【作者】 武胜利；

【导师】 李志忠；

【作者基本信息】 华东师范大学 ， 自然地理学， 2007， 博士

【摘要】 灌(草)丛沙堆是干旱半干旱地区沙漠、半湿润沙地和沙质海岸带常见的风积生物地貌类型。灌(草)丛沙堆的研究在风沙地貌学、土地荒漠化监测与评价、区域环境演变等方面具有重要意义。本文以新疆和田河流域典型的灌(草)丛沙堆为研究对象，以风沙地貌学、风沙物理学、植物地理学、植物生态学和沉积学等学科理论为指导，在沙漠腹地的和田河两岸、和田绿洲与沙漠的过渡带，实测了223个柽柳沙堆、120个芦苇沙堆和123个骆驼刺沙堆的形态参数，在各类沙堆表层共采集了约500个沉积物样品，在洛浦县和墨玉县绿洲边缘实地进行了典型沙堆顶部的风速剖面和风沙流观测，进行了以旨在阐明沙堆发育动力机制的风洞模拟实验和反映沙堆物质机械组成的粒度分析实验。经过综合分析，本文主要结论如下：和田河流域的沙堆类型主要有柽柳沙堆、芦苇沙堆和骆驼刺沙堆，其中柽柳沙堆主要分布在泛滥平原、淤积平坦地、干湖沼平原、河流两岸、高位河漫滩、两岸阶地、典型盐土地段、两岸广大流沙区的丘间洼地和绿洲边缘；芦苇沙堆分布在和田河阶地和积水洼地周缘、绿洲边缘、淤积洼地和洪泛平原上；骆驼刺沙堆分布在河流沿岸沙地、洪积冲积平原土壤水分相对较充足且适度盐化的地块、人为干扰较为频繁的地区以及绿洲边缘。和田河流域沙堆形态主要以迎风坡和背风坡的坡度和长度差异较小、空间几何形态近似半椭球体为主，系区域低风能环境、较弱输沙势作用结果。其中，增长阶段的柽柳沙堆主要呈现近似圆锥形态，成熟稳定阶段近似半球形；芦苇沙堆整体形态则呈现迎风坡短而陡、背风坡长而缓的近似半椭球体；骆驼刺沙堆的整体形态呈现迎风坡长而缓、背风坡短而陡的近似半椭球体。各类沙堆的长轴和短轴在增长发育阶段中是协同增长的，沙堆水平尺度与高度表现出显著的相关性。灌(草)丛引发的近地面流场结构变化，干扰了风沙流的运行，在灌(草)丛后涡流区使风沙流由不饱和状态转变为过饱和状态，再加上灌(草)丛本身对风沙流的阻截，促使风沙流中的部风固体碎屑物质在灌(草)丛中和灌(草)丛后发生沉降堆积，灌(草)丛的存在对于维持灌(草)丛沙堆的形态和促进灌(草)丛沙堆的增长具有重要作用。灌(草)丛周围土壤的蚀积特征表现为：在灌(草)丛的迎风侧根部为明显的风蚀区，灌(草)丛背风侧弱涡流发生部位表现为积沙区，灌(草)丛背风侧气流恢复区和灌(草)丛两侧气流加速区则表现为风蚀区，积沙区即为灌(草)丛沙堆的增长发育区。不同形态沙堆顶部植物改变流场结构的力学作用原理基本相同，都是通过增加沙堆表面的粗糙度，对气流阻滞消能，令气流减速进而改变各个高度气流速度和涡流影响强度范围，导致风沙流结构特征相应变化。灌(草)丛沙堆丘顶植被引发的流场结构变化，促使粉尘沉降堆积、沙堆增长发育。柽柳、芦苇、骆驼刺三种典型灌(草)丛沙堆表面沉积物均为粉砂质砂，沙堆表层沉积物的粒径分布范围依次为0.399～1002.374μm、25.178～282.507μm和0.447～2000μm。沙堆的不同地貌部位沉积物的各粒级、平均粒径、分选系数呈现出有规律的变化，系风沙流、沙堆形态、灌(草)丛和沉积物综合作用的结果。区域沙源和风力的共同影响下，随着柽柳灌丛的生长、繁荣和衰败，和田河流域柽柳沙堆的发育经历增长、稳定和衰退三个阶段，增长阶段以柽柳垂向生长、风沙迅速加积的圆锥形沙堆为主要特征，稳定阶段以柽柳植物动力作用强劲的半球形沙堆为代表，衰退阶段以柽柳枯萎、沙堆迎风侧开始出现弧形沙丘或背风侧发育风影沙丘为标志，丘顶发育风蚀凹坑则表明柽柳沙堆已经发展到风蚀残留阶段。和田河流域灌(草)丛沙堆发育的区域模式主要表现为两种类型：即沙漠腹地河流两岸因河道自然摆动引发的灌(草)丛沙堆演化模式；绿洲-荒漠过渡带人类活动影响下的下的灌(草)丛沙堆演化模式。更多还原

【Abstract】 Nabkha is a common kind of biological wind deposition geomorphy in arid and semi-humid desert, and sandy coast. It has important significance in the aeolian geomorphology, monitoring and evaluating land desertification and regional environmental evolution so on.In this paper, the typical nabkha is the research object in the basin of Hetian River in Xinjiang. Two banks of Hetian River in Taklimakan Desert hinterland and the transition zone of the oasis and the desert have been investigated, according to Aeolian geomorphology, Aeolian physics, Phytogeography, Phytoecology, Sedimentation and other discipline theory. Shape data of 223 Tamarix nabkha, 120 Phragmite nabkha and 123 Alaghi nabkha have been measured, and about 500 sedimentary samples have been collected from the surface of three kinds of nabkhas, and the wind speed section and wind-sand flow at the top of the typical nabkha have been observed at the boundary zone of oasis in Luopu and Moyu county. Furthermore, In order to clarify the dynamic mechanism of nabkha growth and reflect nabkha’s material composition, the wind-tunnel imitative experiment and the grain size analysis have been done. Through comprehensive analysis, the main conclusions can be summarized as follows:In the basin of Hetian River, Tamarix, Phragmite and Alaghi nabkhas are main types. Tamarix nabkhas mainly distribute in flood plain, silty flat, dry lake and marshes plains, river’s banks, terraces, typical saline soil areas, interdunes low ground in moving dunes and oasis edge. Phragmite nabkhas lie in Hetian River’s terraces, oasis edge, silted land and flood plains. Alaghi nabkhas scatter in the sandy land along river’s bank, the land in the flood and alluvial plain which have relatively adequate moisture and moderate salinity, the region which is interfered frequently and oasis edge.The region is lower wind energy environment, and capability of transported sands is weaker, and it results that the space geometry shape of nabkhas are approximate semi-ellipsoid which have few difference in slope-length and slope-gradient of between upward and leeward sides in the basin of Hetian River. At the growth stage, Tamarix nabkha mainly appears approximately conical, and at the mature and stable stage, they are approximate hemispherical. While the whole shape of Phragmite nabkha is approximate semi-ellipsoid which have shorter and steeper upward slopeand longer and lower gradient leeward slope. The shape of Alaghi nabkha presents approximate semi-ellipsoid which have longer and lower gradient upward slope and shorter and steeper leeward slope. At the growth stage, the long axis and short axis of all kinds of nabkhas are in synergic growth. The horizontal scale and height of nabkha show significant correlation.The shrub induces the change of the flow pattern structure on the ground, and interferes with wind-sand flow so that the wind-sand flow converts into over-saturation from not-saturation status in the vortex area behind shrub. In addition, shrub blocks the wind-sand flow so that partly solid fragment material to accumulate in and behind the shrub. So the shrub plays an important role in maintaining the shape and promoting the growth of nabkha.The character of soil erosion and accumulation around shrub shows that the obvious wind erosion area distributes at the upward side of the root, and that area of sand accumulated is in the weak vortex region at the leeward side of the shrub, and that the wind erosion area lies in the air flow recovery area at the leeward side of shrub and the air flow accelerated area at the both sides. The growth area of nabkha is the area of sand accumulation.Plants at the top of different shape nabkhas all enhance the rugosity of nabkhas, retard airflow to get over nabkhas, reduce energy, eliminate common wind-erosion areas by strong wind at the top of nabkhas, and reinforce influence range of vortex at leeward side of nabkhas. These result in the change of the structural character of wind-sand flow. Plant plays a very important role in changing airflow pattern structure, promoting the dusty and sand to accumulate, and nabkhas to grow up.Sediments on Tamarix, Phragmite and Alaghi nabkhas are silty sand. Grain size distribution scopes of sediments on Tamarix , Phragmite and Alaghi nabkhas are respectively from 0.399μm to 1002.374μm , from 25.178μm to 282.507μm, and and from 0.447μm to 2000μm. The combined action of wind-sand flow, nabkha shape, shrub and sediments results that grade, average grain size and sorting of sediments change regularily on different part of nabkhas.The sand source and wind power of region and shrub affect development of nabkha. Tamarix nabkha also experiences the same stage when Tamarix shrub grows, stablizes and declines. Tamarix shrub’s disturbance to wind-sand flow and the shape of nabkha’s dynamic equilibrium are all different in every stage. In the Tamarix nabkha’s growth stage, the Tamarix displays moderate horizontal growth, and sandand dust are rapidly deposited to form conical nabkha. In the stabilization stage, Tamarix nabkha’s shape appears semispherical and is intensely effected by Tamarix shrub’s dynamical action. In the declination stage, Tamarix shrub is withered, and the arc dune starts to appear at upwind side, or the shadow dune arises at leeward side.There are two types of modes of nabkha growth in the basin of Hetian River.One is induced by river migration on banks of Hetian River in Taklimakan Desert hinterland, the other is caused activity of people in the transition zone between the oasis and the desert.更多还原