The functional ecology of plants that inhabit desert regions is the primary focus that guides my research program. Currently, I am engaged in three research areas: (1) the response of a Mojave Desert ecosystem to elevated CO2 (as a P.I. of the Nevada Desert FACE Facility); (2) analysis of ecosystem processes in a complex Mojave Desert alluvial fan system; and (3) using a functional approach to understand the structure and behavior of riparian ecosystems in the desert Southwest.
My primary research focus at present concerns the Nevada Desert FACE Facility (NDFF). This is a unique, integrative research facility that will examine how an intact arid ecosystem may respond to elevated CO2 concentrations expected to occur in the mid-21st century, and is the only FACE facility located in an arid ecosystem (there are currently four operational FACE facilities worldwide, and several more coming on-line). This research program is a collaborative effort between the three research campuses of the University of Nevada System (UNLV, UNR, the Desert Research Institute), and also incorporates the research projects of multiple scientists from research universities and government labs outside Nevada. The facility began experimental fumigation at elevated CO2 (550 ml l-1) on April 28, 1997; three FACE rings will be continuously fumigated at that CO2 concentration and compared to FACE rings at ambient CO2, as well as non-ring control plots. The NDFF project has three primary objectives: (1) analysis of leaf- to plant-level responses of desert vegetation to elevated atmospheric CO2 concentration; (2) analysis of the response of both aboveground and belowground components of a desert ecosystem to elevated CO2; and (3) adapt and/or construct predictive models that will accurately simulate plant and ecosystem responses to elevated CO2. The NDFF Web Page address is: http://www.nscee.edu/unlv/Climate_Change_Research.
Over the past decade, I have been studying the functional ecology of riparian plants in an effort to understand (1) how riparian plants cope with the extreme evaporative demands of desert environments, (2) what regulates evapotranspiration in desert riparian ecosystems, and (3) what are the functional underpinnings of the invasion of desert floodplain environments by the exotic Tamarix ramosissima (saltcedar). Although my lab is not currently funded in this area, we continue to analyze and publish our results from past funded projects; several of our primary publications in aridland riparian ecology are listed below.
I have recently initiated a long-term study with Drs. Joe McAuliffe, Eric McDonald, and Erik Hamerlynck in which we are examining a complex Mojave Desert alluvial fan (bajada) system in order to understand linkages between soil geomorphology/hydrology, plant rooting patterns, and plant physiological responses to stress, and how these linkages act to structure complex desert landscapes. Research to date has uncovered a complex mosaic of soils along a Mojave Desert bajada; these soils are derived from several distinct parent materials and range in age from recently deposited to over 500,000 years old. Our results show that, as soils develop, they become increasingly impermeable to the infiltration and percolation of water through the soil profile. This, in turn, has profound effects on the species composition, cover, and functional ecology of plants that inhabit the site. We are currently utilizing process-based modeling to provide empirical linkages between soil hydrology, plant function, and ecosystem responses to these diverse soil environments, and will use the validated models to predict potential ecological consequences of future environmental changes in this and other Mojave Desert landscapes.
Smith, S.D., R.K. Monson and J.E. Anderson (1997) Physiological Ecology of North American Desert Plants. Berlin:Springer-Verlag.
Cleverly, J.R., S.D. Smith, A. Sala and D.A. Devitt (1997) Invasive capacity of Tamarix ramosissima in a Mojave Desert floodplain: the role of drought. Oecologia (in press).
Sala, A., S.D. Smith and D.A. Devitt (1996) Water use by Tamarix ramosissima and associated phreatophytes in a Mojave Desert floodplain. Ecological Applications 6:888-898.
Smith, S.D., C.A. Herr, K.L. Leary and J.M. Piorkowski (1995) Soil-plant water relations in a Mojave Desert mixed shrub community: a comparison of three geomorphic surfaces. Journal of Arid Environments 29:339-351.
Busch, D.E. and S.D. Smith (1995) Mechanisms associated with decline of woody species in riparian ecosystems of the southwestern U.S. Ecological Monographs 65:347-370.
Smith, S.D., B.R. Strain and T.D. Sharkey (1987) Effects of CO2 enrichment on four Great Basin grasses. Functional Ecology 1:139-143.