【作者】 许信旺；

【导师】 潘根兴；

【作者基本信息】 南京农业大学 ， 土壤学， 2008， 博士

【摘要】 碳储存与变化研究是全球陆地生态系统碳循环和应对气候变化的重要课题,近期研究表明农田土壤具有重大的固碳潜力。中国拥有总耕地面积130M hm~2的农田,约占全球的7%,然而,中国农田土壤固碳潜力和固碳持续期尚未得到量化。农田生态系统土壤碳库受到强烈的人为干扰,同时又可以在较短的时间尺度上进行人为调节,研究不同尺度区域,影响土壤有机碳固定的因素显得更加迫切。本文选择县域(安徽省池州市贵池区)、省域(安徽省)和国家(中国)三种尺度来研究农田土壤有机碳时空差异及影响因素,采用第二次土壤普查资料(安徽省216个土种及218个典型剖面,贵池区66个土种),全国1980-2007年以来的耕作土壤的实测数据(1099个样点,其中,416个水稻土,683个旱作土),典型土种连续监测数据(5个)和县域尺度高密度均衡布点采样(5048个土样)调查分析,研究农田土壤有机碳的分布与变化,讨论了农田土壤有机碳的影响因素。主要结果如下:水稻土土壤有机碳含量及碳密度高于旱作土。贵池区(县域尺度)1984年水田耕层有机碳含量比旱地高出1/3,有机碳密度高出约5%。2005年贵池区土壤调查监测数据,统计分析得出:水田耕层有机碳含量比旱地高出45.18%,有机碳密度高出23.73%。安徽省第二次普查资料统计表明,全省表层土壤平均有机碳密度为31.64±16.39tC/hm~2,其中,水稻土耕层有机碳密度为27.7±6.72tC/hm~2,犁底层有机碳密度为14.11±6.44tC/hm~2。林地土壤表层有机碳密度(36.36±18.75tC/hm~2)高于全省表层土壤平均有机碳密度,旱作土壤表层有机碳密度(17.58±6.07tC/hm~2)则低于全省平均值。近20年来全国水田耕层有机碳含量为旱地耕层有机碳含量的175%-176%。安徽省土壤有机碳库为0.71Pg,其中,表层土壤有机碳总量达0.28Pg。在表层碳库中,林地＞水稻土＞旱地。表层有机碳库按地理区域碳库的大小为:皖南区＞江淮丘陵区＞淮北平原区＞皖西大别山区＞沿江平原区。气候和植被控制着表层土壤有机碳的省域分布,降水与土壤有机碳含量呈正相关。地形和母质影响土壤亚类间的有机碳的差异,土壤总氮与土壤有机质呈极显著相关,平原区土壤粘粒含量与表土有机碳固定有较大关系。近20多年来,中国水稻土和旱作土的有机碳含量70%样本上升,上升或下降幅度超过90%的样本集中在-1%～4%。对比贵池区1984年和2005年两个时段的农田土壤有机碳的含量和碳密度,水稻土有机碳含量年均提高了2.01%,有机碳密度年均提高了3%;旱作土有机碳含量年均提高了1.11%,有机碳密度年均增加了1.3%。农田土壤有机碳与地貌、植被、气候等自然地理因素相关。贵池区(县域尺度)的农田土壤有机碳含量按地貌类型由高到低的顺序为:平原＞盆地＞山地＞丘陵,位于平坦地貌部位的农田土壤有机碳高于处于岗坡地、低洼渍水处的SOC。位于南坡、东坡的农田SOC高于北坡、西坡的田块。安徽省域土壤有机碳密度则是:皖南山区＞皖西大别山区＞沿长江平原＞江淮丘陵区＞皖北平原区。降水和植被类型控制土壤有机碳的省域分布,降水与土壤有机碳含量呈正相关,地形和母质影响土壤亚类的有机碳分布格局。全国尺度农田耕层土壤有机碳的含量受制于气候因素中的年均气温与降水。农田土壤有机碳含量与土壤性质相关。贵池区农田土壤有机碳与速效P、碱解氮呈正相关。水稻土黏粘含量与有机碳呈正相关,而旱作土则无线性相关。安徽省域分析表明:林地、水稻土和旱作土壤表层有机碳量与总氮之间的相关系数(R)均大于0.78,农田土壤粘粒含量与土壤有机碳固定也有一定关系。使用监测数据定量估算了中国农田土壤有机碳固定量和有效持续时间,旱地和水稻土分别需要34年和27年。利用有机碳的年增加率(RAI)的绝对值估算旱地和水稻土分别需要36年和29年。使用这些值估算出表土年均碳增额为32.0±65.4 Tg/yr和33.6±77.5Tg/yr(面积加权),1982-2006整个中国农田表层的总碳增额为0.77±1.57 Pg和0.81±1.86 Pg(面积加权)。旱地和水稻土的RAI值和原始的有机碳量呈负相关关系,表明有机碳含量低的土壤有较大固碳能力,估算得出旱作土和水稻土的固碳潜力为16.1g/kg和26.7g/kg。更多还原

【Abstract】 Carbon（C） storage and sequestration is considered to be an important issue in the study of terrestrial C cycling and global climatic change.Recent studies have shown significant potential for soil C sequestration in croplands.China has a total area of croplands of 130Mhm²,7%to the global total.However,the magnitude and duration of the C sequestration potential of China’s cropland soils has not been quantified.The author selected three spatial scales to study the distribution and dynamic of soil organic carbon（SOC） of cropland:Guichi County as the local scale,Anhui province as the provincial scale and China as the country scale.Using the soil series data collected from the 2^nd National Soil Survey estimates the content and density of soil organic carbon in three scales.In this study,we used data of SOC change at monitoring sites from publications available in 1980-2007 to perform a meta-analysis to project the size,duration and potential capacity of soil carbon sequestration in China’s croplands.The data set comprises 1099 observations including 416 from rice paddies and 683 from dry croplands across China. The main results were as follows:SOC content and carbon density in paddy soil was higher than that in dry cropland.SOC content and density in paddy soil were 1/3 and 5%higher respectively than that in dry cropland in 1984 while they in paddy soil were 45.18%and 23.73%higher respectively than that in dry cropland in 2005 in Guichi county.According to soil survey data from 2005, statistic analysis showed that total topsoil SOC density was 31.64±16.39tC/hm²,with 36.36±18.75 tC/hm² from the forest soils,17.58±6.07tC/hm² from dry cropland soils and 27.7±6.72 tC/hm² from the plow layer of paddy soil and 14.11±6.44 tC/hm² from plow-pan layer in Anhui province.The content of paddy topsoil organic C was 175%-176%of dry lands in China.The results showed total organic carbon pool of Anhui province was 0.71Pg,and total topsoil SOC pool was 0.28 Pg,with the trends of forest soils＞paddy soils＞dryland soils. According to the geographical division,the size of topsoil carbon pool was in this order: south Anhui area＞Jianghuai hill area＞Huaibei Plain area＞Wanxi Dabie Mountain area＞Along the Yangtze River plain area.Climate and Vegetation dominates the provincial scale distribution of content SOC.There was a significant positive correlation between SOC and precipitation.The difference of SOC in soil subspecies depends on terrain and parent of material.The SOC storage was found closely related to the clay（＜0.002mm） content and N enrichment in soils in plain area.SOC content of 70%samples both paddy soil and dry cropland increased in recent 20 years of China,those samples that changed over 90%ranged from-1%and 4%.Compared 1984 to 2005 in Guichi county,SOC content and density in paddy soil raised 2.01%and 3%, respectively,while dry cropland 1.11%and 1.3%every year.SOC content of cropland was relative to physical geography characteristics,such as physiognomy,vegetation,climate and so on.SOC content ranked as Plain＞Basin＞Mountanious Region＞Hill according to physiognomy type on Guichi county scale.SOC content of cropland in flat physiognomy site was higher than that in hillock and low-lying place,and SOC content in south and east slope were higher than that in north and west slope.SOC density of Anhui provincal region ranked as South Anhui mountanious area＞West Anhui Dabieshan mountainious area＞Changjiang Plain＞Jianghuai hill area＞Huaibei Plain area.SOC distribution was positive relative to precipitation,which was influenced by precipitation and vegetation.SOC distribution was affected by landform and parent materials in soil subspecies.Topsoil SOC content of cropland on national scale was controlled by air temperature and precipitation.There was a close relationship between SOC content and soil property.However,there was difference between dry cropland and paddy soil for the factors impacting SOC content in Guichi County.The positive correlation was shown between SOC and available P, available N and clay content for paddy soil.The results also indicated there was a significant correlation between SOC content of topsoil and total N（R²＞0.78） on the scale of Anhui province,and clay content affected the SOC sequestration.The estimated effective duration for SOC sequestration is 34-36 year for dry croplands and 27-29 years for rice paddies.Using the average RAIs,a topsoil C stock increase for the whole of China between 1982 and 2006 can be projected between 32.0±65.4 Tg C/yr and 33.6±77.5;Tg C/yr,with a total C stock increase between 0.77±1.57 Pg C and 0.81±1.86 Pg C.There is still a high potential for C sequestration,as the achievable level under current practices is estimated to be at 16.1 g C/kg and at 26.7 g C/kg for dry croplands and rice paddies,respectively.更多还原