Comparaison de l'accroissement ligneux entre l'éclaircie commerciale par dégagement d'arbres-élites et l'éclaircie par le bas

RÉSUMÉ: Depuis plusieurs décennies, l’exploitation forestière a entraîné d’importantes modifications dans la composition et la structure des forêts du Bas-Saint-Laurent, transformant le paysage en une mosaïque de peuplements réguliers/équiennes. En 2008, une expérience d’éclaircies commerciales, consistant au dégagement de compétiteurs autour d’arbres-élites (AÉ) a été initiée comme première étape de la conversion structurale de ces peuplements réguliers/équiennes vers des peuplements irréguliers/inéquiennes. Ce type d’éclaircie, qui a pour objectif d’accentuer la complexité structurale des peuplements, a récemment été proposé afin de répondre aux exigences de la Loi québécoise sur l’aménagement durable du territoire forestier. Deux types d’éclaircie par AÉ (dégagement de 50 AÉ/ha et 100 AÉ/ha) ainsi qu’une éclaircie par le bas et des blocs témoins ont été implantés dans des plantations d’épinette blanche (Picea glauca) et dans des peuplements issus de régénération naturelle dominés par le sapin baumier (Abies balsamea). En 2014, les placettes-échantillons ont été mesurées pour quantifier l’accroissement ligneux et la diversité structurale. Aucune différence en accroissement en surface terrière n’a été observée entre les traitements. À l’échelle de l’arbre, les AÉ dégagés par l’éclaircie ont montré un accroissement en diamètre à hauteur de poitrine (DHP) significativement plus élevé que les AÉ potentiels dans les placettes-échantillons témoins. Les AÉ ont également eu un accroissement en DHP plus élevé que leurs voisins les plus proches, en plus de faire face à moins de compétition que les AÉ potentiels dans les blocs éclaircis par le bas et les blocs témoins. La complexité des parcelles n’a cependant pas augmenté de façon significative après les éclaircies, le nombre d’AÉ dégagé n’étant probablement pas assez élevé pour changer la structure du peuplement avec une seule éclaircie. Ces résultats indiquent que le temps entre le traitement et l’inventaire forestier (5 ans après traitement) n’est pas suffisant pour que les arbres dépassent leur temps de réaction et atteignent leur pic de croissance. Des interventions subséquentes seront nécessaires pour atteindre les objectifs de diminution d’écart entre la forêt naturelle et la forêt aménagée. -- Mot(s) clé(s) en français : aménagement écosystémique, complexité spatiale, conversion structurale, éclaircie commerciale par dégagement d’arbres-élites, éclaircie commerciale par le bas. -- ABSTRACT: For decades, logging has led to significant changes in composition and structure of the forests of Eastern Canada. In 2008, a commercial thinning trial consisting in the removal of competitors around elite trees (ET) was initiated as the first step of a structural conversion treatment to transform regular/even-aged stands to irregular/uneven-aged stands. Two intensities of thinning by ET release (50 ET/ha and 100 ET/ha) as well as a thinning from below and control blocks were tested in white spruce (Picea glauca) plantations and precommercially thinned balsam fir (Abies balsamea) dominated natural regeneration stands. In 2014, we measured these experimental plots for growth increment and stand structural diversity. At the stand level, no differences were observed amongst the treatments for average cumulative basal area increment since thinning. At the tree level, trees thinned by ET release showed a significantly higher diameter at breast height (DBH) increment than those in the control plots. The released ET also had higher DBH increments than their closest neighbors. The released ET had less competition than the potential ET in both the control and thinned from below plots. The spatial complexity of the plots did not however significantly increase after ET release, the number of ET released is probably not high enough to change the stand structure after only one thinning treatment. These results indicate that 5 years after treatment is not sufficient for trees to reach their peak growth. Further interventions are thus needed to reach the ecosystem-based forest management objectives. -- Mot(s) clé(s) en anglais : commercial thinning by elite tree release, ecosystem-based forest management, structural conversion, spatial complexity, stand structure, thinning from below

Density and diameter distributions of saplings in naturally regenerated and planted coniferous stands in Québec after various approaches of commercial thinning

Key Message A model describing species composition, density and diameter distribution of saplings was developed from operational inventory data. It could be used as an input into growth models calibrated exclusively with merchantable trees to correct some recruitment bias. Important differences in distributions were found between plantations and naturally regenerated stands. Longer-term monitoring would be required to observe the effects of thinning treatments on saplings. Context Saplings play important ecological and structural roles in forest stands. They also constitute the pool of candidate trees that are responsible for recruitment of merchantable sized trees. However, sapling information is often absent from regular inventory measurements (e.g. where no saplings are measured) even though they could be used as inputs in predicting recruitment in merchantable trees. Aims The objectives were to develop models describing density and diameter distribution of saplings from operational inventories, e.g. having only merchantable tree inventory, and to evaluate how stand type (naturally regenerated stands and plantations) and various thinning treatments influence these distributions. Methods Using data from both white spruce (Picea glauca [Moench] Voss) plantations and naturally regenerated balsam fir (Abies balsamea (L.) Mill.) stands having been commercially thinned, a zero-inflated poisson regression was used to model the stand density and a gamma regression to predict the two parameters of the Weibull used to characterize the diameter distribution. Results Despite the fact that the operational inventory data is often limited (e.g. species, dbh, height), the accuracy of the models was good and unbiased. It could be integrated into growth models to complete missing sapling distributions and help to correct some recruitment bias. Important differences in species composition, density and diameter distribution were found between plantations and naturally regenerated stands, but only a moderate response in diameter distribution was observed with thinning treatments. Conclusion These models will enable managers to estimate saplings in intermediate aged softwood forests of eastern Quebec using harvesting inventories or National Forest Inventory. Characterization of differences between plantations and naturally regenerated stands will be useful for integrating intensive plantation silviculture with ecosystem-based management. Longer-term follow-up would be needed to better evaluate the effects of thinning treatments. -- Keywords : Stand structure ; Diameter distribution ; Weibull distribution ; White spruce plantation ; Naturally regenerated softwood stand ; Thinning treatment

Guidelines for the use and interpretation of assays for monitoring autophagy (4th edition)1.

In 2008, we published the first set of guidelines for standardizing research in autophagy. Since then, this topic has received increasing attention, and many scientists have entered the field. Our knowledge base and relevant new technologies have also been expanding. Thus, it is important to formulate on a regular basis updated guidelines for monitoring autophagy in different organisms. Despite numerous reviews, there continues to be confusion regarding acceptable methods to evaluate autophagy, especially in multicellular eukaryotes. Here, we present a set of guidelines for investigators to select and interpret methods to examine autophagy and related processes, and for reviewers to provide realistic and reasonable critiques of reports that are focused on these processes. These guidelines are not meant to be a dogmatic set of rules, because the appropriateness of any assay largely depends on the question being asked and the system being used. Moreover, no individual assay is perfect for every situation, calling for the use of multiple techniques to properly monitor autophagy in each experimental setting. Finally, several core components of the autophagy machinery have been implicated in distinct autophagic processes (canonical and noncanonical autophagy), implying that genetic approaches to block autophagy should rely on targeting two or more autophagy-related genes that ideally participate in distinct steps of the pathway. Along similar lines, because multiple proteins involved in autophagy also regulate other cellular pathways including apoptosis, not all of them can be used as a specific marker for bona fide autophagic responses. Here, we critically discuss current methods of assessing autophagy and the information they can, or cannot, provide. Our ultimate goal is to encourage intellectual and technical innovation in the field

Comparaison de l'accroissement ligneux entre l'éclaircie commerciale par dégagement d'arbres-élites et l'éclaircie par le bas

RÉSUMÉ: Depuis plusieurs décennies, l’exploitation forestière a entraîné d’importantes modifications dans la composition et la structure des forêts du Bas-Saint-Laurent, transformant le paysage en une mosaïque de peuplements réguliers/équiennes. En 2008, une expérience d’éclaircies commerciales, consistant au dégagement de compétiteurs autour d’arbres-élites (AÉ) a été initiée comme première étape de la conversion structurale de ces peuplements réguliers/équiennes vers des peuplements irréguliers/inéquiennes. Ce type d’éclaircie, qui a pour objectif d’accentuer la complexité structurale des peuplements, a récemment été proposé afin de répondre aux exigences de la Loi québécoise sur l’aménagement durable du territoire forestier. Deux types d’éclaircie par AÉ (dégagement de 50 AÉ/ha et 100 AÉ/ha) ainsi qu’une éclaircie par le bas et des blocs témoins ont été implantés dans des plantations d’épinette blanche (Picea glauca) et dans des peuplements issus de régénération naturelle dominés par le sapin baumier (Abies balsamea). En 2014, les placettes-échantillons ont été mesurées pour quantifier l’accroissement ligneux et la diversité structurale. Aucune différence en accroissement en surface terrière n’a été observée entre les traitements. À l’échelle de l’arbre, les AÉ dégagés par l’éclaircie ont montré un accroissement en diamètre à hauteur de poitrine (DHP) significativement plus élevé que les AÉ potentiels dans les placettes-échantillons témoins. Les AÉ ont également eu un accroissement en DHP plus élevé que leurs voisins les plus proches, en plus de faire face à moins de compétition que les AÉ potentiels dans les blocs éclaircis par le bas et les blocs témoins. La complexité des parcelles n’a cependant pas augmenté de façon significative après les éclaircies, le nombre d’AÉ dégagé n’étant probablement pas assez élevé pour changer la structure du peuplement avec une seule éclaircie. Ces résultats indiquent que le temps entre le traitement et l’inventaire forestier (5 ans après traitement) n’est pas suffisant pour que les arbres dépassent leur temps de réaction et atteignent leur pic de croissance. Des interventions subséquentes seront nécessaires pour atteindre les objectifs de diminution d’écart entre la forêt naturelle et la forêt aménagée. -- Mot(s) clé(s) en français : aménagement écosystémique, complexité spatiale, conversion structurale, éclaircie commerciale par dégagement d’arbres-élites, éclaircie commerciale par le bas. -- ABSTRACT: For decades, logging has led to significant changes in composition and structure of the forests of Eastern Canada. In 2008, a commercial thinning trial consisting in the removal of competitors around elite trees (ET) was initiated as the first step of a structural conversion treatment to transform regular/even-aged stands to irregular/uneven-aged stands. Two intensities of thinning by ET release (50 ET/ha and 100 ET/ha) as well as a thinning from below and control blocks were tested in white spruce (Picea glauca) plantations and precommercially thinned balsam fir (Abies balsamea) dominated natural regeneration stands. In 2014, we measured these experimental plots for growth increment and stand structural diversity. At the stand level, no differences were observed amongst the treatments for average cumulative basal area increment since thinning. At the tree level, trees thinned by ET release showed a significantly higher diameter at breast height (DBH) increment than those in the control plots. The released ET also had higher DBH increments than their closest neighbors. The released ET had less competition than the potential ET in both the control and thinned from below plots. The spatial complexity of the plots did not however significantly increase after ET release, the number of ET released is probably not high enough to change the stand structure after only one thinning treatment. These results indicate that 5 years after treatment is not sufficient for trees to reach their peak growth. Further interventions are thus needed to reach the ecosystem-based forest management objectives. -- Mot(s) clé(s) en anglais : commercial thinning by elite tree release, ecosystem-based forest management, structural conversion, spatial complexity, stand structure, thinning from below

Influencing plantation stand structure through close-to-nature silviculture

International audienceNew silvicultural practices to meet the requirements of ecosystem-based forest management are being adopted operationally, even if the long-term outcomes remain unknown. In eastern Quebec, Canada, the conversion of plantations from even-aged to irregular or uneven-aged stands is being carried out in 10% of commercial thinning operations. Existing growth and yield simulators cannot be used to forecast stand development. Here we apply a novel individual tree-level simulator to plantations characterized by high levels of natural regeneration ingrowth, such as those observed in Quebec. The simulator user can either choose distance-dependent or distance-independent competition indices, depending on user preference or simulation needs. Calibration statistics and validation results indicate that both versions perform very well. When applied to operational silvicultural scenarios, the simulator shows that thinning does not influence total stand yield; however, tree spatial aggregation does change. Moreover, the variability among the different simulation runs is greater for spatial statistics than for stand yield. Overall, thinning from below has the greatest effect on stand structure, whereas the smallest is from early crop tree release, used as the initial conversion step. This pattern implies that the first and second thinnings of the conversion process towards irregular or uneven-aged stands may not have a major effect on stand structure. In the case of the conversion process, the consequences for stand structure must thus be viewed as a longer-term issue. More importantly, the conversion process does not reduce stand yield, thereby reducing one of the key concerns of forest managers

Guidelines for the use and interpretation of assays for monitoring autophagy (4th edition)

In 2008, we published the first set of guidelines for standardizing research in autophagy. Since then, this topic has received increasing attention, and many scientists have entered the field. Our knowledge base and relevant new technologies have also been expanding. Thus, it is important to formulate on a regular basis updated guidelines for monitoring autophagy in different organisms. Despite numerous reviews, there continues to be confusion regarding acceptable methods to evaluate autophagy, especially in multicellular eukaryotes. Here, we present a set of guidelines for investigators to select and interpret methods to examine autophagy and related processes, and for reviewers to provide realistic and reasonable critiques of reports that are focused on these processes. These guidelines are not meant to be a dogmatic set of rules, because the appropriateness of any assay largely depends on the question being asked and the system being used. Moreover, no individual assay is perfect for every situation, calling for the use of multiple techniques to properly monitor autophagy in each experimental setting. Finally, several core components of the autophagy machinery have been implicated in distinct autophagic processes (canonical and noncanonical autophagy), implying that genetic approaches to block autophagy should rely on targeting two or more autophagy-related genes that ideally participate in distinct steps of the pathway. Along similar lines, because multiple proteins involved in autophagy also regulate other cellular pathways including apoptosis, not all of them can be used as a specific marker for bona fide autophagic responses. Here, we critically discuss current methods of assessing autophagy and the information they can, or cannot, provide. Our ultimate goal is to encourage intellectual and technical innovation in the field

Guidelines for the use and interpretation of assays for monitoring autophagy (4th edition)

International audienceIn 2008, we published the first set of guidelines for standardizing research in autophagy. Since then, this topic has received increasing attention, and many scientists have entered the field. Our knowledge base and relevant new technologies have also been expanding. Thus, it is important to formulate on a regular basis updated guidelines for monitoring autophagy in different organisms. Despite numerous reviews, there continues to be confusion regarding acceptable methods to evaluate autophagy, especially in multicellular eukaryotes. Here, we present a set of guidelines for investigators to select and interpret methods to examine autophagy and related processes, and for reviewers to provide realistic and reasonable critiques of reports that are focused on these processes. These guidelines are not meant to be a dogmatic set of rules, because the appropriateness of any assay largely depends on the question being asked and the system being used. Moreover, no individual assay is perfect for every situation, calling for the use of multiple techniques to properly monitor autophagy in each experimental setting. Finally, several core components of the autophagy machinery have been implicated in distinct autophagic processes (canonical and noncanonical autophagy), implying that genetic approaches to block autophagy should rely on targeting two or more autophagy-related genes that ideally participate in distinct steps of the pathway. Along similar lines, because multiple proteins involved in autophagy also regulate other cellular pathways including apoptosis, not all of them can be used as a specific marker for bona fide autophagic responses. Here, we critically discuss current methods of assessing autophagy and the information they can, or cannot, provide. Our ultimate goal is to encourage intellectual and technical innovation in the field