红树林与互花米草盐沼交界区空间格局变化规律的遥感分析

红树林和盐沼是世界上重要的滨海湿地类型。在我国东南部沿海,互花米草盐沼和红树林之间的竞争成为一个重要的问题。为了研究红树林和互花米草盐沼之间的空间竞争规律,选取福建漳江口红树林国家级自然保护区为研究区域,收集了1988年至2014年27年间共15期覆盖该区域的Landsat影像和Google Earth影像,采用最大似然分类法提取出红树林与互花米草盐沼的近30 a历史变化信息。历史遥感影像分析表明:1)红树林面积20世纪90年代增长速度最快,2004年以后增长速度变慢;2)互花米草最早出现在2002年,此后以缓慢的速度朝着地势高的区域扩散,2010年后互花米草的扩散速度加快;3)红树林与互花米草的交界区基本保持稳定,部分区域表现为红树林略微向外扩张;4)影响红树林与互花米草盐沼交界区空间格局的因素可能有潮沟的分布和红树林的林冠完整性等。     

近30 a来盐城沿海盐沼时空分布演变规律及影响因素分析

盐沼是全球温带及亚热带地区的主要滨海湿地类型之一,具有重要的生态服务功能。本文以盐城沿海区域为例,利用近30 a来的6期遥感卫星图像,通过简单的植被覆盖指数(NDVI)粗提取和目视解译的方法分析了该区域盐沼的时空演变,并对引起这些变化的影响因子进行了探讨。结果表明,近30 a来研究区盐沼面积呈大幅度先升后降又小幅度上升的趋势,至2015年盐沼面积减少了约18 km²;盐沼的空间位置不断向外扩张,最大扩张距离达到了5.5 km,盐沼的宽度也随着时间不断变化;盐沼植被类型发生了不同程度的演变,景观指数表明景观破碎化程度不断加剧,獐毛、碱蓬、芦苇大量减少,单一的互花米草覆盖湿地。对盐沼时空变化起到影响的自然因素和人为因素中,围垦活动的影响最为显著。     

基于海岸带成像仪CZI的连云港紫菜养殖动态监测

连云港海域的紫菜养殖遥感监测对于规划紫菜养殖空间分布具有重要意义。基于50m空间分辨率的海洋一号C卫星（HY-1C）海岸带成像仪（Coastal Zone Imager, CZI）数据,利用归一化植被指数(NDVI)和人工目视解译,获取了2018年10月-2020年4月连云港沿岸的紫菜养殖遥感监测面积,并分析了紫菜养殖的季节变化特征。结果显示,连云港紫菜养殖区主要分布于海州湾和连岛附近海域;养殖区自9月至次年5月在CZI图像上可见,紫菜养殖遥感监测面积呈先增加后减少的趋势,1-2月其遥感监测面积通常达到一个养殖周期的最大值,3月初面积迅速减少;基于CZI影像的2019年度遥感监测面积为123km2,2020年为160km2。建立HY-1C与哨兵二号(10m)、高分一号(16m)和Landsat-8(30m)监测结果的线性模型,以Google Earth影像目视解译的紫菜养殖区遥感面积作为真实值,并将哨兵二号监测值转换为真实值。换算成真实值的2020年度紫菜养殖区真实面积为94km2,较2015年度的42km2增长了一倍多。本研究展示,CZI可用于紫菜养殖区的业务化观测,本文同时建议,利用其1-2月份的多期遥感影像监测结果作为年度紫菜养殖区遥感监测面积的基准。     

1989-2021年粤港澳大湾区海岸线变迁及土地利用变化

利用1989-2021年7期Landsat TM/Sentinel-2 MSI遥感影像数据，借助Google Earth Engine(GEE)平台，使用改进归一化差异水体指数（Modified Normalized Difference Water Index,MNDWI）、Canny边缘检测算法、遥感解译分类方法等，完成了粤港澳大湾区7期海岸线信息的提取，并从海岸线长度、变化强度、岸线多样性、海岸带陆域面积变化以及海岸带土地利用变化等方面分析了海岸线时空变化特征和驱动因素。分析结果表明：(1)1989-2021年大湾区海岸线长度持续增加，岸线变化强度具有阶段性，2004年以前岸线增长缓慢，之后岸线增长较快，2004-2009年为岸线增长高峰期；(2)研究时期内，大湾区各个区域内的岸线都发生了一定的变化，其中珠海、香港、深圳、澳门岸线变化最强烈，其他地区相对稳定；(3)研究区内岸线类型变化明显，人工岸线逐渐取代自然岸线成为海岸线的主体，人工岸线增长达651.17 km，增幅较高，自然岸线减少407.89 km；(4)大湾区围海造地面积显著增加，增长速率较快，岸带土地利用类型由林地、草...     

基于高分辨率卫星和无人机的广西滨海盐沼面积变化监测

滨海盐沼作为重要的海岸带生态系统,在海岸保护、生物多样性维持、固碳减污等方面发挥了重要的生态服务功能。及时准确地监测滨海盐沼分布情况和动态变化,对于科学地管理和保护本地滨海盐沼生态系统意义重大。本研究基于2019年和2021年多源国产高空间分辨率卫星数据,结合无人机自主性强、灵活机动、不受云遮挡影响的优势,对广西壮族自治区滨海盐沼开展遥感跟踪监测。研究结果表明,广西2021年滨海盐沼总面积为1 341.40 hm2,其中,北海市、防城港市和钦州市3个海滨城市的滨海盐沼面积分别为1 247.82 hm2、49.73 hm2和43.85 hm2。与2019年相比,广西2021年滨海盐沼总面积减少108.96 hm2,其中,北海市互花米草（Spartina alterniflora）面积减少107.05 hm2,钦州市短叶茳芏（Cyperus malaccensis）和芦苇（Phragmites australis）面积减少1.91 hm2,防城港市滨海盐沼面积不变。广西当地对入侵种互花米草的治理卓有成效,互花米草大范围减少,但局部区域的互花米草分布仍呈不断增长的趋势,仍需重视对互花米草的监测与防控工作。     

无人机航测技术在海草床调查中的试点应用

通过无人机飞行参数、飞行高度、潮汐条件和调查范围等试验,采用无人机对东郊椰林近岸海域海草进行航拍,利用PIX4D软件处理得到了高分辨率海草分布影像图,利用ArcGIS软件对海草分布区进行了矢量化提取,选择有代表性的区块结合实地调查进行验证,得出了试验区的海草分布特征和海草种类。结果表明：海草分布在离岸300 m范围内的珊瑚礁砰上,呈斑块状、间隔式分布特征,在试验区中海草分布面积为2 449.6 m2,占比为24.5%。实地调查到海草种类有圆叶丝粉草（Cymodocea rotundata）、单脉二药草（Halodule uninervis）、海菖蒲（Enhalus acoroides）、泰来草（Thalassia hemprichii）和卵叶喜盐草（Halophila ovalis）等5种海草,泰来草为优势种,单脉二药草和卵叶喜盐草分布在潮间带有淤泥的低潮区;圆叶丝粉草分布在低潮带至潮下带的上部,海底堆积和冲刷区的交界处;泰来草在不同水深处均有分布,分布面积最大。     

江苏海岸王港地区盐沼植被变化的TM图像分析

通过对2002~2003年度3个时相的Landsat TM图像进行监督分类处理,研究了盐沼植被的分布和变化。结果表明,目前盐蒿和大米草(Spartina anglica)占据的面积很小,年际变化不大,由于滩涂围垦的影响其面积还在进一步缩小。互花米草(Spartina alterniflora)成为优势种,占据了大部分的盐沼面积,向海蔓延显著,扩张的趋势还在持续,其覆盖面积的年增长速率可达18%。     

植被演替对杭州湾南岸盐沼物质循环的影响

本研究选择杭州湾庵东浅滩作为研究区,选取盐沼区三个不同植被带进行柱状样的采集,通过测量沉积物的粒度、沉积速率、碳氮含量(有机碳、总碳、总氮、碳氮比)等参数,系统分析研究区盐沼湿地植被演替对盐沼物质循环产生的影响。研究结果发现,不同植被覆盖下沉积物粒径差异显著,沿海向陆逐渐变细;沉积速率从海三棱藨草滩、互花米草滩、植被交错区依次递减;总碳、总氮、有机碳含量特征为互花米草滩植被交错区海三棱藨草滩,碳氮比介于6～9,有机碳以海源物质为主;通过计算,发现有机碳埋藏速率为互花米草[159 g/(m2·a)]海三棱藨草[140 g/(m2·a)]植被交错区[119 g/(m2·a)]。从整体上来看,杭州湾南岸盐沼从海三棱藨草群落向互花米草群落演替时,沉积物颗粒发生细化,沉积速率有所变化,而总碳、有机碳、总氮含量增加,盐沼有机碳埋藏速率增加。     

SAR重构分辨率对海冰侧向融化量预测影响研究

利用RADASAT-2的海冰SAR图像,分别采用Prewitt、Sobel和Canny边缘检测算子计算图像范围内的海冰周长,分析不同图像分辨率、不同边缘检测算子分别对周长计算结果产生的影响。结合冰层侧向融化速率参数化方案进行了海冰侧向融化温度敏感性模拟实验,分析了图像重构分辨率对海冰侧向融化结果的影响。结果表明:海冰破碎程度不同时,对应不同的最佳边缘检测算子和最佳分辨率;仅考虑侧向融化时,随着温度升高,3种算子模拟的海冰面积融化趋势基本一致,均呈指数型增加,Prewitt算子模拟效果最好,对应的最佳重构分辨率为30 m×30 m、65 m×65 m和155 m×155 m。     

江苏沿海互花米草盐沼动态变化及影响因素研究

收集了1988-2001年12个时相的江苏盐城幅卫星影像,提取了双洋河口至梁垛：河闸之间的互花米草盐沼;统计了不同时期的分布信息。分析表明：①互花米草盐沼在江苏扩张非常迅速,到2001年7月互花米草盐沼分布面积达129．28km^2,从射阳河口至梁垛河闸之间的潮问中上带泥滩大部分已被互花米草盐沼所覆盖;②由于生态位的影响,互花米草盐沼沿平行于海岸线方向的扩张速度快于垂直于海岸线方向的扩张速度;③依据野外调查和卫星影像分析,互花米草盐沼扩张可分为3个阶段：立地阶段、快速扩张期及成熟期。此外,还对互花米草盐的影响因素进行了探讨。     

Convection of salt fingers in theC-SALT region

We study possible mechanisms of mixing in the northwest part of the Tropical Atlantic (C-SALT) and show that homogeneous layers in the staircase structure can be observed across the entire frontal zone of the North Equatorial Countercurrent. In the central region of the frontal zone, one may observe horizontal motions of the upper parts of quasihomogeneous layers with respect to their lower parts and an essential role in the exchange processes is played by turbulence. The peripheral regions of the frontal zone are characterized by the presence of horizontal advection and isopycnic mixing. Far from the frontal interface, the principal contribution to the exchange processes is made by double diffusion. We demonstrate that, for the analysis of the vertical buoyancy fluxes caused by salt fingers, one can use both the Stern relation and the “law of 4/3”. Translated by Peter V. Malyshev and Dmitry V. Malyshev.     

滨海盐田价值的研究进展

为深入认识滨海盐田功能,研究梳理了国内外滨海盐田价值的相关研究进展。广泛总结认为:盐田的经济价值包括原盐生产、苦卤化工(钾镁盐等的提取)、水产养殖饵料生产(卤虫成虫及卤虫卵)、生物技术提取β-胡萝卜素等方面,盐田生态系统的维持促进了原盐的顺利结晶;盐田的生态价值则主要体现在为海岸鸟类提供栖息地,例如觅食、筑巢繁殖以及休憩等。本研究有益于未来深入研究盐田功能以及更好地保护滨海盐田。     

Estuarine salt conservation: a Lagrangian approach

Understanding tidal and mean flow transport mechanisms that maintain the estuarine salt balance against seaward transport by river flow is one of the fundamental questions of estuarine oceanography. Previous salt transport studies have failed to resolve this problem for two principal methodological reasons, in addition to the inherent variability of estuaries. First, salt transport expansions used to represent the salt balance have included a large number of terms that could not be related to any theory of estuarine circulation and whose physical meaning was thus unclear. Second, it has proven difficult to measure small mean velocities in the presence of much larger tidal variations. A new analysis method that expresses Lagrangian scalar property transport in terms of time and space variations of Eulerian variables is much simpler than expansions previously used and yields new insights into estuarine transport processes. This approach (like previous expansions) is valid for narrow systems in which cross-channel transport processes are weak and the ratio of tidal amplitude to mean depth is small. A surface boundary condition is used to eliminate one class of troublesome terms. The equivalence of the tidal-cycle average transport of tidal variations in salinity and the Stokes transport of mean salinity is then employed to show that the vertically integrated tidal flow plays no role in the overall salt balance. That is, seaward transport of salt caused by the river flow can only be balanced by landward transport resulting from correlations between shear and stratification in the mean, tidal and overtide flows. In a hypothetical inviscid estuary, tide and overtide flows would be vertically uniform, and outward fluvial salt transport could only be balanced by shear and stratification in the mean gravitational circulation. In a more realistic example with strong friction, the gravitational circulation would be severely damped, and inward transport could only be accomplished by correlations of shear and stratification in the tide and overtide flows.     

Arsenic incorporation in a salt marsh ecosystem

Replicate portions of a Delaware salt marsh were enclosed in cylindrical microcosms and exposed to elevated levels of inorganic arsenic (arsenate). All biotic and abiotic components in dosed cylinders rapidly incorporated arsenic. Spartina blades showed the greatest arsenic enrichment, with dosed plants incorporating arsenic concentrations an order of magnitude higher than controls. Spartina detritus and sediments also exhibited greatly elevated arsenic concentrations. Virtually all of the arsenic was incorporated into plant tissue or strongly sorbed to cell surfaces. Thus, elevated arsenic concentrations in estuarine waters will be reflected in living and non-living components of a salt marsh ecosystem, implying that increased arsenic will be available to organisms within the marsh ecosystem.     

Velocity profiles in a salt marsh canopy

Flow velocity profiles, measured in aSpartina anglica canopy in a laboratory flume, change with the location of measurement and plant stem density. The shear velocity above the canopy is larger than that within the canopy. The reduction ofu _* within the canopy will favor the deposition of cohesive sediment. The reducedu _* and flow turbulence within the canopy can enhance particle flocculation and settling velocity. The canopy exerts a strong influence on the concentration, settling velocity of the flocs, and deposition rate of the suspended sediment through effects on bed shear stress and turbulence of flow within the canopy.     

Recent volumetric changes in salt marsh soils

Salt marsh sediment volume decreases from organic decomposition, compaction of solids, and de-watering, and each of these processes may change with age. Variability in the vertical accretion rate within the upper 2 m was determined by assembling results from concurrent application of the ¹³⁷Cs and ²¹⁰Pb dating techniques used to estimate sediment age since 1963/1964, and 0 to ca 100+ years before present (yBP), respectively. The relationship between ²¹⁰Pb and the ¹³⁷Cs dated accretion rates (Sed₂₁₀ and Sed₁₃₇, respectively) was linear for 45 salt marsh and mangrove environments. Sed₂₁₀ averaged 75% of Sed₁₃₇ suggesting that vertical accretion over the last 100+ years is driven by soil organic matter accumulation, as shown for the pre ¹³⁷Cs dated horizon. The ratio of Sed₂₁₀/Sed₁₃₇ declines with increasing mineral content. A linear multiple regression equation that includes bulk density and Sed₁₃₇ to predict Sed₂₁₀ described 97% of the variance in Sed₂₁₀. Sediments from Connecticut, Delaware and Louisiana coastal environments dated with ¹⁴C indicate a relatively constant sediment accretion rate of 0.13 cm year⁻¹ for 1000–7000 yBP, which occurs within 2 m of today's marsh surface and equals modern sea level rise rates. Soil subsidence is not shown to be distinctly different in these vastly different coastal settings. The major reason why the Sed₁₃₇ measurements indicate higher accretion rates than do the Sed₂₁₀ measurements is because the former apply to younger sediments where the effects of root growth and decomposition are greater than in the latter. The most intense rates of change in soil volume in organic-rich salt marshes sediments is, therefore, neither in deep or old sediments (>4 m; >1000 years), but within the first several hundreds of years after accumulation. The average changes in organic and inorganic constituents downcore are nearly equal for 58 dated sediment cores from the northern Gulf of Mexico. These parallel changes downcore are best described as resulting from compaction, rather than from organic matter decomposition. Thus most of the volumetric changes in these salt marsh sediments occurs in the upper 2 m, and declines quickly with depth. Extrapolation forwards or backwards, using results from the ²¹⁰Pb and the ¹³⁷Cs dating technique appear to be warranted for the types of samples from the environments described here.     

耐盐植物牛蒡的研究进展与应用

可耕地和淡水资源的严重匮乏,将严重制约我国经济的可持续发展。充分有效利用中国的土地后备资源(滨海200万hm^2多盐土地和内陆3333万hm^2盐碱地)是解决这一问题的重要途径。发展海水农业,是当今世界上受到重视的研究领域。可是,不论是改良的耐盐传统作物还是驯化的野生盐生植物,其种植经     

潮间带盐沼植物黏附悬浮颗粒物的差异性研究

为了研究潮间带盐沼植物黏附悬浮颗粒物的差异性,在长江口选择了三种盐沼植物群落对它们黏附的颗粒物质量进行测定,结果表明:(1)植物群落距潮沟或光滩越近,生长位置的滩面高程越低,则黏附颗粒物越多,而在盐沼前缘单位滩地面积上植物黏附颗粒物的质量以1%~3%/m(单位水平距离)的速率从水体悬浮颗粒物含量相对较高的盐沼外缘光滩或潮沟向盐沼内部减小;(2)植物黏附的颗粒物量在垂向上从上到下急剧增大,通常在靠近滩面5~10 cm的部分植物的黏附量占植物黏附总量的三分之一以上;(3)相邻群落单位滩地面积的互花米草[(220.6±172.7)g/m2]的总黏附量明显多于芦苇[(64.9±38.1)g/m2]和海三棱藨草[(45.2±31.7)g/m2],而按单位生物量来说单位滩地面积上三种盐沼植物黏附的颗粒物以海三棱藨草最多[(150.5±134.8)g/kg],芦苇最少[(28.8±22.8)g/kg],互花米草介于两者之间[(57.5±32.9)g/kg];(4)海三棱藨草的黏附量在季节上差异性明显,秋初(9月)是春末(5月)的6倍,在冬季该植物消失,其黏附颗粒物的功能也消失。造成盐沼植物黏附悬浮颗粒物差异的根本原因是生物量、悬浮颗粒物含量和淹没条件(淹没的深度、时间、频率)的不同。     

Modeling stress evolution around a rising salt diapir

We model the evolution of a salt diapir during sedimentation and study how deposition and salt movement affect stresses close to the diapir. We model the salt as a solid visco-plastic material and the sediments as a poro-elastoplastic material, using a generalized Modified Cam Clay model. The salt flows because ongoing sedimentation increases the average density within the overburden sediments, pressurizing the salt. Stresses rotate near a salt diapir, such that the maximum principal stress is perpendicular to the contact with the salt. The minimum principal stress is in the circumferential direction, and drops near the salt. The mean stress increases near the upper parts of the diapir, leading to a porosity that is lower than predicted for uniaxial burial at the same depth. We built this axisymmetric model within the large-strain finite-element program Elfen. Our results highlight the fact that forward modeling can provide a detailed understanding of the stress history of mudrocks close to salt diapirs; such an understanding is critical for predicting stress, porosity, and pore pressure in salt systems.