Zoe G. Cardon, Associate Professor (Ph.D., Stanford University)                                         

Contact Information:

Dr. Zoe G. Cardon

Department of Ecology and Evolutionary Biology

University of Connecticut

75 N. Eagleville Road, U-43

Storrs, CT 06269-3043


Office: Torrey Life Sciences Building, Room 180B

Tel: (860) 486-3868

Fax: (860) 486-6364

E-Mail: zoe.cardon@uconn.edu



Cardon Lab People:

Dennis Gray, Patrick Herron, David Hoover, Debbie Tyser

Current Areas of Research:

We study the flow of carbon from the atmosphere, through plants (fixation and transport), and ultimately to microbes (and other members of the decomposer community) in the soil, as well as how water fluxes into and out of plant roots affect microbial activity in the rhizosphere. Several of the major questions we are asking are: What are the consequences of the quality, quantity, and timing of carbon flow from plants to soil for the microbial activity essential to ecosystem carbon and nutrient cycling? Can plants adjust the amount or type of carbon compounds lost from roots to encourage growth of particular microbial communities? How does the ebb and flow of the transpiration stream affect resources available to rhizosphere microbial and soil faunal communities?  How do long-term management regimes, such as till and no-till, or silage harvest vs. grain harvest, affect soil carbon pools and nitrogen trace gas fluxes from agroecosystems? Answers to these questions will have application in understanding the function of natural ecosystems and in managing agricultural and silvicultural systems. 

For a CV, click here.

Selected Publications (listed by topic) :

Soil carbon dynamics, nutrient cycling, and mixed litter decomposition:

Gartner, T.L. and Cardon, Z.G. Site of leaf origin affects how mixed litter decomposes.  Soil Biology and Biochemistry  38: 2307-2317.

Venterea, R.T., Rolston, D. E., and Cardon, Z. G. (2005) Effect of soil water content and other physical and chemical factors on abiotic nitric oxide production.  Nutrient Cycling in Agroecosystems  72:27-40.

Hooker, B.A., Morris, T. F., Peters, R., and Cardon, Z.G. (2005) Long-term effects of tillage and corn stalk return on soil carbon dynamics. Soil Science Society of America Journal, 69 (1) : 188-196.

Johnston, C. A., Groffman, P., Breshears, D. D., Cardon, Z. G., Currie, W., Emanuel, W., Gaudinski, J., Jackson, R. B., Lajtha, K., Nadelhoffer, K., Nelson Jr., D., Post, W. M., Retalack, G., and Wielopski, L.(2004) Carbon cycling in soil.  Frontiers in Ecology and the Environment, 2(10): 522-528.

Gartner, T. L. and Cardon, Z. G. (2004) Decomposition dynamics in mixed-species leaf litter — a review. Oikos.  104: 230-246.

Cardon, Z. G., Hungate, B. A., Cambardella, C. A., Chapin III, F. S., Field, C. B., Holland, E. A., and Mooney, H. A. (2001) Contrasting effects of elevated CO2 on old and new soil carbon pools. Soil Biology & Biochemistry 33: 365-373.


Rhizosphere-specific interactions:

Cardon, ZG and Gage, DJ (2006)  Resource exchange in the rhizosphere:  molecular tools and the microbial perspective.  Annu. Rev. Ecol. Evol. Syst.  37:459-488.

Cardon, Z. G., and Herron, P. M. (2005)  Sweeping water, oozing carbon: long distance transport and patterns of rhizosphere resource exchange. IN: Vascular Transport in Plants.  Holbrook, N.M. and Zwieniecki, M.A. (eds). Academic Press, San Diego, pp. 257-276.

Cardon, Z.G., Czaja, A. D., Funk, J. L., and Vitt, P. L. (2002) Periodic carbon flushing to roots of Quercus rubra saplings affects soil respiration and rhizosphere microbial biomass. Oecologia, 133: 215-223.

Bringhurst, R. M., Cardon, Z.G., and Gage, D. J. (2001) Galactosides in the rhizosphere: utilization by Sinorhizobium meliloti and development of a biosensor. PNAS 98(8): 4540-4545 .

Cardon, Z. G. (1996) Influence of rhizodeposition under elevated CO2 on plant nutrition and soil organic matter. Plant and Soil 187: 277-288.


Photosynthesis, water relations, and gas exchange techniques:

Zanne, A.E., Lower, S.S., Cardon, Z.G., and Orians, C.M. (2006) 15N fertilization of tomatoes: vascular constraints vs. tissue demand.  Functional Plant Biology 33:457-464.

Gray, D.W., Cardon, Z.G., and Lewis, L. A. (2006) Simultaneous collection of rapid chlorophyll fluorescence induction kinetics, fluorescence quenching parameters, and environmental data using an automated PAM-2000/CR10X data logging system. Photosynthesis Research 87:295-301

Jones, C.S, Cardon, Z.G., and Czaja, A.D. (2003) A phylogenetic view of low level CAM in Pelargonium (Geraniaceae). American Journal of Botany, 90:135-142.

Hooper, D. U., Cardon,Z.G., Chapin III, F. S., and Durant, M. (2002) Corrected calculations for whole ecosystem measurements of CO2 flux using the LI-COR 6200 portable photosynthesis system. Oecologia, 132:1-11.

Lodding, C. C., Behling, J., and Cardon, Z. G. (2000) Water relations of Betula cordifolia and Betula allegheniensis rooted together on landslides in Franconia Notch, NH. American Midland Naturalist , 143:321-329.

Cardon, Z. G., J. A. Berry and Woodrow I.E. (1994) Dependence of the extent and direction of average stomatal response in Zea mays and Phaseolus vulgaris on the frequency of fluctuations in environmental stimuli. Plant Physiology 105: 1007-1013.

Cardon, Z.G., Mott, K.A., and Berry, J.A. (1994) Dynamics of patchy stomatal  movements, and their contribution to steady-state and oscillating stomatal  conductance calculated with gas-exchange techniques.  Plant, Cell, and  Environment.  17:995-1007.

Mott, K.A., Cardon, Z.G., and Berry, J.A. (1993).  Asymmetric patchy stomatal closure  for the two surfaces of Xanthium strumarium L. leaves at low humidity.  Plant,  Cell, and Environment. 16:25-34.

Cardon, Z.G., and Berry, J.A. (1992).  Effects of O2 and CO2 concentration on the  steady-state fluorescence yield of single guard cell pairs in intact leaf discs of  Tradescantia albiflora.  Evidence for Rubisco-mediated CO2 fixation and  photorespiration in guard cells. Plant Physiology 99:1238-1244.


Ongoing Projects:

Exploring how hydraulic redistribution of water by Artemisia tridentata (sagebrush) in semi-desert, western U.S. landscapes affects nutrient cycling in the rhizosphere and nutrient availability to plants.  Patrick Herron, graduate student

In desert and semi-desert ecosystems, plant growth and reproduction can be limited by water availability and also by availability of nitrogen and other nutrients in soil.  Activities of soil fungi and bacteria are responsible for recycling nutrients from dead, organic forms in soil into forms that plants can use, but low water availability can limit the ability of those soil microbes to carry out such nutrient transformations.  Interestingly, the roots of some deep-rooted desert plants can act as conduits for passive water movement from more moist to drier, shallow soils where detritus is abundant; the activity of microbes around such plant roots may be stimulated by this water movement out of plant roots into dry soil. 

Our NSF Ecosystems-supported research includes an integrated combination of greenhouse and field studies that take advantage of the demonstrated ability of the common plant Artemisia tridentata (sagebrush) to redistribute water from wetter to drier soils in Western U.S. landscapes.  Using microbiosensors in greenhouse experiments, and soil, plant, and microbial assays in the field in Utah, redistribution of water from moist to dry soil by plant roots will be examined for its ability to promote nutrient cycling around and nutrient availability to plant roots.  Enhanced nutrient availability in turn potentially leads to enhanced photosynthesis, growth, and reproductive yield of plants actively redistributing water in dry landscapes; these plant characteristics will be examined.  Collaborators are Dan Gage in MCB at UConn, and John Stark in Biology at Utah State University. 

As a companion to the research, a museum exhibit will be developed at the Worcester Ecotarium  (http://www.ecotarium.org/)  that provides several primary messages, including: 1. Soil is alive, and microbes aren't necessarily "bad", and 2. Roots are two-way streets, with water being taken up and released by roots depending on time of day and position in the soil.



Mathematical modeling of the rhizosphere – in collaboration with Ed Rastetter, The Ecosystems Center, MBL

The root-soil interface is a central commodities exchange in ecosystems.  In the rhizosphere, an active microbial and microfaunal community capable of influencing nutrient availability to plants is fueled largely by organic carbon "lost" from those roots.  The interaction between plants and soil microorganisms is also influenced, however, by the vast water flow through soil driven by the transpiration stream. Currently, mechanistic representations of organismal interactions in and with soils in the rhizosphere largely fall into two categories, one focusing on physical soil characteristics, and the other focusing on organismal interactions and resultant element cycling. We are knitting these two types of soil models together to explore how spatial distribution and timing of water flow directed by plant roots shapes rhizosphere biogeochemical function.  Model results to date suggest that the diel pulsing of the transpiration stream can drive alternating periods of C- and N-limitation of rhizosphere microbial growth, which (when coupled to the long life of microbial exoenzymes and protozoal grazing) can lead to enhanced availability of mineral nutrients to plants.   


Detecting specific organic compounds around living roots in nonsterile soils, growth rates of bacteria around roots, predation by protozoa, and soil water potential – non-destructive methods at high spatial resolution. –Patrick Herron, graduate student

In collaboration with Dr. Dan Gage's lab in MCB, we are developing genetically engineered soil microbes that we can seed into non-sterile soil in order to detect what specific compounds are found around roots in non-sterile soil, how quickly bacteria grow along zones of roots, and soil water potential. At left is a micrograph showing bright yellow fluorescence around an emerging lateral root of alfalfa growing in non-sterile soils; the fluorescence indicates the presence of galactosides. At right is a micrograph of soil protists that have engulfed red and green fluorescent bacteria in the rhizosphere of alfalfa roots. Other engineered biosensors report, with green fluorescence, when bacteria are growing quickly, allowing us to examine bacterial proliferation patterns along roots. Still others report water potential at microscales never before accessible.  In collaboration with Dr. Ed Rastetter at the Ecosystems Center, Marine Biological Laboratory, we are using spatial and temporal information gathered using these microbiosensors to generate new mathematical models of water fluxes, carbon and nutrient cycling, and food web dynamics in the rhizosphere.


How do long-term management regimes, such as tilling and removal of aboveground biomass, affect soil carbon pools and soil food webs in agroecosystems?  --Beth Hooker, graduate student

At the UConn Research Farm, we are collaborating with Dr. Tom Morris (College of Agriculture) and Steve Olsen (farm manager) analyzing long-term effects of till- and no-till treatments, and silage and grain corn harvest within tillage blocks, on long-term carbon storage in soils.  Dr. Robert Peters set up these plots in 1968, and for more than 30 years, management treatments have been maintained.  Over this time period, extensive differences in soil organic matter content, d13C of carbon pools, soil aggregate structure, and the soil faunal community have developed. 





Desert green algae in microbiotic crusts of western North America – Hilary McManus (Lewis lab), graduate student; Dennis Gray, postdoc.

In collaboration with Dr. Louise Lewis and her graduate student Hilary McManus in EEB, we are exploring the phylogenetic relationships among, and physiology of, unicellular green algae newly isolated from desert crusts of western North America.  We are examining chloroplast structure across the broad phylogenetic range of unicellular desert green algae, as well as investigating desiccation tolerance and photosynthetic physiology in these unusual organisms.  This work is supported by a NASA Exobiology grant.










Cardon Lab Info:
Lab phone: 860 486 5382
Lab address: Torrey Life Sciences 180/184

Lab Technician:
Debbie Tyser(deborah.tyser@uconn.edu)--currently focusing on photosynthetic physiology of desert green algae within a phylogenetic context, and on developing miniaturized sensors to detect glucose "lost" from roots (with Dr. Francis Moussy, at University of South Florida). 


Dennis Gray (denwgray@yahoo.com) is currently focusing on photosynthetic physiology of desert green algae within a phylogenetic context. We are collaborating with Dr. Louise Lewis, EEB, on this project.  

Graduate students:

Patrick Herron (patrick.herron@uconn.edu) — examining water flow in the rhizosphere and its effects on nutrient cycling.   NSF DDIG recipient, EPA STAR fellow.  

David Hoover (david.hoover@uconn.edu) – examining biosphere-atmosphere interactions, particularly effects of rainfall patterns on primary productivity in the Konza prairie system.

Courses Taught:

General Ecology, Introductory Biology, Organisms and Ecosystems, Soil Degradation and Conservation, Integrative Earth System Science (new graduate core course for the Center for Integrative Geosciences), Introduction to Undergraduate Research

Note! People have moved!


Corie Cann is now in the BS-MS program in Conservation Biology at UConn. She can be reached at corie.cann@uconn.edu.

Beth Hooker is now in a one-year faculty position at Mt. Holyoke.  She can be reached at bethhooker@yahoo.com

Tracy Gartner has started a faculty position at Carthage College in Wisconsin.  She can be reached at tgartner@carthage.edu

Kristen Riley has moved to Florida to take a job as a nutrition expert.  She can be reached at szebbie@yahoo.com
Laura Pustell moved on to become a research technician at Harvard Forest, and now she can be reached at lbarbash@hotmail.com
Andy Czaja is finishing a PhD program in Astrobiology, Dr. Bill Schopf's lab, at UCLA. His e-mail address is: aczaja@ess.ucla.edu

Jennifer Funk has finished her PhD at SUNY Stonybrook, and is now a postdoc at Stanford University working in Peter Vitousek’s lab in Hawaii. Her new address is: funk@stanford.edu
Pati Vitt has taken a job at the Chicago Botanic Gardens. She can be reached at: PVitt@chicagobotanic.org

Click here for a downloadable pdf file of the handbook "Scientific units as roadmaps and spies: a guide to units manipulation for undergraduates" (developed by Ari W. Epstein and me with support from a National Science Foundation ILI grant #9796271 to ZGC.)

Click here to see Introductory Biology lab exercises (developed by UConn faculty in EEB, with support from a National Science Foundation ILI grant #9796271 to ZGC.)