發(fā)布時間：2018-04-26 11:18

  本文選題：團聚體孔隙 + 顯微CT�。� 參考：《中國科學院教育部水土保持與生態(tài)環(huán)境研究中心》2017年博士論文

【摘要】：土壤結構是維持土壤功能的基礎,植被恢復改善土壤質量的核心就是改善土壤結構。土壤團聚體作為土壤結構的重要組成單元,其內部結構對土壤水、氣、養(yǎng)分運移以及微生物活動具有重要作用。然而,目前植被恢復對土壤團聚體微結構的影響尚不明確。本研究選取黃土丘陵區(qū)不同植被恢復年限和不同植被恢復類型的典型樣地作為研究對象,研究了土壤理化性質對植被恢復的響應,利用CT技術和圖像分析技術量化表征團聚體微結構特征,分析了團聚體穩(wěn)定性與團聚體孔隙參數(shù)的定量關系,建立了土壤結構評價體系,系統(tǒng)探究植被恢復過程土壤結構的演變特征。主要的研究結果如下:1、闡明了黃土丘陵區(qū)植被恢復過程土壤理化性質的演變特征,揭示了該土壤團聚體的主要破碎機制。土壤有機碳、總氮、土壤持水性、飽和導水率以及土壤有效水含量隨著植被恢復的年限的增加而增加。雖然植被恢復提高了土壤總氮含量、土壤總孔隙度和毛管孔隙度,但與農地相比差異不顯著。隨著植被演替的年限的增加,大粒徑團聚體含量不斷提高,小粒徑含量逐漸降低。隨著撂荒演替進行,團聚體穩(wěn)定性迅速提高,在撂荒6年后,土壤團聚體穩(wěn)定性基本達到穩(wěn)定狀態(tài)。不同植被恢復措施對土壤理化性質改變具有不同作用強度。相較于人工草地和農地,人工喬木、天然草地和人工喬木具有較高的土壤有機質、總氮含量、土壤持水性、飽和導水率、土壤有效水含量、根系生物量以及2 mm團聚體含量和團聚體穩(wěn)定性以及較低的容重。土壤總孔隙度以及毛管孔隙度在不同植被類型恢復之間差異不顯著。Le Bissonnais法三種濕潤處理對團聚體結構的破壞程度不同,團聚體的平均重量直徑(MWD)表現(xiàn)為:快速濕潤預濕潤攪拌慢速濕潤,可見黃土丘陵區(qū)團聚體破碎機制主要是快速濕潤引起的消散作用。2、定量刻畫了土壤團聚體內部結構的二維和三維結構,揭示了黃土丘陵區(qū)植被恢復過程土壤團聚體孔隙結構的演變特征,植被恢復年限以及恢復類型均顯著地改變了土壤團聚體孔隙結構。土壤團聚體二維及三維結構圖顯示,植被恢復使得土壤團聚體內部微結構從緊密的細孔結構發(fā)育到疏松的復雜多孔結構。植被恢復顯著提高了團聚體總孔隙度、75μm孔隙度、瘦長型孔隙度以及分形維數(shù),而降低了孔隙總數(shù)量、75μm孔隙度、規(guī)則和不規(guī)則孔隙度和歐拉值。隨著植被恢復年限的增加,土壤團聚體孔隙結構不斷得到改善。不同的植被恢復類型對團聚體孔隙結構產生了不同的影響,其主要原因是土壤有機物含量和根系系統(tǒng)的差異。分形維數(shù)能夠很好反映團聚體形態(tài)結構的變化,可作為黃土丘陵區(qū)植被恢復過程中土壤質量評價的指標之一。瘦長型孔隙決定著團聚體內水分、空氣的儲存和運輸,因此瘦長型孔隙度可以作為衡量土壤團聚體結構是否改善的一個指標。3、揭示了團聚體孔隙結構與團聚體穩(wěn)定性的定量關系,明確了影響團聚體穩(wěn)定性的主要孔隙因子。通過偏最小二乘回歸分析發(fā)現(xiàn),總孔隙度、孔隙總數(shù)量、100μm孔隙度、長孔隙度以及分形維數(shù)對三種處理下團聚體穩(wěn)定性均起著重要作用,其中總孔隙度、100μm孔隙度、長孔隙度以及分形維數(shù)對團聚體穩(wěn)定性起著正向作用,而孔隙總數(shù)量的增加則會導致團聚體性的下降。植被恢復促進團聚體總孔隙數(shù)量減少,總孔隙度、100μm孔隙度、長孔隙度以及分形維數(shù)增加,可以提高孔隙疏水性,減緩濕潤速度和降低消散應力,從而提高團聚體穩(wěn)定性。4、評價了土壤結構質量對植被恢復的響應,分析了土壤結構質量與重要土壤理化因子的關系。團聚體瘦長型孔隙度、平均孔隙形狀系數(shù)及MWD可作為評價黃土丘陵區(qū)植被恢復下土壤結構質量的關鍵指標。土壤結構指數(shù)與土壤有機質、土壤飽和導水率和土壤有效水含量均具有線性顯著相關性。隨著植被恢復年限的增加,土壤結構指數(shù)不斷升高,且4個植被恢復階段均顯著高于對照農地。植被自然恢復過程中,土壤結構指數(shù)與土壤有機質、土壤飽和導水率和土壤有效水含量演變并不同步。4種植被恢復模式均顯著提高了土壤結構指數(shù),按照土壤結構指數(shù)的分級,5種植被類型分別處于三個不同水平,分別為達到高水平狀態(tài)的人工灌木和天然草地、中等水平狀態(tài)的人工喬木和人工草地以及低水平狀態(tài)的農地。為了更有效地促進侵蝕土壤質量的改善進程,尤其是退化土壤結構的重建,在干旱半干旱地區(qū)宜優(yōu)先選擇人工灌木和天然草地作為主要的植被恢復模式。
[Abstract]:Soil structure is the basis for maintaining soil function. The core of vegetation restoration to improve soil quality is to improve soil structure. Soil aggregate is an important component of soil structure, and its internal structure plays an important role in soil water, gas, nutrient migration and microbial activity. The impact of different vegetation restoration years and different vegetation restoration types in the loess hilly region is selected as the research object. The response of soil physical and chemical properties to vegetation recovery is studied. The characteristics of aggregate microstructures are quantified by CT and image analysis techniques, and the stability and agglomeration of aggregates are analyzed. The quantitative relationship of pore parameters, the soil structure evaluation system was established, and the evolution characteristics of soil structure were systematically investigated. The main results were as follows: 1, the evolution characteristics of soil physical and chemical properties in the vegetation restoration process in the loess hilly region were clarified, and the main breakage mechanism of the soil aggregates was revealed. Soil organic carbon, total soil organic carbon, has been revealed. Nitrogen, soil water holding, saturated water conductivity and soil effective water content increased with the number of years of vegetation restoration. Although vegetation recovery increased the total soil nitrogen content, total soil porosity and capillary porosity, the difference was not significant compared with the farmland. With the increase of vegetation succession, the content of large particle aggregate increased continuously. With the abandonment succession, the stability of aggregate increased rapidly. After 6 years of abandonment, the stability of soil aggregates basically reached a stable state. Different vegetation restoration measures have different effects on soil physical and chemical properties. Compared with artificial grassland and farmland, artificial trees, natural grassland and artificial trees. High soil organic matter, total nitrogen content, soil water holding capacity, saturated water conductivity, soil effective water content, root biomass, 2 mm aggregate content and aggregate stability and low bulk density. The difference between total soil porosity and capillary porosity in different vegetation types is not significant by.Le Bissonnais method and three wetting methods The damage degree of the aggregate structure is different. The average weight diameter of the aggregate (MWD) shows that the rapid wetting and pre wetting agitation is slow and humid. It can be seen that the fragmentation mechanism of the aggregate in the loess hilly region is mainly the dispersing effect of.2, which is caused by the rapid wetting, which quantified the two-dimensional and three-dimensional structure of the internal structure of the soil cluster, and revealed the Yellow River. The evolution of the pore structure of soil aggregates in the vegetation restoration process in the mound mausoleum, the restoration years and the restoration types have significantly changed the pore structure of the soil aggregates. The two-dimensional and three-dimensional structure of the soil aggregates show that the vegetation restoration makes the microstructures of the soil aggregates develop from tight pore structure to loose restoration. The restoration of the total porosity, the porosity of 75 mu m, the slender porosity and the fractal dimension, and the decrease of the total pore volume, the porosity of 75 mu, the regular and irregular porosity and the Euler value. The pore structure of the soil aggregates has been improved continuously with the increase of vegetation restoration. Different vegetation restoration. Complex types have different effects on the pore structure of aggregates, mainly due to the difference in soil organic matter content and root system. The fractal dimension can reflect the changes in the morphology and structure of aggregates well, which can be used as one of the indexes of soil quality evaluation in the process of vegetation restoration in the Loess hilly region. The storage and transportation of water and air, so the thin porosity can be used as an indicator of the improvement of soil aggregate structure, which reveals the quantitative relationship between the pore structure of aggregates and the stability of aggregates and the main pore factors that affect the stability of aggregates. The total porosity is found by partial least squares regression analysis, and the total porosity is found by partial least squares regression analysis. The total pore number, 100 mu m porosity, long porosity and fractal dimension play an important role in the stability of aggregates under three treatments. The total porosity, 100 mu m porosity, long porosity and fractal dimension play a positive role in the stability of aggregate, and the increase of the total pore amount will lead to the decrease of aggregate property. The reduction of total pore volume, total porosity, 100 mu m porosity, long porosity and fractal dimension can increase the pore hydrophobicity, slow down the wetting speed and reduce the dissipation stress, thus improve the stability of aggregate.4, evaluate the response of the soil structure quality to the vegetation restoration, and analyze the soil structure quality and the important soil. The relationship between physical and chemical factors. The lean porosity, the average pore shape coefficient and the MWD can be used as the key indicators to evaluate the soil structure quality under the vegetation restoration in the loess hilly region. The soil structure index has a linear significant correlation with soil organic matter, soil saturated water conductivity and soil effective water content. In the process of natural restoration of vegetation, the soil structure index and soil organic matter, soil saturated water conductivity and soil effective water content are not synchronized with the evolution of soil available water content. The soil structure index is significantly increased by the.4 restoration model, according to the soil structure. Index classification, 5 types of vegetation are at three different levels, respectively, artificial shrubs and natural meadows, artificial trees and artificial meadows of medium level, and low level land. In order to improve the improvement of soil quality, especially the reconstruction of degraded soil structure, In arid and semi-arid areas, it is preferable to choose artificial shrub and natural grassland as the main vegetation restoration mode.

【學位授予單位】：中國科學院教育部水土保持與生態(tài)環(huán)境研究中心
【學位級別】：博士
【學位授予年份】：2017
【分類號】：S152

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