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As the Anthropocene tightens its grip on the world, forests are facing escalating disturbance rates, tree mortality, degradation and risks of catastrophic collapses. A popular and controversial proposition is to enhance forests' response diversity by adding novel tree species with missing functional traits through forest assisted migration (FAM). Beyond tests of the survival and growth of southern species or provenances in colder regions and studies of the socio-ecological challenges facing FAM, little interest has been paid to the silvicultural system for FAM implementation. Yet, the topic could influence its biological success, social acceptability, and economic feasibility. For example, southern light-intolerant tree species introduced into northern uneven-aged forests may experience a lack of light availability. Likewise, implementing FAM in clearcuts raises social acceptability issues. The patch-cut system combines advantages of even- and uneven-aged systems useful for FAM; however, perhaps due to the difficulty of its operationalization, it is rarely used. We propose a new way to implement the patch-cut system, enabling from the get-go to plan the location and timing of treatment of each patch in a stand. We discuss the advantages that this revisited patch-cut system presents for FAM: (i) the testing of various planting environments, (ii) easy monitoring in an adaptative management context where each patch is a replicate of a repeated-measure experiment and (iii) low intensity planting for efficient future dispersion of species adapted to a changing climate. We end with a call for the development of an international network of FAM trials within the revised patch-cut system. [ABSTRACT FROM AUTHOR]

Ephemeral ponds in cold and humid forested regions are often vulnerable because of their small size and ephemeral nature. The aim of this study was to identify the geomorphological and meteorological drivers of ephemeral pond hydrology in the forests of cold and humid climates. A multi‐year study of 40 ponds was conducted in the Kenauk forest located in the Canadian Shield of the Outaouais region (Quebec, Canada). Pond bathymetry, mineral and organic sediment thickness, watershed area, slope, canopy cover and maximum depth were measured in‐situ. The spring hydroperiod (the period during which there is water in the ponds between April and October) as well as the surface and groundwater recession rates were measured throughout the study period, from 2016 to 2020. Data from this study show that ponds located at lower altitudes in the landscape are larger, receive water from a larger area, and have longer hydroperiods than ponds located at higher altitudes. The results demonstrated a connection between the ponds and the surrounding aquifer. Spring and early summer precipitation was shown to affect hydroperiods the most, while summer precipitation influenced the presence of water in the ponds from April to October. Winter precipitation appear determinant for pond recession rates. Simple multiple regression models were able to simulate hydroperiods and hydroperiod indices relatively well, but pond recession rates were not well represented by the models. This study brings original multi‐year and multi‐site data identifying parameters and variables that determine ephemeral pond hydrology in cold and humid climates. The results provide new insights into their resilience on the landscape and bring new arguments for their long‐term protection. [ABSTRACT FROM AUTHOR]

Process-based forest growth models with spatially explicit representation are relevant tools to investigate innovative silviculture practices and/or climate change effects because they are based on key ecophysiological processes and account for the effects of local competition for resources on tree growth. Such models are rare and are often calibrated for a very limited number of species and rarely for mixed and/or uneven-aged stands, and none are suitable for the temperate forests of Québec. The aim of this study was to calibrate and evaluate HETEROFOR (HETEROgeneous FORest), a process-based and spatially explicit model based on resource sharing, for 23 functionally diverse tree species in forest stands with contrasting species compositions and environmental conditions in southern Quebec. Using data from the forest inventory of Quebec, we evaluated the ability of HETEROFOR to predict the short-term growth (5–16 years) of these species at the tree and stand levels and the long-term dynamics (120 years) of red and sugar maple stands. The comparison between the prediction quality of the calibration and evaluation datasets showed the robustness of the model performance in predicting individual-tree growth. The model reproduced correctly the individual basal area increment (BAI) of the validation dataset, with a mean Pearson's correlation coefficient of 0.56 and a mean bias of 18 %. Our results also highlighted that considering tree position is of importance for predicting individual-tree growth most accurately in complex stands with both vertically and horizontally heterogeneous structures. The model also showed a good ability to reproduce BAI at the stand level, both for monospecific (bias of - 3.7 %; Pearson's r=0.55) and multi-species stands (bias of - 9.1 %; Pearson's r=0.62). Long-term simulations of red maple and sugar maple showed that HETEROFOR was able to accurately predict the growth (basal area and height) and mortality processes from the seedling stage to the mature stand. Our results suggest that HETEROFOR is a reliable option to simulate forest growth in southern Quebec and to test new forestry practices under future climate scenarios. [ABSTRACT FROM AUTHOR]

Process-based forest growth models with spatially explicit representation are a relevant tool to investigate innovative silviculture practices and/or climate change effects because they are based on key ecophysiological processes and account for the effects of local competition for resources on tree growth. Such models are rare, often calibrated for a very limited number of species and rarely in mixed and/or uneven-aged stands, and none are suitable for the temperate forests of Québec. The aim of this study was to calibrate and evaluate HETEROFOR, a process-based and spatially explicit model based on resource sharing, for 23 functionally diverse tree species in forest stands with contrasting species compositions and environmental conditions in southern Québec. Using data from the forest inventory of Québec, we evaluated the ability of HETEROFOR to predict the short-term growth (5-16 years) of these species at the tree and stand levels, and the long-term dynamics (120 years) of red and sugar maple stands. The comparison between the prediction quality for the calibration and evaluation datasets showed the robustness of the model performance in predicting individual tree growth. The model reproduced correctly individual basal area increment (BAI) of the validation dataset with a mean Pearson’s correlation coefficient of 0.56 and a mean bias of 18%. Our results also highlighted that considering tree position is of importance for predicting individual tree growth most accurately in complex stands with both vertical and horizontal heterogeneous structure. The model also showed a good ability to reproduce BAI at the stand level, both for monospecific (bias of -3.7%, Pearson’s r = 0.55) and multi-species stands (bias of -9.1%, Pearson’s r = 0.62). Long-term simulations of red maple and sugar maple showed that HETEROFOR was able to accurately predict the growth (basal area and height) and mortality processes from the seedling stage to the mature stand. Our results suggest that HETEROFOR is a reliable option to simulate forest growth in southern Québec and test new forestry practices under future climate scenarios. [ABSTRACT FROM AUTHOR]

• Innovative approach using mobile laser scanning for rapid mapping of forest stands. • Forest management, by itself, had a strong effect on tree mortality probability. • Tree death is more likely in uneven-aged stands than in even-aged or unmanaged stands. • Silviculture can be used to cope with the effects of climate change on mortality. With global change, forest trees will be exposed to increasing stress in the coming decades with various studies demonstrating that stress-related mortality will increase in forests. While tree death can be triggered by a single factor, it is often caused by the accumulation and the complex interaction of various stressors. Several silvicultural strategies have been developed to cope with global change but very few studies have addressed the ways in which silvicultural regimes interact with various stressors to influence tree mortality. This lack of research on the effects of forest management regimes on tree mortality may be due to the challenge of acquiring large (or long-term) datasets to assess tree mortality in forests. Within this context and using a mobile terrestrial LiDAR approach for rapid 3D-mapping of forest stands, we aimed to (i) compare recent tree mortality patterns in temperate forests among contrasting forest management regimes (even-aged silviculture, uneven-aged silviculture and unmanaged forests), and (ii) evaluate the relative influence of regeneration harvest severity on tree mortality compared to other spatially explicit factors (i.e., localized competition and slope position) and non-spatially explicit factors (i.e. tree DBH -diameter at breast height- and tree species group). In a permanent sample plot network, we mapped 15 508 dead and living trees (>9.1 cm DBH) within 37 sugar maple-dominated stands: 14 even-aged, 16 uneven-aged and 7 unmanaged stands. We separated the relative role of forest management on individual tree mortality from other factors such as size, species, slope position, and localized competition by modeling the probability of mortality for each tree. Localized competition or slope position were not significant factors describing tree mortality. Results showed that tree mortality was influenced by tree species, DBH and forest management regime. Models indicated that forest management regime, by itself, had a strong effect on tree mortality proportion. Results also indicated that trees in uneven-aged stands had a higher probability of dying than the those in even-aged or unmanaged stands. However, we do not advocate for the replacement of uneven-aged regimes in favour of even-aged ones. Instead, we believe that, in the context of global change, adjustments should be made to uneven-aged regimes to reduce risk of mortality. Moreover, our study reinforces the idea that silviculture can be applied in such a way as to enhance stand resistance and resilience to cope with global change; for example, by influencing size structure and species composition, which greatly influence tree mortality. [ABSTRACT FROM AUTHOR]