【作者】 韩茜；

【导师】 熊黑钢；

【作者基本信息】 新疆大学 ， 自然地理学， 2008， 博士

【摘要】 土壤盐渍化是一个世界性的资源问题和生态问题,是学者们关注的热点。干旱区绿洲的农田土壤盐渍化和次生盐渍化是影响绿洲生存与发展的重要因素。盐渍化土壤在一定条件下会自然地向良性方向发展。这种土壤盐渍化的恢复过程称之为土壤盐渍化的逆向演替。土壤盐渍化的发生过程可视为可逆反应,这个反应时刻处于动态平衡之中,找出促进其逆反应的催化剂,使反应最大限度地朝着逆反应方向进行,土壤盐渍化就会自然地良性恢复。为了探讨土壤盐渍化逆向演替的过程和特征,本文研究的主要内容和结论如下:(1)在奇台绿洲不同位置选择不同耕种时间的农田,分析其剖面土壤可溶性总盐、pH值、有机质含量随耕种时间的变化。通过对比不同采样地点,不同耕种时间的土壤特性,探讨在地下水埋深不断下降的过程中,不同发展阶段农田土壤盐渍化的时空变化规律。研究表明:奇台县绿洲地下水埋深已低于影响地表盐渍化的水位埋深临界值(5m),地下水矿化度低于3g/L,研究区整体处于有利于土壤盐渍化逆向演替的环境。随着地下水埋深的不断下降以及耕种时间的延长,农田土壤含盐量逐渐减少,土壤有机质逐渐增加,土壤盐渍化逆向演替过程已经发生。地下水埋深是影响土壤盐渍化的逆反应的最主要的因素。地下水埋深在3-5m时,土壤脱盐速度最快,大于5m时,含盐量减少的速率明显降低。(2)在绿洲平原区中部设计中尺度采样区,对比分析了不同耕种时期(耕种10年和20年)的农田土壤盐分、有机质、pH值的空间变异性。结果表明,柳树河子和草原站农田土壤盐分属中等变异性;土壤有机质也表现出中等变异性;土壤pH值属弱变异性。耕种20年和耕种10年的农田土壤盐分、有机质、pH值都具有空间自相关性,前者土壤特性的空间自相关性比后者强,并且前者的自相关距都大于后者。用克里格插值绘制的空间分布图表明两个耕种时期的农田土壤盐分、有机质、pH值的空间分布差别较大。耕种20年的土壤特性在空间上的变化更连续。表明随着人类农业活动(包括耕种、灌水、施肥等农业管理措施)的影响日益增强,盐渍化土壤会自然向良性方向发展。(3)对平原水库下游重度盐渍化区土壤特性的空间变异性研究表明:土壤总盐表现出中-强变异水平,有机质属于中等变异强度,pH值属于弱变异性。土壤总盐和有机质的变异系数由表层向底层逐渐增大,而pH值的变异系数在垂直方向上差异很小。土壤有机质具有强烈的空间相关性,虽然空间总变异较大,但变异主要由内在结构性因素引起。土壤总盐和pH值均表现出中等强度的空间相关性,说明变异是由结构性因素和随机性因素共同作用的结果。(4)平原水库下游重度盐渍化区,随着地下水的开采利用,水位埋深不断下降,预计在2024年降至影响地表盐渍化的地下水埋深临界值5m以下;土壤含盐量在2034年减少到<0.3%,变为非盐渍土。即满营湖地下水埋深低于5m的时间达到10年,盐渍化土壤耕种期达到20-30年,土壤可自然恢复为非盐渍土。(5)分析得出奇台绿洲土壤盐渍化的逆向演替过程具有时空特征,并且可划分为初级、中级、高级三个阶段。时间特征表现在,无论农田在绿洲的什么位置,耕种时间越长,土壤含盐量越低,有机质含量越高,盐渍化逆向发展的越好。当农田耕种时间和地下水埋深低于临界值的时间超过20年时,盐渍土基本可以自然恢复为非盐渍土。空间特征表现在,由绿洲下部向上部,土壤盐渍化逆向演替阶段逐渐向高级过渡。更多还原

【Abstract】 Soil salinization is a global problem of resource and ecology, and scholars pay more attention on it. Soil salinization and secondary soil salinization are the most important factors which influence the survival and development of oasis. Soil salinization will evolve into the benign aspect naturally under certain conditions,which is called reversal evolvement of soil salinization. The course of soil salinization occurrence can be regarded as a reversible reaction, and the reaction always in a dynamic balance. Finding out the activators which can advance the reversible reaction, making the reaction become the counterreaction furthest, soil salinization will restore naturally.In order to discuss the course and feature of reversal evolvement of soil salinization, the main findings of this study are:(1) Choosing farmlands of different cultivated time in plain and oasis-desert ecotone in Qitai oasis, analyzes the changes of soil soluble total salt, pH value, organic matter. Contracting the farmland soil features of different samples and different cultivated time, with the decline of groundwater table, discusses the temporal and spatial changes of farmlands soil-salinization in different phases. The results show that Qitai oasis has already in a circumstance which is valuable for soil-salinization reversal evolvement. Groundwater table is below 5 meters, the critical point which will affect the surface salt accumulation. Groundwater mineralization degree is lower than 3g/L. With the decreasing of groundwater table and the increasing of cultivated time, the content of soil soluble total salt declined and organic matter enhanced, soil-salinization reversal evolvement has already occurred. The relation between soil salt content and groundwater table is close. When groundwater table is 3 to 5 meters, the speed of desalinization is the fastest. While groundwater table is higher than 5 meters, the speed of desalinization slows down obviously.(2) Design middle-scale sample area in middle plain in oasis, analyze and compare spatial variability of soil salt, organic matter and pH value of 10 years and 20 years cultivated farmlands. The variability intensities of soil salt and organic matter are middle, while the variability intensity of soil pH value is low. Both 20 years and 10 years farmlands soil salt, organic matter and pH value are spatially auto-correlated. Both auto-correlations and correlation ranges of the former soil characterization are higher and greater than the latter. Image maps by ordinary Kriging showed distributions of soil salt, organic matter and pH value at different time were different. Spatial changes of 20 years cultivated farmlands soil characterization are more continuous than 10 years cultivated farmlands. That is to say, along with the increasing influence of human agricultural activities (including such culture management as cultivation, irrigation and fertilization, etc.), saline soil will evolve into the benign aspect naturally.(3) Spatial variability of soil properties(soil salt, organic matter, pH value) in serious salinization area of Lower reach of plain reservoir The variability intensities of soil salt, organic matter and pH value are separately middle to high, middle and low.. The variability intensities of soil salt and organic matter are increase from surface to bottom, while the vertical deference of the variability intensities of pH value is unobvious. Auto-correlation of soil organic matter is great, though the total spatial variability is high, the variability is mainly caused by structural factors. Soil salt and pH value have middle auto-correlations, both structural factors and random factors affect spatial variability.(4) Man yinghu, serious salinization area of Lower reach of plain reservoir. With the exploration and utilization of groundwater, the groundwater level will decrease gradually. By forecast, groundwater level will below the zero flux plain, 5 meters, in 2024. Soil salt content will less than 0.3% in 2034. That is to say, the time of groundwater level under 5 meters last 10 years, and the time of farmlands cultivate last 20 to 30 years, saline soil will naturally restore into non-saline soil.(5) Salinization reversal evolvement presents temporal and spatial characters, and can be classified as three different phases: the primary, the middle and the high-level. From the aspect of time, no matter in what physiognomy positions of oasis, the longer the cultivated time last, the more the organic matter and the less the salinity become, the better the salinization reversal evolvement develop. When the time of farmlands cultivate and the time of groundwater table under 5 meters last more than 20 years, saline soil can convert into non-saline soil. In point of space, from the lower to the upside of Qitai oasis, the stage of soil salinization reversal evolvement gradually transfers to high-level.更多还原