Effect Of Light-felling Intensity On Carbon Source/sink Characteristics Of Korean Pine Forests By Planting Conifers And Reserving Broad-leaved Trees In Xiaoxing’an Mountains Of China

The present investigated the influence of forest type and light-felling intensity on the carbon source and sink of Korean pine forests by planting conifers and reserving broad-leaved trees（PCRBT）.We measured the annual net carbon sequestration（ANCS）of vegetation and the net carbon emission（CH₄,CO₂）of soil related to various environmental factors（temperature,water content of soil,organic carbon,and total nitrogen）under different light-felling（LF）intensities（Control,low-intensity LF-1/7,moderate-intensity LF（M）-1/5,and heavy-intensity LF-1/3）were measured using a Static chamber-gas chromatograph and a relative growth equation in three types of Korean pine forests by PCRBT（Mongolian oak forest,white birch forest,and aspen forest;the Korean pines were planted under secondary crown for 25–35 years and light-felling for 25–30 years）in Xiaoxing’an Mountains.（1）Moderate-and heavy-intensity LF significantly increased 8.6%and 22.6%from Mongolian oak-Korean pine forest(155.09～190.19 mg·m^-2h^-1),low-intensity LF had no significant impacts in Mongolian oak-Korean pine forest;the intensity of light-felling had no significant impacts both white birch-Korean pine forest(170.93～206.52 mg·m^-2h^-1)and aspen-Korean pine forest(165.28～207.43 mg·m^-2h^-1);low-and heavy-intensity LF significantly decreased 18.9%and 37.7%from aspen-Korean pine forest,moderate-intensity LF had no significant impacts and the intensity of light-felling had no significant impacts in Mongolian oak-Korean pine forest and white birch-Korean pine forest.（2）Moderate-and heavy-intensity LF significantly decreased14.0%～15.8%on the ANCS of vegetation from white birch-Korean pine forest and heavy-intensity LF significantly decreased 19.2%on the ANCS of vegetation from Mongolian oak-Korean pine forest;the intensity of light-felling had no significant impacts on the ANCS of vegetation in aspen-Korean pine forest.（3）In addition,low-intensity LF significantly increased0.4 times on carbon source from Mongolian oak-Korean pine forest(-0.80～-1.93 t C·hm^-2·yr^-1),low-intensity LF had no significant impact on carbon sink in aspen-Korean pine forest(-0.31～-1.03 t C·hm^-2·yr^-1),and white birch-Korean pine forest(-0.13～1.19 t C·hm^-2·yr^-1);moderate-intensity LF significantly increased 0.68 times on carbon source of Mongolian oak-Korean pine forest and 1.65 times of aspen-Korean pine forest,white birch-Korean pine forest slightly decreased the carbon sink strength;heavy-intensity LF significantly increased 1.14 times and2.23 times on carbon source of Mongolian oak-Korean pine forest and aspen-Korean pine forest,white birch-Korean pine forest switched from a sink to a source of carbon.So the level and direction of the effect of low-and moderate-and heavy-intensity LF were closely related to the forest type.Therefore,the faster recovering white birch-Korean pine forest are more appropriate under moderate-intensity LF for maintaining the forest carbon sink in Korean pine forests by planting conifers and reserving broad-leaved trees,while the slower recovering Mongolian oak-Korean pine forest and aspen-Korean pine forest is suitable under low-intensity LF.