典型湿地生态系统碳循环模拟与预测

Simulating and Predicting of Carbon Cycling in Typical Wetland Ecosystems

以植物生理生态特性和有机碳周转动力学原理为基础,利用室内模拟培养试验结果率定了温度、积水强度、冻融交替对湿地有机碳分解矿化的影响参数,建立了典型湿地生态系统碳循环模拟模型.利用实地观测的数据对模型进行了检验,对模型的灵敏性进行了分析,同时利用该模型进行了情景预测.结果表明,所建模型能较好地模拟中温带(三江平原)和亚热带(洞庭湖)湿地生态系统的碳通量和碳累积特征,沉积物呼吸的模拟值与实测值呈极显著相关关系(p<0.01);三江平原常年积水沼泽有机碳密度约为80×109g.km-2,洞庭湖湿地碳密度约为20×109g.km-2;三江平原常年积水沼泽和季节性积水沼泽每年碳的净固定速率分别为104 g.m-2和76 g.m-2;该模型对温度和大气CO2浓度变化反应敏感.在既定的水文条件下,大气CO2浓度升高和增温可能会使湿地生态系统的碳交换变得更为活跃;在CO2浓度倍增和增温小于2.5℃的气候变化情景时,系统净初级生产力(NPP)和积累的有机碳密度增加,系统仍为大气的CO2汇,但气候变暖的进一步加剧并不利于湿地有机碳的积累,由于CO2施肥效应和温度升高增加的系统NPP补偿不了因温度升高导致的沉积物呼吸速率加快而损失的碳,季节性积水沼泽生态系统积累的有机碳甚至出现明显的下降趋势.

A model was developed based on the theories of physiological ecology and turnover dynamics of organic carbon in wetland ecosystem.It aimed to illustrate the process and characteristics of carbon cycling and its potential changes under climate change scenarios in wetland ecosystems.The key environmental parameters to determine the effects of temperature,water-logging,and freeze-thaw were gained from the results of incubation experiments.Effects of CO2 fertilizing on the carbon sequestration and plant cover on organic carbon mineralization were also taken into account in this model.It was verified by the conventional observed meteorologic data in temperate and subtropical wetland ecosystems.Sensitivity analysis and prediction under climate change scenarios by this model were also discussed.There were significant correlations between the simulated and observed values of sediment respiration in temperate wetlands in Northeast China.It was estimated that the annual net carbon sequestration rate was about 104g·m^-2 in permanently water-logged wetland ecosystems and 76g·m^-2 in the seasonally water logged ones in temperate northeast China.The simulated value of the accumulated organic carbon density was within the changing range of the investigated data.The model was sensitive to the change of parameters of CO2 concentration and temperature.The potential changes in carbon cycling characteristics were also predicted under assumed climate change scenarios of A1B and A1FI.It indicated that the exchange of carbon between the atmosphere and the wetland ecosystem became more active under climate change scenario of warming and increased CO2 concentration assuming no changing of hydrological condition.The net primary production（NPP） and the organic carbon density in temperate wetland ecosystems would increase under the scenario of doubled CO2 concentration and less than 2.5℃ increment of temperature.In this case wetland ecosystem would act as a net carbon sink of the atmosphere.However,it had no advantage to the carbon sequestration and accumulation in wetland ecosystems under the more warming scenarios.Under these more warming scenarios,the amount of increased NPP resulted from CO2 fertilizing and warming could not compensate the carbon loss from the accelerated respiration caused by warming.The organic carbon accumulated in seasonally water-logged wetland even would decrease under the assumed scenarios.