by Marie-Claude Boileau | 15 August 2023
Published in Journal of Plant Hydraulics 9: 001.
Vulnerability curves to cavitation (VC) and their derived parameters, such as P50, are increasingly used and reported to assess forest vulnerability to drought and predict forest responses to climate change. Forest practitioners and policy-makers are encouraged to rely on these parameters to support species selection based on their sensitivity to drought. However, in the majority of studies, we consider that the variability of VC parameters is not clearly reported nor considered, which can lead to counterproductive decisions. In this opinion paper, we demonstrate the importance of precisely reporting the variability around VC parameters and the sources of this variability (plant materials, methods, etc.). We also identify the information that should be provided when reporting mean values of VC parameters. To support our argument, we built VCs for three Picea species and Pinus strobus, using different methods, and compared the value of P50 determined in our experiments with values from a literature review.
by Marie-Claude Boileau | 9 August 2023
Published in Forest Ecology and Management 546(2023): 121298. https://doi.org/10.1016/j.foreco.2023.121298
Global change is reshaping climatic conditions at a tempo that exceeds natural migration rates for most tree species. As climate change amplifies the disparity between species’ adaptive capacity and local climates, tree populations risk becoming geographically stranded in increasingly unsuitable conditions. This mismatch may cause catastrophic losses of key forest ecosystem services such as carbon sequestration, habitat provisioning, and forest products. In response, forest managers and researchers are developing a suite of climate-adaptive strategies designed to sustain forest diversity and function. Among these, forest assisted migration (FAM) involves the movement of planting stock from source populations to locations either within or beyond their current ranges. The goal is to establish forests that can survive in today’s climate and expected to thrive in future conditions, thereby sustaining ecosystem good and services. Because FAM is still in its infancy, implementation is limited by many uncertainties. Climatically derived seed sourcing is needed to ensure that planting stock possesses the ecophysiological amplitude to withstand both current and future climatic conditions at the destination site. Additionally, more knowledge about the impacts of local herbivores and intraspecific competition are needed because these drivers will co-regulate seedling success along with climate. Practically, these uncertainties must be addressed to instill in managers sufficient confidence that FAM investments will fulfill long-term management and societal goals relative to other silvicultural approaches.
The Desired REgeneration through Assisted Migration (DREAM) framework is an international collaboration that uses basic and applied research to reduce these uncertainties and derive climate-informed planting approaches. DREAM is self-reinforcing in that each step in the process informs and strengthens subsequent phases. Namely, it sources seed in a climatically informed manner, experimentally tests this sourced stock to probe for physiological maladaptation under controlled settings, grows the stock in the field under a range of silvicultural scenarios, and finally forecasts long-term outcomes using models parameterized from the controlled- and field-tests. In this paper, we describe the DREAM framework and illustrate aspects of its implementation drawing from two experimental sites: one in Québec, Canada and one in Wisconsin, USA. Moreover, we place the DREAM study into the broader FAM context by briefly contrasting it with other operational examples throughout North America. Knowledge gained from this research-management collaboration will expand current reforestation paradigms to include future climate-adaptive ones that aim to use the right seed, planted in the right places, under the right conditions.
by Claire Morin | 4 August 2023
The purpose of this management framework of the Ministère de l’Environnement, de la Lutte contre les changements climatiques, de la Faune et des Parcs (MELCCFP) is to help determine the issues related to harmonizing uses in the targeted territories, the orientations the MELCCFP intends to pursue and possible solutions to address the issues raised by the local stakeholders concerned.
The proposed management framework applies more specifically to salmon rivers in structured territories where agreements with the MELCCFP are in place to promote access to fishing.
by Marie-Claude Boileau | 28 July 2023
Published in Canadian Journal of Forest Research 00(2023) : 1-16. https://doi.org/10.1139/cjfr-2023-0062
Saplings (tree species whose diameter at breast height ranges from 1.1 to 9.0 cm) are important in forest growth and development. Their abundance and density can lead to specific forest successional trajectories and ecosystem characteristics. Yet, the consideration of saplings in forest management planning is a relatively new topic and is still rarely included in forest growth models. We developed sapling density models for 10 species groups with the objective of providing forest managers with additional tools to support the development of more precise prediction systems. We used dendrometric and environmental variables to model sapling density and species-wise density ratios. We evaluated Poisson and gamma regressions for the modelling of sapling density and zero-inflated logistic regressions to model species ratios. We used repeated measurements (from 1982 to 2019) from permanent sample plots located in hardwood forests in northeastern North America. Our results show that the gamma regression was superior to the Poisson regression. The cross-validated mean bias using gamma regression was 55 stems·ha−1 with a relative percentage error of 2.5% and an R2 of 0.43. The species-wise sapling density ratio model had an overall R2 of 0.93, and the species-wise mean R2 ranged between 0.90 and 0.96. Among the examined model covariates, stem density of merchantable-sized trees and latitude were significant in both models. We believe that the models we developed can be useful for forest management planning and sustainable merchantable production.
by Marie-Claude Boileau | 28 July 2023
Published in Forestry 2023(cpad029). https://doi.org/10.1093/forestry/cpad029
Tree recruitment is affected by numerous biotic and abiotic factors, including climate. However, the relative importance of climate variables in empirical models of tree recruitment remains to be evaluated. We fitted models of tree recruitment to 26 species in the province of Quebec, Canada. For a better understanding of the recruitment process, we used a two-part model to distinguish recruitment occurrence from abundance. The relative importance of the different variables was assessed using Akaike weights. Our main hypothesis was that climate is one of the major drivers of tree recruitment. Our results showed that growing degree-days counted among the major drivers of recruitment occurrence but not of recruitment abundance. Stand variables, such as the presence and abundance of adult trees of the species, and broadleaved and coniferous basal areas were found to be relatively more important than all the climate variables for both recruitment occurrence and abundance. Species occupancy within a 10-km radius also had a significant effect on recruitment occurrence for two-thirds of the species, but it was less important than growing degree-days and other stand variables. Climate change is expected to improve the suitability of habitats located at the northern edge of species distributions. However, our model predictions point to a low probability of colonization in newly suitable habitats in the short term.
