Effects of land use on the content of soil dissolved organic carbon in the typical landscape units in subtropical red earth region

chinois. 在亚热带典型景观尺度上系统分析土地利用方式对土壤溶解有机碳（DOC）含量的影响。分别以广西肯福和湖南盘塘作为亚热带红壤低山与红壤丘陵典型景观单元，对两个景观单元进行密集采样（0～20 cm）分析。红壤低山和红壤丘陵景观单元土壤DOC的平均含量分别为（159.2±75.8） mg/kg和（90.035.4） mg/kg，其中低含量样本均以稻田土壤为主，其平均值分别为（46.7±14.9） mg/kg和（68.023.1）mg/kg。高含量样本以旱地、果园和林地土壤为主，红壤低山景观单元旱地、果园和林地土壤DOC含量分别比稻田土壤高271%、278%和315%，红壤丘陵景观单元比稻田土壤高37%、69%和77%。土壤溶解有机碳与土壤总有机碳的比值（DOC/TOC）显示，两个景观单元稻田土壤DOC/TOC值（0.24%和0.44%）亦明显低于其它利用方式土壤（0.90%～1.50%）。土地利用方式影响土壤DOC含量，同一景观单元长期处于淹水条件下的稻田土壤DOC含量明显低于旱作土壤（如旱地和果园），林地开垦为旱地或果园后土壤DOC含量降低。同时土壤DOC含量存在区域差异，位于亚热带南部的红壤低山景观单元土壤DOC的含量明显高于北部的红壤丘陵景观单元。

anglais. The content of soil dissolved organic carbon (DOC) was investigated under different land use types in the typical landscape units in subtropical China. The dense sampling (0-20 cm) was carried out in two typical landscape units in subtropical red earth region, Kenfu in Guangxi Autonomous Region as a hilly land and Pantang in Hunan Province as a low hilly land. The content of DOC was 159.2±75.8 and 90.035.4 mg•kg-1 in the hilly and low hilly land, respectively. And the lowest value was found in paddy soil, and was 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 dryland, orchard and woodland soil increased by 271%, 278% and 315% in the hilly land and 37%, 69% and 77% in the 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%). Land use types have influences on DOC content, and it is significant lower in paddy soil than those in dryland and orchard soils. The conversion of woodland into dryland or orchard would reduce DOC content. A significant difference between two units is found and DOC content is higher in the hilly land in the south site of subtropical red earth region than in the low hilly land in the north site.