南极苔原沼泽温室气体通量变化特征及其对气候变化的响应

以南极阿德雷岛苔原沼泽为研究区域,2016年12月至2017年1月南极夏季期间观测研究了温室气体CH_4、CO_2和N_2O通量的变化规律及其对环境因子的响应关系。结果表明:光照条件下干旱苔原沼泽表现为CH_4吸收,通量为(–5.4±4.3)μg CH_4·m~(–2)·h~(–1),半干旱苔原与淹水苔原沼泽表现为净排放;三个类型苔原沼泽观测点均表现为N_2O净吸收,最高吸收通量出现在淹水苔原,为(–2.6±2.4)μg N_2O·m~(–2)·h~(–1);黑暗条件下苔原沼泽一致表现为CH_4和N_2O净排放。光照与土壤水分减少增加了苔原CH_4有氧氧化吸收,同时促进了反硝化作用对N_2O的还原转化。观测期间所有观测点均表现为CO_2的汇,最高CO_2净交换量与光合作用强度都出现在淹水苔原区,分别为(–40.1±17.6)μg CO_2·m~(–2)·h~(–1)和(91.2±26.5) mg CO_2·m~(–2)·h~(–1);而最高苔原沼泽呼吸速率出现在干旱苔原观测点,为(73.1±17.6)μg CO_2·m~(–2)·h~(–1)。夏季适宜的温度、降水条件促进了苔原植被的光合作用,增加了苔原沼泽CO_2吸收量。CO_2、N_2O、CH_4通量随时间变化的相互关系规律不显著(P0.05),但在降水与温度波动下,N_2O与CH_4通量都随CO_2通量呈现相似的波动。三种温室气体与各种环境因子之间的响应关系值得进一步研究;不同光照条件对CH_4、N_2O排放量的估算有重要影响。

Variation of summertime greenhouse gas fluxes from tundra marshes and their response to climate change in maritime Antarctica

During the austral summer of 2016—2017, CH₄, CO₂, and N₂O fluxes and selected environmental variables were measured over tundra marshes on Ardley Island in maritime Antarctica. In the presence of sunlight, a net CH₄ flux of–5.4±4.3 μg·m^–2·h^–1 was measured at the dry tundra site, while net CH4 emissions were detected at the mesic and waterlogged sites. Under sunlight conditions, maximum N₂O flux was–2.6±2.4 μg·m^–2·h^–1, and was measured at the waterlogged site; all sites showed net N₂O consumption. In the total absence of sunlight, all sites showed net CH₄ and N₂O emissions. Light and water enhance CH₄ consumption via aerobic oxidation and promote denitrification and the subsequent formation of N₂O. Under sunlight conditions, all three sites acted as CO₂ sinks. The highest net CO₂ flux and photosynthetic flux occurred at the waterlogged site (–40.1±17.6 mg·m^–2·h^–1 and–91.2±26.5 mg·m^–2·h^–1), while the highest ecosystem respiration rate occurred at the dry tundra site (73.1±17.6 μg·m^–2·h^–1). Favorable temperature and precipitation conditions during the Antarctic summer promote photosynthesis in tundra vegetation, resulting in increased CO2 uptake by marshes. Relationship between time and fluxes of the three greenhouse gases is not statistically significant (P>0.05). However, under the conditions of variable precipitation and temperature, fluctuations in N₂O and CH₄ fluxes are similar to those in CO₂. Results indicate that different light conditions, even those under the same sunlight intensity, have considerable influence on estimates of CH₄ and N₂O fluxes. Relationships between the three greenhouse gases and between the gases and various environmental factors deserve further study.