Exploring recruitment dynamics of sugar maple and yellow birch saplings into merchantable stems following harvesting in the Acadian Forest Region of New Brunswick, Canada

The recruitment of saplings in forest stands into merchantable stems is a very complex process, thus making it challenging to understand and predict. The dynamics of recruitment in the Acadian Forest Region of New Brunswick are not well known or well documented. Our objective was to garner information from existing large-scale routine forest inventories regarding the different dynamics behind the recruitment from the sapling layer into the commercial tree size layer. We focused on the density and occurrence of sugar maple (Acer saccharum Marsh.) and yellow birch (Betula alleghaniensis Britt.) following harvesting, by looking at many factors on a wide range of spatial and temporal scales using models. The results suggest that the variation in density and probability of occurrence is best explained by the intensity of silvicultural treatment, by the merchantable stem density in each plot, and by the proportion of merchantable basal area of each group of species. The number of recruits of sugar maple and yellow birch stems tend be higher when time since last treatment increases, when mid to low levels of silvicultural treatment intensity were implemented, and within plots having intermediate levels of merchantable stem density. Lastly, our modeling efforts suggest that the probability of occurrence and density of recruitment of both species tend to increase while its share of merchantable basal area increases. Key words: tolerant hardwoods, generalized linear mixed model (GLMM), Acadian forest, recruitment modeling, zero-inflated. Le passage de gaules a tiges marchandes dans les peuplements forestiers est un processus tres complexe qui le rend difficile a comprendre et a prevoir. La dynamique du recrutement dans la region forestiere acadienne du Nouveau-Brunswick n'est pas bien connue ni documentee. Notre objectif etait de tirer des renseignements a partir des inventaires forestiers a grande echelle realises de facon routiniere en ce qui concerne la dynamique de passage des gaules a arbres de dimension commerciale. Nous nous interessons particulierement a la densite et l'occurrence du recrutement d'erables a sucre (Acer saccharum Marsh.) et de bouleaux jaunes (Betula alleghaniensis Britt.) apres la coupe en examinant de nombreux facteurs sur une large gamme d'echelles spatiales et temporelles a l'aide de modeles. Les resultats des meilleurs modeles indiquent que la densite et la probabilite d'occurrence sont reliees a l'intensite du traitement sylvicole, a la densite des tiges marchandes dans chaque parcelle et a la proportion de la surface terriere marchande occupee par chaque groupe d'especes. Le nombre de recrues d'erable a sucre et de bouleau jaune a tendance a etre plus eleve lorsque le temps ecoule depuis le dernier traitement augmente, lorsque les traitements sylvicoles sont d'intensite faible a moyenne, et dans les parcelles ayant un niveau intermediaire de densite de tiges marchandes. Finalement, nos efforts de modelisation indiquent que la probabilite d'occurrence et la densite de recrutement des deux especes ont tendance a augmenter lorsque leur proportion de la surface terriere marchande augmente. [Traduit par la Redaction] Mots-cles : feuillus tolerants a l'ombre, modele lineaire mixte generalise (GLMM), foret acadienne, modelisation du recrutement, exces de zeros.
1. Introduction Forests are continuously evolving dynamic biological systems that are influenced by a multitude of environmental, ecological, and silvicultural factors (Messier et al. 2019). A key concept at the [...]