【作者】 谭波；

【导师】 傅瓦利；

【作者基本信息】 西南大学 ， 自然地理学， 2011， 硕士

【摘要】 随着人们对环境问题的日益关注,湿地的生态功能及其保护越来越受到重视。湿地是陆地土壤中的主要碳储存库,土壤碳储量较高。湿地通常被认为是温室气体组分的“调节器”和CO2的“汇”,在全球环境变化研究中具有重要意义,湿地生态系统中的碳循环研究已成为当前全球变化研究的热点之一。而氮是湿地土壤中最主要的限制性养分,它是引发江河、湖泊等水体发生富营养化的主要因素。因此,湿地生态系统中氮的物质循环研究具有重要的现实意义。三峡库区消落带是在“自然-人工”双重干扰作用下,由陆地转变为水陆交替的湿地,是一个特殊的湿地生态系统。三峡工程在2008年和2009年两次进行175m试验性蓄水,但只分别蓄水至172.8m和171.43m。本研究于2008年、2009年连续两年在三峡库区小江流域消落带,按海拔段145-160m、160-170m、170-175m采取土壤样品,经室内实验测定土壤的各项基本性质,再利用SPSS 17.0和EXCEL 2007平台对实验数据进行分析,得到主要结论如下：(1)研究区土壤类型主要为紫色土、黄壤和潮土。土壤质地偏轻,砂粒含量偏高,均值为39.11%,最高达到82.33%。土壤pH值大多数分布在7.5-8.5之间,土壤呈中性或弱碱性。土壤养分元素中磷、钾含量偏高,氮含量较低。全氮含量平均值为85.90mg·kg-1,变异系数为27.74%,水解氮含量平均值为63.19mg·kg-1,变异系数为39.40%；全磷含量平均值为1.11g·kg-1,有效磷含量平均值16.71mg·kg-1；土壤全钾含量平均值为21.26g·kg-1,速效钾平均含量为71.24mg·kg-1。(2)研究区内土壤有机碳含量总体上属于偏低水平,介于4.83-20.25g·kg-1之间,平均值为11.18g·k-1。成土母质、覆盖植被、土地利用方式以及淹水时间长短等因素均对土壤有机碳的含量造成影响。从土壤有机碳含量的统计分析来看,研究区内淹水前不同土地利用方式下的土壤有机碳含量差异较大,其平均值大小顺序为：水田>草地>撂荒地>旱地,均值分别为14.75g·k-1、11.94g·kg-1、9.88g·kg-1、9.10g·kg-1。通过对2009年与2008年土壤有机碳含量的比较发现,研究区内2009年土壤有机碳的含量总体上高于2008年,说明淹水环境有利于有机碳的积累。(3)通过对研究区内不同区域、不同土地利用方式下的土壤氮含量进行分析发现,土壤氮含量与有机碳的变化趋势基本一致。不同土地利用类型的土壤全氮含量平均值大小次序均为：水田>草地>撂荒地>旱地。淹水时间的长短同样对土壤氮含量有影响,不过淹水时间较长的地带并不是氮含量最高的地带,而淹水和落干时间相当的地带更有利于土壤中氮的积累,但淹水时间过短也会导致土壤养分的积累减少。研究区2009年土壤氮含量总体上比2008年有所增加,与有机碳含量的变化一致。(4)就研究区内土壤碳和氮含量与土壤淹水状况分析表明,淹水条件有利于土壤中碳和氮的积累。研究表明,土壤有机碳含量和氮含量呈现出良好的相关性,从土壤C/N值来看,不同土地利用方式下的土壤C/N值大小为：水田>撂荒地>旱地>草地。由于高的C/N值能降低有机质的分解从而达到保存有机碳的目的,说明在一定的氮含量水平下,水田土壤的固碳能力高于其它土地利用方式下的土壤,因此,可以认为长期淹水条件下的水田土壤具有“碳汇”潜能。而土壤中的氮主要以有机态的形式存在,土壤有机质含量越高氮含量也就越高。那么,淹水条件下的土壤也在一定程度上发挥了“氮汇”的作用。研究区内土壤碳和氮2009年的含量均高于2008年,可见,三峡库区消落带湿地土壤具有碳/氮的“汇效应”。更多还原

【Abstract】 With growing concern for environmental issues, the ecological function and protection of wetland has been paid attention more and more. On land, wetland is main storage of soil carbon, its soil stocks much carbon. Wetland is generally considered as the "regulator "of greenhouse gas and the "sink" of CO2, it has the vital significance in the global environmental change study. The carbon cycle of wetland ecosystem has become a focus in global change research. And nitrogen is the most important restrictive nutrient of wetland soil and it is the main factor which causes eutrophication of rivers and lakes. Thus, the material cycle of the nitrogen of wetland ecosystems has important practical significance.The water fluctuation zone of Three Gorges Reservoir is wetland which is controlled alternately by land and water formed from the land in the dual interference with nature and human. It is unique wetland ecosystem. The highest water level of Three Gorges Project was 172.8m (in 2008) and 171.43m (in 2009) respectively. In the study, according to altitude section(145-160m,160-170m,170-175m) of water fluctuation zone of the Small River Basin in Three Gorges Reservoir, all soil samples were taken in 2008 and 2009. Through the analysis of experimental data by SPSS 17.0 and EXCEL 2007 after the determination of basic properties of soil samples in laboratory, the main conclusions are as follows.The main types of soil are purple soil, yellow soil and damp soil in the study area. The soil texture of samples was little light and there was much more sand content in the soil. The mean of sand content was 39.11%. the maximum was 82.33%.The distribution of soil pH was mainly at 7.5-8.5. it reflected that the soil was neutral or weak alkaline. There was a lot of K and P in the nutrient elements of the soil, but N was little. The average content of N was 85.90mg·kg-1. CV was 27.74%. The average content of hydrolyzed nitrogen was 63.19mg·kg-1, CV was 39.40%. The average content of total phosphorus and available phosphorus was 1.11g·kg-1 and 16.71mg·kg-1.The average content of total K and available K was 21.26g·kg-1 and 71.24mg·kg-1.SOC was generally at a low level in the study area. Its content ranged 4.83-20.25g·kg-1 and the mean was 11.18g·kg-1. All the factors such as soil parent materials, vegetation, land-use and flooding affect the content of SOC. From statistics analysis about SOC, the content of SOC under different land-use patterns prior to flooding was quite different in the study area. The order of the content of SOC was paddy field(14.75g·kg-1)>grassland(11.94g·kg-1)> abandonment land(9.88g·kg-1)> dry land(9.10g·kg-1). Through the comparison of SOC content in 2009 and 2008, it was found that the SOC content of 2009 was higher than that of 2008 in the study area. Therefore, flooding environment is conducive to the accumulation of soil organic matter.Through the analysis of nitrogen content in the soil of different regions or different land-use patterns in the study area, the result was that the variation of soil nitrogen content and SOC content was consistent. The order of the content of soil total nitrogen and available nitrogen was paddy field> grassland> abandonment land> dry land. The duration of flooding also affected the soil content of nitrogen, but the zone which was flooded longest had not the highest content of nitrogen. Where the soil was flooded as much time as dried there was rather more conducive to the accumulation of nitrogen. If the soil was flooded only extremely short time that can lead to the accumulation of soil nutrients decreased. The soil nitrogen content of 2009 was more than that of 2008 in the study area. It varied with the same trend of SOC.Study on relationship between carbon/nitrogen and soil flooding situation showed that the flooding condition was favorable for the accumulation of carbon and nitrogen in soil. Study showed that there was good correlation between SOC and N. Study on soil C/N value showed that the order of the content of soil C/N value among different land-use patterns was paddy field> abandonment land> dry land> grassland. Because organic matter with high C/N value decomposes slowly, it is favorable for preservation of SOC. Summary, when the nitrogen content is in a certain level, the sequestration capacity of soil carbon in paddy field is stronger than other land-use patterns.Therefore, those may show that paddy soil under long-term flooding is potential "carbon sink". The soil organic nitrogen is main form in the soil N. The more soil organic matter, the more soil nitrogen. To a certain extent, the soil which is in flooded condition plays the role of "nitrogen sink". The content of SOC and N in 2009 was higher than that in 2008 in the study area. It showed that wetland soil of Three Gorges Reservoir played the role of "carbon/nitrogen sink."更多还原