增温与干旱双重变化对若尔盖泥炭CH_(4)排放的影响

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

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CH_(4)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CH_(4)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)CH_(4)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CH_(4)排放都对升温不敏感,而中下层泥炭的CH_(4)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,CH_(4)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CH_(4)总排放量为(204.29±15.13)μg/gC,比其低温高水位显著升高66.43μg/gC(约48%);排水泥炭地高温低水位的CH_(4)总排放量为(75.64±9.41)μg/gC,比其低温高水位升高11.95μg/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CH_(4)排放的剧烈变化,可能最终使本区域CH_(4)排放量显著提高。

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 CH_(4)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 CH_(4)emissions to dual effects of warming and drought in these two typical peatlands.The results showed that:(1)accumulated CH_(4)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)CH_(4)emissions of the surface and deep layers of peat in these two types of peatlands were not sensitive to the temperature increase,whereas accumulated CH_(4)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 CH_(4)emissions were changed dramatically;(4)the total CH_(4)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 66.43μg/gC(about 48%)higher than the emission in original low temperature and high water level conditions;meanwhile,the total CH_(4)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 11.95μg/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 CH_(4)emission in middle layer of peat,and will eventually lead to a significant increase of CH_(4)emission in this region in future.