【作者】 Zoljargal Khavtgai；

【导师】 李勇；

【作者基本信息】 中国农业科学院 ， 土壤学， 2013， 博士

【摘要】 土壤有机碳在改善土壤物理、化学和生物性质方面起着关键作用。土壤有机碳可以分成三种主要形态：活跃态或不稳定态、缓效态和无效态。然而,因为大量的SOM是固定无效太物质,所以总SOM不适合测量由于管理方式导致的土壤质量变化。活跃态的土壤有机碳由微生物量和不稳定的有机化合物,占不到总土壤有机碳的5%。土壤微生物量调节所有SOM的转换,是活跃太有机质的主要组成部分。缓效态通常占总有机碳的20-40%,而无效态占到60-70%。尽管活跃态SOM形成了中SOM中相对较小的部分,但是它在维护和监控土壤质量方面起了重要作用。通常把土壤侵蚀过程分成三步,包括土壤颗粒的分离、搬运和沉积过程。土壤侵蚀将密度小和细颗粒的物质从坡上部搬运到坡下部,因此导致了碳的流失和后续的封存。土壤侵蚀通过土壤的移动和表层土壤深度的减少,对SOC含量产生了不利影响,同时对作物生长和土壤微生物活动产生影响。本研究的目的是评价土壤再分布对不同季节土壤养分和土壤有机质部分的效应。土壤样品采自中国黄土高原梯田坡地,从3个不同深度采样,每个深度三次重复,采样时间分别为2011年4月、2012年的7月、9月和12月,分别代表春天、夏天、秋天和冬天。采集的土壤样品需要进行理化性状分析,如粒度分析(土壤质地)、pH、土壤水分(SM)、容重(BD)、土壤有机碳(SOC)、总氮(TN)、有效氮(AN)、有效磷(AP)、微生物量碳(MBC)和高锰酸盐氧化有机碳(POXC)。POXC通过分光光度计测量,EOC和CPC由熏蒸提取法测定,MBC则由熏蒸何为熏蒸样品C浓度之间的差异来计算。梯田坡地的土壤再分布(侵蚀和沉积)格局用137Cs技术估计。进一步说,质量平衡模型2计算的总土壤再分布表明在坡上部土壤流失39.74t ha-1y-r1、坡低部沉积27.70t ha-1yr1。耕作引起的土壤再分布利用Lindstrom等人(2000年)开发的TEP模型计算。耕作引起的土壤再分布为坡上部土壤流失25.06t ha-1yr-1坡低部沉积4.78t ha1yr1。水蚀引起的土壤再分布通过总的土壤再分布减去耕作引起的土壤再分布来计算。水蚀引起的土壤再分布估计显示坡上部土壤流失14.68t ha-1yr-1坡低部沉积22.93t ha-1yr-1。我们的结果表明,耕作侵蚀在梯田坡地侵蚀中占主导。对于所有深度,所有季节低位置的C/N高于高位置的。我们的研究结果表明耕作侵蚀导致了沉积点SOC含量高,这与其他研究结果一直。在一年四季中,0-30cm内较低位置的SOC, TN, AN, AP, CFC, MBC和POXC平均值高于上部。研究结果表明,在春季节0-10cm深度AP, CFC, MBC和SMC平均含量最高。SOC, TN和POXC受季节变化影响但差异不显著。在所有点不同深度,由于肥料的使用导致AN在秋季含量最高。在上部0-30cm深度,EOC的平均值从春季到夏季增加了106.18%。在下部0-30cm深度,EOC平均值从春季到夏季减少了31.79%,然后从夏季到冬季又增加了51.53%。总的来说,坡上部0-10,10-20和0-30cm深度CFC随季节变化没有差别。坡上部0-30cm,从春季到冬季,CFC平均值增加了14.55%。坡下部0-30cm,从春季到夏季,CFC平均值降低了34.12%,二重夏季到冬季却增加了16.16%。在坡下部0-30cm,冲击的CFC平均值显著高于其他三个季节。在坡上部0-30cm,从春季到秋季,MBC减少了46.31%,而从秋季到冬季提高了6.71%。在坡上部0-30cm,MBC在春季时含量最高,秋季和冬季最低,夏季介于中间。在坡下部0-30cm,从春季到秋季,MBC减少了52.14%,而从秋季到冬季提高了9.89%。在坡下部0-30cm,MBC含量在春季时最高。坡上部0-30cm,从春季到冬季,POXC平均值降低了32.68%。坡下部0-30cm,从春季到秋季,CFC平均值降低了26.46%,从秋季到冬季却增加了24.5%0种植,再说有点不同深度下,POXC在不同季节之间没有显著差异。本研究中的许多测量呈显著相关。由于耕作侵蚀,土壤再分布与SOC, TN, CFC和MBC相关性较好,由于水力侵蚀,土壤再分布与AP相关性较好。在所有采样点,土壤中的137CS和MBC呈很强的正相关关系,这表明它们可能沿着相同物理路线运动。更多还原

【Abstract】 Soil organic matter plays a key role in the improvement of soil physical, chemical and biological properties. Soil organic matter can be divided into three main pools:active or labile, slow and passive. However, total SOM is not a good measure of management-induced change in soil quality because the bulk of total SOM is recalcitrant passive pool material. The active pool, which is comprised of microbial biomass and labile organic compounds, makes up less than5%of the soil organic carbon. Soil microbial biomass regulates all SOM transformations and is considered to be the chief component of the active organic matter pool. The slow pool usually makes up20-40%of the total organic C and the recalcitrant pool makes up60-70%of the soil C. The active pool of SOM forms a relatively small portion of total SOM but it plays important roles in maintaining and monitoring soil quality. Soil erosion traditionally conceived as three-step process involving the detachment, transport and deposition of the soil particles. Soil erosion transport light density and fine particle soil materials from hill down to low-lying land areas, which can lead to carbon loss and subsequent sequestration. Soil erosion adversely affects SOC content by directly removal of soil and reduction of the top soil depth; it also impacts plant growth and soil biological activity. The objective of this study was to assess the effect of soil redistribution on seasonal changes in soil nutrients and soil organic carbon fractions. Soil samples were collected from three depths (0-10,10-20and20-30cm) with three replications in April,2011and July, September and December,2012representing spring, summer, autumn and winter seasons from terraced slope in loess plateau, China. The collected soil samples were subjected to analyses for physico-chemical properties such as particle size analysis (soil texture), pH, soil moisture (SM), bulk density (BD), soil organic carbon (SOC), total nitrogen (TN), available nitrogen (AN), available phosphorus (AP), microbial biomass carbon (MBC), permanganate oxidizable organic carbon (POXC). POXC was determined by spectrophotometer, EOC and CFC were determined by fumigation extraction method, MBC was calculated as the difference in C concentration between the fumigated and non fumigated samples. On cultivated sloping land where tillage practices occur, soil redistribution not only depends on erosion/deposition by water, but also influenced by tillage erosion. Soil redistribution (erosion and deposition) patterns were estimated in terraced slope using the fallout137Cs technique. In details, total soil redistribution estimated from Mass Balance Model2indicated that soil eroded from upper slope position by39.74t ha-1yr-1and deposited on lower position by27.70t ha-1yr-1. Soil redistribution by tillage was determined by using the TEP model developed by Lindstrom. Tillage-induced soil redistribution was25.06t ha-1yr-1soil losses from upper slope and4.78t ha-1yr-1soils deposited on the lower slope. Water-induced soil redistribution was calculated by subtracting tillage-induced soil redistribution from total soil redistribution. The estimated water-induced soil redistribution indicated that soil eroded from upper slope position by14.68t ha-1yr-1and22.93t ha-1yr-1gains on lower position. Our results indicated that tillage erosion was much dominant at our terraced slope. At all depths, C/N ratio was higher in lower site than in upper site in all seasons. Our result agrees with other studies, indicating that tillage erosion results in high SOC inventory at depositional sites.At0-30cm, mean of SOC, TN, AN, AP, CFC, MBC and POXC are significantly higher under lower site than under upper site in all seasons. The result showed that average content of AP, CFC, MBC and SMC was highest in spring at0-10cm depth. SOC, TN and POXC were little altered by seasons but not significantly. In both sites at all depth, AN was highest in autumn, due to fertility. In upper site at0-30cm, mean of EOC increased106.18%from spring to winter. In lower site at0-30cm, mean of EOC decreased31.79%from spring to summer then increased51.53%from summer to winter. In general, in upper site at0-10,10-20and0-30cm depths, CFC was no differences between seasons. In upper site at0-30cm, mean of CFC increased14.55%from spring to winter. In lower site at0-30cm, mean of CFC decreased34.12%from spring to summer then increased16.16%from summer to winter. In lower site at0-30cm, mean of CFC was significantly higher in spring than in other three seasons. In upper site at0-30cm, the MBC decreased46.31%from spring to autumn then increased6.71%in winter. In upper site at0-30cm, MBC was highest in spring, lowest in autumn and winter and intermediate in summer. In lower site at0-30cm, the MBC decreased52.14%from spring to autumn then increased9.89%in winter. In lower site at0-30cm, MBC was higher in spring than in other three seasons. In upper site at0-30cm, POXC decreased32.68%from spring to winter. In lower site at0-30cm, the mean of POXC decreased26.46%from spring to autumn then increased24.5%in winter. In general, in both sites at all depths, POXC was no significantly differences between seasons.Many measurements in this study were significantly correlated with each other. Soil redistribution rates because of tillage erosion gave a better correlation with SOC, TN, CFC and MBC. Soil redistribution rates because of water erosion gave a better correlation with AP. The strong and positive relationships between soil137Cs and MBC in both sites suggest that they are probably moving along similar physical pathways.更多还原