shading) are more photosynthetically active and therefore allocate more C belowground than plots with low leaf area, less shading and therefore higher soil temperatures.  This is consistent with our current results, which indicate that SCF is highest in plots that also have high aboveground and belowground biomass (Craine et al. 2001, Craine et al. 2001GCB, unpublished results), suggesting that plant activity is a strong driver of SCF in BioCON. 
Changes in SCF with elevated CO2 may be related to the influence of elevated CO2 on soil water content (SWC).  The majority of elevated CO2 studies show modest enhancement of SWC under elevated CO2 (Morgan et al. 2004, Kimball et al. 2002), with the enhancement disappearing under very wet conditions (all soils at field capacity) or prolonged drought (all available soil water used).  This soil moisture effect may be a cause of the higher rates of SCF in BioCON’s elevated CO2 plots.  Craine et al. (2001, 2001GCB) found that during the 1998 and 1999 growing seasons, elevated CO2 increased SCF most when soil moisture was low and soils were warm.  The CO2 effect (absolute and relative) was negatively correlated with soil moisture, indicating that the effect of CO2 on SCF increased as soil moisture declined.  This relationship may also be more pronounced for deep rooted versus shallow rooted species (Craine et al. 2001).
Other research also indicates that SCF is strongly controlled by soil water content at low soil water contents (Rey et al. 2002, Yuste et al. 2003, 2005).  SCF increases strongly with increasing SWC, but only up to a threshold soil water content (Rey et al. 2002, Yuste et al. 2003, 2005).   Under wet conditions root respiration (Ra) may contribute up to 90% to total SCF, but when conditions are dry enough to inhibit plant activity, the contribution of Ra may be as low as 10% (Bond-Lamberty et al. 2004, Sulzman et al. 2005), so that at low water availability, declines in SCF may be accompanied by a decline in the ratio of autotrophic respiration (root Ra) to heterotrophic respiration (Rh).  Thus, at low water availability, total SCF may be less tied to aboveground biomass or LAI than it is at high water contents.
Despite the potential importance of soil water in explaining CO2 effects on SCF, we do not yet have a quantitative understanding of how CO2 (or its interaction with plot productivity) affects soil water content in BioCON.  We propose to investigate how CO2, species identity, productivity, and diversity interact to influence soil water content, and how this, in turn, may explain the observed CO2 effects on SCF in BioCON by following SWC and SCF in a subset of plots after rainfall events.  In this fashion, we hope to gain a more complete understanding of the dynamics of soil water content after rainfall events (soil dry down) and define the shape of the relationship between soil water content and soil carbon flux.  This work will therefore provide more detailed information for modeling soil moisture-precipitation relationships and the relationships between soil moisture, temperature, and SCF. It may also provide justification and/or preliminary data for future proposals to include water exclusion/manipulation treatments into the BioCON experiment.
Hypotheses:
Soil water content (SWC)

• We hypothesize that the Elevated CO2 treatments will increase soil water content (SWC) more under ambient than +N treatments because the combination of +N and elevated CO2 will stimulate NPP and LAI, leading to higher ET and thus greater water loss. This will also be true for plots with high biomass due to high diversity or species identity.  When SWC deficits are moderate, elevated CO2 effects will be larger than when soils are very wet of very dry.

Soil Carbon Flux

• We hypothesize that the reduced stomatal conductance caused by elevated CO2 will increase SCF most dramatically when water limitation is moderate, and that the effect of elevated CO2 on SCF will be less under severe water limitation or with no water limitation.  This relationship will be more pronounced (or will last longer) in deep rooted species than in plots with shallow rooted species (after Craine et al. 2001).
• Because N increases the effect of CO2 in BioCON, rather than reducing the effect of CO2 on SCF at moderate water stress (as in #1), high leaf N concentrations in enhanced N plots may increase the ability of plants to fix C at moderate levels of water stress.
• At low water availability (SWC), SCF will be less dependent on aboveground biomass or LAI, as the proportion of Ra contributing to total SCF declines.
• In general, SCF will increase with SWC to a threshold, after which it will remain relatively constant once water is no longer limiting to plant or microbial processes.  Soil temperature will be more important to SCF once water is no longer limiting (within a given biomass range?).

References:
Bond-Lamberty B, Wang C & Gower ST (2004) A global relationship between the heterotrophic and autotrophic components of soil respiration? Global Change Biol. 10(10): 1756-1766.
Craine, J.M., D.A. Wedin, and P.B. Reich. 2001. Grassland species effects on soil CO2 flux track the effects of elevated CO2 and nitrogen. New Phytologist 150:425-434.
Craine, J.M. and D.A. Wedin.  2002. Determinants of growing season soil CO2 in a Minnesota grassland. Biogeochemistry 59:303-313.
Craine, J.M., D.A. Wedin, and P.B. Reich. 2001. The response of soil CO2 flux to changes in atmospheric CO2, nitrogen supply and plant diversity. Global Change Biology 7:947-953.
Morgan JA, Pataki DE, Körner C, Clark H, Del Grosso SJ, Grunzweig JM, et al. 2004. Water relations in grassland and desert ecosystems exposed to elevated atmospheric CO2.  Oecologia 140:11-25
Rey A., Pegoraro E., Tedeschi V., De Parri I., Jarvis P.G. and Valentini R. 2002. Annual variation in soil respiration and its components in a coppice oak forest in Central Italy. Global Change Biology 8: 851–866.
Sulzman, E. W., J.B. Brant, R.D. Bowden, and K. Lajtha. 2005. Contribution of aboveground litter, belowground litter and rhizosphere respiration to total soil CO2 efflux in an old growth coniferous forest. Biogeochemistry 73:231-256.
Yuste, J.C., I.A. Janssens, A. Carrara, L. Meiresonne, and R. Ceulemans. 2003. Interactive effects of temperature and precipitation on soil respiration in a temperate maritime pine forest. Tree Physiology 23:1263-1270.
Yuste, J.C., I.A. Janssens, and R. Cuelmans. 2005. Calibration and validation of an empirical approach to model soil CO2 efflux in a deciduous forest. Biogeochemistry 73: 209–230.

Leslie Brandt
Graduate Student, University of Minnesota, Department of Soil, Water, and Climate
Symposium Topic:A field experiment to assess the role of ultraviolet radiation in decomposition.  This spring, I set up an experiment at Cedar Creek and two other LTER sites (Shortgrass Steppe and Sevilleta) to quantify the role ultraviolet (UV) radiation plays in decomposition of surface litter. Litterbags of two species were placed under special screens that either block or pass UV radiation in the field, and will be collected over a 2.5-year period. Litterbags will be evaluated for mass loss, as well as changes in litter chemistry and microbial abundance and activity. The results of this study will increase our knowledge of the role UV radiation plays in decomposition and improve our ability to better predict decomposition rates in grassland ecosystems.
Research Interests:I am a PhD student in Ecology, Evolution, and Behavior at the University of Minnesota in Dr. Jennifer King’s lab. My dissertation work is focused the role of photodegradation (chemical break-down by ultraviolet radiation) in litter decomposition. In addition to the field experiment described in my talk, I am also in the process of setting up several laboratory experiments using ultraviolet lamps. In the past, I also collaborated on a project at the Shortgrass Steppe LTER site, which focused on understanding UV impacts on decomposition, primary productivity, and soil arthropods.
***Intern Project Ideas:***

• I would be willing to work with a self-motivated intern on a small project at our field site. We mostly need background and monitoring data under our different treatments. Some possible intern projects would be: measuring radiation (visible and UV) at the soil surface, vegetation surveys at our plots, and measuring canopy cover.

Daniel Hernandez
Graduate Student, University of Minnesota
Symposium Topic:  Effects of input diversity on microbial community structure and function.
Research Interests:My research interests are in ecosystem ecology--specifically how changes in the composition and quantity of resources affect the microbial community and ecosystem processes mediated by microbes. I am currently working on two projects at the Cedar Creek LTER. The first project is a decomposition experiment along an experimental fire frequency gradient to determine how changes in oak leaf litter stoichiometry and soil nutrient availability affect rates of decomposition and microbial community dynamics. In the second project, I am examining how variation in inputs to soil affects microbial community structure and function to help understand how plants influence microbial diversity and the consequences of this variation on ecosystem processes.

Bonnie Keeler
Graduate Student, University of Minnesota, Department of Ecology, Evolution, and Behavior
Symposium Topic:  Studying the effects of long-term nitrogen fertilization in forests and grasslands at Cedar Creek.
Research Interests:I am broadly interested in biogeochemistry and microbial ecology.  My current research focuses on characterizing the effects of long-term nitrogen addition on plant, soil, and microbial communities in forested and grassland sites at the Cedar Creek Natural History Area.  I am using eight forested and grassland sites at Cedar Creek to investigate the effects of long-term nitrogen fertilization on soil and litter microbial communities and plant communities.  I am interested in understanding why sites dominated by different vegetation types (oak, pine, maple, aspen, and prairie) vary in their response to nitrogen addition, and how these responses explain variation in rates of litter decomposition and plant productivity.  I have data on decomposition, root productivity, soil carbon and nitrogen, microbial community characteristics, and vegetation % cover and species composition. 
***Intern Project Ideas:***

• I have data on decomposition, root productivity, soil carbon and nitrogen, microbial community characteristics, vegetation percent cover, and species composition.  There are still lots of interesting things to measure in the sites that would help explain differences between the sites as well as further characterizing the effects of the nitrogen treatment.  Intern projects could include (but are not limited to!) short-term soil incubation experiments, vegetation surveys for foliar plant disease, herbivory experiments, root decomposition experiments, and measurements of the soil and litter microbial community.

Anita Antoninka
Graduate Student, Northern Arizona University
***Intern Project Ideas:***

• Implications of carbon dioxide and nitrogen enrichment in the community dynamics of mycorrhizal fungi, nematodes, microarthropods and plants

Research Goals:  I am conducting two experiments and one observational study to examine 1) how the structure and function of arbuscular mycorrhizal (AM) associations and soil mesofauna are affected by resource availability (specifically CO2 and N) and 2) the feedbacks and adaptation of plants and soil communities to soil environments created by different host and N fertilization history.
Background:  Most grassland plants form symbioses with AM fungi. These associations are trading partnerships in which the fungi gain plant photosynthate (carbon) and plant hosts gain improved access to soil resources (P, N, and water).  Mutualism theory predicts that changing the availability of these resources will alter the structure and function of AM associations (Hoeksema & Bruna 2000); however, few empirical studies have tested this prediction. Other studies indicate that plant community composition and function are influenced by feedbacks with communities of AM fungi and other soil organisms (van der Heijden et al. 1998, van der Putten et al. 2001); but the mechanisms that generate these feedbacks are not yet understood.  The three studies that I am conducting for my PhD research will contribute fundamental information about the factors controlling the structure and function of AM associations at individual, community, and ecosystem scales. 
Soil mesofauna, particularly microarthropods and nematodes, have received little ecological research attention, but are important players in carbon and nitrogen cycling (Peterson and Luxton 1982).  Soil mesofauna interact directly and indirectly with both plants and AM fungi and can affect the mycorrhizal symbiosis in both positive and negative ways (Finlay 1985, Klironomos and Kendrick 1996, Roncadori 1997 and Gange 2000).  They can act as propagule dispersers and differentially impact competition of AM fungi with other soil and root-dwelling fungi. There is a need to understand these multi-trophic interactions, especially as the availability of CO2 and N is altered. My PhD research will fill knowledge gaps, providing ecological data to aid our understanding of the roles mesofauna taxa play in carbon and nitrogen cycling, feedbacks with plants and AM fungi, and soil food web dynamics. 
Experiment 3:  CC Mesocosms
            This two year experiment was initiated in May 2005.  I was able to use Dr. Shahid Naeem’s existing field mesocosms (51cm diameter x 44cm deep, 100 l soil capacity) at Cedar Creek with the aims of 1) examining feedbacks between above- and belowground communities (including AM fungi and other soil organisms), and 2) comparing the symbiotic function of AM fungi and other soil organisms from different resource and host plant environments.  To do this I used a full factorial design: 3 host histories (16 species polycultures, monocultures of C3 grasses, and monocultures of C4 grasses) X 2 N histories (with and without N fertilization) X 2 current N levels (with and without N fertilization) X 6 replicates (+12 controls) = 84 mesocosms (Table 1). I added sterile Cedar Creek soil to the mesocosms and a band of live soil taken from the appropriate treatment plots from the FACE rings using a corer.  Because soil samples were collected from BioCON plots in which I analyzed spore communities and EMH, I will be able to compare the beginning AM community with the final AM communities.  All of the mesocosms were seeded with the same mix of seeds of each of 8 species (Table 2).  I used expected germination rates to add appropriate amount of seed from each species to achieve a community with four plants of each species. Half of the mesocosms are receiving N 3 times over the course of each growing season at a total annual rate of 12g N per m2 per year.
Soil samples were taken at the beginning of August 2005 to analyze EMH. At the end of the growing season in October 2005 a 10cm clipstrip of aboveground biomass was cut to 2.5 cm, separated by species, dried and weighed.  The second growing season (2006) will follow the same fertilizer regime.  A complete destructive harvest will be conducted at the end of the growing season to allow the quantification of total above- and belowground biomass by species. A composite soil sample will be taken to analyze soil nutrients, AM spore community, EMH and fatty acid content (both PLFA and NLFA). In addition, microbial communities will be analyzed by Dr. Shahid Naeem’s graduate student at Columbia University. 

Table 1.  Experiment 3 factorial design.

Table 2.  The plant species used in experiment 3 by photosynthetic pathway and level of mycotrophy.

Research Questions:
1. Do communities of AM fungi and other soil microbes from high-N environments influence plant community composition differently than those from low-N environments?
2.  Do communities of AM fungi and other soil microbes from polycultures influence plant community composition differently than those from monocultures?

• 3.  Do communities of AM fungi and other soil microbes from a C3 grass influence plant community composition differently than those from a C4 grass?

4.  How do N history and current N fertilization affect plant and soil community development?
Potential Intern Projects:
Any of the above research questions could fit nicely in a summer internship project.  It would be relatively easy to get some plant height measurements by species to determine how plant community composition has changed.  It would also be possible to answer questions of plant fitness: do plants under with different soil histories lead to differences in plant fitness? This could be measured by counting flowers and seed heads by species.
Another potential avenue would be to do some insect collecting to determine if the treatments affect the insect communities on the plants.
These are a few suggestions.  There are certainly more possibilities that you may come up with!
References:
Egerton-Warburton, L., N.C. Johnson and E.B. Allen.  in prep., Mycorrhizal community dynamics following nitrogen enrichment: A cross-site test in five grasslands.
Finlay, R.D. 1985.  Interactions between soil micro-arthropods and endomycorrhizal associations in higher plants. In: Ecological interactions in soil: plants, microbes and animals.  Fitter, A.H., D. Atkinson, D.J. Read and M.B. Usher.  Blackwell Scientific Publications, Oxford, U.K., pp. 319-331.
Gange, A. and V.K. Brown. 2002.  Actions and interactions of soil invertebrates and arbuscular mycorrhizal fungi in affecting the structure of plant communities. In: Mycorrhizal Ecology. van der Heijden, M.G.A. and I.R. Sanders, eds. Springer-Verlag, New York., pp. 322-344.
Hoeksema, J. D. and E. M. Bruna 2000. Pursuing the big questions about interspecific mutualism: a review of theoretical approaches. Oecologia 125: 321-330.
Johnson, N.C., J. Wolf and G.W. Koch. 2003. Interactions among mycorrhizae, atmospheric CO2 and soil N impact plant community composition.  Ecology Letter 6: 532-540.
Klironomos, J.N. and W.B. Kendrick.  1996.  Palatability of microfungi to soil arthropods in relation to the functioning of arbuscular mycorrhizae.  Biology and Fertility of Soils 21: 43-52.
Peterson, H. and M. Luxton. 1982.  A comparative analysis of soil faunal populations and their role in decomposition processes. Oikos 39: 287-298.
Reich, P.B., D. Tilman, J. Craine, D. Ellsworth, M. Tjoelker, J. Knops, D. Wedin, S. Naeem, D. Bahauddin, J. Goth, W. Bengston, T. Lee. 2001. Do species and functional groups differ in acquisition and use of C, N and water under varying atmospheric CO2 and N deposition regimes? A field test with 16 grassland species. New Phytologist 150:435-448.
Roncadori, R.W.  1997.  Interactions between arbuscular mycorrhizas and plant parasitic nematodes in agro-ecosystems.  In: Multitrophic interactions in terrestrial ecosystems.  Gange, A.C. and V.K. Brown, eds.  Blackwell Publishing, Oxford, U.K., pp. 101-113.
Van der Heijden, M., Klironomos J. N., Ursic, M., Moutoglis, P.,Streitwolf-Engle, R., Boller, T., Wiemken, A., and I.R. Sanders. 1998. Mycorrhizal fungal diversity determines plant biodiversity, ecosystem variability and productivity. Nature 396: 69-72.
Van der Putten, W. H., Vet, L.E.M., Harvey, J.A., and F.L. Wackers. 2001. Linking above- and belowground multitrophic interactions of plants, herbivores, pathogens, and their antagonists. Trends in Ecology and Evolution 16: 547-554.

Chris Clark
Graduate Student, University of Minnesota, Department of Ecology, Evolution, and Behavior
***Intern Project Ideas (in conjunction with John Haarstad):***

• Recovery patterns following N deposition

A well-studied phenomenon currently threatening many global ecosystems is human-induced nitrogen deposition.  This pollutant, largely the product of excessive fertilizer application and fossil fuel combustion, can have a variety of negative impacts on ecosystems, including acidification of soils, losses of plant biodiversity, and increased runoff into groundwater.  Though these initial effects are well-documented, very little is known about the relative permanence of these impacts.  Suppose our federal legislation enacted laws, akin to the Clean Air Act, to limit N deposition…what would the effects be?  At Cedar Creek we are studying these questions and others to address which biogeochemical and community properties may be recoverable or unrecoverable following addition of N.  Many possible projects exist to explore this important effect.

• Community coexistence patterns

Ecologists have long been interested in the dynamics that both maintain and disrupt the coexistence of species.  Many hypotheses have been presented, including spatial variability, trophic interactions, and niche partitioning of resources; however, none have proven champion.  One recent wrench in the discussion involves the idea that “not all resource sources are identical.”  Ecologists have long considered nitrogen a homogeneous source of food for plants, but recent research suggests otherwise.  We are setting up a manipulative experiment at Cedar Creek to explore the potential for different nitrogen sources (i.e. nitrate, ammonium, glycine, etc.) to either support or disrupt coexistence patterns in these biologically diverse grassland communities.

Jared Trost
Research Coordinator, CCNHA
***Intern Project Ideas***

• Hydrologic flowpaths at CCNHA.  Very little is known about the nature of the shallow groundwater at Cedar Creek Natural History Area; where are the primary flowpaths?  Are wetlands an expression of recent rainfall or of water that has been belowground for some time?  What is the water budget of this area?   Since this region lies on the Anoka Sand Plain, the shallow groundwater is very connected to what is happening on the surface.  One of the major changes happening at the soil surface is the conversion of woodlands, pastures, and farmland into surburban development.  CCNHA is becoming an island of natural habitat within this new suburban landscape.  In order to assess future impacts of development on groundwater health it is essential to understand how the shallow groundwater moves through this area.  There are several potential projects that could address this need. 

John Haarstad
Cedar Creek Entomologist and Naturalist
***Intern Project Ideas:***

• Insect Family Survey 

Survey some of the less well-known insect groups found on Cedar Creek.  You will gain familiarity with a particular group, and simply by observing and collecting, some research ideas may suggest themselves.  You can also contribute to the Cedar Creek Insect Web Site by photographing specimens, preparing album pages, and writing informative narratives.  Groups that I would suggest working with include Tipulidae (crane flies), Aphididae (aphids), leaf miners, and gall formers.  In the latter two cases you can attempt to rear the adults.

• Insect Feeding Ecology

Select a particular plant species and collect herbivorous insects found on it.  Can you find some individuals with many herbivores and others with few or none?  Can you explain herbivore distribution?  Are some only found on small trees, or only on shaded trees?  Milkweed is a good forb to examine.  Three species of red-and-black longhorn beetles (Tetraopes spp) use the genus Asclepias.  Compare their host preferences.  What species of milkweed serve as host for monarch caterpillars?  Bur Oak is a good tree to look at.  It has a variety of gall-forming wasps both on stems and leaves, LEP and COL leaf miners, lace bugs, aphids, treehoppers, foliage-feeding LEPS and ORTS.  Other good candidates would be other species of Ouercus (oaks), Salix spp (willows), Rhus spp (sumac), Lespedeza (bush clover), Oenothera (primrose), and Rosa (prairie rose).  Conduct simple lab experiments to determine host preference.  For example, give lacebugs (Tingidae) a spectrum of leaves to feed on in large petri dishes.  Introduce grasshoppers or leaf beetles into a terrarium containing a variety of potential hosts or host extracts. 

• Pollination Biology

See what insects visit the flowers of particular plant species, or track a particular species of bee or butterfly and see how host-specific it is.  Are nectar sources and larval resources the same?  If not, must they be in proximity?  You could also do studies on foraging behavior.  For example, what insect species visit the flowers of Penstemon grandiflora?  Which bumblebee species are nectar robbers, and which are pollinators?  What is the pollinating mechanism in large-flowered beardtongue?  Do unvisited flowers produce seeds?

• Insect Population Biology

Set out a grid of pitfalls and do a mark-recapture study on Carabidae (ground beetles).  Two large species of old fields are the winged fiery caterpillar hunter (Calosoma callidum) and the flightless blue-lined stag (Pasimachus elongatus).  Estimate population size, determine and compare home range in these or other species.  The Tenebrionid (Eleodes tricostatus) is another good candidate.

• Insect Behavioral Biology

Put out tethered mice in field and woodland sites and wait for burying beetles (COL: Silphidae: Nicrophorus spp) to discover them.  How many species are attracted to the mice?  Do they fight over it?  Who gets it?  Bring some adults into the lab and observe their parental care – regurgitating carrion to their larvae.  What is the role of the mites these beetles carry?  Are they free-loaders or do they help the beetles in some way?  Watch dragonflies at a pond.  Which species have defended territories?  Which species mate near water and which retreat to the shore?  Which species oviposit in tandem (male clasping female by the head)?  Males of which species guard females while they are ovipositing?  Witness the spectacular mating rituals of the crepuscular shadowhawk (Epitheca spinigera) in mid-June.

• Insect Community Ecology

Compare the insect communities found in various bodies of water (small pond, marsh, lake, and creek).  Which families predominate in which type of aquatic community?  Sweep a young weedy old field and an old established prairie.  Which grassland type has the most insects (abundance), and which is the more diverse?  How does the insect community of fertilized plots compare with that found in unfertilized plots?

Linda Kinkel
Professor, University of Minnesota, Plant Pathology
Research Interests:  Our research group studies the ecology of plant-associated microbes, including plant pathogens, pathogen antagonists, and saprophytes, and the roles of these microbes in influencing plant fitness.  We are especially interested in exploring the effects of plants on soil microbial communities, of microbes on plant communities, and of microbial interactions on plant communities.  Our research includes basic research on prairie plants in natural habitats, and applied research on the effects of soil microbes on plant disease in agriculture and on the success of invasive plant species.
***Intern Project Ideas:***

• Unfortunately, most of our intern project opportunities require access to a lab that includes an autoclave and a laminar flow hood here on campus.  However, we have had summer interns in the past that came down and used our lab for their project and it worked out pretty well.  SO, if a student is interested in learning some basic microbial ecology, how to isolate, quantify, and study microbes in natural habitats, and is willing to arrange their schedule to get down here at varying intervals (evenings and weekends are fine), some possible projects could include:
1. Characterizing pathogen suppressive activity of soil microbial communities associated with different plant hosts or the same host in different habitats (different N treatments, different CO2, different landscapes, different diversities).
2. Characterizing density (and possibly diversity, depending upon whether the focus were fungal or bacterial) of soil microbial communities associated with different plant hosts, or the same host in different habitats (different N treatments, different CO2 treatments, different landscapes).
3. Quantifying the presence of agriculturally significant plant pathogens on native plant species:  are native habitats a refuge or even a primary habitat for agriculturally significant plant pathogens (focusing on pathogens that grow happily as epiphytic non-pathogens on leaf surfaces).
4. Quantifying plant disease intensity on native prairie species in different habitats.

Other microbial questions that occur to the interns! 

Jennifer Lau
Research Specialist, University of Minnesota, Department of Plant Biology
***Intern Project Ideas:*** 

• How do the BioCON treatments influence higher order predators?  The direct effects of BioCON treatments on the plant community influence herbivores and, therefore, could cascade up the food web to also alter densities or growth rates of higher order predators.  Some of these effects could be due to numerical responses of the predators (i.e. more prey result in higher predator population growth rates), but given the small size of the treatment plots, most effects are likely due to effects of prey abundance on predator behavior.  Similarly, because herbivore size and growth are likely impacted by differences in plant quality between BioCON treatments, higher order predators may also differ in fitness between BioCON treatments.  To test these ideas, the intern could examine aphid parasitism rates or abundance of spiders and other generalist predators in the various BioCON treatments (and/or the fitness/size of predators or parasitoids), potentially using path analysis or other statistical procedures to see how the BioCON treatments influence plant traits which they influence herbivores which then cascade up the food web to influence predators.
• How does eCO2 affect rhizobia/legume mutualisms?  We are currently examining this topic in the St. Paul greenhouses using Lespedeza capitata.  It would be nice to have some field data to go along with the greenhouse project.  The intern could dig up lupine or Lespedeza plants just outside the rings (or maybe in Mark Davis’s natural areas in the rings) and count and measure nodules on the legume roots and plant size to determine how eCO2 influences the success of both mutualism partners.
• And my personal favorite…How does eCO2 affect tick host-finding behavior?  Ticks often locate hosts by following CO2 gradients.  Elevated CO2 could potentially disrupt this process.  The intern could measure how fast marked ticks locate test subjects in elevated vs. ambient CO2 treatments. 

Troy Mielke
Research Coordinator, LTER, Cedar Creek Natural History Area
***Intern Project Ideas:***

• Join the Junior Naturalist Program here at Cedar Creek.  Fish Lake Interpretive Nature Trails is a cooperative project between Cedar Creek and the City of East Bethel.  The city is in need of a few naturalists (total of 40 hours/week, ca$9.30/hr) for this new trail system.  Responsibilities would include the development and deployment of ‘signage’ along nature trails and production of educational pamphlets on the ecology, flora and fauna of the area.  You would also conduct tours for interested visitors (possibly both hiking and canoeing).  Other responsibilities would include park and trail upkeep/maintenance as well as policing the area to ensure that park/trail rules are not violated.  The development of a website about the trails is also a possibility.
• Small mammal trapping

Do small mammal populations differ among old fields undergoing invasion by different types of woody species such as pine, oak, and aspen? This project will look at the small mammal populations in old fields and use mark-recapture techniques to compare the populations.

Kirk Wythers
Research Fellow, University of Minnesota, Department of Forest Resources
***Intern Project Ideas:***

• I am developing a GIS database for Cedar Creek Natural History Area.  A crucial aspect to this project is the incorporation of the historic land cover changes that have occurred at Cedar Creek.  This information is important for future restoration efforts and, when combined with other long-term data sets, will help us better understand long-term changes that occur on a landscape.  If you are interested in GIS, please consider this project and contact me.