Effects of multiaged silvicultural systems on reserve tree growth 19 years after establishment across multiple species in the Acadian forest in Maine, USA

: This study investigated the growth response of mature, isolated reserve trees (n = 528) in two multiaged silvicultural systems in the Acadian Forest Ecosystem Research Project (AFERP). Absolute and percent increases in basal area increment (BAI; [cm.sup.2] x [year.sup.-1]) were assessed for the five predominant reserve tree species in AFERP: Acerrubrum L., Picearubens Sarg., Pinusstrobus L., Thuja occidentalis L., and Tsuga canadensis (L.) Carriere. Absolute growth was significantly greater in the large-gap treatment (23.7 [+ or -] 1.1 [cm.sup.2] x [year.sup.-1]; mean [+ or -] SE) than in the small-gap treatment (16.3 [+ or -] 0.9 [cm.sup.2] x [year.sup.-1]). Percent growth increase was greater in the small-gap treatment (187.6% [+ or -] 15.8%) than in the large-gap treatment (143.4% [+ or -] 19.3%), and both treatments had greater percent increases than the unharvested control (9.6% [+ or -] 5.2%). Species differed in their response to treatment. Pinus strobus had the greatest absolute increase (large-gap, 52.5 [cm.sup.2] x [year.sup.-1]), while Tsuga canadensis (large-gap, 270% [+ or -] 71.6%) and Acerrubrum (small-gap, 262% [+ or -] 42.4%) had the greatest percent increases. Growth responses typically diminished with increasing tree size and pretreatment growth rate; however, reserve trees showed greater growth responses than their paired analogues in the control across all initial tree sizes and prior growth rates. The results suggest that these silivicultural systems accelerate the development of large trees. Key words: basal area increment, ecological forestry, restoration of large- diameter size classes, retention forestry, retention tree. Nous avons etudie le taux de croissance d'arbres de retention isoles et matures (n = 528) dans deux systemes sylvicoles multiages (a grandes ou petites trouees) du Projet de recherche sur les ecosystemes forestiers acadiens (PREFA). Les augmentations absolue et relative en accroissement de la surface terriere ([cm.sup.2] x [an.sup.-1]) ont ete evaluees pour les cinq especes d'arbres de retention predominantes dans la PREFA : Acer rubrum L., Picea rubens Sarg., Pinus strobus L., Thuja occidentalis L. et Tsuga canadensis (L.) Carriere. La croissance absolue etait significativement plus forte dans le systeme a grandes trouees (moyenne [+ or -] erreur-type de 23,7 [+ or -] 1,1 [cm.sup.2] x [an.sup.-1]) que dans le systeme a petites trouees (16,3 [+ or -] 0,9 [cm.sup.2] x [an.sup.-1]). Le pourcentage d'accroissement etait plus grand dans le systeme a petites trouees (187,6 [+ or -] 15,8 %) que dans le systeme a grandes trouees (143,4 [+ or -] 19,3 %), et le pourcentage d'accroissement de ces deux systemes etait plus eleve que dans le temoin non recolte (9,6 [+ or -] 5,2 %). La reaction aux traitements etait differente selon l'espece. La plus grande augmentation absolue a ete observee chez Pinus strobus (52,5 [cm.sup.2] x [an.sup.-1] dans les grandes trouees) alors que les plus grandes augmentations relatives ont ete observees chez Tsuga canadensis (270 [+ or -] 71,6 % dans les grandes trouees) et Acer rubrum (262 [+ or -] 42,4 % dans les petites trouees). Le taux de croissance a generalement diminue avec l'augmentation de la taille des arbres et du taux de croissance pretraitement. Toutefois, le taux de croissance des arbres de retention etait plus grand que celui des arbres qui leur etaient apparies dans le temoin et ce, peu importe la taille initiale des arbres et le taux de croissance pretraitement. Les resultats indiquent que ces systemes sylvicoles accelerent le developpement des gros arbres. [Traduit par la Redaction] Mots-cles : accroissement en surface terriere, foresterie ecologique, restauration des classes de gros diametre, foresterie de retention, arbre de retention.
1. Introduction The majority of the world's forests are managed as multifunctional forests, providing human commodities and other goods and services (Food and Agricultural Organization of the United Nations (FAO) [...]