【作者】 徐畅；

【导师】 谢德体； 高明； 魏朝富；

【作者基本信息】 西南大学 ， 农业资源利用， 2011， 博士

【摘要】 随着我国人口的迅速膨胀以及化肥用量的增加,大量湖泊、河流、近海域都不同程度地出现水体富营养化现象。三峡库区作为我国重要的湖泊水域和战略水资源库,在其成库后逐渐转变成一个受人工调控程度大、且具有典型湖泊和河流双重特征的深水水库,库周地区的生态环境也因此而发生变化。如何掌控库周地区农业土壤中面源污染元素氮的固定及排放就成为保证水库水质安全及库周农业发展的重中之重。然而,目前国内外的氮素面源污染研究主要集中在对湖泊或江河等自然景观的氮磷迁移上,而对于三峡库区这种大型人工水利工程影响背景下的农业土壤氮素迁移转化乃至农田生态环境变化的研究相对较少。因此,阐明三峡库区紫色土氮素在土壤生态系统中的迁移转化机理及动态过程,选择出有效控制氮素流失的调控技术对于发展“库区生态环境保护”和“农业可持续发展”双赢的新型减排农业,增强库区水域系统及农田系统应对环境气候变化的综合能力具有重要意义。本研究选择三峡库区王家沟小流域为研究对象,在实地采样与实验室分析的基础上,采用地统计学方法分析小流域土壤氮素在三维空间的分布特征,剖析地形因子、土地利用方式以及土层深度对土壤氮素分布的影响,以阐明小流域土壤氮素的基础情况与肥力概况；并以好氧培养的方式描述农业土壤中有机氮在温度、湿度、外源氮素等多重环境因子影响下进行矿化的动态特征,揭示土壤氮素矿化过程与各影响因素之间的相关关系,诠释氮素在土壤生态系统中的转化机理；与此同时,通过室内土柱模拟试验,揭示不同质地土壤氮素在土体垂直剖面上的渗漏淋失规律及动态运移特征,充实对土壤氮素垂直迁移机制的认识；在了解氮素迁移转化行为的基础上,利用田间径流小区试验对比各防控措施在农业生产中运用的实际效果,以筛选出适宜三峡库区农业土壤氮素调控的途径和方法,为库区面源污染控制技术的研发和可持续农业的发展提供一定的科学依据。主要研究结果如下：1.三峡库区小流域土壤氮素空间分布特征以三峡库区王家沟小流域为样区,研究了全氮和碱解氮在流域空间上的分布情况以及地形因子和土地利用方式对其分布的影响。结果表明：土壤全氮在流域中部地区的含量偏高,并呈现出由中部向四周逐层递减的分布规律,土壤碱解氮含量最高的区域出现在中部及南部的海拔最低处,含量最低的区域为小流域的西部和西南部,东部及东北部的碱解氮含量居中。垂直空间的分布上,土壤全氮在0～100 cm垂直剖面上的变化规律较为明显且平缓,各种土地利用方式的土壤全氮含量均表现出随土层加深而逐渐减小的整体趋势,各层次间的含量差异不大,土壤碱解氮在0-60 cm的垂直剖面上仍然表现出随土壤层次加深,其含量逐渐减小的变化趋势,但各层次间的碱解氮含量基本都达到极显著差异(p<0.01)。各地形因子对流域内土壤氮素分布的影响较明显。各个坡度上的土壤全氮含量主要集中在1.0-1.5 g/kg之间,低坡度区域土壤全氮含量的分布稳定且适中,高坡度区域的全氮含量则普遍较低,且分布不均；碱解氮含量受坡度影响相对较小,随着坡度的升高或降低,其含量未表现出明显的规律性变化。从坡向上看,除东北坡向的全氮含量较低外,其它各坡向上的全氮含量分布相似,主要集中于1.0-1.5 g/kg之间,只有西南坡向有部分全氮含量较高的地块出现；碱解氮含量的高值则出现在西南坡向,低值出现在南和东南坡向,除此之外的其它坡向上碱解氮含量均适中,且分布均匀。坡位对土壤氮素的影响各不相同,低坡位区域内,土壤全氮及碱解氮含量分布不-高低含量的地块均有出现,而高坡位区域内,全氮及碱解氮含量则较低,未见高值样本的分布,中坡位区域的全氮及碱解氮含量最为适宜,多数集中在80～110 mg/kg之间。不同土地利用方式下土壤全氮含量的高低顺序依次为水田>林地>桑园>旱地>撂荒地,而碱解氮含量高低则基本现出水田>林地>旱地>撂荒地>桑园的规律性变化。该部分研究对土壤氮素分布的影响因子进行了深刻剖析,阐明了小流域土壤氮素的空间分布情况和基础肥力状况。2.三峡库区紫色土氮素矿化动态特征采用室内好氧培养的方法,对小流域紫色土中有机氮在温度、水分、外源氮素等多重环境因子影响下发生矿化的动态特征进行了研究。结果表明,紫色土的净氮矿化量在各个阶段均表现出随培养温度升高而逐渐增大的趋势。其中,砂壤土的净氮矿化量在各温度水平间均达到极显著异,而壤土和粘土的净氮矿化量除了在15℃和25℃两个温度梯度间未达到极显著差异外,15℃和35℃之间以及25℃和35℃之间的净氮矿化量均达到极显著差异。而紫色十净氮矿化量对水分变化的响应也非常规律,同样呈现出随水分含量增加,净氮矿化量逐渐增大的趋势,且各水分含量水平间的净氮矿化量均表现出极显著性差异(p<0.01)。除此之外,土壤温度和水分还对紫色土氮素的矿化作用产生明显的交互效应。当温度和水分条件均为最低水平时,净氮矿化量呈现出负值,即两者的交互作用导致了矿化进程的反向进行：而当温度和水分条件均为最高水平时,净氮矿化量却并未表现出矿化量的最高值。温度对紫色土矿化作用的影响在一定程度上大于水分含量。外加氮源对紫色土氮素的矿化过程表现出非常明显的促进作用。在不同的温度和水分处理下,添加外源氮素后的净氮矿化量在各个培养阶段均显著大于未添加氮素的净氮矿化量,差异达极显著水平(p<0.01),并且当温度和水分含量均较高时,外加氮源的有效性会相应增强,使得有机氮的矿化势大于矿质氮的生物固持,土壤净氮矿化量明显增高。三种质地紫色土的矿化作用在未添加外源氮素的情况下,以壤土的净氮矿化总量最高,粘土次之,砂壤土最低,但添加外源氮素后,三种质地土壤的氮素矿化能力在各温度和水分条件下则呈现出砂壤土>粘土>壤土的变化趋势。壤土或偏砂质壤土的通气状况良好,因而对土壤系统中好氧微生物种类和活性产生积极作用,促进矿化作用的发生。本研究阐明了土壤质地、温度、水分、外加氮源等因素对紫色土氮素矿化的综合影响,有助于更加深入地诠释土壤氮素的转化机理。3.三峡库区紫色土氮素渗漏淋失规律以三峡库区紫色土为例,结合小型原状土柱对不同质地土壤的渗漏淋失规律进行了研究和探讨。结果表明,在相同灌水量处理下,砂壤土的水分淋失量相对较大,壤土次之,粘土的水分淋失量最小,水分渗漏淋失量与灌水量显著相关,整个渗漏阶段中水分淋失量的最大值基本都出现在灌水前期(5-10 d)。比较不同氮肥施用量的铵态氮及硝态氮实时淋失浓度,各渗漏阶段均表现出高氮处理最高、低氮处理次之,未施氮处理最低的总体趋势。氮素实时淋失浓度较高值基本都出现在灌水初期(5-30 d),由于该时段的淋失浓度大,而采样间隔时间较短,因此,三种质地土壤的氮素阶段淋失速率最大值就出现在灌水的最初阶段(5-10 d)。不同氮肥施用量处理下氮素的累积淋失浓度在整个灌水期的各个阶段呈现出先增大后减小的总体变化规律。其中,三种质地土壤的硝态氮累积淋失浓度最高值均出现灌水开始后30 d时,而铵态氮累积淋失浓度最高值所出现的时段则根据土壤质地的不同分布各异,其中,砂壤土和粘土的铵态氮累积淋失浓度最高值出现在灌水开始后20 d时,而壤土的最高值则出现在40 d时。进一步分析各种形态氮素的渗漏淋失规律发现,三峡库区紫色土的硝态氮淋失总浓度在各种氮肥施用量处理下均大于铵态氮淋失总浓度,这说明硝态氮在土壤垂直剖面上的移动性大于铵态氮。除此之外,土壤质地不同,硝态氮和铵态氮的垂直移动性也各不相同。其中,未施氮及低氮处理的硝态氮淋失总浓度基本都表现为砂壤土最高,壤土次之,粘土最低,但高氮处理下硝态氮的淋失总浓度则表现为壤土>砂壤土>粘土；氮肥施用量对三种质地土壤中铵态氮的垂直迁移影响不大,其淋失总浓度在各氮肥施用量处理下均表现为壤土>砂壤土>粘土。该部分研究阐明了土壤氮素的垂直运移动态变化规律,进一步充实了对土壤氮素垂直迁移机制的认识。4.三峡库区小流域旱坡地氮素流失特征及调控技术在掌握三峡库区小流域土壤氮素空间分布特征以及转化迁移规律的基础上,通过对比不同耕作措施下的水土流失和土壤氮素流失状况筛选出适合于研究区的旱坡地土壤氮素调控技术。结果表明,小流域的降雨期主要集中在6月和7月。其中,6月共产生径流三次,最大径流量为21.96L/m2,泥沙流失量的最高值出现在7月,其值为61.85 t/km2,径流量、泥沙流失量均与平均雨强呈现出显著的正相关关系。实施保护性耕作措施后,径流量和泥沙流失量均出现不同程度的减小整个观测期中,T3(免耕+顺坡耕作+稻草覆盖)和T5(免耕+横坡垄作)处理有效地减少了坡面径流量,而T4(顺坡耕作+植物篱)处理则对径流泥沙的拦截效果最佳。小流域旱坡地土壤中的氮素分别通过径流以及径流泥沙两种途径产生流失。其中,径流中氮素的流失量相对较小,铵态氮、硝态氮以及总氮的径流流失量最大值分别为10.75 mg/m2、44.55mg/m2和291.38 mg/m2,且均出现在常规顺坡耕作处理；与之相反,三种形态氮素的径流流失量最小值则分别为5.63 mg/m2、24.06 mg/m2和152.62 mg/m2,均出现在T4处理,除此之外,T2(顺坡耕作+PAM土壤调节剂)处理也对氮素的坡面径流流失表现出较好的拦截作用。径流泥沙中所携带的氮素流失量相对较大,尤以T1和T6(横坡耕作)处理最为明显,也就是说,除常规顺坡耕作处理外,横坡耕作对泥沙中氮素的固持效应最差；比较而言,T4和T5(免耕+横坡垄作)处理则表现出对泥沙中氮素较强的保蓄作用,其氮素流失量在整个观测期的各次降雨产流中均表现为最小。在整个观测期内,通过泥沙携带发生流失的氮素明显大于径流流失的氮素,泥沙中总氮流失量约为径流中总氮流失量的1.83～3.38倍。泥沙中氮素的流失以硝态氮为主,径流中氮素的流失则以颗粒态为主,颗粒态氮的流失量占总氮流失量的53%-62%。综上所述,在地形地貌复杂的三峡库区,其土壤氮素的空间分布主要表现为坡度、坡向、海拔以及土地利用方式等外部条件的共同作用,从而构成库区小流域土壤氮素的基础肥力特征。土壤温度为主导的氮素矿化动力学理论并不足以解释普遍观察到的紫色土有机氮矿化作用机理,氮素矿化作用的驱动力主要来源于温度和水分含量的交互作用,但这种作用也会随着外源氮素以及土壤质地的不同而发生变化,进而影响到紫色土有机氮矿化的综合响应。氮素在土壤剖面的渗漏浓度及速率很大程度上取决于土壤中粘粒含量的比例以及氮肥施用量的高低。坡面土壤有机氮的转化特征与垂直剖面氮素的迁移规律相辅相成,共同决定了适合于三峡库区小流域土壤氮素流失的调控技术,同时也进一步清楚,调控技术只能在一定的外界环境条件下对土壤氮素的行为进行调节,当外界环境的变化程度超过一定临界值时,人为调控的作用就微乎其微了。今后还需开展三峡库区大区域尺度及全境生态系统和气候带背景下的土壤氮素迁移转化机制研究,以了解整个库区不同类型农业土壤中氮素的基础储备及面源污染潜在风险,并加强土壤氮素矿化机理与微生物活性和生物酶作用的耦合机制研究,与此同时,应创建三峡库区生态农业前提下的野外大型原状土柱观测系统,为三峡库区大区域土壤氮素调控综合技术体系的建立提供更加深入、全面的基础研究数据,以设计、整合出对三峡库区农田氮素最合理、有效的技术调控体系。更多还原

【Abstract】 With the rapid expansion of China’s population and increased use of fertilizer, a large number of lakes, rivers and near sea area have broken out the phenomenon of eutrophication in varying degrees. The Three Gorges Reservoir Area, as an important lake water area and strategic water resource reservoir, has gradually turning into a special deep reservoir that can be artificially controlled and with typical lake and river characteristic. The ecological environment of surrounding area has also changed at the same time. So how to control the fixation and emission of nitrogen in agriculture soil around the reservoir has become a top priority of ensure the water quality of reservoir and the agricultural development of reservoir surrounding. However, domestic and international present research of non-point source pollution was focused on the nitrogen and phosphorus movement of lakes, rivers and other natural landscape. Thus, it is of vital importance to elucidate the movement, transformation mechanism and dynamic process of purple soil nitrogen in soil ecosystem, and also choose a effective controlling technology of nitrogen loss for developing the win-win emission reduction agriculture of environmental protection and agricultural sustainable development, and for enhancing the comprehensive capacity of water and farm systems answering to the climatic change in Three Gorges Reservoir Area. In this study, taking the small catchment of Wangjiagou in Three Gorge Reservoir Area as study object, the effect of topography, land use and soil depth on soil nitrogen distribution was analyzed with the statistical method of geostatistics, combined with the test method of field sampling and laboratory analysis, on this basis, to clarify the basic soil nitrogen condition and soil fertility situation in the target area. Secondly, the mineralization dynamic property of soil organic nitrogen under the influence of multiple environmental factors (soil temperature, moisture, and exogenous nitrogen) was described by means of aerobic incubation method, and the correlation between mineralization process and influencing factors was revealed too, in order to elucidate the transformation mechanism of nitrogen in soil ecosystem. Then, the leaching loss characteristic and dynamic movement feature of nitrogen in vertical profile of different texture soil was annotated through soil column simulation in lab, to enrich the understanding about the fixation mechanism of nitrogen in purple soil. Lastly, based on the knowledge of nitrogen movement and transformation, a field trial was carried out to compare the practical application effect under different control measures in agricultural production in order to select the most appropriate way to control soil nitrogen of Three Gorges Reservoir Area and provide scientific basis to the technology exploitation of non-point source pollution controlling and development of sustainable agriculture. The main results are as follows:1. The spatial distribution of soil nitrogen in Three Gorges Reservoir AreaThe nitrogen spatial distribution and the effect of topography and land use on soil total nitrogen and available nitrogen were studied by taking the small catchment of Wangjiagou as sampling area. It showed that the total nitrogen of central region is higher over the whole small catchment, it decreased gradually as the shape of layer from the center to the surrounding. The highest available nitrogen content area was still distributed in central and southern region and the lowest available nitrogen content area was located in the west and southwest, the available nitrogen content of northeast and east area was at the middle level in the whole small catchment. To the nitrogen distribution of vertical space, the variation of total nitrogen in the vertical profile of 0～100 cm was significant and smooth, with the increasing of soil depth, total nitrogen has showed a trend of decreasing gradually under various land use type, and the difference was not significant (p<0.01). The change law of available nitrogen in the vertical profile of 0-60 cm was very similar with total nitrogen, but the difference between different soil layers was highly significant (p<0.01).The effect of topographic factors on soil nitrogen distribution was very obvious. Within the entire small catchment of each slope gradient, the content of soil total nitrogen was concentrated in the content range of 1.0-1.5 g·kg-1, the distribution condition of soil total nitrogen in lower slope gradient region was stable and moderate, but the distribution condition of soil total nitrogen in higher slope gradient region was generally lower and uneven. The effect of slope gradient on available nitrogen was less than total nitrogen, with the increasing or decreasing of slope gradient, soil available nitrogen content has not showed an obvious change. To the effect of slope aspect on nitrogen distribution, in addition to the lower content distribution of total nitrogen on northeast, the distribution condition of other slope aspects of the whole small catchment was nearly similar which was concentrated in the content range of 1.0-1.5 g·kg-1, only in the southwest slope aspect existed some plots which had higher content of total nitrogen. The highest content region of available nitrogen was appeared in the slope aspect of southwest, and lowest content region of available nitrogen was appeared in the slope aspect of south and southeast, in addition, the content of available nitrogen in other slope aspects was moderate and homogeneous. The effect of slope position on soil nitrogen was varied greatly. In the region of low slope position, the distribution of soil nitrogen was extremely uneven, soil sampling with higher nitrogen content and lower nitrogen content were all appeared. But in the region of high slope position, the content of soil nitrogen was lower, there was no soil sampling with higher nitrogen content. The nitrogen content of middle slope position region was in the range of 80～110 mg-kg-1. The content of soil total nitrogen under different land use types showed a decreasing law of paddy field, forest land, mulberry field, dry land and fallow land, and the distribution of soil available nitrogen follow the decline order of paddy field, forest land, dry land, fallow land and mulberry field. In this part, the impact factors of soil nitrogen distribution have anatomized deeply, and the basic soil nitrogen condition and soil fertility situation has clarified at the same time.2. Nitrogen mineralization characteristics of purple soil in Three Gorges Reservoir AreaThrough the method of aerobic incubation, the mineralization dynamic property of soil organic nitrogen under comprehensive influence of soil temperature, moisture, and exogenous nitrogen was described in detail. It showed that a trend of increasing gradually of net nitrogen mineralization in purple soil with the increasing incubation temperature could be found during each culture stage. The net nitrogen mineralization difference of sandy loam between three temperature levels was highly significant (p<0.01), but the net nitrogen mineralization of loam and clay between 15℃and 35℃as well as 25℃and 35℃both showed a highly significant difference, while the net nitrogen mineralization hadn’t showed a significant difference between 15℃and 25℃. The response of purple soil net nitrogen mineralization to the change of moisture was also extremely regular. It showed the trend that the value of net nitrogen mineralization increased gradually with the increasing of incubation moisture, and the difference between three moisture levels was highly significant (p<0.01). In addition, soil temperature and water content has significant interaction effects on nitrogen mineralization of purple soil. When the levels of temperature and moisture were the lowest, the value of net nitrogen mineralization was negative, which indicated that the two factors resulted in the reverse process of mineralization. However, when the levels of temperature and moisture were the highest, the value of net nitrogen mineralization wasn’t the highest. The effect of temperature on nitrogen mineralization of purple soil was more than moisture to a certain extent.Exogenous nitrogen showed a significant promoted role on the process of purple soil nitrogen mineralization. The value of net nitrogen mineralization with exogenous nitrogen was obviously higher than the one without exogenous nitrogen during each culture stage under different temperature and moisture levels, and showed a highly significant difference (p<0.01). When the levels of temperature and moisture were the highest, the effectiveness of exogenous nitrogen would increase corresponding, and the mineralization potential of organic nitrogen would be stronger than the biological immobilization of mineral nitrogen, so the value of net nitrogen mineralization would be significantly higher. Nitrogen mineralization of purple soil under different soil texture without exogenous nitrogen showed a decreasing trend of loam, clay and sandy loam, and the nitrogen mineralization with exogenous nitrogen was followed the decline order of sandy loam, clay and loam. Because of the well aeration condition of loam and sandy loam, it had a positive effect on increase in the species and activity of aerobic microbial and further contributed to the occurrence of nitrogen mineralization. This part had elucidated the comprehensive effect of soil texture, temperature, moisture and exogenous nitrogen on the nitrogen mineralization of purple soil, it was help to deeply annotate the transformation mechanism of soil nitrogen.3. The law of soil nitrate leaching in Three Gorges Reservoir AreaSoil leaching regular of different texture based on purple soil in Three Gorges Reservoir Area were conducted and explored combined with soil core lysimeter. It showed that the water leaching quantity of sandy loam was the most in three types of soil texture, and the quantity of clay was the minimum under the same quantity of Irrigation water. The quantity of water leaching was significantly related with the quantity of irrigation water, In the whole leaching period, the maximum of water leaching almost appeared in irrigation prophase (5-10 d). Compared with the real-time leaching concentration of soil nitrogen under different levels of nitrogen fertilizer using, the real-time leaching concentration with high nitrogen input was more than the one with low nitrogen input, and the leaching concentration with no nitrogen input was minimum. The higher value of nitrogen leaching almost appeared in irrigation prophase (5-30d). Because of the higher leaching concentration and the shorter sampling interval, the nitrogen leaching rate of three sorts of soil texture also appeared maximum in the initial stage of irrigation (5-10 d). In the whole irrigation stage, the cumulative leaching concentration showed a trend of increasing first and reducing afterwards under different levels of nitrogen fertilizer using. The maximum of cumulative leaching concentration of nitrate nitrogen appeared in 30 d after irrigation starting. Being different from nitrate nitrogen, the cumulative leaching concentration maximum of ammonium nitrogen showed a different trend which affected by soil texture, the maximum of it in the sandy loam and clay appeared in 20 d after irrigation starting, while the maximum of it in clay appeared in 40 d after irrigation starting.Compared with a variety of nitrogen forms in the leachate, it was could be found that the leaching concentrations of nitrate nitrogen were all greater than ammonium nitrogen under different fertilizer levels, in other words, the movability of nitrate nitrogen was better than ammonium nitrogen in vertical direction. But deal with different soil texture, the vertical movement regulars of nitrate nitrogen and ammonium nitrogen were different. For example, under no nitrogen or low nitrogen fertilizer using, the leaching concentration of nitrate nitrogen of three texture soil were followed the decreasing order of sandy loam, loam and clay, but under high nitrogen fertilizer using, the decreasing order changed into loam, sandy loam and clay. But there were little effect of nitrogen fertilizer amount on the leaching concentration of ammonium nitrogen, the leaching concentration of ammonium nitrogen under three levels of nitrogen fertilizer using were all followed the decreasing order of loam, sandy loam and clay. In this part, the leaching loss characteristic and dynamic movement feature of nitrogen in vertical profile of different texture soil was annotated, and further enriched the understanding about the fixation mechanism of nitrogen in purple soil.4. Loss features and control measures of soil nitrogen in sloping upland of Three Gorges Reservoir AreaBased on the knowledge of spatial distribution and movement, transformation of soil nitrogen in small catchment of Three Gorges Reservoir Area, combined with comparing the practical application effect under different control measures in agricultural production, this part selected the most appropriate way to control soil nitrogen in Three Gorges Reservoir Area. It showed that the rainfall mainly concentrated in June and July in study area. Meanwhile, there were three times of runoff in June, the maximum of runoff up to 21.96 L·m-2. The highest loss of sediment appeared in July, which was 61.85 t·km-2, the loss of runoff and sediment showed a significant positive correlation with the average rainfall intensity in the rainfall period. In the runoff plots which carried out conservation tillage, runoff and soil erosion decreased in various degrees. Among the whole observation period, T3 (no-tillage+downslope cultivation+straw overlay) and T5 (no-tillage+contour cultivation) were the best ways to prevent the loss of runoff, while T4 (downslope cultivation+hedgerow) was the best way to prevent the soil erosion.Runoff and sediment were the two ways which caused the loss of soil nitrogen from sloping uplands. Among them, the nitrogen loss through runoff was relatively less, the lost of ammonium, nitrate, and the total amount of nitrogen were 10.75 mg·m-2,44.55 mg·m-2 and 291.38 mg·m-2 respectively. All the loss maximums of various forms of nitrogen appeared in T1 (conventional downslope cultivation) which had no measure taken. By the contrast, all the loss minimums of ammonium, nitrate, and total nitrogen were 5.63 mg·m-2,24.06 mg·m-2 and 152.62 mg·m-2 respectively, and all appeared in T4. In addition, the nitrogen loss under T2 (downslope cultivation+PAM soil regulators) was relatively less too. Therefore, T2 and T4 were the best two ways to prevent the loss of nitrogen through runoff. The nitrogen loss through sediment was relatively more, especially when the runoff plots were constructed of T1 and T6 (contour cultivation). That is to say, contour cultivation did little contribution to preventing nitrogen by sediment from losing. Compared with T6, T4 and T5 (no-tillage+contour cultivation) did something stable to the nitrogen in sediment, the loss of nitrogen were the least after every rainfall during all the observation period. During the whole observation period, the loss of nitrogen through sediment was far more than which lost through runoff, the loss amount of nitrogen through sediment was 1.83-3.38 times than the one through runoff. However, the loss of nitrogen through sediment was mainly by the kind of NO3--N, and the loss of nitrogen through runoff was mainly by the kind of particulate, the loss of particulate nitrogen account for 53% to 62% of the total nitrogen.In summary, the spatial distribution of soil nitrogen showed as the interaction of multiple external conditions like slope gradient, slope aspect, altitude and land-use patterns in the Three Gorges reservoir area of complicated topography, which constituted the fundamental fertility characteristics of soil nitrogen in small catchment of reservoir area. The soil temperature-oriented nitrogen mineralization dynamics theory was incompetent to express the nitrogen mineralization mechanism which was widely observed in purple soil, the driving force of nitrogen mineralization derived from the interacted function of temperature and water content which, however, could vary along with the change of outside nitrogen and soil texture, further affecting comprehensive response of nitrogen mineralization in purple soil. The leaching concentration and rate of nitrogen in the soil vertical profile largely depends on the proportion of clay particle and the level of nitrogen fertilizer using in soil. The transformative characteristics of soil nitrogen in slopes and the movement regulation of soil nitrogen in vertical profile were complementary, which commonly decided the suitable controlling technology of soil nitrogen loss in small catchment of Three Gorges Reservoir Area, making it more clearly that only under a certain external environment could the control technology adjust the behavior of soil nitrogen. If the change of external environment exceeds a certain threshold level, the function of artificial adjustment was minimal. In the future, the movement and transformation mechanism of soil nitrogen should be conducted under the background of large-scale, whole regional ecosystems and climate zone in Three Gorges Reservoir Area, to know the fundamental storage of soil nitrogen and the potential risks of non-point pollution under different types of agricultural soil in reservoir area. Also, the study on the coupling mechanism of soil nitrogen mineralization dynamics and enzyme function should be enhanced innovatively. Meanwhile, we should build wild observation system of large natural soil columns under the premise of ecological agriculture in order to supply more in-depth, comprehensive basic research data to found the integrated control technology systems of soil nitrogen to a large-scaled area in Three Gorges Reservoir Area, and also to design and integrate the most reasonable and effective technical control system of farm land Nitrogen in Three Gorges Reservoir Area.更多还原