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以贵州喀斯特地区两种主要土壤类型(石灰土和黄壤)为研究对象,通过测定土壤pH值、土壤有机碳(SOC)含量和植物优势种、枯枝落叶、土壤有机质的稳定同位素(δ13Csoc值)组成,探讨了该地区石灰土和黄壤剖面SOC垂直分布特征和δ13Csoc值组成差异。结果表明,与黄壤相比,石灰土剖面的SOC含量较高,石灰土剖面和黄壤剖面SOC含量变化范围分别在3.6～69.8和2.4～51.2g·kg-1。黄壤和黄色石灰土剖面SOC主要集中在0～20cm深度内,而黑色石灰土剖面从0～60cm逐步减少。黑色石灰土和黄壤剖面δ13Csoc值变化范围分别在-22.9‰～-21.5‰和-25.6‰～-22.4‰,前者较后者变化小。从剖面表土向下,黄壤剖面δ13Csoc值均出现逐步增加的趋势,而石灰土剖面δ13Csoc值从剖面表土向下出现上升-降低-不变的变化趋势。黄色石灰土剖面δ13Csoc值变幅较大,变化范围为-23.7‰～-18.2‰。在枯枝落叶转化为表层土壤有机质的过程中,石灰土剖面δ13Csoc值变幅高于黄壤。其中,黄壤剖面δ13Csoc值升高了2.6‰～3.0‰,石灰土剖面δ13Csoc值升高了5.5‰～6.3‰。上述结果揭示了SOC含量及其δ13C值随深度变化的差异,反映植物残体的输入及其在土壤中分解累积特征,有助于揭示SOC循环过程及规律和了解剖面土壤成土过程。
Taking the two main types of soil (limestone and yellow soil) in karst area of Guizhou as the research object, the stable isotope (δ13Csoc value) of organic matter in litter and soil were determined by measuring the soil pH value, soil organic carbon (SOC) content and plant dominant species, The characteristics of vertical distribution and δ13Csoc value of limestone and yellow soil profiles in this area were discussed. The results showed that SOC content of limestone profile was higher than that of yellow soil, SOC content of limestone profile and yellow soil profile were in the range of 3.6 ~ 69.8 and 2.4 ~ 51.2g · kg-1, respectively. The SOC of yellow soil and yellow limestone soil mainly concentrated in the depth of 0 ~ 20cm, while that of black limestone soil decreased gradually from 0 ~ 60cm. The δ13Csoc values of black limestone soil and yellow soil profile ranged from -22.9 ‰ to -21.5 ‰ and from -25.6 ‰ to -22.4 ‰, respectively. The former changed little from the latter. The δ13Csoc values of the yellow soil profiles show a gradual increase trend from the topsoil to the bottom of the profile, while the δ13Csoc values of the limestone profiles show a upward-downward-invariance trend downward from the topsoil. The δ13Csoc value of the yellow limestone soil section varied greatly from -23.7 ‰ to -18.2 ‰. During the conversion of litter into organic matter in the topsoil, the δ13Csoc value of limestone profile was higher than that of yellow soil. Among them, δ13Csoc of yellow soil profile increased by 2.6 ‰ -3.0 ‰, while δ13Csoc of limestone profile increased by 5.5 ‰ -6.3 ‰. The above results reveal the difference of SOC content and its δ13C value with depth, reflecting the input of plant debris and its decomposition and accumulation characteristics in soil, which can help reveal SOC cycle process and law and understand the soil forming process of profile soil.