洞庭湖区不同利用方式下农田土壤有机碳含量特征

土地利用方式是影响土壤有机碳含量和动态的重要因子之一。其利用方式的改变必将引起土壤有机碳含量发生相应的变化。在洞庭湖腹地选取典型样区，通过调查走访和密集取样，分析了不同土地利用方式（旱地、水旱轮作地、一季稻水田和双季稻水田）下623个农田耕层土样有机碳含量。结果表明，研究区内土壤有机碳含量高低顺序为双季稻水田（28.12 g/kg） > 一季稻水田（27.03 g/kg） > 水旱轮作地（24.79 g/kg） > 旱地（17.96 g/kg），其差异均达到极显著水平（P < 0.01）。土地生产力、秸秆还田量和土壤水文状态是导致不同利用方式下耕层土壤有机碳含量差异的主要原因。进一步分析表明：加强作物秸秆还田（土）、提高土地复种指数、增加地表覆盖是维持和提高洞庭湖区耕作土壤有机碳含量的可行措施，尤其是旱作土壤。

CONTENTS OF SOIL ORGANIC CARBON UNDER VARIOUS LAND-USE TYPES AT FARMLAND IN DONGTING LAKE REGION

Change in land-use type is a key factor affecting the contents and dynamics of soil organic carbon(SOC).The understanding of the characteristics of SOC contents under various land-use types at farmland in Dongting Lake Region is essential to make judicious land-use policy and maintain land productivity.By investigation,sampling and laboratory analysis,the SOC contents at four typical land-use types(including dry-land,flood drought rotation land,single cropping paddy field and double cropping paddy field) at farmland in Dongting Lake Region were studied.The results showed that the difference in the SOC contents at any two land-use types was highly significant(P < 0.01) and the SOC contents order was: double cropping paddy field(28.12 g/kg) > single cropping paddy field(27.03 g/kg) > flood drought rotation land(24.79 g/kg) > dry-land(17.96 g/kg).It is illustrated that the land productivity,amount of straw returning and soil hydrological condition were main factors determining the differences in the SOC contents at various land-use types.The results further revealed that improving amount of straw returning,increasing in plant cropping,strengthening mulch on soil surface can maintain,and even enhance the SOC contents,especially at dry farming land in Dongting Lake Region.