Effect of liberation cutting on the soil carbon storage of a Korean pine forest restored by planting conifers and reserving broad-leaved trees in Changbai Mountains of China.

We studied the effect of liberation cutting on the soil carbon storage and the litter carbon storage of a mid-term (33-year-old) Korean pine forest which was restored by planting conifers and reserving broad-leaved trees by using crown thinning control test method in Changbai Mountains of China. Five levels of cutting intensity were applied, namely, non-cutting (control), mild liberation cutting (25%), moderate liberation cutting (50%), heavy liberation cutting (75%), and clear cutting (100%) (cutting intensity refers to volume percentage). The main research results were as follows. The liberation cutting had certain effects on the soil bulk density ((0.83±0.02)-(1.15±0.03)g/cm3) and the soil carbon concentration ((43.36±1.60)-(70.26±1.94) g/kg) of the Korean pine forest. Compared to the control, moderate liberation cutting decreased the soil bulk density by 8.4% (P0.05), but increased the soil carbon concentration by 14.9% (P0.05). Heavy liberation cutting and clear cutting increased the soil bulk density by 23.3% and 27.1% (P0.05), and degraded the soil carbon concentration by 23.7% and 29.1%, respectively (P0.05). Mild liberation cutting had no significant effect on the two parameters. The liberation cutting had great effect on the soil carbon storage ((13.12±1.57)-(23.46±2.03) kg/m2) of the Korean pine forest. Compared to the control, moderate liberation cutting led to the increase of soil carbon storage by 12.8% (P0.05), while heavy liberation cutting and clear cutting lowered it by 29.9% and 36.9%, respectively (P0.05). Mild liberation cutting had no significant effect on it. The liberation cutting had remarkable effect on the litter carbon storage( (2.13±0.39)-(2.82±0.37) t/ha) of the Korean pine forest. Moderate liberation cutting resulted in the increase of the litter carbon storage by 19.5% (P0.05) compared to the control, while clear cutting reduced it by 9.8% (P0.05). In summary, moderate liberation cutting could increase the soil carbon storage and litter carbon storage of the mid-term Korean pine forest in Changbai Mountains, while heavy liberation cutting and clear cutting would lead to soil carbon storage reducing (the latter also results in the reduction of litter carbon storage). Therefore, mild and moderate liberation cutting should be adopted to maintain or improve the soil carbon sinks for the Korean pine forests.