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AbstractThe installation of drainage ditches and removal of vegetation in preparation for vacuum harvesting alters the carbon dynamics of peatlands. However, we lack the measurements to understand the spatial distribution and environmental and substrate quality controls of carbon dioxide (CO2) and methane (CH4) emissions, as well as how these factors change over the 20–30 year extraction period. For three summers, we measured CO2 and CH4 emissions using the closed chamber method at three actively extracted peatlands near Drayton Valley, Alberta, ranging from 2 to 28 years since the start of extraction. Measurements were made in the ditches, and on segments of peat (fields) between adjacent ditches. Field emissions did not change with distance from ditches, likely due to the observed homogeneity of volumetric water content (VWC) and temperature across the fields. Understanding carbon dynamics in the ditches will be important, as they emitted on average two and 10 times, respectively, the amount of CO2 and CH4 per square meter of the fields. We found moderate to weak relationships between carbon emissions and soil temperature, VWC and ditch water level, though ditch emissions were significantly reduced when there was standing water present. Altering conventional site management, such as increasing ditch spacing, could substantially reduce CH4 emissions from the managed area. Emissions did not decrease with time since start of extraction. We suggest that Canadian emission factor calculations for land‐based emissions consider both peat quality variations among sites, and a site's extraction duration, which has been important in other studies.

Abstract Insect herbivore diet mediates interactions with entomopathogens, yet this is relatively unexplored for microsporidia. Here, we examine a diet‐mediated tri‐trophic interaction between an outbreaking forest defoliator, forest tent caterpillar (FTC) Malacosoma disstria Hübner and Nosema sp. microsporidia. We conducted two experiments where diet quality was manipulated by incorporating lyophilized aspen (Populus tremuloides Michaux) foliage into an artificial diet, which was compared to a standard artificial diet. Diet quantity varied between fully fed and partially starved conditions, simulating an outbreak scenario. Microsporidia infection occurred naturally or was induced via experimental inoculation. We assessed FTC survival, microsporidia infection and load, and sublethal effects of treatments on FTC traits. Plant secondary metabolite concentrations in aspen‐augmented diets varied between experiments. In Experiment 1, the aspen‐augmented diet contained lyophilized aspen foliage with low concentrations of secondary metabolites, which increased FTC survival and reduced microsporidia infection. Diet quality and infection load also interactively influenced adult wing traits in Experiment 1. In Experiment 2, the aspen‐augmented diet contained lyophilized aspen foliage with higher concentrations of secondary metabolites, which negatively affected FTC. No diet‐mediated interactions with microsporidia were observed in Experiment 2. Diet quality (Experiments 1 and 2), diet quantity (Experiment 2) and microsporidia infection (Experiments 1 and 2) directly influenced FTC survival and/or had sublethal effects on FTC that may have cascading effects on population dynamics and dispersal. We demonstrated that diet quality can mediate interactions between FTC and microsporidia, but these interactions depend on the defensive chemistry of the FTC diet. To our knowledge, this is the first study to report diet‐mediated interactions between an outbreaking forest pest and microsporidia and one of only a few studies to examine this tri‐trophic interaction among Lepidoptera.

Roads are known to alter environmental conditions and the composition of road edge plant communities, particularly when exogenous materials are used as road surfacing. In this study, we evaluate the impact of gravel roads on the organic layer thickness (OLT) and aspen distribution in a boreal forest landscape of Eastern Canada. The OLT and aspen distribution were compared at different distances from the roads (0 m, 10 m, and >10 m) to determine whether a reduction in the OLT along the roads could explain the distribution of aspen along the road network, and in particular the role of the roads as habitat corridors. In addition, germination tests were carried out to determine whether mineral soil from the roads could promote aspen establishment, by comparing the germination rate of substrates consisting only of mineral soil or mosses, and substrates consisting of mosses covered with 0.5 cm or 2 cm of mineral soil. The presence of aspen in the study landscape is limited by thick organic deposits (≥50 cm). However, the thickness of these deposits is reduced to approximately 10 cm at the edges of gravel roads, in part by the transport of mineral soil from the roads. This reduction in the OLT facilitates the establishment of aspen and helps explain its distribution along the road network.