Rémy Pouliot

How Fen Vegetation Structure Affects the Transport of Oil Sands Process-affected Waters

Oil sands mining in the Athabasca oil sands region disturbs large tracts of peatlands as the vegetation-soil layer must be removed. Processing oil sands produces large volumes of wet material containing oil sand process-affected water (OSPW) that has elevated concentrations of sodium (Na) and naphthenic acids (NAs). Attempts to reclaim mined landscapes to peat-forming systems command knowledge of the transport, fate and impact of OSPW in organic soils. Four mesocosms placed in a greenhouse were randomly assigned with two treatments: 1) a moss carpet (Bryum pseudotriquetrum) and 2) graminoids (Carex aquatilis and Calamagrostis stricta). Transport of Na and NAs through peat was significantly delayed by sorption and diffusion in peat matrix. After two growing seasons of receiving OSPW, the graminoid plants continued to grow without showing stress from OSPW, while mosses showed a considerable decline in health. Microorganisms were more active under sedges than mosses and their activity varied over time either because of seasonal variation or as a consequence of variation in Na concentration. The findings of this study are limited due to the small number of replicates and the lack of a control, but represent a first step towards the creation of peatlands in the post-mined areas.

Evolution of niche preference in Sphagnum peat mosses.

Peat mosses (Sphagnum) are ecosystem engineers—species in boreal peatlands simultaneously create and inhabit narrow habitat preferences along two microhabitat gradients: an ionic gradient and a hydrological hummock–hollow gradient. In this article, we demonstrate the connections between microhabitat preference and phylogeny in Sphagnum. Using a dataset of 39 species of Sphagnum, with an 18‐locus DNA alignment and an ecological dataset encompassing three large published studies, we tested for phylogenetic signal and within‐genus changes in evolutionary rate of eight niche descriptors and two multivariate niche gradients. We find little to no evidence for phylogenetic signal in most component descriptors of the ionic gradient, but interspecific variation along the hummock–hollow gradient shows considerable phylogenetic signal. We find support for a change in the rate of niche evolution within the genus—the hummock‐forming subgenus Acutifolia has evolved along the multivariate hummock–hollow gradient faster than the hollow‐inhabiting subgenus Cuspidata. Because peat mosses themselves create some of the ecological gradients constituting their own habitats, the classic microtopography of Sphagnum‐dominated peatlands is maintained by evolutionary constraints and the biological properties of related Sphagnum species. The patterns of phylogenetic signal observed here will instruct future study on the role of functional traits in peatland growth and reconstruction.

Estimating moss growth in arctic conditions: a comparison of three methods

Abstract Except for Sphagnum mosses of peatland habitats, reliable methods to assess moss productivity in arctic or boreal biomes give usually highly variable results. Therefore, ecosystem processes are poorly understood in these biomes where mosses are an important component of the system. The aim of this study was to compare three methods to estimate moss growth in polygon patterned fens: cranked wires, natural markers and artificial white marks (an alternative to the spray method). Precision of estimates was significantly higher when natural markers were used (coefficients of variation, CV, between 17 and 27%), compared to cranked wires (CV = 37%) or white marks (CV = 56%). Natural markers also provided estimates for growth of moss stems 32 to 113% higher than the other methods. Although cranked wires were calibrated shortly after snowmelt, some moss growth is still missed and consequently moss growth is underestimated. Accuracy of cranked wires was poor, mainly caused by frost heaving or permafrost activities that can affect wire position. Thus, this method should be avoided in arctic ecosystems. Even if white marks were painted on moss stems at the end of the growing season prior to the sampling year, lower estimates of moss growth were still found. We suspect some interference with moss growth processes during the marking process, at least when used with brown mosses. The natural marker method, which provides increment for an entire growing season, appears to be the most accurate method of the three. Additionally, it is also the easiest and the least time consuming method to use. Its main drawback is that relatively few species have natural growth marks and these species may not always be present among the targeted species under study. Also, measurements of stem growth on the same sample did not differ between observers, even if the second measurement was done 12 years later. In conclusion, when species with natural markers are present, this method should be used to assess moss growth. For arctic/sub-arctic studies where such species are lacking, the artificial white marks method should be refined further.