Untangling methodological and scale considerations in growth and productivity trend estimates of Canada’s forests
In viewof the economic, social and ecological importance ofCanada’s forest ecosystems, there is a growing interest in studying the responseof these ecosystems to climate change.Accurate knowledge regarding growth trajectories is needed for bothpolicymakers and forestmanagers to ensure sustainability of the forest resource.However, results of previous analyses regarding the sign andmagnitudeof trendshave oftendiverged.Themainobjective of this paperwas to analyse the current state of scientific knowledgeon growth andproductivity trends inCanada’s forests andprovide some explanatory elements for contrasting observations.The threemethods that are commonlyused for assessments of tree growth and forest productivity (i.e. forest inventory data, tree-ring records, and satellite observations)havedifferent underlyingphysiological assumptions andoperate ondifferent spatiotemporal scales,which complicates direct comparisonsof trend values between studies.Withinour systematic reviewof 44peer-reviewed studies, half identified increasing trends for tree growthor forest productivity,while theotherhalf showed negative trends. Biases anduncertainties associatedwith the threemethodsmay explain someof the observeddiscrepancies.Given the complexity of interactions and feedbacksbetween ecosystemprocesses at different scales, researchers should consider the different approaches as complementary, rather than contradictory.Here,wepropose the integrationof thesedifferent approaches into a single framework that capitalizes on their respective advantageswhile limiting associatedbiases.Harmonizationof sampling protocols and improvementof data processing andanalyseswould allow formore consistent trend estimations, therebyproviding greater insight into climate-change related trends in forest growth and productivity. Similarly, amore opendata-sharing culture should speed-upprogress in thisfield of research.