The Montana State Parks AmeriCorps Program is an environmental service program of Montana Fish, Wildlife & Parks that promotes healthy, active, and environmentally aware communities by enhancing park land, enriching educational opportunities, increasing volunteerism, and improving community outreach in state parks. Montana State Parks AmeriCorps members educate and engage park visitors about the threat of noxious weeds to parks, public lands, and the state.

Study Goals:

The goal of the study is to examine the efforts of Montana State Parks AmeriCorps members’ treatments of noxious weeds.

Research Questions:

Rather than establishing traditional research questions, this study used treatment objectives to conduct a Before-After Control-Impact analysis. The treatment objectives included:

  • AmeriCorps member’s improvement of habitat functions within selected plots of Montana State Parks by:

  • Reducing the presence of spotted knapweed by 10%

  • Reducing the total presence of invasive plants by 10%

  • Increasing the beneficial plant population by 10%


The evaluation found the following:

  • Knapweed coverage decreased six percent with an end total coverage of two percent in the treatment sites. These figures represented a statistically significant change in comparison to the control group, which saw a 19 percent increase.

  • Three of the nine treatment sites had no detected knapweed on the post test, and another four sites had two or fewer plants present. This extremely low occurrence of knapweed should contribute to a future reduction of knapweed in the seed bank and a reduction of sprouting knapweed in subsequent seasons.

  • The mean total noxious weed coverage decreased by 28 percent, exceeding our program’s 10 percent objective. This significant decrease was realized through two main methods: hand pulling and chemical treatments.

  • On the whole, the AmeriCorps’ weed treatments were quite successful. The intervention nearly cutting the mean, noxious weed cover in half with the exception of one treatment site which saw an increase in total weed presence while another site stayed the same before and after treatment.

  • The mean beneficial plant coverage increased by 13 percent, meeting the 10% percent objective. While this finding was statistically significant (p=.049), it only just surpassed the .05 alpha level. It should be noted that two of the nine treatment transects saw a decrease in beneficial plant coverage.

For more information, download:

Full Report

Full report

Further information

Montana State Parks AmeriCorps
Implementing Organization
Montana Fish, Wildlife and Parks

Montana Fish, Wildlife and Parks

AmeriCorps Program(s)
AmeriCorps State and National
Age(s) Studied
18-25 (Young adult)
Focus Population(s)/Community(s)
Outcome Category
At-risk ecosystems
Study Type(s)
Study Design(s)
Level of Evidence
Joe Naiman-Sessions & Seth Shteir
Published Year
Study Site Location (State)