Mounding treatments set back bryophyte recovery on linear disturbances in treed peatlands

Treed peatlands are dominated by bryophytes, particularly Sphagnum spp., which create the characteristic hummock-hollow microtopography. This, in turn, shapes the distribution of bryophyte communities. Disturbances can lead to a loss of this microtopographic variation, impacting the bryophyte community. Seismic lines are deforested linear disturbances (approximately 3-8 m wide) created during oil and gas exploration and very extensive in Alberta, Canada. Loss of microtopographic variation leads to slow tree recovery on seismic lines in treed peatlands. To facilitate tree establishment, mounding is being applied to restore the microtopography on seismic lines. We compared bryophyte communities on unmounded and mounded seismic lines (18 years after seismic line creation, 3 years after mounding), and in adjacent treed fens as the reference, to evaluate how recovery varies with microtopographic position (i.e., top of hummock, slope or side of the hummock, and level ground). We found that recovery on the unmounded seismic lines was underway 18 years after seismic lines were created, while mounding redisturbed the sites and thus set back recovery, at least in the short term (3 years post-mounding). In unmounded seismic lines, Sphagnum cover was similar to that of reference treatments at all microtopographic positions. In contrast, mounded seismic lines had lower Sphagnum cover and higher cover of true mosses (sans feather mosses) than reference and unmounded treatments. Overall, these results show mounding sets back the recovery of bryophyte communities-the very organisms responsible for the microtopographic variation we are trying to establish. Further monitoring is needed to understand how this changes over time.

Automated summary

Mounding, a method used to restore tree establishment on seismic lines in treed peatlands, has set back the recovery of bryophyte communities responsible for microtopographic variation. Unmounded seismic lines showed recovery after 18 years, while mounded lines had lower Sphagnum cover and higher cover of true mosses compared to reference and unmounded treatments.