Anthropogenic and climate impacts on subarctic forests in the Nain region, Nunatsiavut: Dendroecological and historical approaches

Abstract

Several recent dendrochronological, macrofossil and palynological studies have surveyed modern spruce forests at multiple locations in the Nain region of coastal Nunatsiavut (north-central Labrador) in order to reconstruct past forest composition, growth rates, species diversity and harvesting patterns. The present paper synthesizes original and previously collected data to evaluate the extent to which the dynamics of the region's spruce forests over the past five centuries have been related to anthropogenic impacts. In three key case studies, Picea growth release events demonstrate multiple isolated forest disturbances prior to the late 19th century. In general, these events correspond to the local human settlement history rather than to regional climatic trends, suggesting that ongoing human impacts on the forest extend as far back as the 17th century. Disturbance regimes accelerated by ca 1875 and afterward in all of the study sites. This increase in forest disturbance corresponds to increased demands for wood triggered by socioeconomic changes experienced by the region's Inuit and Settler communities. Ongoing surveys demonstrate the presence of markers of human exploitation of forests throughout the study region, and especially in coastal locations, suggesting that anthropogenic impacts are in fact generalised and not limited to specific areas of recent settlement. RÉSUMÉPlusieurs études dendrochronologiques et paléoécologiques ont récemment porté sur la dynamique forestière dans la région de Nain au Nunatsiavut (centre-nord du Labrador). Ces études ont documenté la composition, le taux de croissance et la diversité des espèces de ces forêts ainsi que les patrons de récolte de bois par les résidents de la région au cours des cinq derniers siècles. La présente étude consiste en une synthèse des données publiées ainsi que de résultats originaux, afin d'évaluer dans quelle mesure la dynamique de la forêt d'épinettes est liée aux impacts anthropiques. Dans les trois études de cas choisies, des événements de détente de croissance radiale de Picea sp. montrent que plusieurs perturbations isolées de la forêt sont survenues avant la fin du XIX e siècle. En général, ces événements correspondaient à des activités anthropiques (remontant au XVII e siècle) plutôt qu'à des tendances climatiques régionales. Le régime des perturbations s'est accéléré vers 1875; cette augmentation est liée à une hausse de la demande en bois due aux changements socio-économiques vécus par les communautés inuit et les colons Européens. Les relevés de terrain en cours mettent en évidence des traces évidentes d'une exploitation forestière à travers la région de Nain et, plus particulièrement, en zone côtière, ce qui suggère que les impacts anthropiques ne se limiteraient pas aux zones spécifiques d'habitation humaine récente.

Evolution of Coastal Subarctic Lakes in the Context of Climatic and Geological Changes and Human Occupation (North-Central Labrador, Canada)

“…As human occupation is evident in the Dog Island area during this period [4,5,10,15,20], the combined influence of anthropogenic activities and associated disturbances in the watershed, climate, and geophysical processes on the physicochemical properties of the lake, including nutrient loading and additional export of sedimentary material, cannot be ruled out. Recently, Roy et al [35] demonstrated that signs of human exploitation of forests around Nain and throughout its archipelago date as far back as the 17th century [5]. The increase in Asterionella formosa species we noted (Figure 7) has also previously been associated with human disturbances, including deforestation activities, which promote the export of nutrients (phosphorus, DOC) to lakes [120,121].…”

“…The scarcity and short time span of the instrumental record (late 19th century), the considerable regional disparities, and the lack of spatial and temporal resolution of palaeoenvironmental reconstructions near settlement areas do not allow us to document, more precisely, the extent and specificity of environmental change in Labrador, particularly in lake ecosystems, in response to late Holocene climatic fluctuations (particularly Medieval Warm Period (MWP), LIA, and recent warming) and anthropogenic forcings. While palaeoenvironmental and geoarchaeological research has demonstrated that anthropogenic activities (e.g., wood harvesting) contributed to the transformation of the terrestrial landscapes of the Nain Archipelago concomitantly with late Holocene climatic variations, notably from the 17th to late 19th century [5][6][7][35][36][37], their effects on aquatic ecosystems have rarely been studied in the region.…”

“…), and willows (Salix spp.) [6,27,29,35]. Graminoids, grasses (Cyperaceae), mosses, and lichens are also present [27].…”

Transpiration and evaporative partitioning at a boreal forest and shrub taiga site in a subarctic alpine catchment, Yukon territory, Canada

“…Warming results in variable changes to land cover and plant communities, but also varying response to disturbance, which has been shown to result in distinct species‐specific responses in T rates (Matheny et al, 2014). Considering the expected increased fire frequency (Baltzer et al, 2021; Kirchmeier‐Young et al, 2017), permafrost degradation (Lawrence et al, 2008), anthropogenic activities (Roy et al, 2021), changes in herbivory intensities (Post et al, 2009) and associated species shifts (Myers‐Smith et al, 2011) across the circumpolar regions, a more comprehensive understanding of above/below canopy evaporative partitioning and species‐specific responses in varying ecosystem structures and under varying climate forcings is critical for future estimates of water availability in these landscapes.…”

“…Considering the expected increased fire frequency (Baltzer et al, 2021;Kirchmeier-Young et al, 2017), permafrost degradation (Lawrence et al, 2008), anthropogenic activities (Roy et al, 2021), changes in herbivory intensities (Post et al, 2009) (Novick et al, 2016). This increase in VPD will increase ET but to varying degrees across ecosystems (Helbig et al, 2020).…”