Growth dynamics of successive post-fire cohorts of black spruce: Is site potential reduced?

Abstract

Black spruce is one of the main commercial species in boreal forests of North America. It usually forms large and single-species natural stands in eastern Canada, yet in recent years, parts of this area have undergone forest cover regression and the conversion of closed-crown forests to open lichen woodlands, partly due to successive disturbances and regeneration accidents. We studied two successive post-fire cohorts growing at the same site, for which a clear forest cover regression trajectory has already been demonstrated, to assess possible changes in the site potential. The Wilcoxon nonparametric test found significant differences in mean diameter and height growth between cohorts, compared by cambial age, generally with higher mean values for the most recent cohort. There were no indications of growth reduction between the previous and the current cohorts. This paper sets the ball rolling for a discussion on the pertinence of reforestation in this type of recently established open formation, where growth potential (as expressed by diameter and height) seems, at least, maintained.Keywords: open lichen woodland, closed-crown forest, black spruce, successive disturbance, reforestation résumé L' épinette noire est l'une des principales espèces commerciales des forêts boréales de l' Amérique du Nord. Elle forme habituellement de vastes peuplements naturels monospécifiques dans l' est du Canada, même si, au cours des dernières années, une partie de ce territoire a subi une diminution de son couvert forestier et vu ses forêts denses converties en dénudés secs, notamment sous l'action des perturbations successives et des accidents de régénération. Nous avons étudié deux cohortes successives après feu poussant sur le même site et manifestant déjà une régression évidente du couvert forestier, afin d' évaluer les changements possibles dans le potentiel du site. Le test non paramétrique de Wilcoxon a relevé des différences significatives du diamètre moyen et de la croissance en hauteur entre les cohortes, sur la base de l'âge cambial, avec de plus fortes valeurs moyennes pour la cohorte la plus récente. On n'a pas observé de réduction de la croissance entre la cohorte précédente et celle d'aujourd'hui. Cet article veut lancer la discussion sur la pertinence de reboiser ce type de formation ouverte d' origine récente, dont le potentiel de croissance (sur la base du diamètre et de la hauteur) semble au moins s' être maintenu.Monts clés : dénudés secs tapissés de lichen, peuplement fermé, épinette noire, perturbation successive, reboisement

Exploring forest productivity at an early age after fire: a case study at the northern limit of commercial forests in Quebec

“…action potential to increase productivity. As a result, plans to afforest dry northern woodlands with jack pine, known for its generally more rapid growth and higher resilience to fire compared with black spruce, may need to be considered with caution (Rapanoela et al 2015), even if preliminary studies have shown some early successes (Tremblay et al 2013;Hébert et al 2014;Côté et al 2014).…”

Examining Naturogenic Processes and Anthropogenic Influences on Tree Growth and Development via Stem Analysis: Data Processing and Computational Analytics

“…Those examining naturogenic processes would include studies quantifying the effects of edaphic variation [1], resource competition [2], abiotic wind stress [3], insect defoliation [4], drought [5], and pathogens [6,7] on tree growth, whereas anthropogenic based investigations would include studies assessing tree growth responses to intensive forest management treatments, such as pre-commercial thinning [8] and commercial thinning [9], atmospheric pollution [10], and global warming [11]. Stem analysis has also been an essential tool for reconstructing ecological disturbance histories (e.g., [12][13][14]) and past climate variability within forest ecosystems (e.g., [15,16]). Furthermore, tree ring sequences have been used as terrestrial-based proxies in reconstructing past continental-scale temperatures and hydroclimatic changes in order to detect anthropogenic-generated climate change and quantifying the associated effects (e.g., [17,18]).…”