Enrico A. Yepez

Research Interests My main areas of research interest include plant functional ecology, ecosystem science, ecohydrology, and global change. My research aim is to develop mechanistic understanding of how organisms interact with their physical environment to shape observed patterns of energy and material exchange of terrestrial ecosystems. I believe that understanding physical and biological processes as an integrated system is fundamental to test predictions of ecosystem-scale responses to different global change scenarios and in some cases to provide information readily available to use in management decisions.

I am interested in questions like...

• What are the principal biological and environmental mechanisms controlling the exchange of water and carbon in the soil-plant-atmosphere continuum?
• Are these controls constant along environmental gradients (e.g. temperature, precipitation, disturbance)?
• How does vegetation structure influence ecosystem responses to altered precipitation regimes?
• What are the consequences of directional changes of functional type composition (e.g. shrub encroachment or tree mortality) on major ecosystem processes?
• How is the ecosystem water balance affected by these changes?

To answer some of these questions my research integrates methodologies from fields like, plant ecophysiology, soil science, and micrometeorology. Particularly, I believe that the use of stable isotopes of light elements to trace, scale and partition plant and ecosystem processes is a robust tool to answer longstanding questions in ecology.

I am currently trying to understand the physiological causes of tree mortality following drought in Piñon-Juniper woodlands within the framework of a newly founded "Projects in Ecosystem Research - DOE" project. In collaboration with Nate McDowell (at Los Alamos National Laboratory) and Will Pockman (at the University of New Mexico), we are conducting an ecosystem-scale rainfall manipulation at the Sevilleta LTER to investigate if the mechanisms leading to tree mortality are merely related to failure in their hydraulic system (desiccation), or if prolonged stomatal closure disrupts patterns of carbon uptake and therefore limits allocation for defenses (e.g. against stem-boring beetles) and weakens the tree's ability to cope with the highly variable precipitation regimes of these semiarid environments. I believe that resolving the underlying causes of tree mortality, and in general how trees respond to wetting and drying cycles, would provide a framework to define physiologically-grounded concepts that will contribute to the advancement of the rapidly growing field of ecohydrology and therefore help to predict the consequences of tree mortality in the functioning of arid and semiarid ecosystems.

Contact

• yepezglz@unm.edu
• (505) 277 8685 LANL Offic
• (505) 507 8756 Cell

Education

• B.S., Biology, Universidad de Guadalajara, México. 1994-1999
• M.S., Rangeland Science, University of Arizona, USA 2000- 2002
• Ph.D. Rangeland Science (Major) and Global Change (Minor), University of Arizona, USA 2002- 2006

Awards

Graduate Fellowship - the "Consejo Nacional de Ciencia y Tecnologia" CONACYT-Mexico. 2000-2005

Experience

Postdoctoral Research Associate. April 2006 - Current
Department of Biology, University of New Mexico, USA.

Research Assistant. 1996 - 1999
Departamento de Ecología, Universidad de Guadalajara, Mexico.

Intern. April-Sep. 1998
CO2 Laboratory
Smithsonian Environmental Research Center, Maryland USA

Scientific Contributions

Scott, R.L., D. Goodrich, L. Levick, R. McGuire, W. Cable, D. Williams, R. Gazal, E. Yepez, P. Ellsworth and T. Huxman. 2006. Determining the riparian groundwater use within the San Pedro Riparian National Conservation Area and the Sierra Vista Sub-Basin, Arizona. In: Hydrologic Requirements of and Consumptive Ground-Water Use by Riparian Vegetation along the San Pedro River, Arizona. Compiled by J.M. Leenhouts, J.C. Stromberg, and R.L. Scott. U.S. Geological Survey Scientific Investigations Report 2005-5163.

Yepez E.A., Huxman T.E., Ignace D., English N.B., Weltzin J.F., Castellanos A.E., Williams D.G. 2005. Dynamics of transpiration and evaporation following a moisture pulse in semiarid grassland: A chamber-based isotope method for partitioning flux components. Agricultural and Forest Meteorology 132, 359-376.

Williams D.G., Cable W., Hultine K., Hoedjes J.C.B., Yepez E.A., Simonneaux V., Er-Raki S., Boulet G., de Bruin H.A.R., Chehbouni A., Hartogensis O.K., Timouk F., 2004. Components of evapotranspiration in an olive orchard determined by eddy covariance, sap flow and stable isotope techniques. Agricultural and Forest Meteorology 125, 241-258

Guerenstein P., Yepez E.A., van Haren J., Williams D.G., Hildebrand J. 2004. Floral CO2 emissions may signal food abundance to nectar-feeding moths. Naturwissenschaften 91, 329-333

Yepez E.A., D.G. Williams, R. Scott., Lin. G. 2003. Partitioning overstory and understory evapotranspiration in a semi-arid savanna ecosystem from the isotopic composition of water vapor. Agricultural and Forest Meteorology 119, 53-68

Pimienta-Barrios E., Zaudo J., Yepez E., Pimienta-Barrios E., Nobel P.S. 2000. Seasonal variation of net CO2 uptake for cactus pear (Opuntia ficus-indica) and pitayo (Stenocereus queretaroensis) in a semi-arid environment. Journal of Arid Environments 44, 73-83

Pimienta-Barrios E, Nobel PS, Robles-Murguia C, Mendez-Moran L, Pimienta-Barrios E, Yepez-Gonzólez E., 1997. Breeding and genetic improvement of cactus varieties ethnobotany, productivity, and ecophysiology of pitaya (Stenocereus queretaroensis). J. of the Prof. Assoc. for Cactus Develop. 2, 29-47

Additional Work in Preparation or Revision

Yepez E.A., Williams D.G. Precipitation pulses and ecosystem carbon and water exchange in arid and semiarid environments. In: De la Barrera E. and Smith W. (ed.) Biophysical plant ecology: Perspectives and Trends. Accepted for Universal Press.

Yepez E.A., Scott R.L., Cable W., Williams D.G. (in rev.). Seasonal variation of ecosystem and vegetation water-use efficiency of semiarid mesquite woodland. In revision for Ecosystems.

Yepez E.A., Gazal R., Ellsworth P.Z., Williams D.G. (in prep.) Heterogeneous water and carbon fluxes in the understory of a semiarid savanna woodland following precipitation pulses. For submission to Oecologia.

Yepez E.A., Gazal R., Ellsworth P.Z., Williams D.G. (in prep.) Responses of net ecosystem fluxes of carbon and water to leaf area removals in the sagebrush steppe. For submission to Rangeland Ecology and Management

Pavao-Zuckerman, M.A., Cable, J., Yepez, E.A., Potts, D.L., Huxman T.E., Williams, D.G. (in prep.) Plant species cover mediates soil community and ecosystem carbon cycling responses to altered precipitation regimes. For submission to Global Change Biology

Relevant Abstracts (**Oral *Poster)

Pavo-Zuckerman, M.A., J. Cable, E. Yepez, D.L. Potts, T.E. Huxman and D.G. Williams. 2005. Responses of soil community structure to plant species and precipitation inputs: Linking soil biota to ecosystem carbon cycling. Annual Meeting of the Ecological Society of America, Montreal, Canada.

Ignace, D., Potts, D., Yepez-Gonzalez, E., Huxman, T., Williams, D., Weltzin, J. 2005 Response of evapotranspiration in a semi-arid ecosystem applied with a simulated precipitation pulse: The role of grass species across geomorphic surfaces. Annual Meeting of the Ecological Society of America, Montreal, Canada.

Yepez, E.A., Scott R.S., Williams D.G. 2004. Unraveling components of evapotranspiration in semiarid woodland from the isotopic composition of water vapor. Annual Meeting of the Ecological Society of America, Portland, Oregon.**

epez, E.A., Scott, R.S, Williams, D.G. 2004. Partitioning of evapotranspiration from the isotopic composition of water vapor: a case study from semiarid woodland. SIBAE-BASIN conference, "partitioning fluxes between the biosphere across spatial scales" Interlaken Switzerland."

Thom C, Guerenstein P, Yepez E, Mechaber W, Vanharen J, Hildebrand J, Williams D. (2003). CO2 emission by Datura flowers and its significance for foraging Manduca sexta moths. The 25th Ann. Meeting of the Assoc. for Chemoreception Sciences (AchemS), Sarasota, FL (USA).

Williams, D.G., W. Cable, K. Hultine, E. Yepez, S. Er-Raki, J.C.B. Hoedjes, G. Boulet, H.A.R. de Bruin, A. Chehbouni, and F. Timouk. (2003). Suivi de la répartition de l'evapotranspiration dans une oliveraie (Olea europaea L.) l'aide des techniques de l'eddy covariance, des flux de seve et des isotopes stables. 5th Journées d'Ecologie Functionnelle, Nancy, France.

Scott, R.L., Watts, C., Goodrich, D., Martens, D., Hultine, K., Yepez Gonzalez, E., Huxman, T., Lin, G. 2002. The Consequences of a Two Water Source Ecosystem on the Surface Carbon and Water Exchange in a Semiarid Riparian Woodland. American Geophysical Union, Fall Meeting, San Francisco California.

Yepez, E.A., P.Z. Ellsworth, W.L. Cable, K.R. Hultine, Williams D.G. 2002. Partitioning evapotranspiration fluxes and sources in desert floodplain ecosystems. Annual Meeting of the Ecological Society of America. Tucson Arizona.*

Pierce, D., J. van Haren, G. Lin, E. Yepez, R. Scott, D. Martins and D. Williams. 2002. Partitioning of CO2 fluxes in a semi-arid ecosystem using stable isotopes: Effects of monsoon rains. Annual Meeting of the Ecological Society of America, Tucson, Arizona.

Yepez E., Williams, D., Scott R., Lin, G., van Haren, J., Goodrich D. d18O of vapor reveals rapid shift in evapotranspiration sources after a monsoon rain pulse in a semi-arid woodland ecosystem. 3rd International Conference on Applications of Stable Isotope Techniques to Ecological Studies. Flagstaff Arizona, April 29-May 1, 2002. *

Yepez E., Lin, G., Williams, D. van Haren, J., Pierce D. 2001. Isotopic partitioning of CO2 and evapotranspiration fluxes in a semi-arid savanna: Effects of sampling height and monsoon rains. American Geophysical Union, Fall Meeting, San Francisco California.*

Yepez E., Drake B., Carbon Storage in Marsh Soil Water. Smithsonian Institution. Washington DC, August 1998.**

Yepez E., Pimienta E., Efecto de la variación de la densidad de cristales de oxalato y el grosor de cutécula en la adaptación de Opuntia a la aridez. 4tas Jornadas de Biologéa. Universidad de Guadalajara. Zapopan Jalisco, July 1997.**

Yepez E., Cambios globales del ambiente, 3ras Jornadas de Biologéa. Universidad de Guadalajara, Zapopan Jalisco, September 1996. **

Peer Review Service

Journal of Arid Environments (1)
Global and Planetary Change (1)