Determining suitable selection cutting intensities based on long term observations on above-ground forest carbon, growth, and stand structure in Changbai Mountain, Northeast China

Abstract

We studied the effects of different cutting intensities (0%, 5-10%, 15%, and 20% basal area removal) on stand growth, structure, and net carbon storage in spruce-fir (Picea asperata Mast.-Abies fabri Mast. Craib) and broadleaf mixed forests on Changbai Mountain (Northeast China) over 19 years. At this site, inventory-based low-intensity selection cutting was used to maintain a continuous forest canopy. After two cutting events, results showed significant differences in growth, structure, and carbon storage among cutting intensities. When increasing cutting intensity, the growth rate of average diameter, basal area, and volume significantly increased, with the highest increment rates found in the plots with 20% basal area removal. Tree diameters for all plots showed a roughly inverse J-shaped distribution before cutting and a left-skewed unimodal distribution after two cuttings. Volume ratio (the relative amount of volume contained in different diameter classes) for small (6-14 cm), medium (14-26 cm), large (26-36 cm), and very large (>38 cm) diameters remained unchanged in the plots with 5 and 10% basal area removal, but increased in the plots with 15 and 20% basal area removal, reaching approximately a 1:2:3:4 ratio in the plots with 20% basal area removal after two selection cuttings. Net carbon storage increased when increasing cutting intensity, reaching maximum storage in the plots with 20% basal area removal (cutting intensity and net C storage increase: 0%, 7.21 Mg C ha-1, 5-10%: 11.68 Mg C ha-1, 15%: 21.41 Mg C ha-1, 20%: 26.47 Mg C ha-1). Therefore, our results show the potential of low-intensity selection cutting to meet demands of both timber production and maintenance of forest cover for biodiversity values.