华南地区尾巨桉和马占相思人工林地表温室气体通量

为探索华南地区尾巨桉人工林和马占相思人工林地表温室气体的季节排放规律、排放通量和主控因子,采用静态箱-气相色谱法,对两种林型地表3种温室气体(CO_2、CH_4、N_2O)通量进行为期1年的逐月测定。结果表明:(1)尾巨桉人工林和马占相思人工林均为CO_2和N_2O的排放源,CH_4的吸收汇。马占相思林地表N_2O通量显著(P0.01)高于尾巨桉林,CO_2通量和CH_4通量无明显差异。(2)两种林型3种温室气体通量有着相似季节变化规律,地表CO_2通量均呈现雨季高旱季低的单峰规律;地表CH_4吸收通量表现为旱季高雨季低的单峰趋势;地表N_2O通量呈现雨季高旱季低且雨季内有两个峰值的排放规律。(3)地表CO_2、N_2O通量和土壤5 cm温度呈极显著(P0.01)正相关,3种温室气体地表通量同土壤含水量呈极显著(P0.01)或显著相关(P0.05)。(4)尾巨桉林和马占相思林温室气体年温室气体排放总量为31.014 t/hm~2和28.782 t/hm~2,均以CO_2排放占绝对优势(98.46%—99.15%),CH_4和N_2O处于次要地位。

Seasonal variation of greenhouse gas emission fluxes from soils of Eucalyptus urophylla×Eucalyptus grandis and Acacia mangium plantations in South China

To study the seasonal variation and the influence factors of fluxes of greenhouse gas (CO₂, N₂O, and CH₄) emissions from the soils of a Eucalyptus urophylla×Eucalyptus grandis plantation and an Acacia mangium plantation, we conducted 1 year of continuous monitoring of the greenhouse gas fluxes from the two types of forest using a static chamber and gas chromatography. We found that the soil of both the E. urophylla×E. grandis plantation and the A. mangium plantation behaved as CO₂ and N₂O sources and CH₄ sinks. The N₂O emission fluxes from the A. mangium plantation soil were significantly higher (P < 0.01) than those from the E. urophylla×E. grandis plantation soil. There were no significant differences in the CO₂ emission fluxes and CH₄ uptake fluxes between the two forests. The seasonal patterns of greenhouse gas fluxes from the soils of the two types of forest were similar. The CO₂ emission fluxes from the soils of the two forests were single-peak curves, high in the rainy season and lower in the dry season. The uptake fluxes of CH₄ were single-peak curves, high in the dry season and lower in the rainy season. The N₂O emission fluxes were higher during the rainy season than during the dry season, with two peaks in the rainy season. The fluxes of CO₂ or N₂O from the soils had highly significant (P < 0.01) positive correlations with soil temperature at 5 cm depth. The fluxes of greenhouse gases (CO₂, N₂O, and CH₄) from the soils had highly significant (P < 0.01) or significant (P < 0.05) positive correlations with soil water content. The emissions of greenhouse gases from the soils of the E. urophylla×E. grandis plantation and the A. mangium plantation were 31.014 t/hm² and 28.782 t/hm², respectively, and were composed mainly of CO₂(98.46%-99.15%) with a small amount of N₂O and CH₄.