高寒泥炭湿地是重要的大气甲烷(CH_4)排放源。由于高寒湿地非生长季的气候条件极其恶劣,过去的原位观测研究大多集中在生长季,致使迄今仍对季节性冻土区高寒泥炭湿地的非生长季CH_4排放缺乏充分认识。以地处青藏高原东北部的若尔盖地区...高寒泥炭湿地是重要的大气甲烷(CH_4)排放源。由于高寒湿地非生长季的气候条件极其恶劣,过去的原位观测研究大多集中在生长季,致使迄今仍对季节性冻土区高寒泥炭湿地的非生长季CH_4排放缺乏充分认识。以地处青藏高原东北部的若尔盖地区典型湿地为例,采用静态暗箱—气相色谱人工观测方法,开展了跨越冬、春季和初夏季连续9个月的原位观测研究,试图了解该湿地的非生长季CH_4排放特征及其相对重要性。结果与初步结论如下:(1)整个观测期间上午09:00(北京时间,下同)至11:00时段在6个空间重复位置的CH_4通量平均值介于0.1~1.0 mg C m^(-2) h^(-1);(2)非生长季也发生着较强CH_4排放,且温度响应系数Q_(10)(18.1~29.8)远远大于生长季(1.4~2.2),这意味着非生长季的CH_4排放对气候变暖更加敏感;(3)结合其他生长季的观测结果,对观测数据的外推估计,该湿地的CH_4年排放量约为29.4 kg C ha^(-1) a^(-1),其中非生长季的贡献率高达50%以上;(4)观测期的CH_4通量具有明显季节变化,可解释为温度季节变化、土壤冻结与消融过程、水位(或土壤湿度)季节动态和植物生长节律等共同作用的结果;(5)CH_4排放年通量在湿地三种微地形之间呈现出显著差异,即凸起处相对最弱,凹陷处相对最强(p<0.05),这主要是水位(或土壤湿度)、植物分布等因素的空间差异所致;(6)考虑到三种微地形在整个湿地的面积占比时,凸起处、凹陷处和过渡带对整个湿地CH_4排放年通量的贡献率依次大约为16%、11%和73%。不过,本研究中原位观测的持续时间相对较短,上述结果或结论能否在年度或更长时间尺度上重现,还需要长期连续观测研究加以检验。展开更多
The effects of freeze-thaw cycles on sorption/desorption of dissolved organic carbon （DOC） in two wetland soils and one reclaimed wetland soil were investigated. DOC concentrations added were 0-600 mg/L. Laboratory ...The effects of freeze-thaw cycles on sorption/desorption of dissolved organic carbon （DOC） in two wetland soils and one reclaimed wetland soil were investigated. DOC concentrations added were 0-600 mg/L. Laboratory incubations of sorption/desorption of DOC had been carried out at -15℃ for 10 h, and then at ＋5℃ for 13 h. Soil samples were refrozen and thawed subsequently for 5 cycles. Initial Mass model was used to describe sorption behavior of DOC. The results indicate that freeze-thaw cycles can significantly increase the sorption capacity of DOC and reduce the desorption capacity of DOC in the three soils. The freeze-thaw effects on desorpfion of DOC in soils increase with the increasing freeze-thaw cycles. The conversion of natural wetlands to soybean farmland can decrease the sorption capacity and increase the desorption capacity of DOC in soils. Global warming and reclamation may increase DOC release, and subsequently increase the loss of carbon and the emission of greenhouse gas.展开更多
Nitrogen （N） cycling in boreal peatland ecosystems may be influenced in important ways by freeze-thaw cycles （FTCs）. Adsorption and desorption of ammonium ions （NH4＋） were examined in a controlled laboratory ex...Nitrogen （N） cycling in boreal peatland ecosystems may be influenced in important ways by freeze-thaw cycles （FTCs）. Adsorption and desorption of ammonium ions （NH4＋） were examined in a controlled laboratory experiment for soils sampled from palustrine wetland, riverine wetland, and farmland reclaimed from natural wetland in response to the number of FTCs. The results indicate that freeze-thaw significantly increased the adsorption capacity of NH： and reduced the desorption potential of NH4＋ in the wetland soils. There were significant differences in the NH4＋ adsorption amount between the soils with and without freeze-thaw treatment. The adsorption amount of NH4＋ increased with increasing FTCs. The palustrine wetland soil had a greater adsorption capacity and a weaker desorption potential of NH4＋ than the riverine wetland soil because of the significantly higher clay content and cation exchange capacity （CEC） of the riverine wetland soil. Because of the altered soil physical and chemical properties and hydroperiods, the adsorption capacity of NH4＋ was smaller in the farmland soil than in the wetland soils, while the desorption potential of the farmland soil was higher than that of the wetland soils. Thus, wetland reclamation would decrease adsorption capacity and increase desorption potential of NH4＋, which could result in N loss from the farmland soil. FTCs might mitigate N loss from soils and reduce the risk of water pollution in downstream ecosystems.展开更多
文摘高寒泥炭湿地是重要的大气甲烷(CH_4)排放源。由于高寒湿地非生长季的气候条件极其恶劣,过去的原位观测研究大多集中在生长季,致使迄今仍对季节性冻土区高寒泥炭湿地的非生长季CH_4排放缺乏充分认识。以地处青藏高原东北部的若尔盖地区典型湿地为例,采用静态暗箱—气相色谱人工观测方法,开展了跨越冬、春季和初夏季连续9个月的原位观测研究,试图了解该湿地的非生长季CH_4排放特征及其相对重要性。结果与初步结论如下:(1)整个观测期间上午09:00(北京时间,下同)至11:00时段在6个空间重复位置的CH_4通量平均值介于0.1~1.0 mg C m^(-2) h^(-1);(2)非生长季也发生着较强CH_4排放,且温度响应系数Q_(10)(18.1~29.8)远远大于生长季(1.4~2.2),这意味着非生长季的CH_4排放对气候变暖更加敏感;(3)结合其他生长季的观测结果,对观测数据的外推估计,该湿地的CH_4年排放量约为29.4 kg C ha^(-1) a^(-1),其中非生长季的贡献率高达50%以上;(4)观测期的CH_4通量具有明显季节变化,可解释为温度季节变化、土壤冻结与消融过程、水位(或土壤湿度)季节动态和植物生长节律等共同作用的结果;(5)CH_4排放年通量在湿地三种微地形之间呈现出显著差异,即凸起处相对最弱,凹陷处相对最强(p<0.05),这主要是水位(或土壤湿度)、植物分布等因素的空间差异所致;(6)考虑到三种微地形在整个湿地的面积占比时,凸起处、凹陷处和过渡带对整个湿地CH_4排放年通量的贡献率依次大约为16%、11%和73%。不过,本研究中原位观测的持续时间相对较短,上述结果或结论能否在年度或更长时间尺度上重现,还需要长期连续观测研究加以检验。
基金Under the auspices of Knowledge Innovation Programs of Chinese Academy of Sciences (No. KZCX2-YW-309)National Natural Science Foundation of China (No. 40871089, 40830535)
文摘The effects of freeze-thaw cycles on sorption/desorption of dissolved organic carbon （DOC） in two wetland soils and one reclaimed wetland soil were investigated. DOC concentrations added were 0-600 mg/L. Laboratory incubations of sorption/desorption of DOC had been carried out at -15℃ for 10 h, and then at ＋5℃ for 13 h. Soil samples were refrozen and thawed subsequently for 5 cycles. Initial Mass model was used to describe sorption behavior of DOC. The results indicate that freeze-thaw cycles can significantly increase the sorption capacity of DOC and reduce the desorption capacity of DOC in the three soils. The freeze-thaw effects on desorpfion of DOC in soils increase with the increasing freeze-thaw cycles. The conversion of natural wetlands to soybean farmland can decrease the sorption capacity and increase the desorption capacity of DOC in soils. Global warming and reclamation may increase DOC release, and subsequently increase the loss of carbon and the emission of greenhouse gas.
基金Supported by the Knowledge Innovation Program of the Chinese Academy of Sciences (No. KZCX2-YW-309)the National Natural Science Foundation of China (Nos. 40830535 and 40871089)
文摘Nitrogen （N） cycling in boreal peatland ecosystems may be influenced in important ways by freeze-thaw cycles （FTCs）. Adsorption and desorption of ammonium ions （NH4＋） were examined in a controlled laboratory experiment for soils sampled from palustrine wetland, riverine wetland, and farmland reclaimed from natural wetland in response to the number of FTCs. The results indicate that freeze-thaw significantly increased the adsorption capacity of NH： and reduced the desorption potential of NH4＋ in the wetland soils. There were significant differences in the NH4＋ adsorption amount between the soils with and without freeze-thaw treatment. The adsorption amount of NH4＋ increased with increasing FTCs. The palustrine wetland soil had a greater adsorption capacity and a weaker desorption potential of NH4＋ than the riverine wetland soil because of the significantly higher clay content and cation exchange capacity （CEC） of the riverine wetland soil. Because of the altered soil physical and chemical properties and hydroperiods, the adsorption capacity of NH4＋ was smaller in the farmland soil than in the wetland soils, while the desorption potential of the farmland soil was higher than that of the wetland soils. Thus, wetland reclamation would decrease adsorption capacity and increase desorption potential of NH4＋, which could result in N loss from the farmland soil. FTCs might mitigate N loss from soils and reduce the risk of water pollution in downstream ecosystems.
