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Project ID: 10-1-01-7

Year: 2010

Date Started: 06/01/2010

Date Completed: 06/11/2014

Title: Pinon and Juniper Tree Mastication Effects in the Great Basin and Colorado Plateau

Project Proposal Abstract: This study will determine effects of masticating piñon and juniper(PJ)trees on fuels, understory vegetation, soils, and modeled fire behavior to support and guide use of this popular fuel-reduction tool (see 8 management support letters). The invasion of PJ trees into former sagebrush steppe communities is considered one of the greatest afforestations of our time. It is estimated that 34% of invaded shrub steppe areas are currently in Phase I (low tree density, shrubs and herbs dominate), 40% are in Phase II (trees are codominant with shrubs and herbs), while 27% are in Phase III (trees dominant over reduced shrubs and herbs). The amount of PJ woodlands in Phase III is expected to increase to 75% within the next 50 years. To reduce the potential for catastrophic crown fires and subsequent weed invasion, as well as to improve resource values, land managers have been masticating trees for over 10 years. Managers often prefer tree mastication because it involves less risk than prescribed fire; it is seen as less hydrologically or ecologically-disruptive than chaining; it is considered to reduce fuel structure and fire spread better than cutting; it is highly versatile in application from thinning to clearing; and it can be done most seasons as long as the soil is not too wet. Yet there are no published studies of fuel, vegetation, or soil responses to PJ mastication, or guidelines on how or where to best apply mastication as a fuel control and ecologically-beneficial practice. We propose to determine the effects of tree mastication on Phase I, II, and III tree invasion across a wide range of sites in the Great Basin and Colorado Plateau. We will evaluate the effects of mastication treatments, with and without follow-up fire on fuel, vegetation, and soil response variables, and also on potential fire behavior. We will use 2 complementary studies: 1) a retrospective study (RS) to determine effects of time since mastication, subsequent fire, climate, and site variables on response variables across a wide range of sites (approximately 40 sites x 3 phases in each site) and 2) a follow-up assessment of SageSTEP (SS) plots on 3 sites measured prior to mastication in 2006-2006 and after mastication from 2007-2009 to determine effects of initial mastication fuel structure on subsequent fuel biomass loss. The SS assessment will also supplement treatment comparisons made in the RS by comparing fuel, vegetation, and soil responses among untreated, pre-masticated and masticated plots. Using the RS study, we will compare response variables on subplots sampled on paired untreated and masticated areas on the same ecological site with similar initial tree cover as determined using NAIP imagery (National Agricultural Imagery Program; 1-m resolution). This paired approach is feasible because land managers often leave areas untreated for wildlife cover near masticated areas. To determine fuel changes over time for the RS, we will compare current masticated biomass with initial masticated biomass, as estimated from pre-masticated tree cover from NAIP imagery. To determine effects of post-mastication fire, we will sample masticated-burned sites where pre-mastication and pre-burn data are available (one SS site and other sites burned by the Salt Lake Field Office BLM). Besides univariate comparisons of response variables from the RS and SS study, we will input climate and site data into a structural equation model to determine direct and indirect effects of these variables on fuel, vegetation, and soil response variables. To determine effects of mastication and subsequent fire on potential fire behavior, we will input untreated and masticated fuel data into fire behavior models, and vary abiotic conditions to determine under what conditions changes in fuel structure could lead to threshold changes in fire behavior. A comprehensive summary will indicate outcomes from mastication and guidelines for future projects.

Principal Investigator: Bruce A. Roundy

Agency/Organization: Brigham Young University

Branch or Dept: Department of Plant & Wildlife Sciences

Other Project Collaborators




Branch or Dept

Co-Principal Investigator

Zachary T. Aanderud

Brigham Young University

Department of Plant & Wildlife Sciences

Co-Principal Investigator

April Hulet

University of Idaho

Department of Forest, Rangeland and Fire Sciences

Co-Principal Investigator

Kert R Young

Brigham Young University

Department of Plant & Wildlife Sciences

Federal Cooperator

Stanley G. Kitchen

Forest Service

RMRS-Shrub Sciences Laboratory

Federal Fiscal Representative

Susan T. Major

Forest Service

RMRS-Rocky Mountain Research Station

Project Locations

Fire Science Exchange Network

Great Plains

Southern Rockies







Interior West


Project Deliverables

Final Report view or print

("Results presented in JFSP Final Reports may not have been peer-reviewed and should be interpreted as tentative until published in a peer-reviewed source.")

  ID Type Title
view or print   1804 Government Publication Pinyon and juniper tree mastication effects in the Great Basin and Colorado Plateau
view or print   1805 Government Publication PJ control by mastication What happens to fuels, soil, and vegetation
view or print   3690 Journal Article Rangeland Ecology and Management
view or print   3508 Journal Article Rangeland Ecology and Management
view or print   3509 Journal Article Forest Ecology and Management
view or print   327 MS Thesis Understory Vegetation Response to Mechanical Mastication of Piñon and Juniper Woodlands
view or print   328 MS Thesis Microbial Responses to Coarse Woody Debris in Juniperus and Pinus Woodlands
view or print   347 MS Thesis Tree islands of fertility structure baterial community assembly and functional genes controbuting to
view or print   329 MS Thesis Fuel Response to Mechanical Mastication of Pinyon-Juniper Woodlands in Utah
view or print   7486 Poster Pinyon and juniper shredded debris influences nutrients in cold deserts
view or print   7487 Conference/Symposia/Workshop What happens when you shred pinyon and juniper trees?
view or print   7488 Conference/Symposia/Workshop Effects of mechanically shredding Utah juniper on fuel characteristics
view or print   7489 Conference/Symposia/Workshop Understory vegetation response to mechanical mastication of pinyon and juniper woodlands
view or print   7490 Conference/Symposia/Workshop What happens when you shred pinyon and juniper trees
view or print   7491 Photo Bullhog machine shredding juniper
view or print   7492 Photo perennial herbaceous response to shredding
view or print   7493 Photo understory after shredding
view or print   7494 Photo understory before shredding
    5495 Conference/Symposia/Workshop Estimating Piñon and Juniper Tree Cover Using NAIP Imagery Across Utah
    5496 Poster Piñon and Juniper Tree Mastication Effects in the Great Basin and Colorado Plateau
    5497 Poster Investigating the Potential for Piñon and Juniper Mastication to Influence Soil Health and Invasibility

Supporting Documents

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