Effects of Thinning on Biomass Growth in Young Populus Tremuloides Plots
Canadian Journal of Forest Research
Stem, branch, and leaf biomass and leaf-area index (LAI) were estimated for 4 years of growth in plots of thinned and unthinned 7-year-old Populustremuloides Michx. In 1978, transmitted photosynthetically active radiation (PAR) was monitored to estimate percent PAR transmitted. Four years after thinning total aboveground biomass and LAI in the thinned plots exceeded prethinning levels, but were still much less than in the unthinned plots. Leaf biomass and LAI in the unthinned plots increased to 3900 kg ha−1 and 5.7, respectively, but were still increasing in the thinned plots. Annual net stem and branch production during the study was relatively constant at about 5300 kg ha−1 year−1 in the unthinned plots, while net production in the thinned plots was still increasing. Transmitted PAR attenuated rapidly to LAI 3.5, approaching asymptote near LAI 5. Results suggest that, in the short term, thinning of young stands will decrease total aboveground biomass, but net annual biomass accumulation may not be greatly different between thinned and unthinned stands. LAI 3.5 may be an acceptable value for 11-year-old stands but should be permitted to increase to near LAI 5 in older stands.
Hocker, H.W. 1982. Effects of thinning on biomass growth in young Populus tremuloides plots. Canadian Journal of Forest Research. 12(4):731-737.