应用δ13C值探讨林地土壤有机碳的分异

在贵州省中部区域采集了4种典型的林地土壤剖面，拟通过分析测定土壤有机碳(SOC)同位素(SO13C)、溶解性有机碳(DOC) 同位素(DO13C)和枯枝落叶碳同位素(13C)的比值，探讨SOC和DOC的来源和迁移转化过程。结果表明:在枯枝落叶转化为表层土壤有机质过程中，δ13CSOC值升高了0.1%～0.3%，有富13C现象。在具备枯枝落叶覆盖的表层土壤中，DOC含量相对较高，δ13CDOC值与枯枝落叶δ13C值非常相近；而在缺乏枯枝落叶覆盖的表层土壤中，DOC含量相对较低，δ13CDOC与枯枝落叶δ13C值差异较大，说明具备枯枝落叶覆盖的表层土壤DOC主要来源于枯枝落叶。在发育较为成熟的土壤剖面中，随着土壤深度的加深δ13CSOC和δ13CDOC值均有偏正趋势。说明在该区域林地土壤有机质降解程度会随着土壤深度的加深更为彻底。δ13CSOC和δ13CDOC变化趋势的一致性，以及Δ(δ13CDOC-δ13CSOC)绝对值随土壤深度的加深有降低趋势，说明在土体内来自于土壤腐殖类物质的DOC占土壤DOC总量的比例随土壤深度的加深有增加趋势。在发育较为年轻的剖面中，δ13CSOC值的变化则反映出剖面中土壤有机质的新旧混合现象。 

Discussing variance of forest soil organic carbon by analysis of δ13C

Four typical samples of forest soil profiles were collected in the middle of Guizhou Province. The processes of source，transport and transformation of soil organic carbon (SOC) and dissolved organic carbon (DOC) were discussed through analyzing the ratios of δ13CSOC， δ¹³CDOCand δ¹³C of litter. The results indicate that the ¹³C was enriched and the δ¹³CSOC increased by 0.1% -0.3% during litter degrading to SOC in surface soil. The litter rich surface soil had high content of DOC and the δ¹³CDOC was similar to δ¹³C of litter. The litter lack surface soil had low content of DOC，and the δ¹³CDOC was different from δ13CSOC. It suggests that DOC derives from litter in the litter rich surface soil. In some mature soil profiles，δ¹³CSOC and δ¹³CDOC have a positive trend with the increase of soil depth. The degradation degree of SOC was more thoroughly with the increase of soil depth. The variation trend of δ¹³CSOC and δ¹³CDOC in soil profiles and the absolute values of Δ(δ¹³CDOC-δCSOC) decreased with the increase of soil depth. The ratio of DOC from degradation of humus to the amount of DOC was on the increase with soil depth. In the premature soil profiles，the variation of δ¹³CSOC reflects the mixture of young and old SOC.