华南丘陵区针叶林和果园地表N2O通量的日变化

Diurnal variations of N_2O fluxes from soil surface of plantation and orchard in a hilly area of south China

利用静态箱-气相色谱法对华南丘陵区典型土地利用类型（针叶林：马尾松Pinus massoniana；果园：龙眼Dimocarpus longan Lour）地表N2O通量日变化进行了原位观测。结果表明，针叶林和果园土壤总体来说为大气N2O的源。地表N2O通量日变化规律不明显，日变化中最大通量和最小通量出现的时间也没有明显的规律。针对林地表N2O通量日平均值变化幅度为0.02-0.12mg·m^-2·h-1，果园为0.03-0.37mg·m^-2·h-1，最大值一般出现在6-8月。地温和气温对地表N2O通量日变化无明显影响。降雨对地表N2O通量有较大的影响，雨季（4-9月）地表N2O通量大于旱季（10-3月）。不同土地利用方式对地表N2O通量有较大影响，果园地表N2O通量较针叶林大。没有发现凋落物对地表N2O通量有明显影响。

Diurnal variation of N2O flux was measured using dark static chambers for 2 years in two typical land-use types in a hilly area of south China： plantation dominated by Pinus massoniana and orchard dominated by Dimocarpus longan Lour. There were two plots at both sites respectively： one was covered with litters on the surface soil and the other had no litters. The result showed that these two land-use types were source of N2O to the atmospheren. Diurnal variations of N2O fluctuated with no rule. The average diurnal N2O flux ranged from 0.02 - 0.12 mg·m^-2·h-1 in the pine plantation and 0.03 - 0.37 mg·m^-2·h-1 in the orchard. Generally, strong N2O source appeared from June to August. Diumal variation of N2O flux had no clear correlation with temperature. Precipita- tion affected N2O flux greatly with higher flux in rainy season （April-September） and lower in dry season （October-March）. Land use types had great effect on N2O flux with higher value in the pine plantation than that in the orchard. Litter layer had no distinct impact on N2O flux in this study.