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,极大地削弱了湿地碳库功能的发挥.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(Phragmnites australis)、扁秆藨草(Bolboschoenus planiculmis)、三江藨草(Schoenoplectus nipponicus)、香蒲(Typha orientalis C.Presl)和碱蓬(Suaeda glauca)),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-10～50 cm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/(m2·h),平均值为8.89 mg/(m2·h),其主要环境影响因素为水深、气温和表层10 cm 土壤含水量;在研究水深范围内,代表性植被生长季CO2排放通量范围为10.59～1891.08 mg/(m2·h),平均值为450.12 mg/(m2·h),其主要环境影响因素为水深、气温和表层10 cm 土壤含水量.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排放通量最高,而藨草的C02排放通量最高.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22 cm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22 cm时,CH4和C02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,当水深小于22 cm时,CH4和C02均呈现出更高的温度敏感性,然而当水深大于22 cm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地改变湿地碳排放格局,从而影响到湿地碳功能的稳定发挥.
Water depth threshold for carbon emissions and its temperature dependence in a typical saline-alkali wetland in Northeast China
As an important carbon pool around the world,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 Momog Wetland as the study area.Five typical vegetation types(Phragmites australis,Bolbos-choenus planiculmis,Schoenoplectus nipponicus,Typha orientalis C.Presl and Suaeda glauca)were selected to simulate 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 in water depth of-10 to 50 cm,the CH4 emission fluxes of five selected vegetation species in the growing season ranged from 0.07 to 86.74 mg/(m2·h),with an average value of 8.89 mg/(m2·h).The main driving factors were water depth,air temperature and surface 10-cm soil moisture.In the water depth range of the study,the CO2 emission flux of the vegetation growing season ranged from 10.59 to 1891.08 mg/(m2 h),and the average CO2 emission flux was 450.12 mg/(m2·h).The main influencing factors were water depth,air temperature and surface 10-cm soil water content.Diverse vegetation had different contribution on carbon emission.Reed and cattails had the highest CH4 e-mission,while Scirpus had the highest CO2 emission.The carbon emission presented a segmented pattern with the water depth change.The CH4 emission showed a trend of first increasing and then decreasing with the water depth change,while the CO2 emis-sion showed an opposite pattern,i.e.,first decreasing and then increasing with the water depth change.The critical threshold of the water depth was 22 cm.In various water depth ranges,the sensitivity of CO2 emissions to water depth was greater than that of CH4.In case of the water depth＞22 cm,both CH4 and CO2 show higher water depth sensitivity.When the water level was less than 22 cm,both CH4 and CO2 show higher temperature sensitivity.However,when the water level was greater than 22 cm,both of them were not sensitive to temperature.The results showed 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.
Carbon emissionswater depthtemperature dependentMomog Wetlandsthreshold value
万方数据
维普
