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目前关于人工造林后土壤有机碳库变化的趋势、幅度及其碳汇功能仍存在很大的不确定性.应用放射性碳(14C)方法,研究河北塞罕坝草甸草原与人工林土壤有机碳周转时间,以加深对人工造林后土壤有机碳库变化的认识.实验结果显示,14C示踪方法所估算出的人工造林后土壤有机碳周转时间可长达几十年至几百年.在草甸草原营造樟子松林后表层土壤全样以及团聚体有机碳的周转时间均明显变短,并随着林龄的增大而改变,这将导致土壤CO2通量的增加,因此,草地造林有可能削弱了表层土壤储存有机碳的能力.对不同林龄的土壤团聚体组分进行稳定同位素与14C分析,发现草甸草原营造樟子松林后土壤中年轻碳库与较老碳库对草地造林的响应存在差异:在幼龄和中龄阶段,土壤中较老碳库CO2排放量的比例呈现出增加趋势,而进入成龄阶段,其比例开始下降,表明林龄对人工林土壤固碳机制有所影响.用14C方法所得到的土壤CO2通量相对较低,这可能与未能有效地从土壤团聚体中分离出较年轻碳库的组分有关.今后的研究应在发展多种组分分离方法的基础上进行碳同位素分析,以提高土壤CO2通量估算的准确性.
At present, there is still a great deal of uncertainty about the trend, magnitude and carbon sequestration of soil organic carbon pool after artificial afforestation.Using radioactive carbon (14C) method to study the changes of soil organic carbon Turnover time to deepen the understanding of the change of soil organic carbon pool after artificial afforestation.Experimental results show that the 14C tracing method estimated the turnover time of soil organic carbon after artificial afforestation can last for several decades to several hundred years.At the grass After the Pinus sylvestris var. Mongolica was planted in meadow steppe, all the surface soil samples and the turn-around time of organic carbon in the aggregates became significantly shorter and changed with age, which led to the increase of soil CO2 flux. Therefore, Which may weaken the ability of topsoil to store organic carbon.Analysis of stable isotopes and 14C of aggregates of soil aggregates in different ages showed that after young Pinus sylvestris var.Mongolica planted in meadow steppe, There was a difference in response: In the young and middle-aged stages, the proportion of CO2 emissions from older carbon pools in soil showed an increasing trend, and the proportion of CO2 emissions began to decline when entering the age group, Soil carbon sequestration mechanism is affected by the relatively low CO2 fluxes obtained by 14C method, which may be related to the failure to effectively separate the components of younger carbon pools from soil aggregates. Development of a variety of component separation methods based on carbon isotope analysis to improve soil CO2 flux estimation accuracy.