增温与干旱双重变化对若尔盖泥炭CH4排放的影响

若尔盖泥炭地经历了长期人为排水,未来又面临着强烈的变暖干旱,会对泥炭地CH₄排放产生复杂影响。在若尔盖选取了近自然和长期人为排水两种泥炭地类型,采集1 m深泥炭柱,采用室内环境控制试验,设定不同的氧气、水分和温度条件,探索这两种典型泥炭地的泥炭CH₄排放对增温与干旱双重变化的响应差异。结果表明:(1)由于水位降低和泥炭有机物质量下降,长期排水泥炭地的中下层泥炭(20—80 cm)CH₄累积排放量显著低于近自然泥炭地。(2)两种泥炭地的表层和深层泥炭CH₄排放都对升温不敏感,而中下层泥炭的CH₄累积排放量从5℃到15℃显著增加。(3)模拟增温10℃同时干旱水位降低20 cm条件下,中层泥炭受到了温度、水分和氧气变化的叠加影响,CH₄排放变化最剧烈。(4)最终整个1 m深泥炭近自然泥炭地高温低水位的CH₄总排放量为(204.29±15.13)μg/gC,比其低温高水位显著升高66.43 μg/gC(约48%); 排水泥炭地高温低水位的CH₄总排放量为(75.64±9.41)μg/gC,比其低温高水位升高11.95 μg/gC(约19%)。综上,升温干旱气候会对若尔盖泥炭地的有机碳稳定性造成破坏性影响,会集中导致中层泥炭CH₄排放的剧烈变化,可能最终使本区域CH₄排放量显著提高。

Dual Effects of Warming and Drought on Peat Methane Emissions in Zoige

Most of peatland in Zoige region has experienced long term artificial drainage, and will probably face strongly warming and drought climate in the future. These multiple artificial and natural changes may have a complex effect on peat CH₄ emissions. In this study, two typical types of peatlands, near-natural and long-term artificial drained peatlands, were selected in Zoige region. One-meter-deep peat columns were collected from these sites and incubated under indoor environmental conditions. Different oxygen, moisture and temperature conditions were set up to explore the different responses of peat CH₄ emissions to dual effects of warming and drought in these two typical peatlands. The results showed that:(1)accumulated CH₄ emissions of middle and lower layers of peat(20—80 cm)in the drained peatland were significantly lower than those in the near-natural peatland due to the decrease of water table and organic matter quality in the drained peatland;(2)CH₄ emissions of the surface and deep layers of peat in these two types of peatlands were not sensitive to the temperature increase, whereas accumulated CH₄ emissions of the middle and lower layers of peat(20—80 cm)increased significantly from 5℃-incubation to 15℃-incubation;(3)under the simulated 10℃ warming and 20 cm water table decline, middle layer of peat was received triple effects from changes in temperature, water and oxygen, and its CH₄ emissions were changed dramatically;(4)the total CH₄ emission of one-meter-deep peat in near-natural peatland was(204.29±15.13)μg/gC at high temperature and low water level conditions, which was 66.43 μg/gC(about 48%)higher than the emission in original low temperature and high water level conditions; meanwhile, the total CH₄ emission of one-meter-deep peat in long-term drained peatland was(75.64±9.41)μg/gC at high temperature and low water level conditions, which was 11.95 μg/gC(about 19%)higher than the emission in original low temperature and high water level conditions. Therefore, the warming and drought climate induced by anthropogenic activities would display a destructive impact on the stability of organic carbon in Zoige peatland, which could cause the dramatic change of CH₄ emission in middle layer of peat, and will eventually lead to a significant increase of CH₄ emission in this region in future.