Regional atmospheric cooling and wetting effect of permafrost thaw-induced boreal forest loss

In the sporadic permafrost zone of North America, thaw‐induced boreal forest loss is leading to permafrost‐free wetland expansion. These land cover changes alter landscape‐scale surface properties with potentially large, however, still unknown impacts on regional climates. In this study, we combine nested eddy covariance flux tower measurements with satellite remote sensing to characterize the impacts of boreal forest loss on albedo, eco‐physiological and aerodynamic surface properties, and turbulent energy fluxes of a lowland boreal forest region in the Northwest Territories, Canada. Planetary boundary layer modelling is used to estimate the potential forest loss impact on regional air temperature and atmospheric moisture. We show that thaw‐induced conversion of forests to wetlands increases albedo: and bulk surface conductance for water vapour and decreases aerodynamic surface temperature. At the same time, heat transfer efficiency is reduced. These shifts in land surface properties increase latent at the expense of sensible heat fluxes, thus, drastically reducing Bowen ratios. Due to the lower albedo of forests and their masking effect of highly reflective snow, available energy is lower in wetlands, especially in late winter. Modelling results demonstrate that a conversion of a present‐day boreal forest–wetland to a hypothetical homogeneous wetland landscape could induce a near‐surface cooling effect on regional air temperatures of up to 3–4 °C in late winter and 1–2 °C in summer. An atmospheric wetting effect in summer is indicated by a maximum increase in water vapour mixing ratios of 2 mmol mol−1. At the same time, maximum boundary layer heights are reduced by about a third of the original height. In fall, simulated air temperature and atmospheric moisture between the two scenarios do not differ. Therefore, permafrost thaw‐induced boreal forest loss may modify regional precipitation patterns and slow down regional warming trends

Direct and indirect climate change effects on carbon dioxide fluxes in a thawing boreal forest-wetland landscape

In the sporadic permafrost zone of northwestern Canada, boreal forest carbon dioxide (CO2) fluxes will be altered directly by climate change through changing meteorological forcing and indirectly through changes in landscape functioning associated with thaw‐induced collapse‐scar bog (‘wetland’) expansion. However, their combined effect on landscape‐scale net ecosystem CO2 exchange (NEELAND), resulting from changing gross primary productivity (GPP) and ecosystem respiration (ER), remains unknown. Here, we quantify indirect land cover change impacts on NEELAND and direct climate change impacts on modeled temperature‐ and light‐limited NEELAND of a boreal forest–wetland landscape. Using nested eddy covariance flux towers, we find both GPP and ER to be larger at the landscape compared to the wetland level. However, annual NEELAND (−20 g C m−2) and wetland NEE (−24 g C m−2) were similar, suggesting negligible wetland expansion effects on NEELAND. In contrast, we find non‐negligible direct climate change impacts when modeling NEELAND using projected air temperature and incoming shortwave radiation. At the end of the 21st century, modeled GPP mainly increases in spring and fall due to reduced temperature limitation, but becomes more frequently light‐limited in fall. In a warmer climate, ER increases year‐round in the absence of moisture stress resulting in net CO2 uptake increases in the shoulder seasons and decreases during the summer. Annually, landscape net CO2 uptake is projected to decline by 25 ± 14 g C m−2 for a moderate and 103 ± 38 g C m−2 for a high warming scenario, potentially reversing recently observed positive net CO2 uptake trends across the boreal biome. Thus, even without moisture stress, net CO2 uptake of boreal forest–wetland landscapes may decline, and ultimately, these landscapes may turn into net CO2 sources under continued anthropogenic CO2 emissions. We conclude that NEELAND changes are more likely to be driven by direct climate change rather than by indirect land cover change impacts

The phytophagous and predatory mites (Acari) on Prunus (Rosaceae) in southeastern Canada

During summer 2015, 192 samples of foliage were taken from 13 different Prunus species found mostly along the Ottawa River (Quebec, Ontario; 148 samples) and in the Vineland region (Ontario; 44 samples). A total of 39 mites species were collected. Estimators of the true species diversity indicated that most of the mite fauna in the areas sampled was captured. One eriophyid mite species appears to represent a new species for science. In terms of host range, phytoseiids appear to be less specific than eriophyoids and both taxa can exhibit host preferences. In addition to providing an overview of the mite fauna of Prunus foliage and galls, this project provides two identification keys to the eriophyid mite species associated with galls, one based on the mite morphology, and the other based on the morphology of the galls.Keywords:Prunus; phytophagous mites; predatory mites; survey; biodiversity

Additions to the boreal flora of the Northwest Territories with a preliminary vascular flora of Scotty Creek

We present the first survey of the vascular flora of Scotty Creek, a peatland-dominated watershed with discontinuous permafrost about 60 km south of Fort Simpson, Northwest Territories (NWT). Of the 140 vascular plant taxa found at Scotty Creek, two are additions to the boreal flora of NWT: Arethusa bulbosa (Dragon’s-mouth, Orchidaceae) and Carex pauciflora (Few-flowered Sedge, Cyperaceae). The occurrence of Arethusa bulbosa extends the known range of this species 724 km to the northwest, making this purportedly eastern American plant almost pan-Canadian. Two other major range extensions (> 200 km) are reported for Carex brunnescens subsp. sphaerostachya (Round-spike Brownish Sedge) and Platanthera dilatata var. dilatata (Tall White Bog Orchid). Furthermore, 15 other rare NWT species are reported, including three species known from a single other locality in the NWT. The flora of Scotty Creek is dominated by circumpolar (55%) and widespread North American (34%) elements. Despite the absence of exposed alkaline rocks and the dominance of deep organic soil almost throughout Scotty Creek, a number of limeindicator plants were found in lakes and minerotrophic wetlands

Le statut de la naïade grêle (Najas gracillima, Najadaceae) au Québec

La présence de la naïade grêle, Najas gracillima (Najadaceae), dans la flore aquatique indigène du Québec est confirmée. Cette espèce sensible à la pollution est en déclin dans toute son aire naturelle nord-américaine en raison de l’eutrophisation des lacs et des cours d’eau. Pour faciliter l’identification de cette rareté, une clé des Najas de la province et une discussion des caractères permettant l’identification du Najas gracillima sont incluses. Le danger de nuire au Najas gracillima en le confondant avec l’exotique et envahissant Najas minor est souligné. De plus, nous présentons les données les plus à jour sur la répartition et l’écologie du Najas gracillima dans le monde et en Amérique du Nord, ainsi qu’une carte de répartition de l’espèce dans l’est du Canada et les territoires adjacents, basée sur un inventaire exhaustif de la littérature et des spécimens de l’Herbier national du Canada (CAN), de l’Herbier des plantes vasculaires d’Agriculture et Agroalimentaire Canada (DAO) et de l’Herbier Marie-Victorin (MT). Nous ajoutons des notes détaillées sur le site de la seule population connue du Québec.The presence of the thread-like naiad, Najas gracillima (Najadaceae), in the indigenous aquatic flora of Québec (Canada) is confirmed. This species is highly sensitive to pollution and, due to the eutrophication of lakes and streams, is in decline throughout its natural range in North America. To facilitate the identification of this rare species, the present article provides a key to the species of Najas occurring in Québec, along with a discussion of the distinguishing characteristics of N. gracillima. The danger of confusing this species with the exotic and invasive N. minor is also highlighted. In addition, the present article provides up-to-date global distribution data for N. gracillima, and a distribution map for the species in eastern Canada and the adjacent United States, based on an exhaustive survey of the literature and of specimens in the National Herbarium of Canada (CAN), the Agriculture and Agri-Food Canada Collection of Vascular Plants (DAO), and the Marie-Victorin Herbarium (MT). Detailed notes on the habitat of the only known location for this species in Québec are also included

Additions to the boreal flora of the Northwest Territories with a preliminary vascular flora of Scotty Creek

Volume: 129Start Page: 349End Page: 36