Visual assessment of tree vigour in Canadian northern hardwood forests: The need for a simplified system

Moreau, Guillaume; Cecil-Cockwell, Malcolm J.L.; Pothier, David D.; Achim, Alexis; Bédard, Steve; Guillemette, François; Caspersen, John P.

doi:10.1016/j.foreco.2022.120720

Cited by 6 publications

(17 citation statements)

References 30 publications

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“…During each inventory, the tree species was recorded and the DBH was measured using a diameter tape. Tree vigour was assessed by measuring crown dieback, which is the proportion of crown lost to dieback or breakage [11]. The death of lower branches due to self-pruning was not considered.…”

Section: Experimental Design and Data Collectionmentioning

confidence: 99%

“…In our analysis, the event is therefore an interval-censored variable [26], and the development of defects related to quality was thus treated as a binary outcome, taking a value of 1 if a tree developed one or more defects and a value of 0 if a tree maintained quality up to a particular point in time, which in this case was the next inventory. Although the appearance of defects was recorded over time using repeated inventory, the candidate explanatory variables were fixed at the time of plot establishment for the purposes of our analysis [11].…”

Section: Experimental Design and Data Collectionmentioning

confidence: 99%

“…Two types of explanatory variables were tested: (1) at the tree-level, the initial DBH (cm) as a continuous variable, crown dieback (%), and species; (2) at the plot-level, the basal area (BA, m 2 /ha) and a categorical treatment variable (managed/unmanaged) were used to quantify stand density, as suggested by Guillemette et al [19] and Moreau et al [11]. The mean annual temperature of the site ( • C), and total precipitation (mm) for 1970-2000 were also tested (WorldClim database (V.2), [27]) The interaction between the candidate explanatory variables was also tested.…”

Section: Experimental Design and Data Collectionmentioning

confidence: 99%

“…In a previous analysis by Moreau et al [11], sugar maple and yellow birch survival were modelled as a function of initial DBH and crown dieback using similar Cox proportional hazards models. The survival analysis were calibrated with the same dataset as this study, with the addition of a second dataset including 528 circular PSPs of 400 m 2 that were established between 1995 and 1999 in 149 operational study sites throughout the northern hardwood forest zone of Quebec [11,28]. For both species, the combined risk of dying or declining in quality was computed as a function of initial DBH and crown dieback over a 30-year period.…”

Section: Combined Probability Of Decline In Quality and Mortalitymentioning

confidence: 99%

“…Controlling stand density and spacing reduces competition among residual trees, which reduces the probability of mortality [9,10]. Retaining vigorous trees, and particularly trees that have little to no crown dieback, also reduces the probability of mortality [11]. While it seems logical that these tree selection strategies would also reduce the probability of decline in quality, it remains uncertain whether, and how, selection management reduces it in uneven northern hardwood stands [5].…”

Section: Introductionmentioning

confidence: 99%

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Quantifying the Probability of Decline in Quality: Implications for Selection Management in Northern Hardwood Forests

Moreau

Cecil-Cockwell

Achim

et al. 2023

Forests

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Northern hardwoods are susceptible to a wide range of defects that can reduce the amount of sound wood with desirable qualities, such as the clear sapwood of sugar maple trees. Yet, the rate at which trees decline in quality due to the development of such defects has never been quantified in northern hardwood forests due to a dearth of repeat inventories that record the appearance of defects over time. As a result, it remains uncertain whether, and how, selection management reduces the probability of decline in quality. In this study, we quantify the rate at which trees decline in quality due to the development of defects, and we test several hypotheses regarding the influence of selection management on quality. Our results show that (1) the probability of decline in quality increases as trees grow larger; (2) crown dieback also increases the probability of decline in quality; (3) the probability of decline in quality is slightly lower in managed stands than in unmanaged stands, and (4) the probability of decline in quality increases with the mean annual temperature of the site. Finally, we combined our estimates of the probability of decline in quality with previous estimates of the probability of mortality to assess the overall risk associated with retaining trees of different species, sizes, and vigour profiles. The resulting metric can inform efforts to improve the management of northern hardwood forests by providing an integrated estimate of the risk that the value of a tree will be reduced, or eliminated, due to mortality or decline in quality.

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Section: Experimental Design and Data Collectionmentioning

confidence: 99%

Section: Experimental Design and Data Collectionmentioning

confidence: 99%

Section: Experimental Design and Data Collectionmentioning

confidence: 99%

Section: Combined Probability Of Decline In Quality and Mortalitymentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 3 more Smart Citations

Quantifying the Probability of Decline in Quality: Implications for Selection Management in Northern Hardwood Forests

Moreau

Cecil-Cockwell

Achim

et al. 2023

Forests

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Simplified tree marking guidelines enhance value recovery as well as stand vigour in northern hardwood forests under selection management

Moreau,

Chagnon,

Cecil-Cockwell

et al. 2023

Forestry: An International Journal of Forest Research

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In northern hardwood forests, tree markers select the trees to be harvested during logging operations using classification systems that assign harvest priorities based on the presence of a wide range of individual defects. According to the most recent advances in our understanding of the impact of defects on both tree vigour (the risk of mortality or decline in growth) and quality (the potential for recovering valuable sawlogs), tree markers should adopt a simpler classification system that considers fewer defects than the current operational practice, and they should prioritize the removal of trees with crown dieback. Since the probability of developing defects and dying increases substantially with tree diameter, tree markers should also favour the removal of larger trees that have maintained their quality. However, these recommendations were developed based on tree-level analyses. To provide further validation at the stand scale, we compared stand improvement and value recovery under three tree marking regimes: a new, simplified regime based on the recommendations above, and two regimes used in the province of Quebec, Canada. To do so, we conducted tree marking simulations and value recovery assessments in 14 managed stands distributed across the northern hardwood range of Quebec. Our results confirmed that the simplified tree marking regime not only facilitated stand improvement by removing a greater proportion of low-vigour trees, but also recovered significantly more value (17% on average) at the stand scale. By prioritizing the removal of trees with crown dieback, the simplified regime was superior at salvaging the current value of low-vigour trees before they die or decline in quality. Based on our results, we propose simplified and empirically-validated tree marking guidelines for northern hardwood forests.

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Age and growth reductions increase the proportion of dark heartwood in sugar maple at the northern limit of its range

Voyer,

Moreau,

Gennaretti

et al. 2024

Forestry: An International Journal of Forest Research

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The wood of sugar maple (Acer saccharum Marsh.) in the northernmost part of the species range often exhibits high proportions of discoloured wood at the centre of the stems, which is referred to as dark heartwood. This defect significantly decreases the wood market value of the species, which, in turn, challenges the implementation of state-of-the art silvicultural treatments. The causes of dark heartwood are associated with trauma and the colder climate of the northern regions. In this study, we investigate factors influencing the occurrence of dark heartwood in sugar maple’s northern populations, considering tree age, vigour, stem growth, and local climate. We also aimed to determine whether the proportion of dark heartwood is higher in northern stands compared to more southern ones. We collected samples from 302 sugar maple stems at 16 sites within two bioclimatic domains of Quebec, Canada, i.e. the balsam fir–yellow birch domain (representing the northern limit of the sugar maple range) and the sugar maple–yellow birch domain (representing a more southern location within the range). Our results indicate a positive relationship between dark heartwood proportions and stem age, as well as with the amplitude of the maximum growth reduction throughout the tree’s lifespan and the length of the longest suppression period. We also observed significantly higher dark heartwood proportion for a given tree age in northern stands. The results suggest that silvicultural systems aiming to release suppressed crop trees through group selection using a cut-to-length system could favour the development of high quality timber.

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Visual assessment of tree vigour in Canadian northern hardwood forests: The need for a simplified system

Cited by 6 publications

References 30 publications

Quantifying the Probability of Decline in Quality: Implications for Selection Management in Northern Hardwood Forests

Quantifying the Probability of Decline in Quality: Implications for Selection Management in Northern Hardwood Forests

Simplified tree marking guidelines enhance value recovery as well as stand vigour in northern hardwood forests under selection management

Age and growth reductions increase the proportion of dark heartwood in sugar maple at the northern limit of its range

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