黄土丘陵区刺槐林深层土壤有机碳矿化特征初探

Soil Organic Carbon Mineralization of Black Locust Forest in the Deep Soil Layer of the Hilly Region of the Loess Plateau,China

土壤剖面100 cm以下的深层土壤有机碳储量在土壤碳储量中占有很大比例,研究深层土壤有机碳矿化特征以揭示其稳定性,可为深层土壤碳汇认证提供依据.本文以浅层土壤(0～100 cm)为对照,模拟深层土壤温度和水分条件(温度15℃、土壤含水量8%),研究了黄土丘陵区刺槐林深层土壤(100～400 cm)有机碳矿化特征.结果表明:①土壤有机碳总矿化量随着土壤深度增加呈下降趋势,亚深层(100～200 cm)、深层(200～400 cm)有机碳总矿化量分别占浅层(0～100 cm)土壤总矿化量的88.1%和67.8%;②亚深层、深层与浅层土壤有机碳矿化过程相似,分为3个阶段.快速分解阶段:亚深层、深层(0～10 d)的矿化量占总矿化量的比值约为浅层(0～17 d)的50%;缓慢分解阶段:亚深层、深层(11～45 d)的矿化量占总矿化量的比值约为浅层(18～45 d)的150%;相对稳定阶段:3个层次(46～62 d)矿化量占总矿化量的比值无明显差异.③浅层、亚深层、深层土壤有机碳矿化率差异不显著(P>0.05),有机碳稳定性基本一致.研究结果反映了深层土壤有机碳也参与土壤碳循环,在评估黄土丘陵区土壤固碳效应时应充分考虑深层土壤有机碳的变化.

The deep soil layer（below 100 cm） stores considerable soil organic carbon（SOC）.We can reveal its stability and provide the basis for certification of the deep soil carbon sinks by studying the SOC mineralization in the deep soil layer.With the shallow soil layer（0-100 cm） as control,the SOC mineralization under the condition（temperature 15℃,the soil water content 8%） of Black Locust forest in the deep soil layer（100-400 cm） of the hilly region of the Loess Plateau was studied.The results showed that： ①There was a downward trend in the total SOC mineralization with the increase of soil depth.The total SOC mineralization in the sub-deep soil（100-200 cm） and deep soil（200-400 cm） were equivalent to approximately 88.1% and 67.8% of that in the shallow layer（0-100 cm）.②Throughout the carbon mineralization process,the same as the shallow soil,the sub-deep and deep soil can be divided into 3 stages.In the rapid decomposition phase,the ratio of the mineralization or organic carbon to the total mineralization in the sub-deep and deep layer（0-10 d） was approximately 50% of that in the shallow layer（0-17 d）.In the slow decomposition phase,the ratio of organic carbon mineralization to total mineralization in the sub-deep,deep layer（11-45 d） was 150% of that in the shallow layer（18-45 d）.There was no significant difference in this ratio among these three layers（46-62 d） in the relatively stable stage.③There was no significant difference（P〉0.05） in the mineralization rate of SOC among the shallow,sub-deep,deep layers.The stability of SOC in the deep soil layer（100-400 cm） was similar to that in the shallow soil layer and the SOC in the deep soil layer was also involved in the global carbon cycle.The change of SOC in the deep soil layer should be taken into account when estimating the effects of soil carbon sequestration in the Hilly Region of the Loess Plateau,China.