辽宁东部山区落叶松人工林非生长季土壤CO_2释放动态

Soil CO_2 efflux during non-growing season in a Korean larch(Larix olgensis Henry) plantation in mountainous area in eastern Liaoning Province

辽宁东部山区冬季寒冷漫长,而且秋冬交替和冬春交替时期表层土壤冻融交替频繁发生,其对土壤CO2释放的影响特征还不明确。以该区典型森林类型长白落叶松(Larix olgensis Henry)人工林为研究对象,在2010—2014年期间额定非生长季冻融交替期和冻结期土壤呼吸速率(Rs)动态变化特征,并量化各时期土壤CO2释放量(F_(CO_2))的贡献。结果表明:非生长季Rs总体呈现出"U"型的变化规律,并且秋冬冻融交替期土壤呼吸速率明显大于冬春冻融交替期。非生长季年际间Rs的差异较大,年平均Rs在(0.42±0.02)^(0.72±0.04)μmol CO2·m-2·s-1。Rs与10 cm深度土壤温度(T10)和空气温度(Ta)呈现相似的动态变化规律并且具有显著的正相关关系。指数模型能够较好地拟合非生长季Rs随T10的变化规律,且2010/2011和2011/2012年的拟合效果优于2012/2013和2013/2014年,冻融交替期的拟合效果要优于冬季冻结期。2010—2014年期间4个非生长季F_(CO_2)分别为137、92、100和159 g C·m-2,年际间差异大。非生长季各时期F_(CO_2)总体上为秋冬冻融交替期最多(29.66~63.48 g C·m-2),冬春冻融交替期次之(14.57~21.48 g C·m-2),秋冬冻融交替期F_(CO_2)是冬春冻融交替期的1.68~4.36倍,二者的累计贡献率在47.69%~54.66%。冻融交替作用对于非生长季F_(CO_2)动态的贡献不可忽视,而秋冬和冬春2个冻融交替期对于F_(CO_2)的影响也存在较大差异,秋冬冻融交替期激发土壤释放CO2的能力比冬春冻融交替期更强。研究结果将有助于更好地理解我国东北地区非生长季森林土壤碳排放的规律。

The mountainous areas of eastern Liaoning Province have a long and cold winter with deep snow cover.At the beginning and end of the non-growing season in late autumn and early spring,however,topsoil undergoes repeated freeze-thaw cycles and soil CO2 emission during these periods can be important in annual carbon budget.In this study,we set up three 20 m × 30 m plots in a Korean larch（Larix olgensis Henry） plantation,a common forest type in eastern Liaoning Province,and measured soil respiration（Rs） to quantify CO2 emission（F（CO2）） during the periods of freeze-thaw cycles in late autumn and early spring.Four polyvinyl chloride（PVC）collars were installed in each plot and Rswas measured,2-3 times a month for 4 winters（2010-2014）,using portable CO2 infrared gas analyzer（Li-8100）.The results showed a ＂U＂ change of Rsin non-growing season from late autumn to early spring.Rswas positively correlated with soil temperature at 10 cm depth（T10） and air temperature（Ta） and the relationship was best fitted with an exponential model.The fitted relationships were stronger in late autumn than in early spring and in 2010/2011 and 2011/2012 winters than in 2012/2013 and 2013/2014 winters.Rs varied substantially among years from（0.42±0.02） to（0.72±0.04） μmol CO2·m^-2·s^-1 by non-growing season averages and the total F（CO2） in non-growing season was 137,92,100 and 159 gC·m^-2 for the 4 study winters,respectively.Within a non-growing season,the F（CO2） in late autumn ranged from 29.66 to 63.48 g C·m^-2 in the 4 years,about 0.68-3.36 times greater than that in early spring.The overall contribution of F（CO2） in the two freeze-thaw periods in late autumn and early spring to the total F（CO2） in the non-growing season ranged from 47.69% to 54.66% across the 4 study winters.The acceleration capacity of soil CO2 release of freeze-thaw cycles during the alternation of autumn to winter was stronger than that during alternation of winter to spring.These results help understand the patterns of forest soil carbon emission during non-growing season in northeastern China.