【作者】 许泉；

【导师】 卞新民；

【作者基本信息】 南京农业大学 ， 生态学， 2007， 博士

【摘要】 随着全球环境变化,尤其是以温室气体升高为起因的变化趋势日益明朗,世界各国学术界和政界对如何减缓全球环境变化趋势给予高度重视。土壤有机碳是大气和陆地生态系统地上部碳储量的2到2.5倍,土壤有机碳动态直接关系到大气CO2浓度的变化,对全球环境变化的作用巨大。耕作制度是以作物种植和土壤管理为核心的种植技术体系,对农田土壤有机碳的稳定和累积作用显著。越来越多的研究表明,我国近20年来耕作制度演变下农田土壤呈现碳汇效应,尤其是我国南方农区水田土壤碳汇效应尤其突出,固碳潜力大。本文在充分了解南方农区特征的前提下,通过历史数据收集、文献资料查阅、田间试验、农户调查、生产调研等手段,采用多种定量与定性结合的分析方法,重点研究了南方水田土壤有机碳氮特征、人为干扰对水田土壤有机碳的影响、农户行为与土壤碳氮的关系,拟为南方水田土壤增碳保氮提供理论依据、技术途径和相关配套政策建议。主要研究结果如下:水田土壤有机碳密度可能更多地受生产技术影响,人为调控潜力大。农田耕层土壤有机碳密度介于0.81～12.68 kg/m2,平均为3.15 kg/m2。农田土壤有机碳密度的变异系数为57%,显著比非农业土壤的变异系数低35个百分点。水田耕层有机碳密度比旱地的平均高13个百分点,但水田有机碳密度的区域变异显著低于旱地。农田土壤有机碳密度与降水和气温的相关性显著低于非农业土壤,农田中水田土壤有机碳密度与降水和气温的相关性又显著小于旱地。农田土壤有机碳氮之间存在显著的耦合关系,相同氮水平下水田土壤可能储存更多的有机碳。不同种植方式下,水田土壤平均有机碳和全氮含量比旱地分别高47.8%和41.4%,但水田碳氮的区域变异低于旱地。全国土壤有机碳氮在水田和旱地利用下平均分别为10.8和9.9,区域内水田土壤碳氮比普遍高于旱地,其中东北地区水田最高,而华东旱地和西北旱地为最低。区域之间相比,旱地碳氮比的区域变异显著,水田的不显著。不同类型水田土壤的有机碳氮特征及其关键影响因子差异显著,在增碳保氮技术选择上要充分考虑区域土壤类型差异。潜育型水田土壤有机碳密度最高,比最低的淹育型土壤高75.97%,两者的碳氮比差值为1.31,也达到显著水平。影响土壤有机碳密度关键因子是耕层厚度和土壤全氮含量,除潴育型土壤外,均达到了显著的正相关关系。不同类型土壤碳氮比的关键作用因子不同,其中耕层厚度与所有土壤的碳氮比相关不显著。有机无机肥配合施用是土壤增碳保氮的关键技术,秸秆还田能提高土壤有机碳密度,但提高幅度有限。无论是双季稻区或单稻区,长期有机无机肥配合施用下,土壤有机碳密度和土壤C/N比均显著提高。近20年来,有机无机肥配合施用与纯化肥区相比,土壤有机碳密度和C/N比在双季稻区分别提高了20.46%和6.43%,但肥力水平较高的单季稻区仅分别提高了3.73%和4.51%。秸秆还田达到一定值后,进一步提高秸秆还田,土壤增碳效应不明显。保护性耕作技术具有很好的增碳保氮效应,但技术之间的效应差异显著。以长三角区域为例,油菜面积的扩大、小麦的少免耕和作物秸秆的还田分别约增加土壤耕层有机碳0.94 Tg、2.76 Tg和3.95 Tg,其中以麦稻复种转向油稻复种的单位面积碳收集效应为最高。计量经济模型分析表明,农户生产行为及土地政策对土壤有机碳氮影响显著。农户行为主要与农户的年龄、受教育程度和土地政策相关,不同的农户对于不同土地使用权的土地投入方式不同。而投入的差异,尤其是有机肥投入,显著影响土壤有机碳和氮水平。完善土地使用权,扩大地块规模,可以促进农户采取有利于土壤质量提高的投入增加和技术选择。更多还原

【Abstract】 As the global environmental change is going on,especially global warming,great emphasis is given on how to slow down the trend by the scientists and politicians all over the world.The storage of soil organic carbon is about 2 to 2.5 times of that in the atmosphere and the above of the terrestrial ecosystem and its dynamic changes are related to the concentration of CO₂ and then the global environmental change.Farming system which includes both the cropping system and soil management plays an important role in the soil organic carbon stability and accumulation.Researches showed that the farmland soil had been carbon sequestration storage under the farming system evolution about recent 20 years,especially in the paddy soil of South-China whereas little research had been done. Under the condition of knowing the characteristics of southem region adequately,and also based on the historic data,published literature,field experiments and household survey data, the characteristics of soil organic carbon and nitrogen in the paddy soil of south-China,the effect of anthropogenic disturbances on the paddy soil carbon and the relationship between farmer behavior and soil organic carbon and nitrogen was studied through the integration of qualitative analysis and quantitative analysis.The main results were as follows:The results suggested that anthropogenic disturbances had great impacts on soil organic carbon density in paddy soils,indicating a high control potential of soil organic carbon density.Results showed that soil organic carbon density in the plow layer was about 3.15 kg/m² in average which ranged from 0.81 kg/m² to 12.68 kg/m².The variation coefficient of soil organic carbon density in the plow layer of farmland was 57%,which was 35 percentages lower than that of non-farmland soils.Compared to soil organic carbon density in the dry land,SOC density in paddy soils was 13 percentages higher with a lower variation coefficient between different regions.In addition,the relationships between the climatic factors（annual average temperature and annual precipitation） and soil organic carbon density were lower in farmland than those in non-farmland soils,as well as in paddy soils than that in dry land of farmland.There existed close coupled relationship between soil organic carbon and total nitrogen in the plow layer of farmland,and maybe more carbon could be sequestrated in the paddy soil than that of in the upland soil under the same nitrogen level.Results showed that soil organic carbon and total nitrogen contents were higher in paddy fields than in upland fields by 47.8%and 45.5%,respectively,but spatial variation of soil organic carbon and total nitrogen were found higher in upland than in paddy fields.Soil organic carbon and total nitrogen ratio（C/N） was about 10.8 in paddy fields,higher than 9.9 in upland fields.The highest C/N ratio value was found in the paddy fields in Northeast China while the lowest in the up land fields in Northwest China and East China.Meanwhile,results also show significant regional variation of C/N ratio in up land fields,but little significant variation in paddy fields.The soil organic carbon and total nitrogen characteristics and its key effect factors were differ between different paddy soil types,so the different technologies must be selected according to the variation of regional soil types.Results showed that the highest soil organic carbon density was found in the gleyed paddy soil,which was about 75.97%higher than the lowest（submergenic paddy soil）.The gap of the total nitrogen between the above two types of soil was 1.31,and showed significant difference between them.Correlation analysis indicated that the soil organic carbon density was significantly and positively correlated with the plow layer depth and total nitrogen content.But to the carbon and nitrogen ratio,the key factor were much more complicated and differed for each other.Integrated fertilization with organic mature and chemical fertilizers was the key technology to the carbon sequestration and nitrogen utilization.Straw application could increase the soil organic carbon density but with limited extent.Long application of integrated fertilization with organic mature and chemical fertilizers could not only enhance the soil organic carbon density but the carbon and nitrogen ratio whether in double cropping rice region or single cropping rice region.Compared to the region where only the chemical fertilizers was used,the soil organic carbon density and C/N ratio in the integrated fertilization region was about 20.46%and 6.43%higher,respectively.But it was only 3.37%and 4.15%respectively in the single cropping rice region where the soil was much fertilizer.In addition,the carbon sequestration effect was not so significant through the straw applications when the quantity of the residues reached to some level.Conservational farming system technology was beneficial to the increasing of carbon and nitrogen in the soil,but the effect of each technology differed from each other.Taken the Yangtze delta plain for example,results showed that the increases in sown oilseed rape area,reduced-tillage wheat area and straw application area had increased organic carbon about 0.94 Tg,2.76 Tg and 3.95 Tg in surface soils（15 cm）,respectively.The highest effect of carbon sequestration occurred under the transformation of Wheat-rice system to Oilseed rape-rice system.Based on the econometric model,results showed that the farming production behaviors and the land policy had great effect on soil organic carbon and soil nitrogen.Farmer behavior was closely correlation with the farmer’s age,their educational level and land policy.Besides those,different individual opted dissimilar land management especially in the application of organic manure which was greatly related to the soil organic carbon and nitrogen content.Consequently,Perfecting the land use and enlarging the land scale may promote the farmer to increase the investment on the soil and select appropriate technology which will contribute to the enhancement of soil quality.更多还原