Knowledge Resource Center for Ecological Environment in Arid Area
| 高寒干旱地区风蚀坑形态及地貌演变过程 ——以共和盆地三塔拉地区为例 | |
| 其他题名 | The geomorphology and geomorphic evolution of blowout in Alpine Arid Areas——A case study of San Tala, Gonghe Basin |
| 王中原 | |
| 出版年 | 2017 |
| 学位类型 | 硕士 |
| 导师 | 罗万银 |
| 学位授予单位 | 中国科学院大学 |
| 中文摘要 | 共和盆地位于青藏高原东北部，是我国干草原与荒漠草原地带沙漠化发展的主要地区之一。沙漠化是导致当地生态环境恶化、制约牧区经济持续发展的重要因素。在诸多沙漠化土地景观中，风蚀坑是主要的风蚀地貌类型。特别是在盆地东南部的塔拉滩地区，在适宜的风况以及沉积条件下，形态各异风蚀坑的分布广泛，并与横向沙丘共同构成了荒漠化景观的主体。但是，作为古沙丘活化的一种重要表现形式，却鲜有文献对塔拉滩地区高密度、大形态的风蚀坑做过相关报道，对于其发生与演变机理更是缺乏一个系统完备的认知过程。所以，本文以共和盆地塔拉滩东南部三塔拉地区作为研究区，采用野外考察、原位定位监测、室内实验、分析以及影像解译等技术手段，对风蚀坑沉积物、形态以及演变过程进行了研究。主要结论如下：（1）三塔拉地区年均风速3.44m/s，冷季以西向气流为主，暖季多东北风。年输沙势为352.1UA，合成输沙势为264.4UA，合成输沙势方向为127.9°，风向变率指数为0.75，属单峰风况、风向变率为中等的中等风能环境。不同季节相比，春、冬两季输沙势要显著大于夏、秋两季。（2）古风沙沉积物是风蚀坑发育的主要物质来源。不同发育阶段风蚀坑沉积物尽管空间尺度相差很大，但因为动力学过程的相似性，沉积物粒度变化依然在宏观尺度上表现出了一致性。两侧坍塌壁相比，东北壁受到更强的风力掏蚀且分选性更好。随着风蚀坑面积的扩大，粗沙粒会在坑底以及迎风坡中下部富集，并有可能会形成风蚀坑的侵蚀基准面，抑制风蚀坑的下蚀过程。（3）三塔拉地区风蚀坑可按照形态特征可分为风蚀斑、典型风蚀坑以及复合风蚀坑三大类。风蚀坑平均面积2669.78m2，最大可达十余万平方米，要远远大于世界其它地区发育的风蚀坑。其长度与宽度之间呈高度线性正相关，且走向与起沙风主风向以及合成输沙势方向基本保持一致。随着风蚀坑的发展，其走向会越来愈加集中，积沙体与坑体的面积比逐渐减小，而风蚀坑的长宽比则会逐渐增大。（4）研究区大部分风蚀坑表现出了扩张趋势，且边缘扩张主要由陡坎坍塌引起，是冻融、风蚀、水蚀以及人类活动等多种营力共同作用的结果。在不同地貌部位之间，以坑头部位的溯源侵蚀现象最为显著，年最大坍塌幅度超过6m。东北侧坡壁的形变也比较明显，年均扩张速率接近1m。从表面变化特征上看，小型风蚀坑整体受到了侵蚀，而大型风蚀坑内部总体维持蚀积平衡。不同风蚀坑的增长速率相差很大，且不同时期内扩张速率的变化趋势也并没有表现出一致性。此外，其形态发展也并不是一个无限扩张的过程，存在着最大尺度。除形态发生增长的风蚀坑外，也监测到了一些边缘被植被固定，形态出现微弱收缩的固定风蚀坑。而在风蚀坑分布比较密集的区域，相邻风蚀坑很有可能发生频繁的相互作用，主要包括融合以及吞噬两种过程。（5）研究区可根据风蚀密度划分为轻度风蚀区、中度风蚀区、核心风蚀区、风蚀-风积过渡区以及流动沙丘区这五个区域。其中在上风向的轻度、中度、核心风蚀区，风蚀坑的发育比较迅速，而在下风向的过度区域则表现出了较为突出风积现象。因此，我们应根据不同区域的具体沙害类型有针对性地部署防沙治沙策略。而保护原始草场，防止风蚀坑的发生，掐断沙质沉积物的释放源头，是控制沙漠化土地蔓延的关键。对于已经形成的风蚀坑，应根据其形态演变规律，布置不同的机械沙障。关键词：风蚀坑；沙漠化；粒度特征；地貌形态；形态演变 |
| 英文摘要 | Located in the northeastern of the Qinghai-Tibet Plateau, Gonghe basin is one of the main area where is suffering serious desertification in the steppe and desert steppe. Desertification is an important factor that leads to the deterioration of the local ecological environment and the sustainable development of economy. In many desertified lands, blowouts are the main types of wind erosion landforms. Especially in the Tara Shoal in the southeastern part of the basin, a site with appropriate wind conditions and sedimentary conditions host high densities of blowouts, and together with the transverse dune constitute the main type of the desertification landscape.However, as an important form of the activation of ancient dunes, few literatures have reported the widely distributed blowout in the Tara shoal. There is a lack of a complete understanding of the mechanism of its occurrence and evolution. So this paper has chosen San Tara Shoal located at southeast of Tara Shoal as stduy area, and studies the sediments, morphology and evolution of blowout, by using the methods of field investigation, In-situ monitoring, laboratory experiment and analysis, and satellite image interpretation. The main conclusions are as follows:(1)The annual wind speed is3.44m/s, and prevailing wind direction is westerly in cold season while northeast in warm season in Three Tar. The annual sediment potential is 352.1 UA, and the annual resultant sand-transporting potential(RDP) is 264.4 UA with the direction of 127.9°, and the wind direction variability index is 0.75, belonging to the intermediate wind directional variability, with a wind regime of unidirectional and intermediate wind variablity. Compared with different seasons, the annual sediment potential in spring and winter seasons were significantly higher than this in summer and autumn. (2) The surface sediment in researched blowout mainly come from fossil sediment. The blowouts that have different sizes and shapes emerge the similar grain size variation because of the similar aerodynamic process. Compare to different erosion walls, northeast erosion wall exhibits better sorting. As the expansion of blowout area, the coarse and very coarse sand will gather in the middle-lower part of windward slope and deflation basin. And coarser sand may forms the erosion base of blowouts, so blowout basin may stop to develop.(3) Blowout in San Tala can be divided into three forms according to the morphological characteristics: micro-blowout, typical blowout and composite blowout. The average area of blowout in study area is 2669.78m2, and the largest is up to more than 100000 m2, which are far greater than the other blowouts that develop in other country. We find that its length and width are highly linearly positive correlation, while the direction of it conform with the prevailing wind and the direction of resultant sand-transporting. With the development of blowout, its trend will be more and more concentrated, the depositional lobe and blowout area ratio will gradually decrease, and the blowout’s aspect ratio will gradually increase.(4) Most of the blowout in the study area show an expansion trend, and the edge expansion is mainly caused by the collapse of the steep. The occurrence of steep collapsing is the result of a combination of freezing and thawing, wind erosion, water erosion and so on. In the different landforms, headward erosion in the upwind of blowout cause serious expansiong, with largest annual variation up to more than 6m.. The deformation of the northeast side of the slope is also obvious, and the average annual expansion rate is nearly 1m. According to the measurement of surface change, the small blowout are obviously eroded, but the large-scale blowout maintained erosion-deposition equilibrium. The growth rate of different blowouts is very different, and the trend of expansion rate in different periods does not show consistency. Moreover, the expansion of blowout is not an infinite process, and the development feature of blowout shows that its landform may exist a critical scale. Apart from the growth blowout, we also have monitored some shrunken forms which edge was fixed by vegetation. And the closed blowout may occur coalescence and burial in the area where host high densities.(5) According to the distribution characteristics of blowouts, the study area can be divided into five areas: mild wind erosion area, moderate wind erosion area, core wind erosion area, wind erosion - wind deposition transition zone and mobile dune area. The development of blowouts in the mild, moderate and core wind erosion areas of the upwind direction is relatively rapid, while the transition zone in the downwind direction shows more depositional feature. Therefore, we should be based on the specific types of sandstorms in different regions targeted deployment of sand control strategy. It is necessary to take some measurements to protect the original grassland and prevent the occurrence of blowouts, so as to cut off the source of sandy sediments to restrain the spread of desertification land. For the formed blowout, we should be based on its morphological evolution feature to arrange mechanical sand barrier targeted.Key Words: blowout; desertification; grain composition; geomorphology; geomorphic evolution |
| 中文关键词 | 风蚀坑 ; 沙漠化 ; 粒度特征 ; 地貌形态 ; 形态演变 |
| 英文关键词 | blowout desertification grain composition geomorphology geomorphic evolution |
| 语种 | 中文 |
| 国家 | 中国 |
| 来源学科分类 | 自然地理学 |
| 来源机构 | 中国科学院西北生态环境资源研究院 |
| 资源类型 | 学位论文 |
| 条目标识符 | http://119.78.100.177/qdio/handle/2XILL650/287946 |
| 推荐引用方式 GB/T 7714 | 王中原. 高寒干旱地区风蚀坑形态及地貌演变过程 ——以共和盆地三塔拉地区为例[D]. 中国科学院大学,2017. |
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