红壤坡地不同植被类型的干湿季土壤水分动态规律研究

发布时间：2018-06-21 13:54

本文选题：红壤干旱 + 植被　；参考：《华中农业大学》2017年硕士论文

【摘要】：我国热带亚热带的红壤区降水分布不均,由此造成的水土流失和季节性干旱问题十分突出,严重制约了该区的农业生产和发展。红壤坡地的土壤水分状况影响农林生态系统的功能,也是导致季节性干旱形成的原因。然而,近年红壤坡地上植被的种植结构改变对干湿季红壤水分动态规律的影响机制还不清楚。本文研究干湿两季红壤坡地不同植被类型的土壤水分变化规律,为改善红壤季节性干旱提供理论依据。本研究在湖北省咸宁市贺胜桥镇江里头的一个典型红壤缓坡地(坡地面积约13667 m2,坡长约136 m,平均坡度约4°,坡向正南,第四纪红色粘土母质)上开展,于2015年4月12日至2016年10月3日进行高频连续定位监测试验。试验设置在上坡、中坡、下坡三个坡位,植被类型分别是乔木(杉木)、小乔木(红叶石楠)、作物(油菜),每个植被地块中心埋设4个EC-5水分探针,分别监测20、40、60、90 cm深度的土壤含水量(记录间隔为30 min),坡地自然降雨量监测与土壤含水量同步。2016年3月12日(进入湿季前)沿坡地纵向中心线,每个地块均匀设置3~5个采样点,采用烘干法测定土壤含水量。2016年4月21日,进行植物根系挖取及扫描试验,获取根长、根表面积、根体积等指标。得到以下研究结果:(1)不同植被类型的土壤水分宏观特征不同。2016年湿季水涝、干季干旱分别都比2015年严重。乔木的土壤储水量在两年之间几乎无差异,但是2016年小乔木的土壤储水量明显降低,而作物的土壤储水量明显增加。2015年,小乔木40 cm深度在干季的土壤平均含水量明显相对湿季降低;乔木40 cm深度土壤平均含水量在两季中都最小;作物60 cm深度土壤平均含水量在湿季最小。乔木浅层土壤水分在湿季的活跃程度(变异系数)较大且大于干季,而小乔木的各深度土壤水分在干季的活跃程度大于湿季。乔木干季60 cm深度和作物干季20 cm深度、湿季60 cm深度的土壤水分时间稳定性较弱,但水分活跃程度较大。作物60 cm深度存在一个频率较小、但又跨度较大的高含水量集中区域,尤其是在2016年的高含水量区域明显较大。(2)不同植被类型的根系特征与吸水能力密切相关。乔木和小乔木在土壤40 cm深度的RLD(总根长密度)大于20 cm深度且最大,60、90 cm深度的RLD随着土壤深度增加而减小;小乔木在不同土壤深度上的RLD都大于乔木,尤其是土壤40 cm深度;作物20 cm深度的RLD、RSD(总根表面积密度)、RVD(总根体积密度)都最大且随土壤深度增加而递减。在湿季,这三种植被的根系相对吸水率在土壤剖面上的变化特征与细根根长量的分布特征基本一致。在2015、2016年的干旱期内,乔木和小乔木的根系相对吸水率变化规律几乎相同,二者在2016年干旱早期的根系相对吸水率下降不是很稳定,而在干旱后期则缓慢趋于平稳且其变化规律与2015年干旱阶段一致,这主要与干旱持续时间长短有关。(3)不同植被土壤20 cm深度的干旱强度和干旱程度的变化特征差异明显。整体上,乔木的土壤干旱强度、干旱程度都随着干旱天数的增加而增加,小乔木和作物的土壤干旱程度虽然在两年干旱期中都呈增加趋势,但二者的干旱强度变化在两年干旱期中有不同的表现,2016年的干旱强度大于2015年且总体呈下降趋势。干旱期初始,乔木、小乔木的土壤干旱程度都大于作物,而在干旱过程中(除了2015年干旱期Ⅱ之外)的土壤干旱强度是作物小乔木乔木;作物和小乔木的表层土壤含水量在干旱过程中都较早降低到最小值,而乔木滞后。(4)不同植被土壤水分—降雨的响应过程在不同降雨事件中表现不同。在大暴雨、暴雨事件下,乔木、小乔木和作物的土壤水分—降雨的响应过程都主要受到优先流(根系通道或地表裂缝)和壤中流(来自上坡的土壤水分补给)的共同影响,其中作物休闲期的表层土壤水分波动没有乔木、小乔木剧烈。中、小雨事件对这三种植被土壤水分的影响相对减小,而作物种植期表层土壤水分对中雨的响应最明显且迅速,含水量波动较乔木、小乔木更为剧烈。因此,湿季,乔木和小乔木的土壤水分—降雨响应过程相似,但作物种植期的表层土壤水分波动比乔木、小乔木明显,而休闲期恰好相反;干季,不论土壤干旱程度高低,涵养水源能力最弱的植被都是乔木;小乔木和作物(休闲期)的涵养水源能力受土壤干旱程度的影响较大。总之,红壤坡地水分时空分布,在湿季更大程度地受到植被和地形的协同影响;干季的植被因素影响仍重要,而地形因素影响程度减小。
[Abstract]:The distribution of precipitation in the red soil region of tropical and subtropical regions of our country is uneven, and the problems of soil and water loss and seasonal drought are very prominent, which seriously restrict the agricultural production and development in this area. The soil moisture status of the red soil slope land affects the function of the agroforestry system and causes the seasonal drought. The influence mechanism of the change of vegetation structure on the dynamic law of water dynamics in dry and wet red soil is not clear. This paper studies the soil moisture change law of different vegetation types in the dry and wet two season red soil slope, and provides a theoretical basis for the improvement of the seasonal drought in red soil. This study is a typical red soil in Zhenjiang, Xianning, Hubei province. The gentle sloping area (the slope area is about 13667 m2, the slope length is about 136 m, the average slope is about 4 degrees, the slope to the south, the Quaternary red clay matrix) is carried out on the high frequency continuous location monitoring test from April 12, 2015 to October 3, 2016. The experiment is set up on the slope, the middle slope and the lower slope, and the vegetation types are tree (Cunninghamia lanceolata) and small tree (red leaf stone). 4 EC-5 water probes were embedded in the center of each vegetation block. The soil water content of 20,40,60,90 cm depth was monitored respectively (the interval of record was 30 min). The natural rainfall monitoring on the slope land was synchronized with the soil water content in March 12th (before the wet season) in the longitudinal center line along the slope, and each plot was evenly set by 3~5 sampling points. The soil moisture content of the soil was measured by the drying method in April 21st.2016 years. The root length, the root surface area and the root volume of the plant were obtained. The following results were obtained: (1) the macroscopic characteristics of soil moisture in different vegetation types were different from the wet season in the wet season in.2016, and the dry season drought was more serious than that in 2015. There was almost no difference between two years, but the soil water storage of small trees decreased obviously in 2016, and the soil water content of the crop increased obviously in.2015 years, the average water content of the 40 cm depth in the dry season decreased obviously in the dry season, and the average water content of the 40 cm depth soil in the tree was the lowest in the two season, and the average crop 60 cm depth soil was average. The water content in the wet season is the smallest. The activity of soil moisture in the wet season is larger and larger than the dry season, but the depth of soil moisture in the dry season is greater than that in wet season. The depth of 60 cm in the dry season and 20 cm depth in the dry season of the tree, and the soil moisture time of 60 cm depth in the wet season are weak, but the water activity is less than that of the wet season. The degree of leaping was larger. There was a small, high water content area with a larger span of 60 cm depth, especially in the high water content area in 2016. (2) the root characteristics of different vegetation types were closely related to the water absorption capacity. The RLD (total root length density) of trees and small trees in soil 40 cm depth (total root length) was greater than 20 cm depth. And the maximum RLD of 60,90 cm depth decreased with soil depth increasing, and the RLD of small trees in different soil depth was greater than that of trees, especially soil 40 cm depth; RLD, RSD (total root surface area density) at 20 cm depth of crops, RVD (total root volume density) were all largest and decreased with soil depth. In wet season, these three roots were planted roots. In the 20152016 year drought period, the relative water absorption of the roots of the trees and the small trees is almost the same, the two in the early drought in the early 2016, the relative water absorption of the root is not very stable, but in the late period of drought it tends to be slow. The regularity is consistent with the drought stage in 2015, which is mainly related to the duration of drought duration. (3) the variation characteristics of drought intensity and drought degree of different vegetation soils at 20 cm depth are distinctly different. Although the degree of soil drought was increasing during the two years' drought period, the drought intensity of the two had different performance during the drought period in two years. In 2016, the drought intensity was greater than that in 2015 and generally declined. The soil drought degree of trees and small trees was greater than that of crops in the beginning of drought period, but in the drought process (except 2015). The soil drought intensity outside the drought period is small arbor trees; the water content in the surface soil of the crops and small trees decreased early to the minimum, while the trees lagged. (4) the response process of soil moisture to rainfall in different vegetation was different in different rainfall events. Under heavy rain and rainstorm events, trees and small Joe The response of soil moisture to rainfall in wood and crops is mainly influenced by the priority flow (root channel or surface fissure) and soil water supply from the upper slope (from the soil water supply from the upper slope). There is no tree in the surface soil water fluctuation in the crop leisure period, and the small trees are violent. The effect of the rain event on the soil moisture of the three plants is affected by the small rain events. The response of soil moisture to medium rain was most obvious and rapid in crop planting period, and the fluctuation of water content was more intense than that of trees and small trees. Therefore, in wet season, the soil moisture and rainfall response process of trees and small trees was similar, but the fluctuation of surface soil moisture in crop planting period was more obvious than that of trees and small trees, while the leisure period was just right. On the contrary, dry season, no matter the degree of soil drought, the weakest vegetation of water conservation is arbor; the water conservation ability of small Qiao Muhe crops (leisure period) is greatly influenced by the degree of soil drought. In a word, the spatial and temporal distribution of water in the red soil slope is influenced by the synergistic effect of vegetation and terrain in the wet season; the vegetative factors of the dry season The impact is still important, while the impact of topographic factors is reduced.
【学位授予单位】：华中农业大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：S152.7

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