关键词: 红壤丘陵, 红壤低山, 景观单元, 土地利用, 土壤溶解有机碳

Abstract: 【Objective】 The content and distribution of soil dissolved organic carbon (DOC) was investigated as well as the relationships between DOC and total organic carbon (TOC) or pH under different land use types in the typical landscape units in subtropical China. 【Method】The dense sampling (0~20cm) was carried out in two typical landscape units in subtropical red earth region, Kenfu in Guangxi Autonomous Region as a high hilly land and Pantang in Hunan Province as a low hilly land. 【Result】 The content of DOC averaged (159.2±75.8) and (90.0±35.4) mg kg-1 in high and low hilly land, respectively. And the lowest value was found in paddy soil, and averaged (46.7±14.9) and (68.0±23.1) mg kg-1 in two units, respectively. Comparing with paddy soil, the content of DOC in upland, orchard and woodland soil increased by 271%、278% and 315% in high hilly land and 37%、69% and 77% in low hilly land, respectively. The ratio of DOC to TOC (DOC/TOC) was smaller in paddy soil (0.24% and 0.44%) than in other land uses (0.90%~1.50%). The content of DOC was positively correlated with TOC for upland, orchard and woodland soils in two units, and no relationship (in high hilly land) or negative relationship (in low hilly land) for paddy soil. The content of DOC under different land use types in two units was significant negatively correlated with pH except woodland soil in low hilly land. 【Conclusion】Land use types had influences on DOC content, and it was significant lower in paddy soil than those in upland and orchard soils. The conversion of woodland into upland or orchard would reduce DOC content. A significant difference between two units was found and DOC content was higher in high hilly land in the south site of subtropical red earth region than in low hilly land in the north site.

Key words: High hilly land in red earth region, Low hilly land in red earth region, landscape unit, land use, soil dissolved organic carbon