Risk, Rate, and Impact of Medusahead Invasion of California Savannas

Project Overview

Project Type: Graduate Student
Funds awarded in 2007: $19,971.00
Projected End Date: 12/31/2008
Grant Recipient: UC Davis
Region: Western
State: California
Graduate Student:
Principal Investigator:

Annual Reports


  • Animals: sheep


  • Education and Training: on-farm/ranch research
  • Pest Management: weed ecology

    Proposal abstract:

    Medusahead (Taeniatherum caput-medusae) is an invasive noxious grass that is unpalatable to livestock and wildlife and slow to decompose (Young 1992, George 1992). Accumulation of medusahead (Mh) residue forms a heavy thatch layer that inhibits other plant species, leads to near Mh monoculture, and promotes fire (Knapp 1998). By 1999, over 5 million acres in central and northern California contained Mh (Miller et al. 1999). Spatial patterns of Mh infestation from the region to the landscape to the patch may indicate its ability to invade and form patches large enough to develop dense thatch with consequent total loss of grazing value and biodiversity. Thus, assessment of risk and spatial pattern of Mh invasion will enhance the application of precision grazing currently being developed in related research projects. This proposal addresses the following questions: (Q1) What areas are at risk of Mh invasion at the landscape level and why? What areas resist invasion? (Q2) Is Mh density increasing in areas already infested? If so, is increase due to more patches or larger patches? (Q3) What is Mh’s impact on forage production, quality, and acceptability by livestock, and how does Mh patch size and density affect this impact?

    Project objectives from proposal:

    1. Determine the risk that a pasture or a land management unit will be invaded by Mh, and use this information to prioritize areas for prevention of new Mh infestation in participating ranches. 2. Improve effectiveness of precision grazing to control Mh by determining how Mh patch size and patch density affect utilization by livestock and subsequent Mh spread. 3. Establish thresholds for Mh control by assessing the effects of Mh spatial distribution and patch size on loss of grazing capacity and biodiversity.

    Any opinions, findings, conclusions, or recommendations expressed in this publication are those of the author(s) and do not necessarily reflect the view of the U.S. Department of Agriculture or SARE.