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1.
Coastal salt marshes represent an important coastal wetland system.In order to understand the differences between boundary layer parameters of vegetated and unvegetated areas,as well as the mechanisms of sediment transport,several electromagnetic current meters (AEM HR,products of Alec Electronics Co.Ltd.) were deployed in coastal wetlands in Quanzhou Bay,China,to measure current velocity.During the low tide phase,the surficial sediment was collected at 10 m intervals.In situ measurements show that the current velocities on the bare flat were much higher than those in the Spartina alterniflora marsh.Current velocity also varied with distance from marsh edge and plant canopy height and diameter.Around 63% of the velocity profiles in the tidal creek can be described by a logarithmic equation.Over the bare flat and Spartina alterniflora marsh,a logarithmic profile almost occurs during the flood tide phase.Sediment analysis shows that mean grain size was 6.7 Φ along the marsh edge,and surface sediments were transported from bare flat to marsh;the tidal creeks may change this sediment transport pattern.The hydrodynamics at early flood tide and late ebb tide phases determined the net transport direction within the study area.  相似文献   

2.
Cord grass colonization on the Jiangsu coast, eastern China, modifies the native salt marshes in terms of ecosystem structure. The Landsat TM images from 1992 to 2003 were analyzed to identify salt-marsh vegetation distribution patterns and their changes over this coastal region, in order to evaluate the effects of the spreading of the artificially introduced halophyte Spartina. Supervised classification was performed using Bands 3, 4 and 5 in conjunction with in situ training samples, to derive the distribution pattern of the vegetation in the study area. Further, in order to identify the intertidal areas with different tidal elevations, a data treatment procedure was designed to combine regional water level data using harmonic analysis with the waterlines on the TM images extracted by density slice. The results show that: (1) the Spartina alterniflora area has been expanding towards the sea rapidly since it was introduced, especially at initial stages; (2) in the upper part of the inter-tidal zone, the local marsh plant Suaeda salsa and the exotic species Spartina anglica were present only near the sea dyke, occupying only a small part of the entire salt marsh, and the area of these two species has been reduced by land reclamation; (3) there has been a trend for Spartina alterniflora to become the dominant species in the salt marshes in the study area; and (4) the elevation of Spartina alterniflora’s seaward fringe was close to mean high water on neaps, and its landward boundary was slightly higher than mean high water. The salt marsh environment of the study area has been modified rapidly by the Spartina vegetation for the last 12 years.  相似文献   

3.
选取江苏王港潮滩的盐蒿滩、大米草滩及互花米草滩,分析这三类滩面的地面以上生物量、初级生产力、动物洞穴参数和沉积物粒度,探讨大米草和互花米草引种区的湿地生态系统相对于盐蒿滩的变化.分析结果表明,互花米草滩的生物量远大于盐蒿滩和大米草滩;单位面积上动物洞穴数量相近,但洞穴大小有一定差异,互花米草滩动物洞穴稍大,数量也相对较多,这可能与初级生产力的提高有关.表层底质的粒径以互花米草滩为最细,盐蒿滩最粗,这种分布状况与互花米草引种前不同,说明互花米草促进了细颗粒物质的堆积.互花米草的引种在江苏海岸具有促淤和提高初级生产力的作用,而它对湿地生态系统的结构和功能的影响需要进一步研究.  相似文献   

4.
互花米草作为黄河三角洲外来入侵物种, 2010年开始爆发式蔓延, 2020年面积最大时可超6 000 hm2,对潮间带生物多样性造成了严重影响。自2020年起,黄河三角洲自然保护区开始大规模的互花米草整治与盐地碱蓬生态修复工作。互花米草具有较强的消浪、缓流、促淤、固滩能力,短期内、大范围的植被去除,可能导致波流和沉积动力环境的突变。基于现场观测数据和考虑植被作用的浪、流、沙耦合数值模型,研究分析了互花米草整治和盐地碱蓬修复对黄河三角洲湿地动力过程的影响,重点关注风暴作用下黄河三角洲潮滩湿地的防灾减灾能力和沉积效应变化。研究结果表明,互花米草可有效抵御极端风暴潮,最大风暴潮位衰减率可达15 cm/km。互花米草整治将导致湿地防灾减灾能力显著下降,堤前风暴潮峰值可抬升10～30 cm,同时潮间带的泥沙捕集能力大幅下降。受限于植被密度、高度,盐地碱蓬完全修复后湿地衰减风暴潮、捕集泥沙的能力显著低于原互花米草湿地。研究建议,互花米草整治工程应考虑短期内植被去除导致的近岸风暴潮抬升、侵蚀加剧等潜在风险。  相似文献   

5.
To examine the spatial and temporal variability of sediment grain size in exposed tidal wetlands with ample sediment supply, we sampled sediments and measured hydrodynamics, accretion/erosion rates, and vegetation characteristics in the Yangtze Delta. Sediment grain size exhibited a landward/upward decreasing trend. This trend is mainly attributed to attenuation of hydrodynamics. A 630-day series of daily surface sediment sampling at a fixed site on an unvegetated intertidal flat revealed significant seasonal and storm-cyclic changes in grain size. This temporal variability was related to alternating accretion/erosion events, with erosion associated with coarser grain size. Such temporal dynamics were not present in vegetation, where sediment remained fine grained throughout the year. In the marsh, vegetation cover enables the trapping of fine-grained sediments in the following ways: (a) adherence of suspended sediments onto plants; (b) deposition of suspended sediments stimulated by attenuation of hydrodynamics through plant obstruction; and (c) prevention of resuspension of fine-grained deposits due to the protection of the plant canopy. The influence of vegetation on sediment grain size was clearly seen when comparing sediment trapped by different vegetation types and seasonal patterns of trapped sediment on different vegetation canopy densities. The relatively high plant biomass of the recently introduced Spartina alterniflora enhanced the trapping effect, whereas plant degradation due to buffalo grazing reduced the trapping effect. We conclude that for exposed tidal wetlands with ample sediment supply such as the Yangtze Delta, the spatial and temporal variability of sediment grain size is governed predominantly by physical controls on the unvegetated flat and predominantly by biophysical interaction of hydrodynamics and vegetation in the salt marsh, rather than by sediment supply.  相似文献   

6.
A simple, rapid, precise and reproducible procedure is described for sample preparation, extraction and measurement of total mercury in peaty sediments, plants and animal tissues. Various amounts of a heavy metal containing dried sewage sludge were applied to experimental plots in a New England salt marsh. This treatment resulted in elevation of mercury levels in the surface 5 cm of the soil. Discrepancies in the bulk density of marsh sediments corresponded with interparticle spaces and detritus/mineral ratios in the peat matrix. Mass balance calculations showed that wetlands covered with tall Spartina alterniflora lost mercury considerable faster than higher marsh locations which retained virtually all mercury added. The shortest halflife of mercury calculated was four years. Grain size analyses of peat and sewage sludge suggested that mercury in the higher intertidal range remained associated with sludge components. Biochemical and physical processes affecting the dissipation of mercury from creek side sediments are discussed.  相似文献   

7.
Spartina alterniflora leaf litter bundles were placed in a North Carolina salt marsh to study the effects of environmental heterogeneity on decomposition and animal colonization. Sediment type (mud vs. sand), tidal inundation zone (near bay, mid-marsh and upper marsh) and Spartina growth form (tall vs. short) were studied. Tidal zone had the greatest effect on decomposition rate. The main effects of sediment type and growth form were not significant. All treatments affected animal distribution patterns in the leaf bundles. Nearly all common taxa were more common on mud than sand. Most taxa showed a strong association with one tidal zone. Half of the taxa were associated with one of the Spartina growth forms. Many interactions among the treatments were also significant.This study demonstrates the significance of environmental heterogeneity in a Spartina marsh both for litter decomposition and animal distributions.  相似文献   

8.
The North Branch, separated by the Chongming Island, was once the main channel in the estuary of the Changjiang River. Reclamation and a decrease in runoff to the North Branch had led to the narrowing and shallowing of the channel. The Yuantuojiao Point is located at the intersecting point connecting the North Branch of the Changjiang River and the Jiangsu coastline. Erosion cliffs are developed between the typical silty-muddy tidal flat and the salt marsh occupied by Spartina alterniflorea, and this has changed rapidly over the past few years. The sediment grain size analysis results of the surficial and two core samples indicate that the Yuantuojiao Point tidal flat experienced continuous accretional processes. Based upon 137 Cs analysis results of the YT and YY Cores sampled from the tidal flat at the Yuantuojiao Point, the average sedimentation rate of the YT Core was 2.30 cm/a from 1963 to 2007, and 2.38 cm/a from 1954 to 2007 for the YY Core. The sedimentation rates of both core locations have declined since the 1960s corresponding to the seaward reclamation at the Yuantuojiao Point. The average sedimentation rates at the Yuantuojiao Point were similar to that of the silty-muddy tidal flat at the northern Jiangsu coast, but lower than that of the south of the Changjiang River Estuary. According to field morphological investigations from 2006 to 2008 on the salt marsh at the Yuantuojiao Point, cliffs retreated markedly by storm surges and disappeared gradually because of the rapid sedimentation on the silty-muddy tidal flat. The maximum annual retreat reached 10 m. The recent sedimentation and morphological changes of the Yuantuojiao Point tidal flat not only displayed the retreat of the salt marsh and the disappearance of cliffs, but also was accompanied by rapid sedimentation of the silty-muddy tidal flat and the salt marsh, indicating the responses to the tidal currents, storm surges, Spartina alterniflorea trapping sediments and large-scale reclamation. The sediment grain size and their trends, southward coastal flow, and sandspits of the longshore bars suggest that the main sediment source at the Yuantuoijao Point, estuary of the North Branch was possibly from the Changjiang River before 1958, since then, it has been from the south of the submarine radial sand ridges of the southern Huanghai Sea (Yellow Sea).  相似文献   

9.
Invasive smooth cordgrass (Spartina alterniflora, hereafter Spartina) has been expanding rapidly in the estuarine wetlands at Chongming Dongtan (East China) at the expense of native sea-bulrush (Scirpus mariqueter, hereafter Scirpus) and common reed (Phragmites australis, hereafter Phragmites). To examine the potential impacts of the Spartina invasion on bird diversity, we compared the abundance and species richness of birds in habitats created by Spartina, Phragmites, Spartina mixed with Phragmites, Scirpus, and the bare intertidal zone at Chongming Dongtan in spring 2008. Most birds were recorded in the native habitats, with songbirds and breeding birds being most abundant in the Phragmites habitats, and waterbirds and migrants being most abundant in the Scirpus habitats and bare intertidal zone. Both species number and population densities of birds were lower in the exotic Spartina habitats than in the other four habitats. Although some songbirds and breeding birds used the Spartina-invaded habitats, and even preferred Spartina-invaded habitats to Scirpus habitats and bare intertidal zone, their densities were lower in the Spartina-invaded habitats than in the native Phragmites habitats. This might have resulted from the dense Spartina stands restricting bird movement and providing insufficient useable food for most birds. We conclude that the spread of exotic Spartina has negative impacts on local bird communities. Because Chongming Dongtan is an important stopover site for energy replenishment of shorebirds in the East Asian–Australasian Flyway, urgent measures are needed to control further spread of Spartina and to restore the native habitats for birds.  相似文献   

10.
为探讨互花米草(Spartinaalterniflora)入侵对三沙湾光滩、红树林湿地的生态影响,分别于2013年10月和2014年9月在三沙湾选择了2条互花米草断面、2条红树林断面和1条光滩进行底栖生物生态调查,分析了大型底栖动物群落分布的时空差异、底栖动物与环境因子之间的关系。经鉴定,该调查海域大型底栖动物共68种,隶属于7门40科,其中短拟沼螺(Assiminea brevicula)为互花米草区优势物种;宁波泥蟹(Ilyoplaxningpoensis)为光滩的优势物种;巴林虫(Barantollasp.)为红树林区优势物种。对各生境大型底栖动物物种数、生物量和栖息密度组成进行双因素无重复方差分析(two-way ANOVA),结果显示不同生境大型底栖动物物种数差异极显著(P0.01),互花米草入侵红树林后,大型底栖动物物种数稍有下降,但是互花米草入侵光滩后,大型底栖动物物种数有所增加;不同生境大型底栖动物生物量差异极显著(P0.01),栖息密度差异不显著(P0.05)。利用大型底栖动物的ABC曲线分析群落结构的稳定性,显示光滩群落结构稳定,互花米草入侵后,优势物种变化显著,双齿围沙蚕数量迅速增加,降低了原有大型底栖动物群落结构的稳定性。除生境影响外,互花米草入侵的潮位区域、生长密度差异、入侵阶段等也均会对大型底栖动物造成影响。  相似文献   

11.
互花米草对泉州湾盐沼表层沉积物输运的影响   总被引：1，自引：0，他引：1  
海岸盐沼是海岸湿地系统的重要组成部分，具有很强的环境调节功能．互花米草（Spartina alterniflora）的引种对海岸盐沼的沉积动力产生很大影响．粒度分析结果表明，互花米草盐沼边缘与沉积物平均粒径为6．7φ的等值线分布一致．现场观测表明，互花米草对流速具有明显的阻滞作用，使得光滩流速明显大于互花米草内的流速；在互花米草滩内，随着离盐沼边缘距离、植被高度、植株直径的不同，涨落潮流速也表现出不同的变化趋势．粒径趋势分析结果显示，互花米草盐沼边缘的表层沉积物由光滩向盐沼内输运，潮水沟的存在对沉积物的输运格局具有显著影响．对比分析表明落潮后期的水动力条件控制着研究区内表层沉积物的净输运方向．  相似文献   

12.
Biological invasion has received considerable attention recently because of increasing impacts on local ecosystems. Expansion of Spartina alterniflora, a non-native species, on the intertidal mudflats of Jiuduansha Shoals at the Yangtze River Estuary is a prime example of a spatially-structured invasion in a relatively simple habitat, for which strategic control efforts can be modeled and applied. Here, we developed a Cellular Automata (CA) model, in conjunction with Remote Sensing and Geographical Information Systems, to simulate the expanding process of S. alterniflora for a period of 8 years after being introduced to the new shoals, and to study the interactions between spatial pattern and ecosystem processes for the saltmarsh vegetation. The results showed that the CA model could simulate the population dynamics of S. alterniflora and Phragmites australis on the Jiuduansha Shoals successfully. The results strongly support the hypothesis of space pre-emption as well as range expansion with simple advancing wave fronts for these two species. In the Yangtze River Estuary, the native species P. australis shares the same niche with the exotic species S. alterniflora. However, the range expansion rate of P. australis was much slower than that of S. alterniflora. With the accretion of the Jiuduansha Shoals due to the large quantity of sediments deposited by the Yangtze River, a rapid range expansion of S. alterniflora is predicted to last for a long period into future. This study indicated the potential for this approach to provide valuable insights into population and community ecology of invasive species, which could be very important for wetland biodiversity conservation and resource management in the Yangtze River Estuary and other such impacted areas.  相似文献   

13.
The analysis of vegetation-environment relationships has always been a study hotspot in ecology. A number of biotic, hydrologic and edaphic factors have great influence on the distribution of macrophytes within salt marsh.Since the exotic species Spartina alterniflora(S. alterniflora) was introduced in 1995, a rapid expansion has occurred at Chongming Dongtan Nature Reserve(CDNR) in the Changjiang(Yangtze) River Estuary, China.Several important vegetation-environment factors including soil elevation, tidal channels density(TCD),vegetation classification and fractional vegetation cover(FVC) were extracted by remote sensing method combined with field measurement. To ignore the details in interaction between biological and physical process,the relationship between them was discussed at a large scale of the whole saltmarsh. The results showed that Scirpus mariqueter(S. mariqueter) can endure the greatest elevation variance with 0.33 m throughout the marsh in CDNR. But it is dominant in the area less than 2.5 m with the occurrence frequency reaching 98%. S. alterniflora has usually been found on the most elevated soils higher than 3.5 m but has a narrow spatial distribution. The rapid decrease of S. mariqueter can be explained by stronger competitive capacity of S. alterniflora on the high tidal flat. FVC increases with elevation which shows significant correlation with elevation(r=0.30, p0.001). But the frequency distribution of FVC indicates that vegetation is not well developed on both elevated banks near tidal channels from the whole scale mainly due to tidal channel lateral swing and human activities. The significant negative correlation(r=–0.20, p0.001) was found between FVC and TCD, which shows vegetation is restricted to grow in higher TCD area corresponding to lower elevation mainly occupied by S. mariqueter communities. The maximum occurrence frequency of this species reaches to 97% at the salt marsh with TCD more than 8 m/m2.  相似文献   

14.
Spartina species are commonly used for salt marsh manipulative projects, where aboveground and belowground biomasses are functional traits that play important roles, showing high spatial and temporal variations. This work analyses variations in AGB and BGB of Spartina maritima and abiotic environmental parameters along a chronosequence of six marshes created from 1997 to 2003 with disparate sediment dynamics, and adjacent natural marshes and unvegetated tidal flats. S. maritima behaved as an autogenic engineer, as its colonization of bare sediments yielded abiotic environmental changes: specifically, bed level rise accompanied by higher oxygenation and salinity. These modifications of the environment were site-specific, depending mainly on sedimentary dynamics. At the same time, abiotic environmental changes determined biomass production rates of S. maritima that were higher in more-accreting marshes; however, AGB was kept constant from early in its development (2 years). The increase in BGB with elevation seemed to be related to the inhibition of subsurface tissue development in anoxic sediments. Biomass accumulation and production varied markedly, depending on the spatial scale, indicating the relevance of the plot size chosen for the analysis of biomass of cordgrasses. Our results show that managers of salt marshes should consider sedimentary dynamics carefully when setting realistic expectations for success criteria of created and restored wetlands.  相似文献   

15.
-The detritus from the decomposition of dead plant materials of Spartina with great biomass provides abundant food for the heterotrophs in estuarine and nearshore coastal waters. It is for this reason that the decomposition rates of S. anglica and S. alterniflora near the estuary of obsolete Huanghe River were studied. The changes in nutritive components during decomposition are also studied.Results showed that the decomposition rate of dead leaves of S. anglica on ultra-low marsh was about 90% for the first year. In the eighth month, it was 80% and 76 % respectively for S. anglica and S. alterniflora on low marsh. Protein content of the two species of Spartina increased in the course of decomposition, with a maximum increment of 100% or more. The energy value also increased, whereas cellulose content decreased markedly. The percentage content of ash and lipid varied significantly with zonal differences.  相似文献   

16.
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.  相似文献   

17.
Elemental (TOC, TN, C/N) and stable carbon isotopic (δ13C) compositions and n-alkane (nC16–38) concentrations were measured for Spartina alterniflora, a C4 marsh grass, Typha latifolia, a C3 marsh grass, and three sediment cores collected from middle and upper estuarine sites from the Plum Island salt marshes. Our results indicated that the organic matter preserved in the sediments was highly affected by the marsh plants that dominated the sampling sites. δ13C values of organic matter preserved in the upper fresh water site sediment were more negative (−23.0±0.3‰) as affected by the C3 plants than the values of organic matter preserved in the sediments of middle (−18.9±0.8‰) and mud flat sites (−19.4±0.1‰) as influenced mainly by the C4 marsh plants. The distribution of n-alkanes measured in all sediments showed similar patterns as those determined in the marsh grasses S. alterniflora and T. latifolia, and nC21 to nC33 long-chain n-alkanes were the major compounds determined in all sediment samples. The strong odd-to-even carbon numbered n-alkane predominance was found in all three sediments and nC29 was the most abundant homologue in all samples measured. Both δ13C compositions of organic matter and n-alkane distributions in these sediments indicate that the marsh plants could contribute significant amount of organic matter preserved in Plum Island salt marsh sediments. This suggests that salt marshes play an important role in the cycling of nutrients and organic carbon in the estuary and adjacent coastal waters.  相似文献   

18.
钦佩  经美德  谢民 《海洋科学》1988,12(4):62-67
互花米草引种到福建罗源湾两年后,使海滩盐沼土有机质提高35—44%,含N量提高80%左右,总P和总K没有多大变化,速效P含量降低3.5—7%。在互花米草盐沼生态系统中,不同相中的N、P、K元素分布量的关系是:植物〉土壤〉海水。10月中旬采样测试表明,互花米草的含N量,地上部分高于地下部分;含P及含K量则相反。在对N、P、K的吸收、分布方面,三个生态型差异不显著。  相似文献   

19.
We studied the population ecology of the snail Melampus bidentatus in relation to patch composition and landscape structure across several salt marsh systems in Connecticut, USA. These marshes have changed significantly over the past 40–50 years including loss of total area, increased areas of short Spartina alterniflora, and decreased areas and fragmentation of Spartina patens. These changes are consistent with tidal inundation patterns that indicate frequent flooding of high marsh areas. Melampus bidentatus densities were highly variable, both among different salt marsh systems and locations within specific marshes, but were generally similar among short Sp. alterniflora and Sp. patens patches within locations. Densities were lowest where the marsh was regularly inundated at high tide and only remnant Sp. patens patches remained. Almost no snails were found in bare patches. Areas that had large Sp. patens patches adjacent to short Sp. alterniflora supported the highest M. bidentatus densities. Population size‐structure varied significantly among patch types, with higher proportions of large individuals in short Sp. alterniflora and hummocked Sp. patens patches than in large and remnant Sp. patens patches. This was likely due to size‐selective predation and/or higher snail growth rates due to better food resource conditions in short Sp. alterniflora patches. Egg mass densities and the number of eggs per egg mass were highest in short Sp. alterniflora. Our results indicate that M. bidentatus is resilient to the level and patterns of salt marsh change evident at our study sites. Indeed, snail densities were significantly higher than reported in other field studies, suggesting that increased patch areas of short Sp. alterniflora and associated environmental conditions at our study sites may provide more favorable habitats than previously when marshes were dominated by extensive Sp. patens meadows. However, there may be threshold conditions that could overwhelm the ability of M. bidentatus to maintain itself within salt marsh systems where changes in hydrology, sedimentation and other factors lead to increased numbers of bare patches and ponds and loss of short Sp. alterniflora and Sp. patens. Studies of the responses of resident and transient fauna to salt marsh change are critically needed in order to better understand the implications for salt marsh ecosystem dynamics and services.  相似文献   

20.
Spartina alterniflora Loisel., widely recognised as an aggressive invader of estuaries and salt marshes around the world, was discovered growing in the temporarily open/closed Great Brak Estuary on the southern Cape coast of South Africa in 2004. This is the first record of this invasive plant in Africa as well as its first occurrence in an estuary that closes to the sea. Plant traits and sediment characteristics were measured in 2009 and 2011 and found to be comparable to those reported elsewhere. Prior to the 2011 sampling, S. alterniflora stands had been flooded for almost eight months. As a result, sediment redox potential (?268 + 4 mV) was significantly lower in 2011. Sediments were mostly clay in 2009 (71 ± 0.01%) compared to a predominance of sand in 2011 (40 ± 0.02%). These differences were related to the artificial breaching of the estuary one month prior to sampling in March 2011. The grass currently occupies 1.1 ha in the salt marsh, sandflat and mudflat habitats of the estuary where its cover is expanding at a rate of 0.162 ha y?1. Individual stands numbered about 12 in 2006, but have increased to 24 in 2011. These stands are expanding laterally at 0.9 m y?1 although the long period of inundation during 2010 reduced this to 0.6 m y?1. Expansion is due to vegetative spread as an analysis of the sediment seed bank showed no S. alterniflora seeds and very few salt marsh seeds (1 132 seeds m?2). If left unchecked, S. alterniflora has the potential to replace 42.9 ha or 41% of the total estuary habitat in the Great Brak Estuary, but also has the potential to invade other estuaries in South Africa, especially those with extensive intertidal habitat and containing S. maritima (19 estuaries in total). This study illustrates the adaptive potential of this invasive marsh plant and indicates the possibility of invasion in seasonally closed estuaries in other locations around the world.  相似文献   

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