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Interactions Between Changing Climate, N-Deposition, and Bromus Tectorum L. Establishment in the Great Basin Desert Ecosystem

EPA Grant Number: F07F10950
Title: Interactions Between Changing Climate, N-Deposition, and Bromus Tectorum L. Establishment in the Great Basin Desert Ecosystem
Investigators: Concilio, Amy
Institution: University of California - Santa Cruz
EPA Project Officer: Just, Theodore J.
Project Period: September 1, 2007 through August 1, 2010
RFA: STAR Graduate Fellowships (2007)
Research Category: Fellowship - Terrestrial Ecology , Academic Fellowships , Global Climate Change

Description:

Objective:

Climate change, invasive species establishment, and nitrogen (N) deposition are each likely to affect plant species composition in the eastern Sierra Nevada, though it is unclear how these disturbances will interact. This research seeks to determine: (1) how increased N-deposition coupled with changing precipitation patterns will affect establishment of the invasive species, Bromus tectorum L., and the abundance of dominant native plant species; (2) whether there are differences in Bromus establishment and native plant abundance with pulsed or chronic N inputs; and (3) how changes in nutrient and water availability affect native and invasive plant physiological processes.

Approach:

To mimic the effects of predicted climatic and edaphic changes to the ecosystem, different precipitation zones will be created with snowfences and rainout shelters, and N amendments will be made to plots within each zone. Precipitation zones will include increased snow, decreased snow, ambient snow, and summer drought. N amendments will be made at four levels and with pulsed and chronic timing. Pulsed amendments will be made to simulate wet deposition with natural snowmelt and rainfall patterns, while N will be added continually over the year to simulate chronic dry deposition due to anthropogenic activities. Bromus growth and seed production will be monitored in each subplot throughout the growing season until senescence. Dominant native herbaceous and shrub species will also be monitored for biomass and abundance. Gas exchange and leaf N content of dominant plant species and Bromus will be monitored throughout the growing season each year to calculate N and water use efficiency. Soil samples will also be collected for N concentration. Meteorological conditions are available from several nearby weather stations.

Expected Results:

Bromus may respond more favorably to increased N and changes in nutrient and precipitation pulses than native species for two primary reasons: (1) Bromus is likely to demonstrate high plasticity to climatic and edaphic changes, since it has colonized and even out-competed native plants over a broad range of conditions, and (2) N-deposition in California has been correlated with increased growth and dominance of invasive annual grasses in low-productivity systems. However, native species in the Great Basin evolved in a water-limited environment and may consequently have an advantage over Bromus during drought. This research will provide an increased understanding of how plant communities respond to multiple stresses and contribute to the development of management strategies for native species conservation and invasive species control.

Supplemental Keywords:

Bromus tectorum, cheatgrass, climate change, invasive species, nitrogen deposition, nutrient pulse, Great Basin, Sierra Nevada, snowpack,

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The perspectives, information and conclusions conveyed in research project abstracts, progress reports, final reports, journal abstracts and journal publications convey the viewpoints of the principal investigator and may not represent the views and policies of ORD and EPA. Conclusions drawn by the principal investigators have not been reviewed by the Agency.

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