Effects of tending intensity on carbon source/sink of Korean pine forests with different forest types by planting coniferous forest and reserving broadleaved forest

  Objective  This paper aims to reveal the influencing rule of forest type and light-felling intensity on the carbon source and sink of Korean pine forests by planting coniferous forest and reserving broadleaved forest (PCRBT), and to provide basis for the restoration of zonal climax vegetation broadleaved Korean pine forest.

  Method  The annual net carbon sequestration of vegetation, net carbon emission (CH₄, CO₂) of soil heterotrophic respiration with related environmental factors (temperature, water content of soil, organic carbon, total nitrogen, etc.) under different light-felling intensities (control, low-intensity, heavy-intensity) were measured simultaneously by static chamber-gas chromatograph and relative growth equation in three types of Korean pine forests by PCRB (Mongolian oak-Korean pine forest and white birch-Korean pine forest, and Korean pine was planted under secondary crown for 25−35 years and light-felling for 25−30 years) in temperate in Xiaoxing’an Mountains of northeastern China, in order to reveal the influence of forest type and light-felling intensity on the carbon source/sink of Korean pine forest according to the net carbon balance of ecosystem.

  Result  (1) The annual average efflux of soil CO₂ (159.94−207.43 mg/(m²·h)) in three forest types was influenced by both the intensity of light-felling (heavy-intensity light-felling significantly increased by 18.9% from Mongolian oak-Korean pine forest), and the forest type (control was white birch-Korean pine forest, which was significantly higher than aspen-Korean pine forest and Mongolian oak-Korean pine forest, low and heavy light-felling had no significant impacts among three forest types); low and heavy light-felling had no significant impacts on the annual average flux of soil CH₄ uptake (−0.047 − −0.028 mg/(m²·h)) from three forest types but white birch-Korean pine forest and aspen-Korean pine forest were significantly higher than Mongolian oak-Korean pine forest. (2) Low and heavy-intensity light-felling made the annual net carbon sequestration of vegetation (1.66−3.99 t/(ha·year)) from three forest types had no significant effect, but white birch-Korean pine forest was significantly higher (105.4%−124.1% and 31.0%−32.6%) than aspen-Korean pine forest and Mongolian oak-Korean pine forest , aspen-Korean pine forest was significantly higher(55.7%−71.1%) than Mongolian oak-Korean pine forest. (3) Low-intensity light-felling had no significant impacts on carbon sink in Mongolian oak-Korean pine forest (−1.93 − −1.12 t/(ha·year)) and aspen-Korean pine forest (−1.03 − −0.65 t/(ha·year)) and White birch-Korean pine forest (−0.13−0.46 t/(ha·year)), but the level and direction of the effect of heavy-intensity light-felling were closely related to the forest type, Mongolian oak-Korean pine forest had significantly increased by 72.3%, white birch-Korean pine forest converted into carbon source, aspen-Korean pine forest had slightly increased carbon source.

  Conclusion  Therefore, considering the maintenance of forest carbon sink in Korean pine forests by PCRBT, the faster recovering white birch-Korean pine forest and aspen-Korean pine forest is more appropriate to take heavy-intensity light-felling, while the slower recovering Mongolian oak-Korean pine forest is suitable to be low-intensity light-felling.