Identifying Conifer Tree vs. Deciduous Shrub and Tree Regeneration Trajectories in a Space-for-Time Boreal Peatland Fire Chronosequence Using Multispectral Lidar

Wildland fires and anthropogenic disturbances can cause changes in vegetation species composition and structure in boreal peatlands. These could potentially alter regeneration trajectories following severe fire or through cumulative impacts of climate-mediated drying, fire, and/or anthropogenic disturbance. We used lidar-derived point cloud metrics, and site-specific locational attributes to assess trajectories of post-disturbance vegetation regeneration in boreal peatlands south of Fort McMurray, Alberta, Canada using a space-for-time-chronosequence. The objectives were to (a) develop methods to identify conifer trees vs. deciduous shrubs and trees using multi-spectral lidar data, (b) quantify the proportional coverage of shrubs and trees to determine environmental conditions driving shrub regeneration, and (c) determine the spatial variations in shrub and tree heights as an indicator of cumulative growth since the fire. The results show that the use of lidar-derived structural metrics predicted areas of deciduous shrub establishment (92% accuracy) and classification of deciduous and conifer trees (71% accuracy). Burned bogs and fens were more prone to shrub regeneration up to and including 38 years after the fire. The transition from deciduous to conifer trees occurred approximately 30 years post-fire. These results improve the understanding of environmental conditions that are sensitive to disturbance and impacts of disturbance on northern peatlands within a changing climate.

Response of vegetation and soil biological properties to deformation in logging trails in drained boreal peatland forests

In the boreal region, peatland forests are a significant resource of timber. Under pressure from a growing bioeconomy and climate change, timber harvesting is increasingly occurring over unfrozen soils. This is likely to cause disturbance in the soil biogeochemistry. We studied the impact of machinery-induced soil disturbance on the vegetation, microbes, and soil biogeochemistry of drained boreal peatland forests caused by machinery traffic during thinning operations. To assess potential recovery, we sampled six sites that ranged in time since thinning from a few months to 15 years. Soil disturbance directly decreased moss biomass and led to an increase in sedge cover and a decrease in root production. Moreover, soil CO2 production potential, and soil CO2 and CH4 concentrations were greater in recently disturbed areas than in the control areas. In contrast, CO2 and CH4 emissions, microbial biomass and structure, and the decomposition rate of cellulose appeared to be uncoupled and did not show signs of impact. While the impacted properties varied in their rate of recovery, they all fully recovered within 15 years covered by our chronosequence study. Conclusively, drained boreal peatlands appeared to have high biological resilience to soil disturbance caused by forest machinery during thinning operations.

PEAT SURFACE COMPRESSION REDUCES SMOULDERING FIRE POTENTIAL AS A NOVEL FUEL TREATMENT FOR BOREAL PEATLANDS

The wildfire regime in Canada’s boreal region is changing; extended fire seasons are characterized by more frequent large fires (≥200 ha) burning greater areas of land, whilst climate-mediated drying is increasing the vulnerability of peatlands to deep burning. Proactive management strategies, such as fuel modification treatments, are necessary to reduce fire danger at the wildland-human interface (WHI). Novel approaches to fuel management are especially needed in peatlands where deep smouldering combustion is a challenge to suppression efforts and releases harmful emissions. Here, we integrate surface compression within conventional stand treatments to examine the potential for reducing smouldering of near-surface moss and peat. A linear model (adj. R2=0.62, p=2.2e-16) revealed that ground cover (F(2,101)=60.97, p<0.001) and compression (F(1,101)=56.46, p<0.001) had the greatest effects on smouldering potential, while stand treatment did not have a significant effect (F(3,101)=0.44, p=0.727). On average, compressed Sphagnum and feather moss plots showed 57.1% and 58.7% lower smouldering potential, respectively, when compared to uncompressed analogs. While practical evaluation is warranted to better understand the evolving effectiveness of this strategy, these findings demonstrate that a compression treatment can be successfully incorporated within both managed and unmanaged peatlands to reduce fire danger at the WHI.

Growing (with) Muskeg: Oil Sands Reclamation and Healing in Northern Alberta

Scientists working for oil companies in the Athabasca region are developing methods by which to reclaim muskeg (boreal peatlands) on land disturbed by oil sands extraction. The Alberta government requires companies to reclaim disturbed land by achieving equivalent capability of the landscape to support an end land use. Indigenous community members instead define reclamation as establishing not only quantifiable ecological functions, but also relationships to their traditional territories. Tensions emerge as Indigenous concerns are often subsumed within bureaucratic discourses that favour scientific classification and quantification of land uses in reclaimed areas. Divergent responses to muskeg in reclamation activities are informed in part by these competing emphases on quantifiable landscapes as opposed to those that are relational and growing. This article traces this multiplicity through the examination of government and scientific literature and ethnographic fieldwork with Indigenous communities in northern Alberta. Muskeg is used as an analytical tool to explore competing conceptions of land reclamation. Mistranslation of polysemantic terms like muskeg occur on an ontological level, and settler colonial relations and power imbalances between competing languages and knowledge systems proliferate in reclamation activities.

The rhizosphere responds: rich fen peat and root microbial ecology after long-term water table manipulation

Hydrologic shifts due to climate change will affect the cycling of carbon (C) stored in boreal peatlands. Carbon cycling in these systems is carried out by microorganisms and plants in close association. This study investigated the effects of experimentally manipulated water tables (lowered, raised) and plant functional groups on the peat and root microbiomes in a boreal rich fen. All samples were sequenced and processed for bacterial, archaeal (16S rDNA—V4), and fungal (ITS2) DNA. Depth had a strong effect on microbial and fungal communities across all water table treatments. Bacterial and archaeal communities were most sensitive to the water table treatments, particularly at the 10-20 cm depth—this area coincides with the rhizosphere or rooting zone. Iron cyclers, particularly members of the family Geobacteraceae, were enriched around the roots of sedges, horsetails, and grasses. The fungal community was affected largely by plant functional group, especially cinquefoils. Fungal endophytes (particularly Acephala spp.) were enriched in sedge and grass roots, which may have underappreciated implications for organic matter breakdown and cycling. Fungal lignocellulose degraders were enriched in the lowered water table treatment. Our results were indicative of two main methanogen communities: a rooting zone community dominated by the archaeal family Methanobacteriaceae and a deep peat community dominated by family Methanomicrobiaceae. Importance This study demonstrated that roots and the rooting zone in boreal fens support organisms likely capable of methanogenesis, iron cycling, and fungal endophytic association, and are directly or indirectly affecting carbon cycling in these ecosystems. These taxa, which react to changes in water table and associate with roots and particularly graminoids, may gain greater biogeochemical influence as projected higher precipitation rates could lead to an increased abundance of sedges and grasses in boreal fens.