| 摘要: |
| 作为全球重要的碳库，湿地在缓解气候变化方面发挥了重要作用，然而在全球变暖背景下，湿地的碳排放（尤其是甲烷（CH4）排放）存在高度变异性和不确定性，极大的削弱了湿地碳汇功能的发挥。为了探究不同水深梯度下东北盐碱湿地碳排放通量的特征，本研究以莫莫格湿地为主要研究区，选取5种代表性植被（芦苇（Phragmites australis）、扁秆藨草（Bolboschoenus planiculmis）、三江藨草（Schoenoplectus nipponicus）、香蒲（Typha orientalis C. Presl）、碱蓬（Suaeda glauca）），通过布设Marsh Organ中型实验生态系统模拟不同水深生境，揭示CH4和二氧化碳（CO2）排放通量变化及其环境影响因子。 结果表明，莫莫格湿地-10~50cm水深范围内5种代表性植被生长季CH4排放通量范围为0.07~86.74 mg·m-2·h-1，平均CH4排放通量为8.89 mg·m-2·h-1，其主要环境影响因素为水深、气温和表层10cm土壤水分；研究水深范围内，代表性植被生长季CO2排放通量范围为10.59~1891.08 mg·m-2·h-1，平均CO2排放通量为450.12 mg·m-2·h-1，其主要环境影响因素为水深、气温和表层10cm土壤水分。不同植被对碳排放的贡献量有所差异，具体来说，芦苇和香蒲的CH4排放量最高，而藨草的CO2排放量最高。碳排放随水深变化呈现分段规律，CH4排放随水深变化呈现先增加后减少的趋势，而CO2则呈现相反规律，随水深变化先减小后增加，其水深临界阈值均出现在22cm处。在不同水深范围内，CO2排放对于水深的敏感性均大于CH4，且当水深大于22cm时，CH4和CO2均呈现出更高的水深敏感性。碳排放在不同水深范围对温度的敏感程度不同，当水位小于22cm时，CH4和CO2均呈现出更高的温度敏感性，然而当水位大于22cm时，二者对温度均不敏感。结果表明升温背景下，东北典型盐碱湿地水陆过渡区关键生态系统在不同水深范围内呈现出不对称的响应模式，频繁的水位波动会极大的改变湿地碳排放格局，从而影响到湿地碳功能的稳定发挥。 |
| 关键词: 碳排放 水深 温度依赖性 莫莫格湿地 阈值 |
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| 基金项目:国家重点基础研究发展计划（973计划）,,国家自然科学基金项目（面上项目，重点项目，重大项目） |
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| Water depth critical threshold and corresponding temperature dependence of carbon emissions in the typical saline-alkali wetlands in Northeast China |
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Li Shuzhen1, Liu Qiang1, Gan Luoyang1, Wu Haitao2, Wang Bo3
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1.School of Environment, Beijing Normal University;2.Chinese Academy of Sciences, Changchun Branch;3.Momoge Nature Reserve, Zhenlai County, Baicheng, Jilin Province
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| Abstract: |
| As an important global carbon pool, wetlands play an important ecological carbon sink function in mitigating climate change. However, in the context of climate warming, carbon emissions (especially CH4 emissions) are highly variable and uncertain. In order to explore the characteristics of carbon emission fluxes in Northeast saline-alkali wetlands under different water depth gradients, this study took the Mormog wetland as the main research area, selected five representative vegetation types (Phragmites australis; Bolboschoenus planiculmis; Schoenoplectus nipponicus; Typha orientalis C. Presl and Suaeda glauca), and simulated habitats with different water depths through the Marsh Organ medium scale experimental ecosystem to reveal the changes of CH4 and CO2 emission fluxes and their environmental impact factors. The results showed that the CH4 emission fluxes of five representative vegetation species in the growing season ranged from 0.07 to 86.74 mg·m-2·h-1 in water depth of -10 to 50cm, and the average CH4 emission fluxes were 8.89 mg·m-2·h-1. The main environmental factors were water depth, air temperature and surface 10cm soil moisture. In the water depth range of the study, the CO2 emission flux of the representative vegetation growing season ranged from 10.59 to 1891.08 mg·m-2·h-1, and the average CO2 emission flux was 450.12 mg·m-2·h-1. The main environmental influencing factors were water depth, air temperature and surface 10cm soil moisture. The contribution of different vegetation to carbon emission was different. Specifically, the CH4 emission of reed and cattails was the highest, while the CO2 emission of Ribes was the highest. The carbon emission presented a segmented pattern with the water depth change, and the CH4 emission showed a trend of first increasing and then decreasing with the water depth change, while the CO2 emission showed an opposite pattern, first decreasing and then increasing with the water depth change, and the critical threshold of the water depth all appeared at 22cm. In different water depth ranges, the sensitivity of CO2 emissions to water depth is greater than that of CH4, and when the water depth is greater than 22cm, both CH4 and CO2 show higher water depth sensitivity. When the water level is less than 22cm, both CH4 and CO2 show higher temperature sensitivity, but when the water level is greater than 22cm, both of them are not sensitive to temperature. The results show that under the background of warming, the key ecosystems in the water-land transition zone of typical saline-alkali wetlands in Northeast China typically show asymmetric response patterns in different water depth ranges, and frequent water level fluctuations will greatly change the wetland carbon emission pattern, thus affecting the stable play of wetland carbon function. |
| Key words: Carbon emissions water depth temperature dependent Momog Wetlands threshold value |
