Objective Logging is one of the most important forest management methods affecting the carbon sequestration capacity of forest vegetation. At present, there is a lack of understanding in the response of vegetation carbon storage and carbon increment in uneven aged multi-layer mixed forest to logging disturbance. The objective of this study was to reveal the dynamic changes of tree aboveground carbon storage and carbon increment of broadleaved Korean pine forest following logging of different intensities, and thus providing a theoretical basis for optimizing logging intensity to promote carbon sink potential of the broadleaved Korean pine forest.
Method We established four permanent sample plots in a broadleaved Korean pine forest in Jiaohe, Jilin Province of northeastern China, ranging in logging intensities from low (17.3% of basal area removed on average), medium (34.7%) to high (51.9%), together with an unlogged control sample plot. Growth, recruitment and mortality of all individual trees with DBH greater than 1 cm were documented. Changes in carbon storage due to growth, recruitment and mortality were compared among different logging intensities, as well as among tree size classes.
Result Tree aboveground carbon storage in the low sample plot was recovered to pre-logging level within 10 years. The accumulated carbon storage in the low logging sample plot was even greater than the control. Nevertheless, the loss of carbon storage due to logging in medium and high logging sample plots was hardly compensated by increasing tree growth within a short period, and about 22 and 44 years were needed for medium and high logging sample plots, respectively, to recover to their pre-logging levels. Net carbon storage increment differed significantly among the four treatments. Compared with control, low intensity logging promoted the annual increment of carbon storage, while medium to high logging resulted in a remarkable low rate of carbon increment. Although logging enhanced the growth of survivors and recruitment, heavy logging altered the understory environmental conditions and tended to induce mechanical damage during logging, leading to a high mortality rate and a low net increment of carbon storage. Logging favored the growth (carbon storage increment) of small-sized trees (DBH < 20 cm), whereas the carbon increment of large trees was not affected by logging operations. By plotting logging intensity against carbon increment, we found that carbon storage increment peaked at a logging intensity of 28.4%.
Conclusion Based on our results, a logging intensity between 15%−30% is suitable in this broadleaved Korean pine forest. Low and medium logging reduces vegetation carbon storage, but the enhanced growth and recruitment due to adjusted stand structure may accelerate carbon storage increment. Meanwhile, size class of DBH between 20 and 30 cm contributes the most to the whole stand carbon storage accumulation, indicating that we should give priority to these trees in forest management because they have great growth potential. To sum up, the determinations of logging intensity should take a variety of factors into consideration, such as wood production, ecosystem restoration and carbon sink potential of forest vegetation.