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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.
Deep soil organic carbon storage below 100 cm soil profile occupies a large proportion of soil carbon storage, and deep soil organic carbon mineralization characteristics in order to reveal its stability, can provide a basis for deep soil carbon sink certification.In this paper, (0 ~ 100 cm) were used as the control to simulate the deep soil temperature and moisture conditions (temperature 15 ℃, soil moisture 8%). The mineralization characteristics of organic carbon in deep soil (100 ~ 400 cm) The results showed that: (1) Total soil organic carbon mineralization decreased with soil depth increasing. Total organic carbon mineralization in the deep (100-200 cm) and deep (200-400 cm) layers accounted for 0-100 cm ) 88.1% and 67.8% of the total soil mineralization; ② Sub-deep, deep and shallow soil organic carbon mineralization process is similar and divided into three stages: rapid decomposition stage: sub-deep and deep (0 ~ 10 d) The ratio of mineralization to total mineralization is about 50% of shallow (0 ~ 17 d); slow decomposition: the ratio of mineralization to total mineralization in sub-deep and deep (11 ~ 45 d) Which is 150% of the shallow layer (18-45 days). In the relatively stable stage, there is no obvious difference between the mineralized amount and the total mineralized amount in the three levels (46-62 days) (P> 0.05), and the stability of organic carbon was basically the same.The results showed that deep soil organic carbon was also involved in soil carbon cycle, and in the assessment of loess hilly Soil carbon sequestration should take full account of deep soil organic carbon changes.