黄土丘陵区植被恢复过程土壤团聚体结构演变特征及其量化表征

发布时间：2018-04-26 11:18

本文选题：团聚体孔隙 + 显微CT　；参考：《中国科学院教育部水土保持与生态环境研究中心》2017年博士论文

【摘要】：土壤结构是维持土壤功能的基础,植被恢复改善土壤质量的核心就是改善土壤结构。土壤团聚体作为土壤结构的重要组成单元,其内部结构对土壤水、气、养分运移以及微生物活动具有重要作用。然而,目前植被恢复对土壤团聚体微结构的影响尚不明确。本研究选取黄土丘陵区不同植被恢复年限和不同植被恢复类型的典型样地作为研究对象,研究了土壤理化性质对植被恢复的响应,利用CT技术和图像分析技术量化表征团聚体微结构特征,分析了团聚体稳定性与团聚体孔隙参数的定量关系,建立了土壤结构评价体系,系统探究植被恢复过程土壤结构的演变特征。主要的研究结果如下:1、阐明了黄土丘陵区植被恢复过程土壤理化性质的演变特征,揭示了该土壤团聚体的主要破碎机制。土壤有机碳、总氮、土壤持水性、饱和导水率以及土壤有效水含量随着植被恢复的年限的增加而增加。虽然植被恢复提高了土壤总氮含量、土壤总孔隙度和毛管孔隙度,但与农地相比差异不显著。随着植被演替的年限的增加,大粒径团聚体含量不断提高,小粒径含量逐渐降低。随着撂荒演替进行,团聚体稳定性迅速提高,在撂荒6年后,土壤团聚体稳定性基本达到稳定状态。不同植被恢复措施对土壤理化性质改变具有不同作用强度。相较于人工草地和农地,人工乔木、天然草地和人工乔木具有较高的土壤有机质、总氮含量、土壤持水性、饱和导水率、土壤有效水含量、根系生物量以及2 mm团聚体含量和团聚体稳定性以及较低的容重。土壤总孔隙度以及毛管孔隙度在不同植被类型恢复之间差异不显著。Le Bissonnais法三种湿润处理对团聚体结构的破坏程度不同,团聚体的平均重量直径(MWD)表现为:快速湿润预湿润搅拌慢速湿润,可见黄土丘陵区团聚体破碎机制主要是快速湿润引起的消散作用。2、定量刻画了土壤团聚体内部结构的二维和三维结构,揭示了黄土丘陵区植被恢复过程土壤团聚体孔隙结构的演变特征,植被恢复年限以及恢复类型均显著地改变了土壤团聚体孔隙结构。土壤团聚体二维及三维结构图显示,植被恢复使得土壤团聚体内部微结构从紧密的细孔结构发育到疏松的复杂多孔结构。植被恢复显著提高了团聚体总孔隙度、75μm孔隙度、瘦长型孔隙度以及分形维数,而降低了孔隙总数量、75μm孔隙度、规则和不规则孔隙度和欧拉值。随着植被恢复年限的增加,土壤团聚体孔隙结构不断得到改善。不同的植被恢复类型对团聚体孔隙结构产生了不同的影响,其主要原因是土壤有机物含量和根系系统的差异。分形维数能够很好反映团聚体形态结构的变化,可作为黄土丘陵区植被恢复过程中土壤质量评价的指标之一。瘦长型孔隙决定着团聚体内水分、空气的储存和运输,因此瘦长型孔隙度可以作为衡量土壤团聚体结构是否改善的一个指标。3、揭示了团聚体孔隙结构与团聚体稳定性的定量关系,明确了影响团聚体稳定性的主要孔隙因子。通过偏最小二乘回归分析发现,总孔隙度、孔隙总数量、100μm孔隙度、长孔隙度以及分形维数对三种处理下团聚体稳定性均起着重要作用,其中总孔隙度、100μm孔隙度、长孔隙度以及分形维数对团聚体稳定性起着正向作用,而孔隙总数量的增加则会导致团聚体性的下降。植被恢复促进团聚体总孔隙数量减少,总孔隙度、100μm孔隙度、长孔隙度以及分形维数增加,可以提高孔隙疏水性,减缓湿润速度和降低消散应力,从而提高团聚体稳定性。4、评价了土壤结构质量对植被恢复的响应,分析了土壤结构质量与重要土壤理化因子的关系。团聚体瘦长型孔隙度、平均孔隙形状系数及MWD可作为评价黄土丘陵区植被恢复下土壤结构质量的关键指标。土壤结构指数与土壤有机质、土壤饱和导水率和土壤有效水含量均具有线性显著相关性。随着植被恢复年限的增加,土壤结构指数不断升高,且4个植被恢复阶段均显著高于对照农地。植被自然恢复过程中,土壤结构指数与土壤有机质、土壤饱和导水率和土壤有效水含量演变并不同步。4种植被恢复模式均显著提高了土壤结构指数,按照土壤结构指数的分级,5种植被类型分别处于三个不同水平,分别为达到高水平状态的人工灌木和天然草地、中等水平状态的人工乔木和人工草地以及低水平状态的农地。为了更有效地促进侵蚀土壤质量的改善进程,尤其是退化土壤结构的重建,在干旱半干旱地区宜优先选择人工灌木和天然草地作为主要的植被恢复模式。
[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.

【学位授予单位】：中国科学院教育部水土保持与生态环境研究中心
【学位级别】：博士
【学位授予年份】：2017
【分类号】：S152

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