THE DYNAMIC MONITORING OF HORQIN SAND LAND USING REMOTE SENSING

Horqin Sand Land is regarded as the t ypical region for studying the probl em of desertification.The integra-tion of 3S(GIS,GPS and RS)techniques offer a most helpful meth od to study and monitor the dynamics o f desertification.Based on the data derived from3perio ds’ multitemporal Landsat TMimagery of the 1990s,the regional land use a nd dynam-ics of desertification in Horqin San d Land were studied.The main results revealed that:1)as long as the general change tendency was concerned,the deserti fication of Horqin Sand Land would co ntinue to spread;2)there was a gradual de-crease in the area of both moving sand dunes and semi-stabilized ones,whi ch meant that fruitful progress had b een made to control the desertification during the 1990s;3)as a result of unreasonable cultivation,the total area of stabilized san d dunes and grassland in the middle and western region decreased obviously.It suggested that the increasing damage caused by human was leading to the hazard of further desertification.So i n the future,it is necessary to take more effec-tive measures to control the spread o f desertification and restore the degraded ecosystems for the purpose of optimizing the global eco-environment in Horqin Sand Land.

Tree-ring based PDSI reconstruction since AD 1842 in the Ortindag Sand Land,east Inner Mongolia

epartment of Wood Science, University of Hamburg, Hamburg D-21031, GermanyBased on three Chinese pine (Pinus tabulaeformis Carr.) and one Meyer spruce (Picea meyeri Rehd. et Wils.) ring-width chronologies, a 163-year drought history was reconstructed in the eastern Ortindag Sand Land. All tree-ring chronologies show large inter-annual variations and strong common signals and fairly consistent variation between different chronologies, indicating that they are excellent proxy of regional climate. A regional chronology (RC) was established by averaging the four standard chronologies and further employed for the analysis and climatic reconstruction. The analysis revealed that tree growth is primarily limited by low precipitation in February-March and June-July and high temperature in May-July. In addition, RC has high correlations with the monthly Palmer drought severity index (PDSI) prior to and during the growing season because the PDSI considers the accumulation of the droughts. Response function analysis revealed that RC only exhibits significant correlations with the PDSI in June and July (close to the 95% significance level in May). Because May―July is a critical period for tree growth, the average May-July PDSI (PDSI5-7) was reconstructed back to 1842 using RC in the Ortindag Sand Land. The reconstruction can explain 52% of the PDSI variance and the equation was rather stable over time. It agrees well with the variation of the average dryness/wetness indices in North China,and captures the decline process of the East Asian summer monsoon since the mid-1960s. It is worth noting that the Ortindag Sand Land has experienced the most severe drought in the recent 40 years based on the 163-year drought reconstruction. Like summer precipitation in North China the reconstructed PDSI5-7 also displays a 20-year oscillation.

Sand-dust storms in China: temporal-spatial distribution and tracks of source lands

Sand-dust storm is a special natural disaster that frequently occurs in deserts and their surrounding areas. With the data published onSurface Meteorological Monthly Bulletin andSurface Chart during 1971–1996, the temporal-spatial distribution and annual variation of sand-dust storms are analyzed on the basis of the case study of atmospheric processes. Furthermore, the tracks and source areas of sand-dust storms are determined with the aid of GIS. The results show that except some parts of Qinghai Province and Inner Mongolia as well as Beijing, sand-dust storms decrease apparently in time and space in recent decades in China. Sand-dust storms occur most frequently in spring, especially in April. According to their source areas, sand-dust storms are classified into two types, i.e., the inner-source and outer-source sand-dust storms. Most of the outer-source sand-dust storms move along the north and west tracks. The north-track outer-source sand-dust storms always intrude into China across the Sino-Mongolian border from Hami, a city in the eastern part ofXinjiang, to Xilin Gol, a league in Inner Mongolia, while the west-track ones intrude into China from both southern and northern Xinjiang. The source lands of inner-source sand-dust storms concentrate in the Taklimakan Desert and its surrounding areas in southern Xinjiang, southern part of the Junggar Basin in north of Xinjiang, the Hexi Corridor in western Gansu Province, the dry deserts of Inner Mongolia and the Qaidam Basin in Qinghai.

Characteristics of Sand Dune Pattern and Fluvial-aeolian Interaction in Horqin Sandy Land, Northeast Plain of China

The interaction between fluvial and aeolian processes can significantly change surface morphology of the Earth. Taking the Horqin Sandy Land as the research area and using Landsat series satellite remote sensing images, this study utilizes geomorphology and landscape ecology to monitor and analyze the aeolian geomorphology characteristics of the Horqin Sandy Land. Results show that the sand dunes of the Horqin Sandy Land are mainly distributed on alluvial plains along the banks of the mainstream and tributaries of the Western Liao River, and the sand dune types tend to simplify from west to east and from south to north. The aeolian geomorphology coverage tend to be decreasing in the past 40 years, with an average annual change rate of 0.31%. While the area of traveling dunes decreased, the area of fixed and semi-fixed dunes increased. The fractal dimensions of various types of sand dune have all remained relatively constant between 1.07 and 1.10, suggesting that they are experiencing a relatively stable evolutionary process. There is a complex interaction between fluvial and aeolian processes of the Horqin Sandy Land, which plays a central role in surface landscape molding. Sand dunes on both sides of different rivers on the Horqin Sandy Land present certain regularity and different characteristics in terms of morphology, developmental scale, and spatial pattern. There are six fluvial-aeolian interaction modes in this area: supply of sand sources by rivers for sand dune development, complete obstruction of dune migration by rivers, partial obstruction of dune migration by rivers, influence of river valleys on dune developmental types on both sides, influence of river valleys on dune developmental scale on both sides, and river diversion due to obstruction and forcing by sand dunes. This study deepens our understanding of the surface process mechanism of the interaction between fluvial and aeolian processes in semi-arid regions, and provides a basis for researches on regional landscape responses in the context of global environmental change.

A quantitative analysis on the sources of dune sand in the Hulun Buir Sandy Land:application of stepwise discriminant analysis (SDA) to the granulometric data

Quantitatively determining the sources of dune sand is one of the problems necessarily and urgently to be solved in aeolian landforms and desertification research. Based on the granulometric data of sand materials from the Hulun Buir Sandy Land, the paper employs the stepwise discriminant analysis technique (SDA) for two groups to select the principal factors determining the differences between surface loose sediments. The extent of similarity between two statistical populations can be described quantitatively by three factors such as the number of principal variables, Mahalanobis distance D 2 and confidence level 琢for F-test. Results reveal that: 1) Aeolian dune sand in the region mainly derives from Hailar Formation (Q 3 ), while fluvial sand and palaeosol also supply partially source sand for dunes; and 2) in the vicinity of Cuogang Town and west of the broad valley of the lower reaches of Hailar River, fluvial sand can naturally become principal supplier for dune sand.

A Sand Control and Development Model in Sandy Land Based on Mixed Experiments of Arsenic Sandstone and Sand: A Case Study in Mu Us Sandy Land in China

Serious desertification caused by human activity and climate change,in addition to water loss and soil erosion related to arsenic sandstone in the Mu Us Sandy Land,lead to severe scarcity of soil and water resources,which causes worse local agricultural conditions accordingly.Many physical properties of arsenic sandstone is complementary with that of sand,arsenic sandstone is therefore supposed to be blended to enhance water productivity and arability of sandy land.Container experiments are carried out to study the enhancement of water holding capacity of the mixture,the blending ratio of arsenic sandstone and sand,and the proper size of the arsenic sandstone particles,respectively.The results of the experiments show that particle size of 4 cm with a ratio of 1∶2 between arsenic sandstone and sand are the proper parameters on blending.Both water content and fertility increase after blending.Water use efficiency in the mixture is 2.7 times higher than that in sand by the water release curves from experiments.Therefore,a new sand control and development model,including arsenic sandstone blending with sand,efficient water irrigation management and reasonable farming system,is put forward to control and develop sandy land so that water-saving agriculture could be developed.Demonstration of potato planting about 153.1 ha in area in the Mu Us Sandy Land in China indicates that water consumption is 3018 m3/ha in the whole growth period.It means that about 61%of irrigation water can be saved compared with water use in coarse sand without treatment.Recycle economic mode and positive feedback of sand resource-crop planting-soil resource are constructed,which changes sand into arable soil and make it possible to develop water-saving agriculture on it.The proposed model will be helpful for soil-water resources utilization and management in the Mu Us Sandy Land.

南亚抗震不利地段海陆交互复杂互层地基加固性能研究

针对孟加拉国某港口工程海陆交互相复杂互层地基加固中遇到的地层特性复杂、加固效果难以预测以及软黏土和粉细砂互层土场地地震液化的问题,结合场地地质条件、使用功能、工程特点等,对插板预压联合降水强夯在该场地条件下的加固效果展开研究。依托项目试验区块,通过对加固前后土体物理力学指标的对比分析和沉降-时程曲线、孔隙水压力-时程消散曲线等的研究,得到插板预压联合降水强夯加固的过程特性以及对原状土和吹填土的加固效果。研究表明,插板预压联合降水强夯法对于复杂互层土上吹填砂场地具有较好的适应性,加固效果可满足设计承载力和工后沉降控制要求,该法对于减轻砂土层的液化具有一定的作用。研究成果对于南亚地区复杂互层土吹填场地设计具有指导意义。

旱区连作砂田土壤质量和土地生产力演变与调控研究进展

砾石覆盖在改变旱区水文循环和物质转化方面有着至关重要的作用。然而,长期连作给砂田土壤质量及土地生产力带来危机和不确定性。以连作砂田为研究对象,归纳总结了连作年限对砂层质地结构、土壤物理结构、土壤水盐热效应、土壤养分状况、土壤酶活性、土壤微生物特性、作物生长发育以及产量品质的影响效应和可能机制,发现砂田土壤生态环境和土地生产力在人类活动及自然侵蚀的扰动和破坏下整体呈现退化态势,但对不同覆盖条件、施肥水平和种植结构等农田管理措施的响应过程表现出差异性。继而,基于土壤质量和土地生产力的协同和互作效应深入揭示了砂田性能逐年退化机理,并简述了生物、农业及工程调控措施在砂田退化阻控和修复方面的应用进展。在此基础上,提出了砂田退化进程中急需解决的关键科学问题和未来发展方向,主要包括土壤质量演变的基本过程及其发生机制、“砾石-土壤-微生物-植物”系统的叠加和互作效应及其分子机理、土壤改良与生物防治措施的定量化及其调控机制三个方面。在气候变化、植被演替和土地退化背景下,废弃风化砾石的劣化增肥机制及其环境效应将是今后研究的重点。

复合型治沙措施对土壤细菌群落结构及功能的影响

以流动沙丘地人工梭梭林土壤(Asd)为对照,选取尼龙网格沙障+人工梭梭林(Nn)和黏土沙障+人工梭梭林(Cy)2种复合型治沙措施区土壤为研究对象,采用Illumina高通量测序和PICRUSt2功能预测技术,探究复合型治沙措施对土壤细菌群落结构及功能的影响,并采用冗余分析解释影响土壤细菌群落及功能的主要理化因子。结果表明:1)2种复合型治沙措施区土壤细菌隶属于35门、90纲、172目、259科和436属。放线菌门、变形菌门和绿弯菌门是研究区土壤优势菌群,平均相对丰度累计达71.84%,其中放线菌门相对丰度最高,占32.16%~37.09%。Cy措施区土壤拟杆菌门和蓝藻菌门显著高于Asd样地(P<0.05)。2)2种措施区土壤细菌Chao1指数显著高于流动沙丘土壤(P<0.05),但主坐标分析显示,3组样地土壤细菌群落结构组成相似。3)在17个次级功能中,碳水化合物代谢功能等为土壤细菌的主要生态功能,且在治沙措施区表现出高度冗余特点。4)相较流动沙丘土壤,复合型治沙措施区土壤有机质等养分含量呈显著增加的共性趋势(P<0.05),且冗余分析表明土壤有机质和速效钾等理化因子显著影响细菌群落结构及生态功能。5)土壤优势菌门与绝大多数代谢功能呈显著相关,且Mantel检验表明土壤细菌群落结构差异与功能潜势差异之间呈显著正相关。综上,复合型治沙措施的实施有助于改善荒漠土壤微环境,研究结果可为沙化土壤微环境生态修复提供理论依据。

毛乌素沙地盐池地区固定沙丘主要固沙灌木的空间分布格局与空间关联性研究

种群的空间分布格局与关联性的研究对预测种群的演替趋势和植被重建具有重要意义。基于毛乌素沙地固定沙丘上固沙灌木的地理位置和生长发育阶段数据,采用单变量、双变量成对相关函数和Monte-Carlo拟合检验方法,对油蒿(Artemisiaordosica)、杨柴(Hedysarummongolicum)和柠条(Caraganakorshinskii)三种优势种群进行空间分布格局和关联性分析。结果表明:(1)三个种群在小尺度下呈现聚集分布,大尺度下呈现随机或均匀分布;杨柴和柠条种群在研究尺度范围内主要表现为聚集分布。(2)种间关系表明:油蒿和杨柴在小于5 m尺度下负相关,其他尺度下基本不具有相关性。(3)种群不同生长发育阶段之间的种内关联关系表明:在小尺度下,3个种群的种内关系基本呈正相关;在大尺度下,油蒿种内关系呈负相关,杨柴和柠条的种内关系不存在相关性。

深回填土砂泥岩组合地层桩锚围护基坑的变形规律

[目的]目前工程界针对基坑的研究大多数基于软土基坑和岩质基坑的经验,重庆地区为深回填土砂泥岩组合地层,需展开基坑变形规律研究。[方法]以重庆轨道交通10号线兰花湖停车场基坑工程为背景,基于现场监测数据,总结围护结构水平位移,围护桩后地面沉降的变化规律,进而围护结构水平位移与桩后地面沉降相关性。[结果及结论]围护桩最大侧移δh变化范围为0.048%H~0.103%H(H为开挖深度),远小于软土地区的统计结果;最大地面沉降δv介于0.033%H~0.220%H,小于卵石和软土基坑,与青岛土岩组合基坑较为接近;基坑开挖影响范围为H~1.5 H;基坑最大地面沉降δv与围护结构最大侧移δh关系可表示为δ_(v)=0.45δ_(h)~2.35δ_(h),均值为1.31δ_(h);地面沉降包络面积和围护结构侧移包络面积比值近似为1.67。

一种改进的黑土农田风蚀集沙仪

风蚀监测可反映风沙运动规律,集沙仪是风蚀监测的必备仪器,而以往研究大多在沙漠或沙地开展,较少涉及黑土农田。本研究基于BSNE(Big Spring Number Eight)集沙仪,将采沙盒底部阻风结构中的18目孔径筛网改进为逆向百叶窗式的阻风挡板,采用模拟试验对比分析BSNE集沙仪和改进后rBSNE(Revised Spring Number Eight)集沙仪的保沙和集沙能力,并将其应用于野外黑土农田风蚀监测。研究结果表明:与BSNE集沙仪相比,rBSNE集沙仪降低了小粒级颗粒的损失率,当风速低于20 m·s~(-1)时,对<0.25 mm粒径的土壤颗粒的损失率显著降低74.3%~87.1%;当风速达到20 m·s~(-1)时,对所有试验粒径的土壤颗粒的损失率显著降低46.9%~74.3%。与BSNE集沙仪相比,rBSNE集沙仪有助于对小粒级颗粒的收集,当风速低于20 m·s~(-1)时,对粒径为<0.5 mm的集沙量显著增加了9.0%~44.0%;当风速达到20 m·s~(-1)时,对所有试验粒径的集沙量均显著增加7.3%~34.4%。野外监测结果显示风蚀输沙量随高度增加呈指数函数递减趋势,说明rBSNE集沙仪可应用于黑土农田风蚀的监测。

2005-2020年鄱阳湖沙地输沙势特征分析

鄱阳湖沿岸风沙活动对经济发展和生态环境产生较大危害。探究环湖风沙环境和输沙势(DP)的时空变化,了解鄱阳湖沙地侵蚀规律,对鄱阳湖防沙的重点区域具有重要意义。基于2005—2020年鄱阳湖沿岸九江、庐山、星子、永修、都昌、鄱阳和南昌7个气象站点的风况数据,利用输沙势分析其沙地的风能环境特征。结果表明:1)2005—2020年鄱阳湖沿岸的起沙风速波动减小,起沙风风频冬季最高,夏季最低,风向偏北。2)研究区内DP年际变化整体呈下降趋势,季节差异性较大,春冬季大于夏秋季;空间异质性显著,呈北高南低,西高东低的空间格局,庐山和星子最大,鄱阳最小。庐山站处于中风能环境,其他6个站点属于低风能环境。DP的风向集中分布在N-NE,合成输沙方向指向偏西南。3)风向变率存在明显的区域差异现象,南昌和永修表现出较大变率的单峰状态,其他5地则较多处于中等变率的双峰状态。总体上,DP时空演变差异与沙地面积变化一致,合成输沙势与沙地面积同期增大或减小,高值区分布在沙地面积较大处。建议以鄱阳湖西北部、都昌、永修为沙化防治的重点区域。

内蒙古沙尘源空间格局及转化情况分析

我国北方地区春夏季节沙尘天气频发,识别沙尘源区对于沙尘天气预报及区域生态环境治理意义重大。本文以内蒙古自治区为目标区,采用2005、2010、2015和2020年4个年度土地利用/土地覆被数据,分析了内蒙古沙尘源的空间分布格局,并基于土地类型转移矩阵分析了不同类型沙尘源的转化情况。结果显示:内蒙古沙尘源空间格局的时间变化特征并不明显,但通过定量化的分析发现,每种类型沙尘源的面积均随时间波动变化,但总体看,2005—2020年,内蒙古全区沙尘源总面积减少了7771.05km^(2);从内蒙古沙尘源正、逆向转化的分析看,稀树草原、有林草原、落叶阔叶林、农田/自然植被混合区域这几种土地类型是沙尘源转化的活跃区域或者敏感区,要特别给予关注;稀疏的灌木土地类型转化为草原型沙尘源的面积占比降低的事实,从另一个侧面说明内蒙古地区灌木的固沙效果要好;内蒙古荒漠交错带面积广阔,但其生态系统脆弱,为潜在的沙尘源区,应科学划定生态保护区,禁止人为活动。本文研究结果有望为区域生态环境治理及农牧业发展提供科学依据。

土地沙化与林业防沙治沙措施探究

随着社会经济的高速发展,人们对土地资源的需求量越来越大,明显加大了土地使用压力,土地利用缺乏合理性的现象普遍存在,再加上人们过度开发利用,导致自然环境遭到严重破坏。在自然、人为双重因素的影响下,我国的土地沙化问题愈发显著,直接影响着人们正常的生产、生活。基于此,本文主要围绕土地沙化与林业防沙治沙措施展开论述。首先概述了土地沙化的内涵、现状、危害,其次分析了造成土地沙化的主要原因,最后提出了利用林业防沙治沙的有效措施。

Precipitation Pulses and Soil CO_2 Emission in Desert Shrubland of Artemisia ordosica on the Ordos Plateau of Inner Mongolia,China

Precipitation is the major driver of ecosystem functions and processes in semiarid and arid regions. In such water- limited ecosystems, pulsed water inputs directly control the belowground processes through a series of soil drying and rewetting cycles. To investigate the effects of sporadic addition of water on soil CO 2 efflux, an artificial precipitation event (3 mm) was applied to a desert shrub ecosystem in the Mu Us Sand Land of the Ordos Plateau in China. Soil respiration rate increased 2.8-4.1 times immediately after adding water in the field, and then it returned to background level within 48 h. During the experiment, soil CO 2 production was between 2 047.0 and 7 383.0 mg m -2 . In the shrubland, soil respiration responses showed spatial variations, having stronger pulse effects beneath the shrubs than in the interplant spaces. The spatial variation of the soil respiration responses was closely related with the heterogeneity of soil substrate availability. Apart from precipitation, soil organic carbon and total nitrogen pool were also identified as determinants of soil CO2 loss in desert ecosystems.

Modeling and Mapping Sand Encroachment Risk as an Aid for Urban Planning in the United Arab Emirates (UAE)

Sand encroachment into urban areas represents a high risk factor for transportation infrastructural and urban development in the United Arab Emirates. The UAE is located in one of the world’s largest arid regions with a strong prevalence of sand movement and encroachment into urban areas, particularly in the last few years. The objective of this research is to develop a land surface process platform that models sand movements and further generates an encroachment risk index map of potential encroachment risk areas season-wise in the UAE. To achieve this objective, this research used elevation and land cover maps generated from Lands at 8 Operational Land Imager (OLI) data which represent the topography of the study area coupled with meteorological information on wind speed, temperature and precipitation. Furthermore, the study considered the vegetation cover as a major contribution factor to reduce sand encroachment. Using developed sand movement model for this research, sand encroachment risk maps were generated to help urban planners in cities making informed decisions of future urban protection structures and transportation networks that mitigate the effects of sand dunes encroachments in the UAE. A major finding of this research results conclude that during the summer season encroachment risk reaches 30% higher compared to the winter season due to the extremely high temperature which leads to reduced vegetation in the country. Urban planning decision maker may consider the finding of this research for future infrastructural adjustments.

Effects of sand burial on growth and antioxidant enzyme activities of wheat(Triticum aestivum L.) in northern China

Growth and physiological responses of wheat to sand burial were studied in Horqin Sandy Land, to determine the impact on productivity and survival as well as antioxidant enzymes responses. This study consisted of one control （no sand） and four sand burial treatments： 25%, 50%, 75% and 100% of seedling height, respectively. Minor burial （25%） had no effect on wheat growth and survival; deep burial （100%） was fatal, and the others had an intermediate effect. Thus, the survival limit to sand burial was equal to seedling height. Sand burial mainly decreased shoot biomass and crop yield, but had small effects on belowground biomass. Superoxide dismutase （SOD） activity increased with time after burial in all treatments with surviving plants. Peroxidase （POD） activity increased after six days under burial, and catalase （CAT） activity de- creased after burial, but recovered after 12 days. The concentration of malondialdehyde （MDA）, a marker for oxidative stress, was low on the sixth day, but increased thereafter with burial depth. Thus, sand burial 〉25% should be avoided due to growth rate reduction leading to reduced crop yield, and even 25% burial showed physiological indicators of stress.

Impact of Sand Mining and Sea Reclamation on the Environment and Socioeconomic Activities of Ikate and Ilubirin Coastal Low Income Communities in Lagos Metropolis, Southwestern Nigeria

Land reclamation is gradually posing negative impact on man due to unplanned urbanization. A study was carried out on impact of land reclamation through sand mining of coastal communities in Ikate and Ilubirin in Lagos, Nigeria. Ten waters (8 surface and 2 groundwater sources), 10 soil samples and air were collected and taken for analysis. Results of water revealed concentrations lower than WHO (2017) and SON (2007) standards. Soil/sediment with average crustal value revealed Pb and Cd above standard values, which is attributed to anthropogenic influence on soils. Quality of air in the study was mainly particulate matter arising from the sea and reclaimed land in the surroundings of the environment with the highest Total Suspended Particulate of 0.8 mg/m3 in sulfur dioxide. This explains corrosion found on the roofs of the communities. Therefore, in the development planning adequate precautions should be put in place to avert environmental degradation.

Change Detection of Desert Sand Dunes: A Remote Sensing Approach

Deserts are one of the major landforms on the Earth. While deserts occupy about one-fifth of Earth’s land surface, they have been studied to a much lesser extent. All over the world, desert landforms are expanding ever rapidly and more and more human settlements are finding place in desert regions for habitation. Thus, quantifying and monitoring dunes becomes more relevant from a managerial perspective. Analyzing desert areas using satellite imagery is a challenging task due to weak textural differences and nearly homogeneous spectral responses in most parts of the terrain. In this paper, a post-clustering methodology for change detection of desert sand dunes is proposed. Features based on Radon spectrum are used to cluster dunes of various orientations. These clustered boundaries are used to detect if there are any changes occurring in the dune regions. In the experiments, remote sensing data covering various dune regions of the world are observed for possible changes in dune orientations. In all the cases, it is seen that there are no major changes in desert dune orientations since three decades.