發(fā)布時(shí)間：2018-03-19 18:06

  本文選題：土壤水分　切入點(diǎn)：土地利用變化　出處：《西北農(nóng)林科技大學(xué)》2017年碩士論文　論文類(lèi)型：學(xué)位論文

【摘要】：黃土高原嚴(yán)重的土壤侵蝕對(duì)人們賴(lài)以生存的生態(tài)環(huán)境造成嚴(yán)重的破壞,進(jìn)而制約著區(qū)域經(jīng)濟(jì)發(fā)展。為此,國(guó)家開(kāi)展了退耕還林還草等大量水土保持工作,導(dǎo)致黃土塬區(qū)的土地利用方式近年來(lái)發(fā)生了巨大的變化,進(jìn)而影響水循環(huán)機(jī)制。因此,土地利用變化引起的水文效應(yīng)備受關(guān)注。在此背景下,具體分析水循環(huán)中間環(huán)節(jié)的土壤水分特征與土地利用的關(guān)系,將為水資源管理和生態(tài)建設(shè)提供重要的參考依據(jù)。本研究以黃土高原白草塬為研究區(qū)域,測(cè)定塬區(qū)降水和土壤水分的同位素和水化學(xué)組成,研究了白草塬土壤水分特征,并分析了其影響因素。通過(guò)對(duì)大氣降水氫氧穩(wěn)定同位素組成和降水水汽氣團(tuán)后向回溯軌跡分析,探討塬區(qū)不同月份的水汽來(lái)源及變化特征,進(jìn)而為研究區(qū)域水文效應(yīng)提供依據(jù);分析不同土地利用方式土壤水分及其同位素特征,探討土壤水分運(yùn)動(dòng)情況;分析土地利用變化產(chǎn)生的水文效應(yīng),并利用CMB法量化土壤水分深層滲漏,揭示土地利用變化對(duì)土壤水分的影響。本研究主要有如下結(jié)論:1、闡明了白草塬區(qū)降水的氫氧同位素特征及水汽來(lái)源。降水氫氧穩(wěn)定同位素特征在全年范圍內(nèi)變化幅度較小,δD和δ18O除大降雨事件外基本不存在溫度效應(yīng)和降雨量效應(yīng)。對(duì)大氣降水線、氘盈余和水汽氣團(tuán)后向回溯軌跡綜合分析,塬區(qū)夏秋季有多種水汽來(lái)源,主要為西風(fēng)帶環(huán)流、東南亞季風(fēng)和大陸內(nèi)循環(huán)等輸送的水汽,而春冬季主要為西風(fēng)帶環(huán)流輸送的水汽。2、探討了不同利用方式土壤水分及其同位素特征。土壤水分氫氧穩(wěn)定同位素組成主要位于塬區(qū)大氣降水線右下側(cè),降水在淺土壤層與老水發(fā)生混合作用,并受蒸騰蒸發(fā)作用而富集。對(duì)比降水和土壤水同位素組成特征,土壤水分主要受夏秋季降水補(bǔ)給。不同利用方式土壤水分的δD和δ18O剖面分布特征及其Cl-濃度具有差異性,土地利用變化對(duì)土壤水分運(yùn)動(dòng)具有重要影響。3、揭示了土地利用變化對(duì)土壤水分的影響。不同利用方式對(duì)土壤水分的影響程度和深度不同,6種土地利用方式0~10 m平均含水量表現(xiàn)為:農(nóng)地荒草地苜蓿地杏林地杏林檸條間作地杏林苜蓿間作地,苜蓿地與荒草地的影響集中在0~5 m,而包含杏樹(shù)類(lèi)利用方式對(duì)土壤水分的影響向深層推進(jìn)甚至貫穿整個(gè)剖面。土地利用變化造成土壤水分儲(chǔ)水量減少和干燥化現(xiàn)象嚴(yán)重,形成了深厚的土壤干層。農(nóng)地轉(zhuǎn)變?yōu)槠渌梅绞胶笊顚油寥浪秩霛B速率變化幅度不大,但塬區(qū)降雨量少、土壤水分下滲緩慢以及土壤干層嚴(yán)重削弱了土壤水分入滲到深土壤層以及地下水的可能性。
[Abstract]:The serious soil erosion on the Loess Plateau has caused serious damage to the ecological environment on which people depend for their survival, thus restricting the development of regional economy. For this reason, the state has carried out a great deal of soil and water conservation work, such as returning farmland to forests and grassland, etc. In recent years, great changes have taken place in the land use mode in the loess plateau, thus affecting the mechanism of water circulation. Therefore, the hydrological effects caused by the land use change have attracted much attention. The analysis of the relationship between soil moisture characteristics and land use in the intermediate link of water cycle will provide an important reference for water resources management and ecological construction. The isotopic and hydrochemical compositions of precipitation and soil water were measured, the characteristics of soil water in Baicaoyuan were studied, and the influencing factors were analyzed. The hydrogen and oxygen stable isotopic composition of precipitation and the backtracking trace of precipitation vapor and air mass were analyzed. The source and variation characteristics of water vapor in different months were discussed in order to provide the basis for the study of regional hydrological effects, and the characteristics of soil moisture and their isotopes in different land use patterns were analyzed, and the soil moisture movement was discussed. The hydrological effect of land use change was analyzed, and the CMB method was used to quantify the deep leakage of soil water. The main conclusions of this study are as follows: 1. The hydrogen and oxygen isotopic characteristics and water vapor sources of precipitation in Baicaoyuan region are expounded. The stable isotopic characteristics of hydrogen and oxygen in precipitation vary throughout the year. The amplitude is small, 未 D and 未 18O have no temperature effect and rainfall effect except for heavy rainfall events. The comprehensive analysis of deuterium surplus and water vapor backward trace shows that there are many kinds of water vapor sources in the tableland in summer and autumn, mainly from the circulation of the westerly zone, the Southeast Asian monsoon and the continental circulation, etc. In spring and winter, the water vapor transported by westerly circulation is mainly. 2. The characteristics of soil moisture and its isotopes in different utilization patterns are discussed. The stable isotopic compositions of soil water hydrogen and oxygen are mainly located at the lower right side of the precipitation line in the plateau. Precipitation is mixed with old water in shallow soil layer and enriched by transpiration and evaporation. Soil moisture is mainly recharged by precipitation in summer and autumn. The distribution characteristics of 未 D and 未 18O profiles and the Cl-concentration of soil moisture in different uses are different. Land use change has an important effect on soil moisture movement, which reveals the influence of land use change on soil moisture. The average water content was: alfalfa field, alfalfa field, alfalfa field, alfalfa field, alfalfa field, alfalfa field, alfalfa field, alfalfa field, alfalfa field, The effects of alfalfa land and wasteland were concentrated at 0 ~ 5 m, and the effects of apricot use patterns on soil moisture were pushed forward to the deep layer, even through the whole section. The soil water storage and desiccation phenomenon was serious due to the change of land use, which resulted in the decrease of soil water storage and the desiccation of alfalfa land. A deep dry layer of soil was formed. The infiltration rate of deep soil water changed little after the conversion of farmland to other forms of utilization, but the rainfall in the plateau region was less. Slow infiltration of soil water and soil dry layer seriously weaken the possibility of infiltration of soil water to deep soil layer and groundwater.
【學(xué)位授予單位】：西北農(nóng)林科技大學(xué)
【學(xué)位級(jí)別】：碩士
【學(xué)位授予年份】：2017
【分類(lèi)號(hào)】：S152.7

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