浙北典型稻作区近30年表层土壤碳氮含量变化

农业土壤碳库作为表生碳库的重要组成部分,对研究陆地生态系统碳循环具有重要意义。水稻土作为农业土壤的重要类型之一,其固碳能力研究对研究陆地生态系统碳循环具有现实意义。文章通过嘉善县20世纪80年代、2002年、2008年3次土壤调查数据,对嘉善县表层土壤中有机碳、氮含量及分布进行了分析,有机碳平均值在80年代到2002年呈下降趋势,2002—2008年微弱上升。全氮的平均值在80年代到2002年亦呈下降趋势,2002—2008年呈较快上升。以高密度网格化（1点/4km2）实测数据,计算得到2008年表层土壤有机碳、氮平均密度为44.36t·hm-2和5.3t·hm-2,平均容量为22.182kg·m-3和2.67kg·m-3,总储量分别为1.122×109kg和0.135×109kg,依据2002年、2008年两次可对比的实测数据,采用GIS和地统计学工具,进行了含量的空间分析,以1点/4km2精度,计算了2002—2008年县域内农用地表层土壤的有机碳、氮的变化。2002—2008年每年平均储碳速率为30.8kg·hm-2,储氮速率为156kg·hm-2。2002—2008年碳氮比平均值下降了2.3,依据土壤粒级数据和Hassink的碳保持容量公式,计算出嘉善县土壤平均固定容量为2.478%,初步估算,全县耕地表层土壤还具有42.43万t的固碳潜力,影响表土有机碳储汇的自然因素主要为土壤含水量和质地。

The content change of carbon and nitrogen in surface soil of typical rice area in Northern Zhejiang

Carbon in agricultural soil,an important part of the surface carbon reservoir,has important significance to carbon cycle of the terrestrial ecosystem.Rice soil is a major type of agriculture,and thus studies on its carbon fixation have practical significance to carbon cycle.Based on data obtained during the three investigations on surface soils of Jiashan county,the carbon and nitrogen contents and distribution are analyzed.The results show that the average organic carbon decreases from 1980s to 2002,but slightly increases from 2002 to 2008.The average total nitrogen from 1980s to 2002 also declined,followed by a rapid rise from 2002 to 2008.The surface soil organic carbon and nitrogen average density is 44.36 tc·hm-2,5.3 t·hm-2;average capacity is 2.182 kg·m-3and 2.67 kg·m-3,as shown by high-density grid（1 point/4 km 2）sampling results obtained in 2008,and correspondingly,total reserves of 1.122×109kg and 0.135×10 9kg,respectively.The spatial changing rates of organic carbon and nitrogen in the surface soil from 2002 to 2008 were calculated using GIS data and statistics tools.The average annual rate of carbon storage is 30.8 kg·hm-2,that for nitrogen is 156 kg·hm-2.From 2002 to 2008,the average ratio of C/N dropped by 2.3.On the basis of the soil grain grade Hassink data and the carbon keep capacity formula,the average capacity of carbon fixation has been calculated,the results show that the average fixation capacity for Jiashan soil is 2.478%,and preliminary estimate the surface soil also has the potential of 0.42 million tons of carbon sequestration.The most important factors affecting surface organic carbon storage are soil moisture and texture.