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To masticate or not: Useful tips for treating vegetation

Date: August 21, 2019

When is mastication an appropriate tool to manage vegetation?


A masticator works on mulching vegetation near a building.
Urban interface mulching. Photograph by Dana Mitchel, USFS

Background

Forest managers use mastication to grind or shed vegetation competition, prepare a site for natural or artificial regeneration, or release sapling-sized trees or use mastication to convert ladder fuels to surface fuels and enhance decomposition of biomass. However, determining the best mastication configuration within the context of management objectives and site limitations is challenging.

Research

We prepared a general technical report that synthesizes our current knowledge on mastication as a forest management tool. We found that excavators, skid steers, and tractors can all be carrier machines and different types of vertical and horizontal cutting heads exist that can be front-end mounted or boom mounted, each with its own advantages and disadvantages. We provide a summary on the ecological effects from mastication. Although there were several studies on plant and soil impacts, there is limited information on impacts to wildlife habitat. Although costs widely vary depending on machine size, the physical setting, size and configuration of pre-treatment biomass, and operator skill, mastication does have market and non-market benefits. Depending on the management objective, if mastication is an option, then a thorough site evaluation should consider slope, nonnative species invasions, vulnerability of soils to erode or compact, and treatment costs.

Key Findings

  • There are a variety of cutting head and machine configurations that enable the use of mastication as a vegetation management tool; which configuration is the best choice for the particular job.
  • The more experienced the operator, the more cost efficient the project will be, regardless of the configuration of the machine.
  • Attributes that affect mastication costs include: tree diameter, site conditions, amount of biomass, and particle size requirements
  • Vegetation establishment is limited when the masticated mulch is deeper than 4 inches.
  • Although mastication did not adversely affect the soils in these studies, good management practices (such as executing mastication on dry soils, driving on slash, deciding whether the machine needs to drive to each tree; or if a boom-mounted cutting head is desired) are preferred. All of these factors will help diminish soil scarification or compaction.
  • In general, the wildlife species of concern and their habitat needs will determine if mastication will affect wildlife.

Featured Publications

Heinsch, Faith Ann ; Sikkink, Pamela G. ; Smith, Helen Y. ; Retzlaff, Molly L. , 2018
Jain, Terrie B. ; Sikkink, Pamela G. ; Keefe, Robert ; Byrne, John C. , 2018
Sikkink, Pamela G. ; Jain, Terrie B. ; Reardon, James ; Heinsch, Faith Ann ; Keane II, Robert E. ; Butler, Bret W. ; Baggett, L. Scott. , 2017


Forest Service Partners: 

Research Location: 
Rocky Mountains