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 2 ·year −1 ) were assessed for the five predominant reserve tree species in AFERP: Acer rubrum L., Picea rubens Sarg., Pinus strobus L., Thuja occidentalis L., and Tsuga canadensis (L.) Carrière. Absolute growth was significantly greater in the large-gap treatment (23.7 ± 1.1 cm 2 ·year −1 ; mean ± SE) than in the small-gap treatment (16.3 ± 0.9 cm 2 ·year −1 ). Percent growth increase was greater in the small-gap treatment (187.6% ± 15.8%) than in the large-gap treatment (143.4% ± 19.3%), and both treatments had greater percent increases than the unharvested control (9.6% ± 5.2%). Species differed in their response to treatment. Pinus strobus had the greatest absolute increase (large-gap, 52.5 cm 2 ·year −1 ), while Tsuga canadensis (large-gap, 270% ± 71.6%) and Acer rubrum (small-gap, 262% ± 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.