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Restoration of Weed-Infested Rangeland on the Paws Up Ranch 2005

First year of a three-year study.

Introduction

An objective of sustainable invasive plant (weed) management is to shift the plant community to a desired state that is relatively weed resistant while meeting other land use objectives such as forage production. This project tests an integrated approach for restoring a weed infested pasture to a desired plant community. Our objective is to decrease spotted knapweed while increasing native forage grasses. We attempt this through an integrated weed management approach that addresses the ecology of the plant community. Our techniques can be realistically applied by land managers/owner in a cost effective manner.

Restoring weed-infested rangeland requires realistic objectives that consider the extent of the damage on the ecosystem processes, ecological potential, and land use goals. Since plant communities are dynamic and constantly changing, it is possible to redirect ecosystem processes toward a desired trajectory to assist recovery of the system. Three primary ecosystem processes are the nutrient cycle, hydrologic cycle, and energy flow. By addressing these processes with our management practices, we can improve the ability of the plant community to repair and/or maintain itself at a functioning state.

Objectives

The overall objective of this project is to improve revegetation technology by using revegetation combined with sheep-grazing and trampling effects to change a spotted-knapweed-dominated plant community to a perennial-bunchgrass-dominated community.

The specific research objectives are to:

  1. Determine whether sheep will utilize spotted knapweed in the spring.
  2. Determine the effect of revegetation on desirable grasses and spotted knapweed.

The specific land objectives are to:

  1. Increase forage production by 30% in 3 years.
  2. Decrease spotted knapweed by 50% in 3 years.

The specific education objective is to:

Create a field site and data to be used to educate public and private landowners on the use of integrated techniques for restoring weed-dominated rangeland to desired plant communities.

Study Area

Located 38 km east of Missoula, Montana, in the Blackfoot River Valley, the Paw’s Up Ranch is one of western Montana’s largest and oldest cattle ranches. The Paw’s Up Ranch has been managed for cattle grazing for the last century. The ranch currently raises approximately 400 Angus cow/calf pairs. Our two study sites are located within the Ninemile Prairie at Greenough, MT, and are approximately 0.5 km apart. Historically, the sites were a rough fescue/bluebunch wheatgrass (Festuca scabrella/Agropyron spicatum) (Pseudoroegneria spicata) grassland (Mueggler & Stewart 1980). This habitat type is one of the most productive grasslands in Montana averaging 1000 (± 300) lbs. per acre. The historic plant community likely contained rough fescue, bluebunch wheatgrass, Idaho fescue (F. idahoensis), prairie Junegrass (Koeleria macrantha), fringe sage (Artemisia frigida), yarrow (Achillea millefolium), and lupine (Lupinus sericeus) (Mueggler & Stewart 1980). In recent history, desired forage production has decreased due to drought, noxious weed invasion, and intensive grazing from previous ranch owners. One invasive species dominates the pasture, spotted knapweed (Centaurea maculosa). Spotted knapweed accounts for 89% of the forage produced per acre while perennial grasses account for only 11% of the forage production.

Methods

The project is established to further our scientific knowledge of ecologically-based management of invasive-plant-dominated lands. The study consists of four revegetation treatments and a control. All treatments were grazed by sheep in June 2005 for 15 days.

A summary of the five treatments are as follows:

  1. No revegetation (control)
  2. Broadcast seeding
  3. Broadcast seeding + mulch
  4. Broadcast seeding + sheep trampling
  5. Broadcast seeding + mulch + sheep trampling

Treatments are arranged in a randomized complete-block design with four replications at each site for a total of 40 plots. Plots are 5m x 5m in size and marked with chaining pins.

To account for sheep forage utilization, three 1m2 grazing exclosures were constructed at each site in 2004. At each exclosure, three plots of the same size are marked outside of the exclosure and are grazed by sheep.

The revegetation mix selected represents long-lived, late-successional species of the native plant community. The seed mix included Festuca scabrella (rough fescue), Pseudoroegneria spicata (bluebunch wheatgrass), Festuca idahoensis (Idaho fescue), Poa ampla (Big bluegrass), Koeleria macrantha (prairie Junegrass), Pascopyrum smithii (western wheatgrass), and Gaillardia aristata (blanketflower). The seed mix was applied at 28 lbs PLS/ac (200 seeds/ft2) using a hand-held broadcast seeder. The seed treatments were applied the day sheep entered the pasture for the trampling treatments and the day sheep leave the pasture for the no-trampling treatments. Straw Net is organic, pelletized bluegrass straw mulch with a tackifier. This mulch was applied with the seed mix using a hand-held broadcast seeder. The mulch was added to the revegetation treatment at a rate of 0.1 lb/ft2 (25 lbs/plot). Half the mulch was applied during the first seeding, and the remainder of the mulch was applied during the post-trampling seeding.

Results

The test plots were established in May, 2005. Sheep grazing occurred and seed/mulch applied in June, 2005. Plots were sampled in July and data analyzed in August and September.

Data from the sheep grazing exclosures is still being processes to determine utilization of spotted knapweed and desired grasses. This data will be sent to GLCI at a later date.

To date, our statistical analysis has found no significant difference in spotted knapweed and desired species percent cover, density and biomass between revegetation treatments (p> 0.05). However, we did not expect to see significant differences this early after applying the treatments, particularly seeding. During a site visit on September 30th, grass seedlings were emerging in the plots. Plots will be sampled in 2006 and 2007 to evaluate seedling establishment success and the effect of sheep trampling to incorporate the seed and potentially increase establishment.

Contact Information

Monica Pokorny, Research Associate
Montana State University
334 Leon Johnson Hall
Bozeman, MT 59717-3120
(406) 994-6599

Project Cooperators: The Montana Sheep Institute, Paws Up Ranch, sheep producer Pachy Burns, Center for Invasive Plant Management

Last Modified: 04/05/2006