Award Date


Degree Type


Degree Name

Doctor of Philosophy (PhD)


Biological Science

First Committee Member

Stanley D. Smith

Number of Pages



Growth and gas exchange are predicted to be most responsive to future atmospheric CO2 concentrations within and ecosystems. It is hypothesized that elevated CO2 will result in enhanced seasonal growth, increased leaf area and extension of the growing season via increased water-use efficiency (WUE). Greater WUE could result in increased survivorship and productivity of desert shrubs, and may increase the importance of this biome in the global carbon budget. Elevated CO2 is also expected to influence future species distribution and abundance, which could alter structure and function, especially in arid ecosystems. For these reasons, we measured aboveground production, gas exchange, and water relations of species from different functional types in order to evaluate how future atmospheric CO2 concentrations may affect desert shrubs. Elevated CO2 significantly enhanced growth and gas exchange of the dominant evergreen perennial during an exceptionally wet year, but had less effect on spring- and summer-active drought-deciduous shrubs. During dry years, growth and seasonal carbon assimilation rates were much reduced across all functional types. Overall it appears that water availability strongly interacts with CO2 concentration to affect growth and gas exchange. As such, unpredictable and infrequent rainfall patterns typical of the desert southwest may prevent significant CO2 affects on growth in dry years. However, predictions of increased atmospheric CO 2 concentrations and rainfall in the desert southwest may have important implications for the future productivity of the region.


California; Carbon; Carbon Dioxide; Desert; Dioxide; Ecosystem; Effects; Elevated; Mojave; Mojave Desert; Primary; Primary Productivity; Productivity

Controlled Subject

Ecology; Botany

File Format


File Size

2918.4 KB

Degree Grantor

University of Nevada, Las Vegas




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