---

作 者 ：刘实,王传宽*,许飞

期 刊 ：生态学报 2010年 30卷 15期 页码：4075~4084

关键词：非生长季；冬季；冻融循环；土壤解冻；温室气体；

Keywords:non-growing season, winter, freezing-thawing circle, soil thawing, greenhouse gas,

摘 要 ：中高纬度森林土壤在漫长的非生长季中对重要温室气体——二氧化碳（CO2）、甲烷（CH4）和氧化亚氮（N2O）的释放或吸收在碳氮年收支中作用很大，但目前研究甚少。采用静态暗箱-气相色谱法，比较研究东北东部4种典型温带森林土壤表面CO2、CH4和N2O通量在非生长季中的时间动态及其影响因子。结果表明：4种森林土壤在非生长季中整体上均表现为CO2源、N2O源和CH4汇的功能。红松林、落叶松林、蒙古栎林、硬阔叶林的非生长季平均土壤表面CO2通量分别为（65.5±8.1） mg m-2 h-1（平均值±标准差）、（705±102） mg m-2 h-1、（77.1±8.0） mg m-2 h-1、（805±23.5） mg m-2 h-1；CH4通量分别为（-17.2±4.6） μg m-2 h-1、（-15.4±4.2） μg m-2 h-1、（-31.5±4.5） μg m-2 h-1、（-23.6±4.1） μg m-2 h-1；N2O通量分别为（19.3±5.1） μg m-2 h-1、（11.5±2.5） μg m-2 h-1、（16.4±4.0） μg m-2 h-1、（14.4±5.4） μg m-2 h-1；其中非生长季土壤表面CO2总排放量分别为143.4 g m-2、162.8 g m-2、189.9 g m-2、252.7 g m-2，分别占其年通量的7.3%、106%、8.4%和85%。所有林型非生长季土壤表面CO2通量在春季土壤解冻前均维持在较低水平；在解冻进程中随温度升高而增大。土壤表面CO2通量与5cm深土壤温度（T5）呈极显著的指数函数关系。在隆冬时节出现CH4净释放现象，但释放强度及其出现时间因林型而异，其中以红松林的释放强度较大，高达43.6μg m-2 h-1。土壤表面CH4通量与T5呈显著的负相关。土壤表面N2O通量的时间动态格局在林型间的分异较大，但在春季土壤解冻阶段均释放出N2O，而释放峰值和出现时间因林型而异。土壤表面N2O通量与0—10cm深土壤含水量呈显著的正相关（红松林除外）。研究展示了不同温带森林类型的土壤水热条件对其非生长季土壤CO2、CH4和N2O通量的重要影响，但这3种温室气体的林型间分异的生物学机理尚需进一步研究。

Abstract:The forests in mid- and high-latitudes experience a long non-growing season, during which the forest soil emission or consumption of greenhouse gases such as carbon dioxide (CO2), methane (CH4) and nitrous oxide (N2O) plays an important role in ecosystem carbon and nitrogen budgets. However, fluxes of these trace gases in non-growing seasons have been scarcely quantified in the temperate forests in northeastern China. In this study, we investigated temporal dynamics of soil CO2, CH4 and N2O effluxes and their controlling factors for four representative temperate forests in this region with a static closed chamber and gas chromatograph technique. These forests were Korean pine ( Pinus koraiensis ) plantation, Dahurian larch ( Larix gmelinii ) plantation, Mongolian oak ( Quercus mongolica ) forest, and hardwood forest (dominated by Fraxinus mandshurica, Juglans mandshurica, and Phellodendron amurense ). Six static chambers (40 cm×50 cm×50 cm) were randomly installed in each forest type. From early November of 2008 to May of 2009, gas samples were collected and analyzed every 1-2 weeks, 16 times in total. The results showed that all forest soils were overall atmospheric CO2 source, N2O source, and CH4 sink during the non-growing season. The mean values of soil CO2 efflux in the non-growing season were (65.5±8.1) mg m-2 h-1 (mean±standard deviation), (705±102) mg m-2 h-1, (77.1± 8.0) mg m-2 h-1, and (805±23.5) mg m-2 h-1 for the pine plantation, larch plantation, oak forest, and hardwood forest, respectively; those of soil CH4 efflux were (-17.2±4.6) μg m-2 h-1 (negative values represent sink), (-15.4±4.2) μg m-2 h-1, (-31.5±4.5) μg m-2 h-1, and (-23.6±4.1) μg m-2 h-1, respectively; and those of N2O efflux were (19.3±5.1) μg m-2 h-1, (11.5±2.5) μg m-2 h-1, (16.4±4.0) μg m-2 h-1, and (14.4±5.4) μg m-2 h-1, respectively; the estimated accumulative CO2 emission during the non-growing season were 143.4gm-2, 1628gm-2, 189.9gm-2, and 252.7gm-2, respectively, which accounted for 7.3%, 106%, 8.4%, and 8.5% of annual soil CO2 efflux, respectively. The soil CO2 efflux remained fairly low until the spring soil thawing started when it increased with soil temperature increasing. There was a significant exponential relationship between soil CO2 efflux and soil temperature (P <0001). There was a net CH4 source occurring in the mid-winter for all forests, but the source strength, occurring time and duration changed with forest types. The largest mid-winter CH4 source was observed in the pine plantation (43.6 μg m-2 h-1). The soil CH4 efflux was negatively correlated with soil temperature (P <0001). The temporal variability of soil N2O efflux among the forest types was greater than those of soil CO2 and CH4 effluxes. All forest soils emitted N2O during the spring soil thawing period, but the maximum efflux and its occurring time varied with forest types. The soil N2O efflux was positively correlated with soil water content between 0 and 10 cm depths for all forests except for the pine plantation (P<001). This study illustrated the significant influences of soil temperature and water content on the variability of soil CO2, CH4 and N2O effluxes in non-growing seasons among the temperate forests, and also highlighted the necessity of further studies on potential biological mechanisms contributed to these variations.

---