Louis De Grandpré, Maryse Marchand, Daniel Kneeshaw, David Paré, Dominique Boucher, Stéphane Bourassa, David Gervais, Martin Simard, Jacob M. Griffin, Deepa Pureswaran. Defoliation-induced changes in foliage quality may trigger broad-scale insect outbreaks. 2022. Community Ecology 5:463
DOI : 10.1038/s42003-022-03407-8
Top-down effects, like predation, are drivers of insect outbreaks, but bottom-up effects, like host nutritional quality, also influence outbreaks and could in turn be altered by insect-caused defoliation. We evaluated the prediction that herbivory leads to a positive feedback on outbreak severity as nutrient concentration in plant tissues increases through improved soil nutrient availability from frass and litter deposition. Over seven years of a spruce budworm outbreak, we quantified litter nutrient fluxes, soil nitrogen availability, and host tree foliar nutrient status along a forest susceptibility gradient. As the outbreak progressed, both soil nutrient fluxes and availability increased which, in turn, improved foliage quality in surviving host trees. This is consistent with boosted insect fitness and increased population density and defoliation as outbreaks grow. Our results suggest that a positive bottom-up feedback to forest ecosystems from defoliation may result in conditions favorable to self-amplifying population dynamics in insect herbivores that can contribute to driving broad-scale outbreaks.
Maryse Marchand, Jeanne Moisan Perrier, Louis-Étienne Robert, Loïc D'Orangeville, Mathieu Bouchard, Daniel Kneeshaw, Louis De Grandpré. Forest Structure and Composition Diverge Following Harvesting Compared to a Spruce Budworm Choristoneura fumiferana (Clem.) Outbreak 2022. Frontiers in forests and global change 5
DOI : 10.3389/ffgc.2022.680262
Balsam fir (Abies balsamea) is the most vulnerable species to the spruce budworm (Choristoneura fumiferana), one of the most devastating defoliators in the world. For decades, pest managers have advocated for reducing its abundance in the landscape to minimize losses to the spruce budworm (SBW). Although reduction of fir occurred during the endemic phase of the SBW cycle, there is little information about the extent to which this general principle (reduction of fir) was applied during an outbreak and whether it occurs at both stand and landscape levels. The objective of this paper is to compare the effect of insect and harvest disturbances on forest structure during the 1970–80s outbreak in Québec. We evaluate whether, (i) forest management activities targeted fir forests and whether patch size of host species influences management or SBW disturbance, (ii) SBW outbreaks and logging have similar or divergent effects on forest composition. Although data are from an earlier outbreak, they are at a scale rarely studied and will be useful in guiding decisions made at larger scales in the current and future outbreaks. Our results show that spruce was targeted preferentially by harvesting (up to 69% of plots) during the outbreak period, while it represented less than one third of plots defoliated by the SBW. On the other hand, fir stands represented up to 75% of plots that were defoliated by the SBW but less than 35% of plots that underwent harvesting. Harvesting targeted large blocks of spruce forest more than large blocks of fir-dominated forest while the opposite was observed for the SBW. In terms of regeneration, SBW tends to reduce fir and favor spruce recruitment, along with non-host species, whereas the opposite tendency was observed following harvesting. In terms of spatial organization of stands, our results support the suggestion that small stands of fir and large stands of spruce undergo the least SBW damage. Thus, in order to attenuate SBW impacts in the future, efforts should be made to ensure that spruce recruitment is favored and that its abundance increases at both the stand and landscape scale.
Christoforos Pappas, Yves Bergeron, Nicolas Bélanger, Han Y. H. Chen, Philip G. Comeau, Sylvain Delagrange, Olivier Blarquez, Amanda Diochon, Loïc D’Orangeville, Pierre Drapeau, Louis Duchesne, Elise Filotas, Fabio Gennaretti, Benoit Lafleur, Louis De Grandpré, Annie DesRochers, David Langor, François Lorenzetti, Charles Nock, Daniel Houle, Miguel Montoro Girona, Christian Messier, Barb R. Thomas, Simon Lebel Desrosiers, Rongzhou Man, Timothy Work, Daniel Kneeshaw. Smartforests Canada: A Network of Monitoring Plots for Forest Management Under Environmental Change. 2021. Climate-Smart Forestry in Mountain Regions 521-543
DOI : 10.1007/978-3-030-80767-2_16
Monitoring of forest response to gradual environmental changes or abrupt disturbances provides insights into how forested ecosystems operate and allows for quantification of forest health. In this chapter, we provide an overview of Smartforests Canada, a national-scale research network consisting of regional investigators who support a wealth of existing and new monitoring sites. The objectives of Smartforests are threefold: (1) establish and coordinate a network of high-precision monitoring plots across a 4400 km gradient of environmental and forest conditions, (2) synthesize the collected multivariate observations to examine the effects of global changes on complex above- and belowground forest dynamics and resilience, and (3) analyze the collected data to guide the development of the next-generation forest growth models and inform policy-makers on best forest management and adaptation strategies. We present the methodological framework implemented in Smartforests to fulfill the aforementioned objectives. We then use an example from a temperate hardwood Smartforests site in Quebec to illustrate our approach for climate-smart forestry. We conclude by discussing how information from the Smartforests network can be integrated with existing data streams, from within Canada and abroad, guiding forest management and the development of climate change adaptation strategies.
Marion Germain, Daniel Kneeshaw, Mélanie Desrochers, Patrick James, Udayalaksmi Vepakoma, Louis De Grandpré, Jean-François Poulin, Marc-André Villard. Insectivorous songbirds as early indicators of future defoliation by spruce budworm. 2021. Landscape Ecology 36:3013-3027
DOI : 10.1007/s10980-021-01300-z
Although the spatiotemporal dynamics of spruce budworm outbreaks have been intensively studied, forecasting outbreaks remains challenging. During outbreaks, budworm-linked warblers (Tennessee, Cape May, and bay-breasted warbler) show a strong positive response to increases in spruce budworm, but little is known about the relative timing of these responses.
Brian Sturtevant, Enrique Doblas-Miranda, Patrick James, Dominique Tardif, Philip J. Burton, Daniel Kneeshaw, Louis De Grandpré. The Vision of Managing for Pest-Resistant Landscapes: Realistic or Utopic? 2021. Forest Entomology
DOI : 10.1007/s40725-021-00140-z
Purpose of Review
Forest managers have long suggested that forests can be made more resilient to insect pests by reducing the abundance of hosts, yet this has rarely been done. The goal of our paper is to review whether recent scientific evidence supports forest manipulation to decrease vulnerability. To achieve this goal, we first ask if outbreaks of forest insect pests have been more severe in recent decades. Next, we assess the relative importance of climate change and forest management–induced changes in forest composition/structure in driving these changes in severity.
Forest structure and composition continue to be implicated in pest outbreak severity. Mechanisms, however, remain elusive. Recent research elucidates how forest compositional and structural diversity at neighbourhood, stand, and landscape scales can increase forest resistance to outbreaks. Many recent outbreaks of herbivorous forest insects have been unprecedented in terms of duration and spatial extent. Climate change may be a contributing factor, but forest structure and composition have been clearly identified as contributing to these unprecedented outbreaks.
Current research supports using silviculture to create pest-resistant forest landscapes. However, the precise mechanisms by which silviculture can increase resistance remains uncertain. Further, humans tend to more often create pest-prone forests due to political, economic, and human resistance to change and a short-sighted risk management perspective that focuses on reactive rather than proactive responses to insect outbreak threats. Future research efforts need to focus on social, political, cultural, and educational mechanisms to motivate implementation of proven ecological solutions if pest-resistant forests are to be favoured by management.
Eliana Molina, Osvaldo Valeria, Louis De Grandpré, Jorge Andres Ramirez, Dominic Cyr, Yan Boulanger. Projecting future aboveground biomass and productivity of managed eastern Canadian mixedwood boreal forest in response to climate change 2021. For. Ecol. Manage. 119016
DOI : 10.1016/j.foreco.2021.119016
Eastern Canadian boreal forests are mainly influenced by natural wildfires and forest management activities. To evaluate forest dynamics under possible interactions among fire and timber harvest in a future climate warming scenario (RCP 2.6, RCP 4.5 and RCP 8.5) the forest landscape model Landis II was used to simulate the dynamics of the 78000 km2 of boreal forests in eastern Canada. Forest management intensity scenarios were modeled considering the changes in the annual harvested area (0.5%, 1%, and 2%) and the age that conifers and hardwoods can be harvested (50 and 30 years, 70 and 50 years, and 90 and 70 years). The results of the 300-year model projections implied that both forest management intensity and climatic scenarios explained most of the variability in aboveground biomass, aboveground net primary productivity and forest composition. Forest management seems to be the most important factor that modified the landscape in the southern forests because there were scheduled stands with the age and composition required by each harvesting prescription to deal with the annual allowable cut volume. On the contrary, in the northern forests there was a mixed effect of climate change and forest management because many of the areas suitable for harvesting were previously burned limiting the amount of area available for harvesting. Thus, although it is expected an increase in wildfire area burned due to climate change, the intensification of forest management seems to be the most important driver of the increase of hardwoods and mixed stands and the decrease of conifers stands on the mixedwood boreal landscape, mainly in the southern forests. These results suggest that timber supply would be at risk in the Abitibi Plain, therefore, some strategies should be applied to adapt forest management to climate change.
Lorena Balducci, Angelo Fierravanti, Sergio Rossi, Sylvain Delzon, Daniel Kneeshaw, Annie Deslauriers, Louis De Grandpré. The paradox of defoliation: Declining tree water status with increasing soil water content. 2020. Agric. For. Meteorol. 290:108025
DOI : 10.1016/j.agrformet.2020.108025
Defoliation can enhance tree water status by reducing canopy transpiration under drought. During long-lasting insect outbreaks however, this effect can be transient as reduced foliage affects not only transpiration but also the entire soil-plant-atmosphere continuum. In this study, we investigated the effects of defoliation and vapor pressure deficit (VPD) on plant and soil water status in balsam fir and black spruce defoliated by spruce budworm, Choristoneura fumiferana (Clemens). We sampled 48 fir trees and 36 spruce trees subjected to differing severities of defoliation. In May–September 2014 and 2015, we monitored the relative shoot water content (RWC) and soil volumetric water content (VWC), and midday shoot water potential (?md, only in 2015). We applied linear mixed models (LMMs) to assess changes in RWC, ?md, and VWC to defoliation and VPD and we ran structural equation models (SEM) to determine the causal relationships between the measured variables in relation to defoliation and VPD. In LMMs models, defoliation and VPD, as individual factors, reduced ?md in both balsam fir and pooled species models but did not affect RWC. Defoliation alone increased VWC in balsam fir and in pooled models. We observed no interaction between VPD and defoliation on tree water status, but significant effect on VWC (in balsam fir and pooled models), indicating that both factors had independent and additive effects on plants but not on soil. However, in SEM models, RWC was negatively correlated to defoliation, suggesting a hydraulic safety margin. Under conditions of multiple-years of natural defoliation during a spruce budworm outbreak, the decrease in ?md reflects the amount of internal water capacitance that could be caused by both a lower ?md due to larval feeding and a negative feedback between defoliation and xylem vulnerability.
Zelin Liu, Changhui Peng, Jean-Noël Candau, Timothy Work, Louis De Grandpré, Xiaolu Zhou, Daniel Kneeshaw. Aerial spraying of bacterial insecticides to control spruce budworm
defoliation leads to reduced carbon losses. 2020. Ecosphere 11(1):e02988
DOI : 10.1002/ecs2.2988
Spruce budworm (SBW) outbreaks are a major natural disturbance in boreal forests of eastern North America. During large?scale infestations, aerial spraying of bacterial insecticides is used to suppress local high?density SBW populations. While the primary goal of spraying is the protection of wood volume for later harvest, it should also maintain carbon stored in trees. This study provides the first quantitative analysis of the efficacy of aerial spraying against SBW on carbon dynamics in balsam fir, spruce, and mixed fir–spruce forests. In this study, we used the TRIPLEX?Insect model to simulate carbon dynamics with and without spray applications in 14 sites of the boreal forest located in various regions of Québec. We found that the efficacy of aerial spraying on reducing annual defoliation was greater in the early stage (<5 yr since the outbreak began) of the outbreak than in later (5–10 yr since the outbreak began) stage. Our results showed that more net ecosystem productivity is maintained in balsam fir (the most vulnerable species) than in either spruce or mixed fir–spruce forests following spraying. Also, average losses in aboveground biomass due to the SBW following spraying occurred more slowly than without spraying in balsam fir forests. Our findings suggest that aerial spraying could be used to maintain carbon in conifer forests during SBW disturbances, but that the efficacy of spray programs is affected by host species and stage of the SBW outbreak.
David L.P. Correia, Wassim Bouachir, David Gervais, Deepa Pureswaran, Daniel Kneeshaw, Louis De Grandpré. Leveraging artificial intelligence for large-scale plant phenology studies from noisy time-lapse images. 2020. IEEE Access 8(1):13151-13160
DOI : 10.1109/ACCESS.2020.2965462
Phenology has become a field of growing importance due to the increasingly apparent impacts of climate change. However, the time-consuming, subjective and tedious nature of traditional human field observations have hindered the development of large-scale phenology networks. Such networks are rare and rely on time-lapse cameras and simplistic color indexes to monitor phenology. To automatize rapid, detailed and repeatable analyzes, we propose an Artificial Intelligence (AI) framework based on machine learning and computer vision techniques. Our approach extracts multiple ecologically-relevant indicators from time-lapse digital photography datasets. The proposed framework consists of three main components: (i) a random forest model to automatically select relevant images based on color information; (ii) a convolutional neural network (CNN) to identify and localize open tree buds; and (iii) a density-based spatial clustering algorithm to cluster open bud detections across the time-series. We tested this framework on a dataset including thousands of black spruce and balsam fir tree images captured using our phenological camera network. The performed experiments showed the efficiency of the proposed approach under challenging perturbation factors, such as significant image noise. Our framework is exceedingly faster and more accurate than human analysts, reducing the time-series processing time from multiple days to under an hour. The proposed methodology is particularly appropriate for large-scale and long-term analyzes of ecological imagery datasets. Our work demonstrates that the use of computer vision and machine learning methods represents a promising direction for the implementation of national, continental, or even global plant phenology networks.
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Sophie Perigon, Maryse Marchand, Deepa Pureswaran, Dominique Boucher, Daniel Kneeshaw, Martin-Philippe Girardin, Louis De Grandpré. Adverse climatic periods precede and amplify defoliator?induced tree mortality in eastern boreal North America. 2019. Journal of Ecology 107(1):452-467
DOI : 10.1111/1365-2745.13012
- As major alterations are occurring in climate and pest ranges, it is imperative to evaluate their combined contribution to tree mortality in order to propose mitigation measures and limit losses in forest productivity. The objective of this study was to explore the association between declines in tree growth resulting from climatic and biotic (spruce budworm) disturbances, and their interactions on tree mortality of two dominant tree species, Abies balsamea and Picea mariana, of the eastern North?American boreal forest.
- We disentangle the influences of abiotic and biotic components on growth through a combination of model?data comparison techniques. First, we characterized the variability in tree growth and mortality in the study area using a network of tree?ring width measurements collected from living and dead trees. Subsequently, a bioclimatic simulation model was used to estimate the past annual, nonlinear, responses of stand?level net primary production (NPP) to climate variability (period 1902–2012). From these two data sources, we defined the biotic stress events as the variance in the tree?ring data unexplained by the bioclimatic forest growth simulation.
- Throughout the 20th century, two periods of adverse climatic conditions preceded spruce budworm outbreaks episodes and induced tree mortality. Climatic stress events were associated with cold springs, warmer than average summers. We found that past stress history in interaction with tree characteristics and species predisposed trees to mortality. In addition, co?occurring events (climatic and biotic) increased the severity of mortality episodes.
- Synthesis. Our study challenges the belief that spruce budworm outbreak is the primary driver of broad?scale tree mortality in eastern boreal forest. Rather, tree mortality is the result of cumulative events that combine unfavourable conditions for growth, resulting in loss of tree vigour and subsequently, mortality. Co?occurrence of stresses in the future may lead to more severe episodes of mortality, as extreme climatic events become more frequent.
Sabrina Brisson, Kaysandra Waldron, Daniel Kneeshaw, Louis De Grandpré. Facteurs de mortalité chez la régénération préétablie en contexte d'épidémie de tordeuse des bourgeons de l'épinette et de coupes de récupération 15e colloque annuel du CEF, Université de Sherbrooke, Québec (2022-09-28)
Louis De Grandpré Changements climatiques, tordeuse des
bourgeons de l épinette et impacts potentiels sur
la composition de la forêt boréale du Québec Colloques du SCF-CFL (2021-01-27)
Daniel Kneeshaw, Louis De Grandpré. PRÉSENTATION ANNULÉE :
Influence des stress climatiques et biotiques sur le processus de mortalité de l'épinette noire (Picea mariana) dans la forêt boréale du Québec 21e colloque de la Chaire AFD. Université du Québec en Abitibi-Témiscamingue, Rouyn-Noranda, Québec. (2019-11-30)
Philippe Marchand, Miguel Montoro Girona, Mathieu Bouchard, Élise Filotas, Hubert Morin, Louis De Grandpré, Yves Bergeron, Pierre Therrien, Anouschka R. Hof, Matthew Duveneck. Projections de l’activité de la tordeuse des bourgeons de l’épinette dans un contexte de changement climatique 21e colloque de la Chaire AFD. Université du Québec en Abitibi-Témiscamingue, Rouyn-Noranda, Québec. (2019-11-30)
Louis De Grandpré Des événements climatiques extrêmes précèdent la mortalité des arbres induite par la tordeuse des bourgeons de l’épinette dans l’est de la forêt boréale Midi-foresterie (2016-03-22)
Eliana Molina, Osvaldo Valeria, Louis De Grandpré. L'évolution du paysage forestier à l'échelle régionale dans le nord-ouest de la région de l’Abitibi (Québec) au cours des 25 dernières années 14e colloque de la Chaire AFD. Université du Québec en Abitibi-Témiscamingue, Rouyn-Noranda, Québec. (2012-11-29)
Louis De Grandpré S’inspirer de l’empreinte de perturbations partielles pour aménager la pessière à mousse de l’est. S’inspirer de l’empreinte de perturbations partiel (2004-03-30)