Charles Nock

Chaire CRSNG/Hydro-Québec sur le contrôle de la croissance des arbres

Directeur: Christian Messier

  • Ph.D. - University of Natural Resources and Life Sciences Vienna, 2010
  • M.Sc.F - University of Toronto, 2006
  • HBSc. - University of Toronto, 2003

Charles Nock s'intéresse à la dynamique de la stabilité biomécanique des arbres. Il s'intéresse également aux effects anthropiques (e.g. changements globeaux, silviculture) sur la dynamique des forêts boréale, mixte et tropicale.

Afin d’optimiser les méthodes d’intervention et de permettre une cohabitation plus harmonieuse entre les arbres et les infrastructures d’Hydro-Québec, les projets de recherche de la Chaire sont regroupés selon 3 grands Axes de recherche complémentaires.

  • 1er axe : Comprendre la dynamique de la croissance de l'arbre et de sa cime en relation avec sa physiologie, sa morphologie, son architecture et son environnement : Bastien Lecigne (M.Sc.); Jorge Ramirez (Ph.D.)
  • 2e axe : Étudier la dynamique de la stabilité biomécanique des arbres en fonction des conditions structurales et biophysiques : Charles Nock (Post-doc)
  • 3e axe : Développer des modèles et algorithmes pour permettre le suivi et la prédiction de la croissance des arbres en fonction des conditions biophysiques retrouvées sur l'ensemble du Québec. Jari Pertunnen (Post-doc)

Dans leur ensemble, ces travaux permettront de faire converger nos connaissances en écophysiologie de la croissance, en biomécanique de la stabilité, en modélisation 3D de la croissance d’arbres individuels et en modélisation dynamique et spatiale de groupes et communautés d’arbres de l’Est du Canada afin (i) de tester une série d’hypothèses scientifiques théoriques et appliquées concernant la croissance et le développement des arbres et les facteurs contribuant à leurs coexistences en peuplements complexes, (ii) d’optimiser les interventions de maîtrise de la végétation arborée le long du réseau de distribution électrique d’Hydro-Québec et (iii) de mieux planifier le déploiement des arbres en milieu habité. Ce projet permettra d’élaborer, en milieu urbain comme en milieu rural, des stratégies de déploiement et de maîtrise de la végétation arborée mieux adaptées, moins intrusives, moins coûteuses et plus efficaces, afin de les rendre plus acceptables socialement.

Current research projects

1. An experimental approach to studying ice accumulation and the resistance of trees to freezing rain

2. Functional traits of tree species common to urban areas


Figure from Mayfield et al., Global Ecology and Biogeography, (Global Ecol. Biogeogr.) (2010) 19, 423–431

Areas of research

Previous research has examined: 1) ontogenetic changes in intra-crown LAI in tolerant hardwood forests, 2) the effects of global change on forest fire occurrence at a national scale in Canada, 3) seed dispersal in big-leaf mahogany, 4) radial gradients in wood density and their biomechanical and carbon implications, and 4) long-term growth responses of tropical trees to global changes (e.g. CO2, warming) using tree-rings and stable isotopes.

Crown thinning with tree age and sources of heterogeneity in light transmission

The widespread occurrence of age-related changes in leaf morphology and allocation suggests that the leaf area index of individual trees (intra-crown LAI) may decline late in ontogeny. We used direct, within-canopy measurements to quantify the LAI of canopy trees with exposed crowns of two temperate deciduous species. Intra-crown LAI declined from ;7 to 4 in Acer saccharum, and from ;9.5 to 6.5 in Betula alleghaniensis, as tree size increased (from 15 to 72 cm diameter at breast height [dbh]). For A. saccharum, age (which varied from 30 to 160 years) was a significantly better predictor of LAI decline than dbh. We also modeled the effect of ontogenetic declines in LAI on understory light availability and found that light transmission increases significantly as canopy trees grow and mature. Our results thus suggest that gradual declines in LAI with tree age may play an important and overlooked role in contributing to the heterogeneity of sub-canopy light regimes in mature forests

Working with a canopy crane to make direct measurements of LAI using a line-drop method,
we found large declines in LAI with tree age/diameter, with significant implications for light transmission

Masters work with Sean Thomas  and John Caspersen 

Nock et al. 2008, Ecology 

Radial gradients in wood density
x-ray density analysis

Wood density is a key variable for understanding life history strategies in tropical trees. Differences in wood density and its radial variation were related to the shade-tolerance of six canopy tree species in seasonally dry tropical forest in Thailand. In addition, using tree ring measurements, the influence of tree size, age and annual increment on radial density gradients was analysed.The results indicate that average wood density generally reflects differences in shade-tolerance in seasonally dry tropical forests; however, inferences based on wood density alone are potentially misleading for species with complex life histories. In addition, the findings suggest that a ‘whole-tree’ view of life history and biomechanics is important for understanding patterns of radial variation in wood density. Finally, accounting for wood density gradients is likely to improve the accuracy of estimates of stem biomass and carbon in tropical trees

with Daniela Geihofer BOKU, Austria), Michael Grabner (BOKU, Austria) , Patrick Baker (Monash, Australia) , Sarayudh Bunyavejchewin (National Parks, Thailand) and Peter Hietz (BOKU, Austria)

Nock et al. 2009, Annals of Botany 

Predicting changes in forest fire frequency with climate change in Canada

The structure and function of the boreal forest are significantly influenced by forest fires. The ignition and growth of fires depend quite strongly on weather; thus, climate change can be expected to have a considerable impact on forest fire activity and hence the structure of the boreal forest. Forest fire occurrence is an extremely important element of fire activity as it defines the load on suppression resources a fire management agency will face. We used two general circulation models (GCMs) to develop projections of future fire occurrence across Canada. While fire numbers are projected to increase across all forested regions studied, the relative increase in number of fires varies regionally. Overall across Canada, our results from the Canadian Climate Centre GCM scenarios suggest an increase in fire occurrence of 25% by 2030 and 75% by the end of the 21st century. Results projected from fire climate scenarios derived from the Hadley Centre GCM suggest fire occurrence will increase by 140% by the end of this century. These general increases in fire occurrence across Canada agree with other regional and national studies of the impacts of climate change on fire activity. Thus, in the absence of large changes to current climatic trends, significant fire regime induced changes in the boreal forest ecosystem are likely.

with Mike Wotton (CFS, U of T)  and Mike Flannigan (CFS)

Wotton et al. 2010, IJWF 

The use of tree-rings and stable isotopes in tropical trees to fingerprint the effects of global change on tropical forests

Rising atmospheric carbon dioxide [CO2] can accelerate tree growth by stimulating photosynthesis and increasing intrinsic water-use efficiency (iWUE). Little evidence exists, however, for the long-term growth and gas-exchange responses of mature trees in tropical forests to the combined effects of rising [CO2] and other global changes such as warming. Using tree rings and stable isotopes of carbon and oxygen, we investigated long-term trends in the iWUE and stem growth (basal area increment, BAI) of three canopy tree species in a tropical monsoon forest in western Thailand (Chukrasia tabularis, Melia azedarach, and Toona ciliata). To do this, we modelled the contribution of ontogenetic effects (tree diameter or age) and calendar year to variation in iWUE, oxygen isotopes, and BAI using mixed-effects models. Although iWUE increased significantly with both tree diameter and calendar year in all species, BAI at a given tree diameter was lower in more recent years. For one species, C. tabularis, differences in crown dominance significantly influence stable isotopes and growth. Tree ring delta 18O increased with calendar year in all species, suggesting that increasing iWUE may have been driven by relatively greater reductions in stomatal conductance – leading to enrichment in delta 18O – than increases in photosynthetic capacity. Plausible explanations for the observed declines in growth include water stress resulting from rising temperatures and El Nino events, increased respiration, changes in allocation, or more likely, a combination of these factors.

with Patrick Baker (Monash, Australia)  , Peter Hietz and Michael Grabner (BOKU, Austria), Wolfgang Wanek (University of Vienna, Austria), Albrecht Leis (Joanneum Research, Austria) and Sarayudh Bunyavejchewin (National Parks, Thailand)

Nock et al. 2010, Global Change Biology 

The Importance of Tree Size and Fecundity for Wind Dispersal of Wind Dispersal of Big-Leaf Mahogany

Seed dispersal by wind is a critical yet poorly understood process in tropical forest trees. How tree size and fecundity affect this process at the population level remains largely unknown because of insufficient replication across adults. We investigated seed dispersal by the endangered neotropical timber species big-leaf mahogany (Swietenia macrophylla King, Meliaceae) in the Brazilian Amazon at 25 relatively isolated trees using multiple 1-m wide belt transects extended 100 m downwind

with Julian Norghauer (Institute of Plant Sciences, University of Bern) and James Grogan (Yale University School of Forestry and Environmental Studies)

Norghauer JM, Nock CA, Grogan J (2011) The Importance of Tree Size and Fecundity for Wind Dispersal of Big-Leaf Mahogany. PLoS ONE 6(3): e17488. doi:10.1371/journal.pone.0017488 

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La référence vedette !

Jérémie Alluard (2016) Les statistiques au moments de la rédaction 

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