鼎湖山主要森林土壤CO_2排放和CH_4吸收特征

Soil CO_2 emission and CH_4 uptake in the main forests of Dinghushan in subtropical China

研究了鼎湖山生物圈保护区马尾松林、混交林和季风常绿阔叶林(季风林)在2000~2001年期间土壤CO2排放和CH4吸收特征。季风林、混交林和马尾松林土壤CO2排放速率在研究期间的平均值分别为(kgCO2-C·hm-2·d-1):18.6±2.6,20.5±3.7和17.8±3.8,土壤CH4吸收速率则分别为(gCH4-C·hm-2·d-1):-5.5±1.8,-3.3±1.6和-7.7±1.8。土壤CO2排放速率和土壤CH4吸收速率在三种森林类型中均表现明显的季节性变化,且其季节性变化根据森林类型和年份不同而异。总的来说,土壤CO2排放速率在所有森林中均呈现夏季最高而冬季最低的变化,土壤CH4吸收速率的季节性变化则相反,基本上表现为冬季最高而夏季最低的变化。三种森林土壤的CO2排放速率和CH4吸收速率在两观测年间的差异均不显著。土壤CO2排放速率在不同森林类型间的差异也不显著,但土壤CH4吸收速率在马尾松林显著高于混交林。在两观测年中,土壤CO2排放速率与土壤CH4吸收速率之间在季风林呈现显著的负相关关系,在混交林和马尾松林中它们之间也趋向呈负相关关系,但未达显著水平。土壤CO2排放速率与土壤温度之间在季风林呈现显著的指数正相关关系,但在其余森林(混交林和马尾松林)中它们之间的关系则不明显。

Soil CO2 emission and CH4 uptake in pine（PF）, pine-broadleaf mixed （MF） and monsoon evergreen broadleaf（MEBF）forests of Dinghushan in subtropical China were estimated in this study. The mean CO2 emission rates in MEBF,MF and PF forests during the study period of 2000 to 2001 were （kg CO2-C·hm^-1·d^-1） ： 18.6±2.6,20. 5±3. 7 and 17.8±3.8, respectively. The mean soil CH4 uptake rates were （g CH4-C·hm^-1·d^-1 ） ：-5.5±1.8 ,-3.3±1.6 and -7.7±1.8, respectively. Both CO2 emission and CH4 uptake rate exhibited significant seasonal variation and its seasonal pattern varied depending on forests and years. Overall, the soil CO2 emission rates in the studied forests showed the highest in summer and the lowest in winter,in contrast, the soil CH4 uptake rates exhibited the highest in winter and the lowest in summer. No significant difference was found in soil CO2 emission rates among these studied forests. The soil CH4 uptake rates, however,showed the following order：PF^MEBF^MF,and the difference between PF and MF forest was significant. The soil COz emission rates showed a significant negative correlation with CH4 emission in MEBF forest during the monitoring period. The soil COz emission rates also showed a negative but not significant correlation with CH4 up- take in MF and PF forests during the studied period. MEBF forest was the only forest that its soil CO2 emission rates increased exponentially with soil temperature during the monitoring period of 2000 to 2001.