Quantifying the Impact of Invasive Plants in California Grassland Systems and Facilitating Conservation Strategies

EPA Grant Number: FP916389
Title: Quantifying the Impact of Invasive Plants in California Grassland Systems and Facilitating Conservation Strategies
Investigators: Hulvey, Kristin B.
Institution: University of California - Santa Cruz
EPA Project Officer: Lee, Sonja
Project Period: January 1, 2004 through December 31, 2006
Project Amount: $107,762
RFA: STAR Graduate Fellowships (2004) RFA Text |  Recipients Lists
Research Category: Fellowship - Terrestrial Ecology and Ecosystems , Academic Fellowships , Ecological Indicators/Assessment/Restoration


Diversity-invasibility investigations are of conservation interest because increasing rates of biological invasion may create positive feedback cycles of: biological invasion→ diversity loss→ ecosystem simplification→ invasion susceptibility. A better understanding of when and how invaders impact natural systems may prevent ecosystem services losses, decreases in biodiversity, and subsequent changes in ecosystem functioning. The objective of this research is to investigate the susceptibility of California grasslands to invasive plants by examining the effect of absolute and functional diversity changes on invader impact. I will build on past invasion-diversity experiments by: (1) focusing on invader impacts as well as invader establishment; (2) using as treatments the known, nested variation of species and functional group diversity found in California grasslands rather than using random assemblages of species as treatments; and (3) investigating impacts of invaders at two ecological scales, population and ecosystem levels.


Nested diversity plots will be constructed in California grassland through removal and replanting of appropriate grassland species for each diversity level. After 1 year of growth, two common noxious weeds with differing functional characteristics, yellow starthistle (Centaurea soltitialis) and medusahead (Taeniatherum caput-medusae), will be introduced to the plots as experimental invaders. The abundance, cover, and biomass of all species will be measured yearly to determine the population and ecosystem impacts of yellow starthistle and medusahead. Throughout this investigation, I will work with land managers and policy makers to help translate study findings into effective methods of yellow starthistle and medusahead control.

Supplemental Keywords:

fellowship, biodiversity, invasive species, natural ecosystems, California, grasslands, population dynamics, weeds, yellow starthistle, medusahead,, RFA, Scientific Discipline, ENVIRONMENTAL MANAGEMENT, Ecosystem Protection/Environmental Exposure & Risk, Ecosystem/Assessment/Indicators, Ecosystem Protection, Resources Management, Ecological Effects - Environmental Exposure & Risk, Environmental Monitoring, Ecological Risk Assessment, Ecological Indicators, California grasslands, biodiversity, ecosystem assessment, yellow starthistle, ecosystem integrity, environmental risks, conservation, changes in species composition

Relevant Websites:

2004 STAR Graduate Fellowship Conference Poster (PDF, 1p., 163KB, about PDF)

Progress and Final Reports:

  • 2004
  • 2005
  • Final