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Evaluating Postfire Seeding Treatments Designed to Suppress Cheatgrass (Bromus tectorum) in a Ponderosa Pine Forest on the Colorado Plateau

 
Applying seeding treatments to the Pine Valley Meadow study site.  --Photographer: Matt Brooks
The restoration of historical fuel conditions and fire regimes is one of the primary land management goals on the Colorado Plateau. Fire is the primary tool used in this region to reduce fuel loads and shift landscapes back to historical conditions of a low intensity, 8-15 year return interval, surface fire regime. However, the invasive plant cheatgrass (Bromus tectorum) has become the dominant understory vegetation and fuel type following initial fire treatments in many areas. There is significant concern that repeated burning at historically appropriate fire return intervals for ponderosa pine forest will benefit this invasive plant to the detriment of native species. There is additional concern that the high flammability of cheatgrass fuelbeds will lead to fire return intervals that are more frequent than occurred historically and that are prescribed in the agency fire management plans, potentially preventing recruitment of pine seedlings and leading to type conversion of native forests to alien grasslands.

Project Details

Federal land managers and research scientists have noted that cheatgrass does not typically co-occur with two of the dominant perennial grasses in the Shivwits plateau region, bottlebrush squirreltail (Elymus elymoides) and blue grama (Bouteloua gracilis). This suggests that these natives may be competing with and excluding the establishment of cheatgrass. If these species can be established in postfire landscapes, they may be able to pre-empt the establishment of cheatgrass and promote the restoration of native plant communities and natural fuel characteristics. This report provides results of an experimental seedings of these two perennial grasses.

Seeding with or without raking had no detectable effects on any of the species or groups of species in this study as measured by: 1) the density, cover, and species diversity of standing vegetation during the first 5 post-treatment years; or 2) the density and species diversity of the soil seedbank during the first 3 post-treatment years. Blue grama had an overall low standing density and cover, and seedbank density, at the study site, whereas bottlebrush squirreltail had relatively high standing density and cover, and seedbank density, at least during some of the sampling years. Cheatgrass did not differ among treatments, including raked and unraked plots, and only increased from 1.1 seeds per 18 cubic cm of soil immediately following the fire in fall 2003 to 1.5 seeds by the fall of the third postfire year.

These results suggest that blue grama may be an inappropriate species for seeding at this study site, whereas bottlebrush squirreltail may be an appropriate species. Although the natural recovery of the latter species within a few years following fire suggest that seeding may not be necessary. In addition, cheatgrass may not be a significant postfire management concern at this study site. Additional research is needed to more definitively evaluate the effects of seeding treatments, document the postfire recovery rates of cheatgrass and other species under a wider range of environmental conditions, and determine if there is a specific fire prescription that can both control cheatgrass and accomplish other fire management objectives.

Objectives

  1. Determine if raking after seeding improves establishment rates of bottlebrush squirreltail (Elymus elymoides) and blue grama (Bouteloua gracilis).

Hypothesis:    Bottlebrush squirreltail and blue grama density, cover, and seedbank density will be higher in plots that were raked immediately after seeding than in plots that were not raked.

 

  1. Determine if raking after seeding affects the productivity of cheatgrass and other alien plants.

Hypothesis:    Cheatgrass and other alien plant density, cover, and seedbank density will be different in raked than in unraked seeded plots.

 

  1. Determine if postfire seeding of bottlebrush squirreltail and blue grama decreases the productivity of cheatgrass and other alien plants.

Hypothesis:    Cheatgrass and other alien plant density, cover, and seedbank density will be lower in seeded than unseeded plots.

 

  1. Determine if postfire seeding of bottlebrush squirreltail and blue grama increases productivity and diversity of native plants.

Hypothesis:   Native species standing density, cover, and diversity, and seedbank density and diversity, will be higher in seeded than unseeded plots.

 

  1. Develop recommendations regarding the use of postfire seeding and raking to reduce growth and reproduction of cheatgrass in recently burned ponderosa pine forest.

 

  1. Establish a demonstration site and interpretive materials to illustrate the relative effects of postfire seeding, seeding plus raking, and no seeding on cheatgrass dominance and native plant productivity and diversity.

 



USGS Contact For This Project
Matthew Brooks
mlbrooks@usgs.gov
(559) 240-7622
Yosemite Field Station
40298 Junction Dr., Suite A
Oakhurst, CA 93644
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