%0 Research article
%T Long-term effects of precommercial thinning on the stem dimensions, form and branch characteristics of red spruce and balsam fir crop trees in Maine, USA
%A Weiskittel, Aaron R.
%A Kenefic, Laura S.
%A Seymour, Robert S.
%A Phillips, Leah M.
%D 2009
%J Silva Fennica
%V 43
%N 3
%R doi:10.14214/sf.196
%U https://silvafennica.fi/article/196
%X The effects of precommercial thinning (PCT) on stem dimensions, form,  volume, and branch attributes of red spruce [Picea rubens Sarg.] and  balsam fir [Abies balsamea (L.) Mill.] crop trees were assessed 25 years  after treatment in an even-aged northern conifer stand. Treatments were  a uniform 2.4 x 2.4-m spacing and a control (no PCT). The PCT treatment  significantly increased individual tree diameter at breast height  (DBH), height growth, crown ratio, and crown width, while it reduced the  tree height to DBH ratio. PCT also significantly increased stem taper  and consequently, regional volume equations overpredicted observed stem  volume by 2 to 15%, particularly for the spaced trees. PCT also  increased the number and maximum size of branches on the lower bole. The  sizes of knots on half of the sampled spruce crop trees in the spaced  plots precluded them from being used as select structural lumber; there  were no other effects on log grade. Our findings indicate that PCT can  have a long-term influence on the structural attributes of individual  trees, and that improved stem-volume prediction equations are needed in  the Acadian region of North America.