新疆荒漠化监测分析评价--基于RS与GIS的荒漠化监测研究

The land desertification in Xinjiang was monitored and analyzed based on RS and GIS techniques. Satellite data interpretation was adopted to obtain the general situation of Xinjiang‘s land desertification in assistance with the sampling method and on-the-spot investigations. Related monitoring and investigations showed that Xinjiang was facing with severe wide range land desertification, and its desertified area made up 77.08% of the total monitoring area. As for land types,the desertified farmland accounted for 1.92% of the total monitoring area, desertified woodland 4%,desertified grassland 45%, and unused land 49%. Accordingly, as for desertification degrees,non-desertified land occupied 22.92%, weak desertified land 5.69%, medium-degree desertified land 16.58%, severe desertified land 33.19% and super severe desertified land 21.61%. Finally, as for inducing factors, wind-eroded desertification made up 58.23%, water-eroded desertification 8.69%,salinization desertification 6.52% and frozen-melt eroded desertification 3.64%. Xinjiang‘s land desertification tended to get worse and the harnessing mission remained hard.     

基于遥感和GIS技术的荒漠化动态分析——以宁夏盐池为例

荒漠化是当今全球和中国最为严重的环境与社会经济问题之一,它的危害已深入到自然与社会经济的各个方面。选取荒漠化问题突出的宁夏盐池县作为研究区,通过3期遥感TM影像(1986年、1996年、2000年),运用GIS的分析手段,综合土地利用图、地形图和其他资料形成盐池县3期荒漠化现状图及两阶段动态图。盐池荒漠化土地类型的结构变化表明,荒漠化受非荒漠化类型土地限制,其面积有所减小,但程度在加重。荒漠化发展的原因是自然因素与人为因素共同作用的结果。     

我国沙漠化研究的若干问题——2.沙漠化的研究内容

我国开展沙漠化的研究与防治已有半个世纪,但沙漠化土地一直在加速扩展,目前仍然处于"局部治理,整体恶化"的严峻态势,其重要的原因之一,就是未能在认识沙漠化关键科学问题的基础上,建立比较完善的沙漠化科学的基本理论体系来指导防治实践。沙漠化过程研究与防治实践中许多科学问题的解决,是需要以沙漠化科学为主的多学科交叉与综合集成的研究。作者就我国沙漠化学科的主要研究内容开展讨论,认为沙漠化研究应以人-地关系为主线,在时间序列上,将沙漠化环境背景的形成演化、沙漠化与沙尘暴的现代过程及其在全球变化格局下的发展趋势的研究系统化,以揭示沙漠化的形成与演变;在空间结构上,将沙漠化地区的生态环境退化过程与区外乃至全球的大气环流格局视为统一的环境动力系统进行研究,以揭示沙漠化与沙尘暴的空间分异及其对环境和社会经济的影响。通过定量认识人类活动和自然因素影响下研究沙漠化的演变规律及其调控的理论依据和技术途径,为沙漠化防治提供科学基础。据此,提出沙漠化的主要研究内容为:沙漠化过程的自然与人文背景研究、沙漠化(沙尘暴)动力学过程及其调控、沙漠化的生物学过程与植被恢复重建机理和沙漠化综合防治战略与模式。     

20世纪60年代以来中亚地区的盐尘暴

中亚是盐尘暴高发地区之一,由自然因素和人文因素引起的沙质和盐质荒漠广泛分布。据初步估计,平均每年从干涸的咸海盆地通过空气输送出的盐尘为05×10⁶t到20×10⁶~30×10⁶t不等。这些盐尘的沉降受地形、风力和距源地的距离的影响。中亚地区盐尘暴的季节性和频率受降雨的影响很大。盐尘不仅影响气候,还会给人们的健康与经济活动带来不利影响。通过对过去近40年研究工作的总结和分析,对中亚地区盐尘暴的现状及其未来变化有了基本的认识:(1)盐尘的产生、搬运和沉积在中亚地区是目前的普遍现象,特别是在咸海区域。(2)过去近40年的咸海危机证明:适当的自然保护需要很长的时间和大量的资本投入。(3)要缓和目前的现状并创建一个稳定的、健康的环境,在实施各项计划中需要综合考虑社会、经济与生态问题。     

Identifying mechanisms of shore platform erosion using Structure-from-Motion (SfM) photogrammetry

Shore platforms control wave energy transformation which, in turn, controls energy delivery to the cliff toe and nearshore sediment transport. Insight into shore platform erosion rates has conventionally been constrained at millimetre-scales using micro-erosion metres, and at metre-scales using cartographic data. On apparently slowly eroding coasts, such approaches are fundamentally reliant upon long-term observation to capture emergent erosion patterns. Where in practise timescales are short, and where change is either below the resolution or saturates the mode of measurement, the collection of data that enables the identification of the actual mechanisms of erosion is hindered. We developed a method to monitor shore platform erosion at millimetre resolution within metre-scale monitoring plots using Structure-from-Motion photogrammetry. We conducted monthly surveys at 15 0.25 m² sites distributed across the Hartle Loup platform in North Yorkshire, UK, over one year. We derived topographic data at 0.001 m resolution, retaining a vertical precision of change detection of 0.001 m. We captured a mean erosion rate of 0.528 mm yr^-1, but this varied considerably both across the platform and through the year. We characterized the volume and shape of eroded material. The detachment volume–frequency and shape distributions suggest that erosion happens primarily via removal of shale platelets. We identify that the at-a-point erosion rate can be predicted by the distance from the cliff and the tidal level, whereby erosion rates are higher closer to the cliff and at locations of higher tidal duration. The size of individual detachments is controlled by local micro-topography and rock structure, whereby larger detachments are observed on more rough sections of the platform. Faster erosion rates and larger detachments occur in summer months, rather than in more energetic winter conditions. These results have the potential to form the basis of improved models of how platforms erode over both short- and long-timescales. © 2019 John Wiley & Sons, Ltd.     

基于MODIS时间序列数据的沙漠化遥感监测及沙漠化土地图谱分析——以内蒙古中西部地区为例

土地沙漠化是内蒙古中西部地区主要的生态环境问题之一,遥感与图谱分析为其研究提供了有效的技术手段。基于MODIS数据产品,反演时间序列的沙漠化监测指标,结合决策树分类法提取沙漠化土地信息,并提出新的沙漠化修正指数进行沙漠化土地动态分析;采用地学图谱分析方法提取了3个不同时间尺度上沙漠化土地的时空复合图谱信息,对沙漠化土地类型变化、土地沙漠化的程度等进行分析。结果表明:(1)遥感监测指标与决策树分类方法相结合可以有效地提取沙漠化土地信息。(2)2000-2014年内蒙古中西部地区的沙漠化程度与面积总体上呈减轻与减少趋势,2011-2014年间沙漠化总面积年平均值约为17.2万km²,比2000-2010年沙漠化总面积年平均值减少约2万km²。(3)沙漠化土地变化具有多时间尺度的特征,短时间尺度与较长时间尺度上沙漠化的动态变化趋势不同。各类型沙漠化土地动态度的绝对值随时间尺度的增加而降低。不同时间尺度沙漠化土地的净逆转比例也不同,2005-2010年和2005-2014年沙漠化土地净逆转比例较大,分别为13.95%和9.08%。受研究时段长度的限制,10 a或更长时间尺度上进行沙漠化动态变化趋势及其成因机制的分析可能更为合理;而5 a或更短的时间尺度,可能仅对揭示沙漠化高风险区或快速恢复区等热点地区有帮助。(4)2000-2014年毛乌素沙地及阴山北麓的农牧交错区等地区呈现相对稳定逆转的态势,而浑善达克沙地中西部等部分地区沙漠化土地变化较不稳定,近5 a仍呈现恶化的态势。     

塔里木河下游居民沙漠化认知

居民的沙漠化认知直接影响着居民行为,正确的居民沙漠化认知有助于公众参与沙漠化防治。以问卷和访谈的方式对新疆塔里木河下游当地居民的土地沙漠化认知进行调查。结果表明：当地居民对沙漠化变化和沙漠化成因有较清楚认知,但受活动范围影响存在一定局限性;对沙漠化治理措施认识较为全面,认为政府和社会所有成员是沙漠化治理的主体,部分居民愿意承担部分治理费用;沙漠化信息获取的途径较单一,主要来源于广播电视。提出推动当地居民参与沙漠化治理3条建议：关注绿洲内部沙漠化,研究适合的沙漠化治理物权,建立立体交叉的沙漠化信息传播网。     

塔克拉玛干沙漠地区沙尘暴研究进展

作为中国最大的沙漠和世界第二大流动性沙漠,塔克拉玛干沙漠是中国主要沙尘暴中心和黄土沉积的物源区之一,在中国北方乃至欧亚大陆自然环境和生态格局中具有重要影响,研究塔克拉玛干沙漠地区的沙尘暴具有十分重要的理论与实践意义。本文综述了塔克拉玛干沙漠地区沙尘暴过程及数值模拟预报研究的主要进展,阐明了沙尘暴的成因,进而总结了沙尘暴孕育发展的主要特征,提出了塔克拉玛干沙漠地区沙尘暴研究中亟待解决的科学问题。     

The formation of beaches on shore platforms in microtidal environments

Beaches are common features of many rocky shorelines and can be considered to be constrained by the underlying geology. In mesotidal to macrotidal areas the slope of the substrate and sediment supply are the primary factors in constraining the size and development of beaches on shore platforms. In microtidal settings it is not known if these factors are wholly responsible for determining the presence of beaches on shore platforms, nor the contribution of other factors such as hydrodynamics. The microtidal coast of Victoria, Australia, is surveyed in this study in order to quantify the morphological boundary conditions that constrain beach development on semi‐horizontal shore platforms. An ample sediment supply indicates that the underlying geology is controlling the presence and absence of beaches. Where beaches occur they always overlie a rock ramp which is the steepest part of the platform. The two most important morphological constraints were platform width and height both of which significantly correlated with beach volume. An elevational threshold exists at just over +1.0 m where beaches cannot accumulate. Below this threshold, platform width appears to be the principle constraining factor in beach accumulation. An evolutionary model is inferred which suggests that dissipation of wave energy associated with platform widening plays an important role in allowing beaches to accumulate. The model suggests beaches on platforms will be particularly sensitive to sea level rise. Copyright © 2014 John Wiley & Sons, Ltd.     

Trophic ecology of the rocky shore community associated with the Ascophyllum nodosum zone (Roscoff,France): A δC vs δN investigation

This study aimed to characterize the structure and functioning of the benthic food web associated with the Ascophyllum nodosum zone of the rocky shore of Roscoff by using δ¹³C and δ¹⁵N. Several characteristics of the trophic ecology of the invertebrates associated with this mid-littoral habitat and which belong to different functional groups (e.g., grazers, filter-feeders, predators and omnivores) were highlighted. In particular, the filter feeder species (including mostly sponges) used macroalgae-derived organic matter as a substantial food requirement. The results also pointed out an important stable isotopes variability for strict coexisting primary consumers which: (1) is directly related to the high δ¹⁵N range of the food sources; (2) makes it impossible to establish a unique trophic level scale based on δ¹⁵N values, as previously done in coastal environments; and (3) points out the existence of major co-occurring trophic pathways which characterise the Ascophyllum nodosum habitat.