Long-term Growth and Yield Response of Young Fir to Manual and Chemical Release from Shrub Competition

Abstract

Long-term growth responses from manually and chemically releasing balsam fir (Abies balsamea (L.) Mill.) seedlings from shrub competition were examined on five 0.4-ha plots in northwestern New Brunswick. Manually releasing seedlings from mountain maple (Acer spicatum Lam.) competition by clearing a 1-m radius circle around each seedling in one plot resulted in increases of 64% for total fir volume, 36% for mean dbh, and 22% for mean height, in comparison with a control plot, 32 years later. Application of a 2,4-D — 2,4,5-T mixture to two plots resulted in 265 and 157% greater fir volume than the control plot 28 years later. Herbicide treatment dramatically changed the species composition of the treated plots, favoring fir and spruce (Picea sp.) over pin cherry (Prunus pensylvanica L.f.) and white birch (Betula papyrifera Marsh.), but had lesser effects on individual-tree growth rates.