【作者】 刘守龙；

【导师】 吴金水；

【作者基本信息】 华中农业大学 ， 土壤学， 2006， 博士

【摘要】 稻田在亚热带农业生态系统中占居主要地位，其土壤碳氮循环与积累具有显著的特点。系统地研究该区稻田生态系统土壤有机碳氮的演变、关键驱动机制并预测其变化趋势，对于稻田优化管理具有重要的意义。本研究以典型生态景观单元调查、长期定位监测结果和历史资料讨论了近30年来稻田土壤碳、氮积累的变化及其驱动机制；利用土壤有机碳循环模型（SCNC）预测了稻田土壤有机碳的演变趋势。主要结果如下： 1．亚热带稻田土壤有机碳氮积累量较高，但不同地区之间存在显著差异，平原湖区、低山区、丘陵区依次降低。地形是引起土壤有机碳、全氮区域差异的主要自然因子，耕作历史、种植制度、施肥水平也具有重要的影响。稻作显著提高了土壤碳氮的积累量（与旱地比较增加18％～65％）。随地形的不同，稻作对土壤碳氮积累的影响幅度存在明显差异。总体上，地形的复杂程度（相对高差、坡度）增加，稻田与旱地之间碳氮积累量差异也随之增加。 2．亚热带地区稻田土壤有机碳氮在过去近30年中呈明显的增加趋势，是CO₂循环的“汇”。2003年盘塘样区稻田土壤有机碳含量平均比分别1990年和1979年提高了16.8％和35.6％，其提高幅度明显高于其它利用方式。长期定位监测点结果也显示稻田土壤有机碳在13年（1991～2004）中提高10％～45％。与有机碳比较，全氮尽管也有所增加，但其积累速率较低。盘塘样区稻田及长期定位监测土壤全氮提高幅度仅为10％左右，且长期定位监测中土壤全氮1994年后基本呈平衡状态。种植制度的变更、施肥量的增加、新品种的选用所引起的作物生产力提高是近年来稻田土壤有机碳、氮素积累的主要原因。 3．亚热带地区稻田种植制度中，水田改为旱作（种植经济作物）后土壤有机碳氮积累量显著降低，单季中稻种植土壤碳氮含量显著低于双季稻。水稻．油菜，水稻-绿肥的种植方式下土壤有机碳、全氮与单季稻差异不明显，但对于土壤微生物生物量碳氮含量提高则具有重要的积极作用。目前，亚热带地区稻田种植方式具有多样化（双季稻改为水旱轮作或旱作种植经济作物等）或简单化（单季稻）的发展趋势，而这种趋势不利于土壤碳、氮的积累。为维持和提高亚热带稻田土壤肥力和有机碳积累，应合理的规划种植方式，增加有机肥的施用或采取其它措施。 4．随有机物质投入量的提高，稻田土壤有机碳氮积累速率呈提高趋势。长期定位试验显示，化肥施用仅在部分监测点对土壤有机碳的积累产生了促进作用。中量有机肥（LOM）施用后，土壤有机碳在17年内增加27.5％～87.2％。高量有机肥（HOM）施用则使土壤有机碳积累速率则明显高于中量有机肥。施肥对于土壤氮素积累的作用基本与有机碳一致。土壤微生物生物量也随有机物投入量的提高而增大。更多还原

【Abstract】 Rice cultivation systems are the most important production system in subtropical region of China. The turnover of organic C and N in paddy soils is different from that in the uplands. Studies on the accumulation, driving mechanisms and simulation of soil organic C and N have major significance for the optimal management of paddy soils. With data from typical regions, history data, and long-term field experiments, the regional differences, the changes of soil organic C （SOC） and total N （TN） in the last 30 years and driving mechanisms were discussed. The soil C and N cycling （SCNC） model was validated using data from long-term field experiments, then the model was used to estimate and predict the carbon storage potential in paddy soils. The main results were as follows:（1） There were significant differences in SOC and TN accumulation in paddy soils between different regions. SOC and TN contents of plain region were higher than those of hilly regions. The regional discrepancies of soil microbial biomass C and N （SMBC and SMBN） were different with SOC and TN, Dacai region （hilly） has the highest SMBC and SMBN. Landform was the main factors that that caused the regional discrepancy of SOC and TN. Due to the sensitivity of soil microbes, soil microbial biomass （SMB） could not reflect the effects of stable factors （climate, landform, tillage history） on soil organic C and N cycles. Rice cultivation enhanced the accumulation of SOC and TN significantly （Compared with dryland, increased by 18%～65%）. The enhancement was varied with the landform. The difference between paddy soil and dryland in the plain area was lower than that in hilly area. Rice cultivation also increased the SMBC and SMBN, but the enhancement of SMBC was far stronger than SMBN.（2） SOC contents of paddy soils increased by 35.6% from 1979 to 2003 in Pantang region, which are higher than of dryland （27.5%）. Compared with 1979, TN content of paddy soils in 2003 increased 12.8%, which are also higher than for dryland （9.8%）. Long-term field experiment in Shaoyang also showed that SOC contents in paddy soils increased by 10%～45% in 13 years （1991～2004）, whereas TN showed little enhancement, especially after 1994. This shows that in the last 30 years, paddy fields in subtropical China have acted as a "sink" for CO₂. Changes of rotation, addition of fertilizer, new genetype adoption and the enhancement of rice production are the main reasons for the accumulation of SOC and TN in paddy soils.更多还原