Mixedgrass vegetation is tolerant to a short‐term but not season‐long access mat use during mitigation of industrial traffic

Abstract

Grasslands are impacted by many disturbances, including energy development. While temporary working platforms using access mats to support large equipment can minimize soil disturbance, less is known about matting impacts on grassland vegetation.We assessed heavy traffic effects on sandy and loamy Mixedgrass Prairie in southeast Alberta, Canada, where traffic occurred in 2015 either directly on grassland or on temporary matting. Vegetation was assessed in 2016 and 2017. Treatments varied in type (with/without matting), timing (spring vs. fall vs. season-long) and duration (6 vs. 12 weeks, and 24 weeks for season-long) of occurrence. While grass biomass was unaffected by direct wheeled traffic, native forb biomass declined, particularly during the first growing season; 1 year later, plots with prior long-term matting had more native forbs. Where traffic occurred on mats, grass biomass decreased when mats were placed for 6 or 12 weeks in spring, or for the entire growing season. Longer mat use also increased introduced forbs, which were positively associated with soil nitrogen supply rates. Plant biomass changes from matting (less grass, more introduced forbs) were more apparent in loamy-sand than loam soils. Overall, while direct traffic had limited impacts on vegetation, matting was more likely to alter vegetation, particularly when placed in spring or for longer periods, and further varied with ecosite type and the timing of traffic disturbance. We recommend that access mats be limited to placement for short periods (≤12 weeks), preferably in falling, to conserve mixedgrass prairie, while longer placement intervals be avoided.