Boreal forest soils store more carbon than the aboveground vegetation and play a critical role in the global carbon cycle and ecosystem function. Despite their importance, the long-term impacts of forest management on soil organic carbon (SOC) remain unclear, especially in boreal forests with contrasting climatic conditions. This study assesses the effects of commercial thinning on SOC stocks (20-year post-treatment) in black spruce stands across two boreal regions in Québec: the warmer, drier Abitibi and the colder, wetter Cote-Nord, accounting also spatial variability from skidding strips. We measured SOC stocks at three soil depths (forest floor, mineral layer: 0–15 and 15–30 cm) in both thinned and unmanaged stands, using bulk density and SOC concentration. Soil pH, cation exchange capacity (CEC), and macronutrients were also conducted to characterize soil fertility. Thinning had no effect on total SOC stocks of the whole profile in either region, but horizon-specific differences were detected. A decrease in forest floor SOC stocks was observed in Côte-Nord, whereas SOC stocks in Abitibi remained similar. These contrasting outcomes reflect regional differences in soil fertility (higher CEC, potassium in Abitibi) and climatic conditions which may have influenced vegetation regrowth and, consequently, SOC stocks’ recovery over time. Although SOC stocks decreased in skidding strips, their small proportion within the stand minimized their effect on total SOC stocks at the plot level. Overall, the study emphasizes the need to consider climatic and soil context, as well as limited spatial extent of skidding strips, in evaluating silvicultural impacts on boreal carbon sequestration.

Reconstructing past climate conditions in boreal ecosystems remains a complex challenge due to the intricate interactions between both external and internal forcings, ecological dynamics, and methodological constraints. In this study, we present pollen- and chironomid-based temperature reconstructions from five boreal forest sites in eastern Canada, assessing their sensitivities, limitations, and potential for improving paleoclimatic interpretations. By applying multiple inference techniques and evaluating their reliability through statistical indices, we identify key internal factors that influence reconstruction accuracy. Our findings reveal that pollen-based temperature estimates are affected by multiple biases, including the impact of forest fires on vegetation dynamics, postglacial migration lags, and uncertainties in the temperature optima of overrepresented taxa. These biases vary considerably across different vegetation zones. Chironomid-based reconstructions, in contrast, generally exhibit stronger alignment with regional climate trends, but may be sensitive to local, lake-specific conditions. Integrating these insights, we refine the Holocene climatic history of eastern Canada, reconciling discrepancies with previous studies and producing more robust estimates of temperature variations during key climatic intervals, including the deglaciation, the Holocene Thermal Maximum, and the Neoglacial Period. These results enhance our understanding of past climate variability in boreal environments and provide a critical foundation for assessing future ecological responses to ongoing climate change.