用天然13C丰度法评估贵州茂兰喀斯特森林区玉米地土壤中有机碳的来源

当森林生态系统转变成农田生态系统时，会把C4植物有机质导入到曾在C3植被下发育的土训中去，使土壤中含有来源不同的土壤有机质，引起碳同位素组成变化。因此，可以利用碳同位素来区分土壤有机质来源，实验结果表明，耕作几十年后原森林土壤有机质的含量仍占有主要地位，来源于原始C3植被的有机碳的比例为66.7％，但容易矿化的、对植物营养有效的有机质含量较低，这与当地的耕作方式有关，需要加强对植物残留物返回土壤工作的管理。

Origins of soil organic carbon with the method of natural 13C abundance in maize fields

Following the conversion of forest ecosysterm to agricultural ecosysterm, the introduction of C4 plant to a soil,previously developed under C3 vegetation,brings to a different origin of soil organic carbon.In consequently it leads to the isotopical change in the composition of organic carbon. The results showed that the proportion of soil organic carbon derived from the forest still predominates after several decades of cultivation in maiz fields in Guizhou Maolan Karst Forest. The soil organic carbon originated from initial C3 vegetation amounts to 66.7 % of the total. The contents of easily mineralizable organic carbon which can efficiently supply nutrients to plant are very small. Therefore, it is necessary to optimize the management of plant residues incorporated into the soils.