Mitigating effects of access mats on construction traffic in Mixedgrass Prairie of Alberta

• Author / Creator

  James, Kassia

• Grasslands ecosystems are increasingly subject to anthropogenic alterations, including conversion to cropland or tame pasture, and dissection by urban infrastructure. Linear disturbances, like roads, oil and gas pipelines, and electrical transmission lines, can fragment these ecosystems, directly alter underlying soils, and serve as vectors for plant invasions. A novel construction method, adapted from oil and gas extraction in the northern boreal forest, uses technology to redistribute equipment weight during construction in native grassland in an effort to decrease the footprint created from industrial development. The technology is comprised of an interlocking matrix of three-ply wooden mats, called access mats, used to create temporary road and work areas.This study was conducted on the University of Alberta’s Mattheis Research Ranch to examine the impact of various access mat placement treatments on native grassland of the Dry Mixedgrass prairie in SE Alberta, and reflected ongoing construction activities of ATCO’s Eastern Alberta Transmission Line, which was located nearby. Treatments were conducted in which the timing and duration of mat placement were varied from spring to fall, and from 6 to 24 weeks, on each of two ecosites (loam and loamy-sand), and monitored for up to 3 years of recovery. Main areas of focus were soil physical attributes, such as soil bulk density, penetration resistance, and water infiltration, along with nutrient supply rates, as well as vegetation responses such as biomass and nutrient components. Results of the field trials indicated traffic without mats (TWOM) increased soil penetration resistance (PR), while traffic with mats (TWM) initially had lower PR when mats were removed and soil moisture contents (SMC) two to three times the Control; however, SMC and PR within the TWM returned to Control levels six weeks after mat removal. Grass biomass was reduced under mats in place for 12 weeks or more compared to Controls in the first and second year (p = 0.0007) of recovery after treatment application. Introduced and ruderal forb biomass increased during first year of recovery (p < 0.0001). Biomass responses were more apparent on loamy-sand soils than loam soils. Light levels of traffic in this study did not create impacts that differed from the Controls for either grasses or introduced forbs under TWOM. Soil nutrient availability increased under TWM the year of treatment application relative to Controls; more specifically, nitrogen was ten times higher, sulfur double, iron four times higher, and manganese five times higher than those measured in the Control. Available soil nutrients quickly dissipated and led to levels similar to those of the Control by the following spring. Soil available nutrients under TWOM saw slight or no increase compared to Controls. Under the conditions of this study soil physical properties and vegetation were maintained close to those of the Controls under TWM when mats were in place for no longer than 6 weeks, while simultaneously mitigating the effects of wheeled industrial traffic. Results indicate that soil and vegetation recovery are influenced by the dominant soil texture as well as the season and duration of access mat use. Mats moderated soil compaction at the cost of vegetation biomass in placements longer than six weeks. Mats would be recommended to extend work time frame and possibly increase levels of traffic with consideration for the plant community underneath, and removal before plant death or with a revegetation strategy for recovery in place.

• Subjects / Keywords

  • Prairie
  • Access mat
  • Mixedgrass Prairie
  • Traffic
  • Construction mitigation
  • Grassland
  • Minimum construction

• Graduation date

  Spring 2019

• Type of Item

  Thesis

• Degree

  Master of Science

• DOI

  https://doi.org/10.7939/r3-sve2-yg79

• License

  Permission is hereby granted to the University of Alberta Libraries to reproduce single copies of this thesis and to lend or sell such copies for private, scholarly or scientific research purposes only. Where the thesis is converted to, or otherwise made available in digital form, the University of Alberta will advise potential users of the thesis of these terms. The author reserves all other publication and other rights in association with the copyright in the thesis and, except as herein before provided, neither the thesis nor any substantial portion thereof may be printed or otherwise reproduced in any material form whatsoever without the author's prior written permission.