THE DYNAMIC MONITORING OF HORQIN SAND LAND USING REMOTE SENSING

Horqin Sand Land is regarded as the typical region for studying the problemof desertification. The integration of 3S(GIS, GPS and RS) techniques offer a roost helpful methodto study and monitor the dynamics of desertification. Based on the data derived from 3 periods'multitemporal Landsat TM imagery of the 1990s, the regional land use and dynamics of desertificationin Horqin Sand Land were studied. The main results revealed that: 1) as long as the general changetendency was concerned, the desertification of Horqin Sand Land would continue to spread; 2) therewas a gradual decrease in the area of both moving sand dunes and semi-stabilized ones, which meantthat fruitful progress had been made to control the desertification during the 1990s; 3) as a resultof unreasonable cultivation, the total area of stabilized sand dunes and grassland in the middleand western region decreased obviously. It suggested that the increasing damage caused by human wasleading to the hazard of further desertification. So in the future, it is necessary to take moreeffective measures to control the spread of desertification and restore the degraded ecosystems forthe purpose of optimizing the global eco-environment in Horqin Sand Land.

Effects of adding water on seasonal variation of soil nitrogen availability under sandy grasslands in semi-arid region

Water is usally thought of a limiting factor for the restoration of semi-arid ecosystem. In the growing season of 2006, a study was conducted to determine the effects of modeling precipitation on seasonal patterns in concentrations of soil-available nitrogen and to describe the seasonal patterns in soil nitrogen availability and seasonal variation in the rates of net nitrogen mineralization of topsoil at Daqinggou ecological station in Keerqin sand lands, Inner Mongolia Autonomous Region, China. Manipulation of water （80 mm） was designed to be added to experiment plots of sandy grasslands in dry season. Water addition （W） treatment and control （CK） treatment were separately taken in six replications and randomly assigned in 12 plots （4 m×4 m for each） with 2-m buffers betweens. Results showed that the content of soil inorganic nitrogen and net nitrogen mineralization rate were not affected by adding water in sandy grassland of Keerqin sand lands. Net ni- trogen mineralization rates ranged from 0.5μg·g^-1,month^-1 to 4 μg.g^-1.month^-1. The highest values of soil inorganic nitrogen and net nitrogen mineralization occurred on October 15 in control plots. The seasonal changes of soil inorganic nitrogen contents exhibited ＂V＂ shape pattern that was related to seasonal patterns of soil ammonium-N （ascending trend） and nitrate-N transformation （descending trend）.

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.

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 waterlimited 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 CO2 effux, 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 CO2 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.

Relationships among Glomalin Related Soil Protein,Soc and Soil Texture under Different Land Use Types

[Objective] The aim was to reveal the effects of different land use types on soil composition. [Method] GPRS,soil organic carbon content and soil texture in 3 depths (0-10,10-20,20-50 cm) of 5 main kind of selected land use type were examined in Hainan. [Result] The results showed that GRSP and SOC content of four artificial land use types decreased compared with the natural secondary forest land,the GRSP content of all samples ranged from 0.53-4.80 mg/g,accounting for 7.9%-23.4% of the SOC,which means that GRSP was one important component of SOC pool in soil. The ratio of GRSP to SOC was significantly different among land use types but the depths. GRSP and SOC exhibited obvious vertical distribution pattern. GRSP was significantly positively related to SOC and sand content but negatively related to silt and clay content. [Conclusion] The sand content determined the GRSP content significantly and loam was better matrix for GRSP accumulation than clay.

中卫市退砂土地农作物复垦的可行性分析研究

本研究旨在分析宁夏中卫市沙坡头区退砂地的土壤质量提升及农作物种植适宜性。通过连续3年的田间试验,收集并分析了8种宁夏地区广泛栽培的耐旱作物对土壤理化性质的影响及其经济效益。分析了退砂耕地适生农作物对当地土壤质量的影响及经济效益。结果表明,朝天椒和红葱在退砂地上表现出较高的产量和产值,且投入产出比大,是退砂地优先选择的作物。此外,玉米和小杂粮等作物轮作种植也显示出改良土壤结构和提高肥力的潜力。本研究为退砂地的科学利用提供了理论依据和实践指导,有助于推动中卫市经济社会可持续发展。

贵州省砂石矿山开采对生态环境的影响研究

正确认识砂石开采对生态环境的影响,对于调整砂石政策,保护矿区生态环境和制定矿区生态修复措施具有重要意义。以贵州省砂石矿山为例,通过分析砂石矿山开采对土地利用类型和生态系统服务功能的影响,揭示砂石矿山开采对生态环境的影响。研究结果表明:1)2010—2020年,贵州省砂石矿山开采占地共计11502.45 hm^(2),其中,占用农田4923.12 hm^(2),破坏森林面积4446.24 hm^(2);2)根据贵州省2020年砂石矿山开采现状,砂石矿区未来最适宜恢复的土地类型排序为森林>建设用地>农田;3)2010—2020年,贵州省因砂石开采损失的生态系统服务价值约6.34亿元,从生态系统服务功能看,对气候调节功能影响最大,对维持养分循环服务的影响最小。

黄河上游高寒沙地生态经济型治沙植物筛选评价

为助推黄河上游高寒区乡村振兴工作,在调查黄河上游沙生植物种质资源的基础上,采用层次分析法,从适应能力、扩繁能力、生态价值和经济价值4个方面确定地带性乡土植物、自然分布海拔、自然分布坡向等21个评价指标,构建黄河上游高寒沙地生态经济型治沙植物筛选层次结构模型,从22种具有经济价值的乡土治沙植物中筛选出沙棘、金露梅、银露梅、变叶海棠、垂穗披碱草、高山羊茅、高山绣线菊和窄叶鲜卑花等8种优良生态经济型治沙植物,为黄河上游高寒沙地植被恢复治沙植物选择提供科学依据。

退耕年限对压砂地植物群落及土壤化学计量特征的影响

宁夏压砂地由于长年连作,土壤质量降低,植被类型单一、稀疏,生态破坏严重,生境破碎。本研究以宁夏中部干旱带不同退耕年限压砂地为研究对象,通过分析退耕恢复过程中植物群落结构及土壤生态化学计量特征,阐明退耕年限对植物群落及土壤生态化学计量特征的影响。结果表明,植物群落特征在不同退耕年限之间差异显著(P<0.05),Shannon-Wiener多样性指数、Pielou均匀度指数呈逐步增加趋势,Margalef丰富度指数呈逐渐减少趋势;不同退耕年限下土壤化学计量特征具有显著性差异(P<0.05),有机碳含量在退耕20 a时最高,退耕10 a时最低,全氮、全磷含量呈波动增加的趋势;不同退耕年限、植物群落特征、土壤养分含量三者之间具有显著的相关关系(P<0.05)。因此,建议对不同退耕恢复年限的压砂地适当增施肥料,以加快促进植物群落结构重建与生物多样性恢复。

基于捐赠土壤种子库方法的沙丘植被恢复模拟实验

退化沙地土壤种子库数量不足限制了其自然恢复能力,传统的种子库添加植被恢复技术措施存在添加物种数量、配比难以确定的限制,针对上述问题,提出了捐赠土壤种子库的植被恢复方法,即从邻近植被生境相似的长期稳定群落转移包含土壤种子库的表层土壤进行受损区植被恢复的方法。该方法在受损湿地、草地和林地的恢复方面取得了较好的应用效果,但是该方法能否用于荒漠化区域的植被恢复尚未见报道。采用室内盆栽和模拟降雨相结合的实验办法,以长期稳定的固定沙丘为捐赠土壤种子库源区,以流动沙丘和半固定沙丘为受捐对象,对比分析了捐赠固定沙丘土壤种子库对流动沙丘和半固定沙丘植被恢复的效果,并模拟了降雨变化对恢复效果的影响作用。结果表明:1)捐赠土壤种子库显著提高了半固定沙丘和流动沙丘模拟处理的种子萌发数量和幼苗地上生物量,有利于促进流动沙丘和半固定沙丘向固定沙丘进行演替;2)捐赠土壤种子库方法在半固定沙丘的植被恢复效果优于流动沙丘;3)捐赠土壤种子库可以增加流动沙丘实现跨越式恢复的可能性,加快其向固定沙丘的演替进程;4)小幅度的降雨量增减对受捐区种子萌发数量和地上生物量无显著影响;5)极端降雨可以显著提高受捐区种子萌发数量和地上生物量。综上所述,在模拟实验条件下,捐赠土壤种子库技术可以有效地促进退化沙丘植被恢复,极端降雨事件对捐赠土壤种子库实施后的恢复效果影响更加显著。研究为捐赠土壤种子库在退化沙地植被恢复的野外实际应用提供了理论支持。

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。

鄂尔多斯区内毛乌素沙地1987—2022年植被覆盖时空演变

毛乌素沙地作为我国四大沙地之一,是沙漠化和防沙治沙研究的重点区域。遥感已成为地表时空分析的重要手段,但当前毛乌素沙地区域基于长时间序列、中高分辨率影像研究不足。利用Google Earth Engine云平台,结合Landsat-5 TM、Landsat-7 ETM+和Landsat-8 OLI长时序归一化植被指数,采用Sen+Mann-Kendall方法探究鄂尔多斯地区毛乌素沙地1987—2022年近35年植被覆盖时空演变,并结合气象数据进行驱动力分析。结果表明:(1)鄂尔多斯地区毛乌素沙地植被不断改善,植被覆盖整体呈增长趋势,NDVI变化量为+0.0028 a^(-1),NDVI增势呈先缓-后急-再缓的趋于平稳的阶段式变化特征;(2)植被改善的区域面积占比达98%以上,退化区域面积占比小于0.5%,空间上植被覆盖改善东部优于西部,南北部优于中部;(3)植被覆盖变化与自然水热变化无显著相关性。

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。

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。

宁夏沙坡头国家级自然保护区流动沙丘移动与固定沙地风蚀的研究

【目的】深入探究宁夏沙坡头国家级自然保护区流动沙丘营建植被后土壤风蚀抑制效率的定量关系,以期为我国干旱区制定合理的防风固沙方案提供理论依据。【方法】在宁夏沙坡头国家级自然保护区内3处流动沙丘各设置3个观测点,采取插钎法观测流动沙丘的移动;同时在保护区3处固定沙地采集栽植沙柳地段、栽植樟子松地段与栽植油蒿、花棒、柠条地段的原状土和各自对照的原状土开展室内风洞实验,风洞内观测在不同风速下的吹蚀变化。【结果】宁夏沙坡头国家级自然保护区流动沙丘一个风季平均前移3.23 m。风洞内不同风速吹蚀下,栽植沙柳地段样地土样的风蚀模数与对照相比,在风速为15 m/s时减少96.78%,在风速为20 m/s时减少97.07%;在10、15、20 m/s的风速吹蚀下,栽植樟子松地段样地土样的风蚀模数分别比对照减少53.13%、99.61%、99.84%,栽植油蒿、花棒、柠条地段样地土样的风蚀模数分别比对照减少50.00%、65.01%、3.65%。【结论】流动沙丘采用机械草方格固定后栽植人工植被能够促进地表生物结皮形成,进而土壤风蚀大为减弱。在干旱半干旱区进行植物固沙工作时要高度重视生物结皮的防治土壤风蚀的作用,以促进我国的生态恢复。