Proximal and Distal Factors in Desert Annual Seed Germination

EPA Grant Number: U915606
Title: Proximal and Distal Factors in Desert Annual Seed Germination
Investigators: Fotheringham, Connie J.
Institution: University of California - Los Angeles
EPA Project Officer: Michaud, Jayne
Project Period: September 1, 1999 through September 1, 2002
Project Amount: $79,411
RFA: STAR Graduate Fellowships (1999) RFA Text |  Recipients Lists
Research Category: Academic Fellowships , Ecological Indicators/Assessment/Restoration , Fellowship - Ecology and Ecosystems


The objective of this research project is to determine how plant communities in harsh environments respond to multiple stresses and have evolved mechanisms to capitalize on semi-predictable "extreme events" that radically alter environmental parameters. Semi-predictable refers to an event that will occur within a given time frame, but when that event will occur within that time frame is unpredictable.


This research project addresses the hypothesis that desert annuals, like post-fire chaparral annuals, germinate in response to nitrogen oxides (NOx). To test this hypothesis, germination trials will be conducted based on known dormancy-breaking cues of closely related chaparral species and the results of studies on soil chemistry. This project also hypothesizes that NOx is produced naturally by soil microbial processes only under specific conditions of water saturation, temperature, and organic content of the soil. To test this hypothesis, studies will be conducted on native desert soils under variable water saturation levels, temperatures, and organic content. These studies will use standard tests to understand the effect of these variables on microbial activity and soil chemistry, including nitrite/nitrate accumulation, trace gas efflux, and changes in pH.

Expected Results:

Seed germination in dormant species will have a linear correlation with specific soil conditions. Specifically, increase in soil organic matter and nitrogen, such as following drought years, will produce more germination cue (NOx) and a greater proportion of germination in response to rainfall and subsequent microbial activity. A model of conditions optimal for germination can be constructed using known parameters and explored to predict the effects of environment perturbations such as seasonality of rainfall, nitrogen deposition, and soil acidification.

Supplemental Keywords:

seed germination, nitrogen oxides, desert, annual plant, California, CA., Geographic Area, Ecosystem Protection/Environmental Exposure & Risk, State, Habitat, extreme weather events, habitat parameters, ecological consequences, soil chemistry, environmental stress, nitrogen compounds, California (CA)

Progress and Final Reports:

  • 2000
  • 2001
  • Final