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1.
Sedimentation in Mangrove Forests 总被引：1，自引：0，他引：1
The tidal currents in mangrove forests are impeded by the friction caused by the high vegetation density. The tidal currents are also complex comprising eddies, jets and stagnation zones. The sediment particles carried in suspension into the forest during tidal inundation are cohesive, mainly clay and fine silt, and form large flocs. These flocs remain in suspension as a result of the turbulence created by the flow around the vegetation. The intensity of sedimentation is largest for trees forming a complex matrix of roots such as Rhizophora sp. and smallest for single trees such as Ceriops sp. The flocs settle in the forest around slack high tide. At ebb tides the water currents are too small to re-entrain this sediment. Hence the inundation of coastal mangrove forests at tidal frequency works as a pump preferentially transporting fine, cohesive sediment from coastal waters to the mangroves. Mangroves are thus not just opportunistic trees colonising mud banks but actively contribute to the creation of mud banks. 相似文献
2.
惠州市考洲洋海岸带作为自然滩涂及围网养殖水域,生态
环境破坏较为严重,面临红树林退化严重、水体富营养化、航道
堵塞、海岸景观缺乏等问题,其海岸整治、生态修复面临一定的
技术难点如红树林成活率提升、滩涂整治、红树林栽植等。基于
“美丽海湾建设”背景,针对生态环境问题及工程技术难点,提
出整治及修复策略,包括加强陆源污染控制、堆填整治滩涂、科
学合理栽植及养护、营造多功能红树林生境、建设海洋环境观测
设施以及构建海岸带生态湿地公园。并对项目实施之后产生的生
态效益、社会效益和经济效益进行总结与评价。 相似文献
3.
The dependence of dispersion in a tidal creek on the vegetation density in a fringing mangrove swamp is discussed through a numerical model. A secondary circulation prevails everywhere in the tidal creekmangrove swamp system and is generated by the overflow into the swamp at every high tide. As a result, dissolved and suspended matter moving with the circulation is trapped in the swamp for a fraction of the tidal cycle; it flows out of the swamp at ebb tide and disperses in the creek. The relation between the dispersion coefficient and the mangrove vegetation density is shown to be nonlinear. Dispersion is large both for bare and high vegetation densities and minimum for intermediate vegetation density. The ecological and management applications may be profound as our study suggests that such systems may be unstable and cannot naturally recover from excessive anthropogenic disturbances. 相似文献
4.
We present the distribution of Cd and Zn in sediment cores taken under Spartina alterniflora Loisel. marsh and compare with adjacent mud flats without plant cover. Vertical distribution of Cd and Zn in the mud flat and S. alterniflora cores were different. From 0 to 5 cm of depth Zn and Cd concentrations did not change with depth in the two cores but were higher in the mud flat. From 5 to 15 cm, corresponding to maximum root biomass under S. alterniflora, Zn and Cd concentrations remained constant in the mud flat cores, but increased by a factor of nearly 4 under S. alterniflora. Below this depth concentrations dropped in both cores. Manganese distribution in S. alterniflora cores suggests that oxides are precipitated at the depth of maximum root biomass. More oxic environment under S. alterniflora (average Eh = +5 mV) with low sulfide concentration (0.58 mg l-1) relative to the mud flat cores (average Eh = –204 mV; sulfide 47.1 mg l-1), may favor Fe and Mn oxi-hydroxides precipitation, causing an accumulation of Cd and Zn at the root zone. In the mud flat cores, Zn and Cd highest concentrations were at the sediment water interface, where oxic waters favor their precipitation with Fe and Mn oxi-hydroxides. The results discourages the indiscriminate use of salt marsh sediments in environmental monitoring of trace metals, since the possibility of post-deposition mobilization of trace metals due to root metabolism, will make correlation with trace metal loading rates impossible. 相似文献
5.
Spatial variations of groundwater salinity in a mangrove-salt flat system,Cocoa Creek,Australia 总被引：2，自引：0，他引：2
In this work the average groundwater salt concentration in a mangrove swamp and tropical salt flat system adjacent to Cocoa Creek near Townsville in North Queensland was measured with ground conductivity probes based on low frequency EMI (Electromagnetic Induction) and V-I (Resistivity) Methods. Transects of conductivity were measured with the conductivity probes and the spatial variations in the average groundwater salt concentration were determined from conductivity measurement with both probes. Lower concentrations occurred within mangrove forest as well as near the edges of the salt flats. Comparison of the results above 0.8 m and below 0.8 m showed that as depth increases, the concentrations become more homogeneous. For example at 0.4 m, salt concentrations across the salt flat vary from 75 g/l to 175 g/l where at 2 m the variation is only from about 75 g/l to 125 g/l. High lateral groundwater salt concentration gradients occured at the boundary between the mangroves and salt flat and also at the edges of the salt flat. Typical gradients were about 6 g/l/m and 2 g/l/m respectively. 相似文献
6.
海平面上升引起潮汐水位降低和淹水时间增加,探明红树林对潮汐淹浸适应的生理生态特性有助于科学保护和修复红树林,而且科学选取红树林营林宜林地也需要了解红树林与潮汐浸淹之间的相互关联。文中从红树林潮汐浸淹的研究方法出发,重点论述水淹胁迫对红树植物形态表征、光合作用、呼吸作用、抗氧化系统、渗透调节物质和化学计量特征的影响,以及潮汐浸淹下红树植物分子生物学机制,以期为揭示红树植物对潮汐浸淹的适应机制以及全球气候变化背景下我国红树林造林实践和宜林地选择提供参考。 相似文献
7.
Sediment mixing and accumulation in a mangrove ecosystem: evidence from 210Pb, 234Th and 7Be 总被引：1，自引：0，他引：1
210Pb, 234Th and 7Be activities were measured to establish sediment accumulation rates, estimate sediment mixing rates, and determine the depth of the sediment mixed layer in the Sepetiba Bay mangrove ecosystem near Rio de Janeiro City, Brazil. Three sediment cores were collected from Enseada das Garças, a typical exposed tidal flat region with a sequence of sedimentary features. The seaward edge of this sequence is a mud flat with the landward portion covered with Spartina alterniflora followed by mangrove vegetation. An additional core was collected on an overwash island near Barra de Guaratiba, which is cover with mangroves without a mud flat or Spartina alterniflora sequence. Sediment accumulation rates were determined to range up to 1.8cm/yr with the Spartina alterniflora having the maximum rate. Mixing rates were estimated for the Spartina alternifloracore at 40cm2/yr based on 210Pb and 7Be from the upper mixed region of the core. The 234Th activity in this core suggested that either mixing or the input of 234Th were not in steady state. The sediment mixed region depth ranged from 4cm to greater than 30cm. At the Enseada das Garças site the mixing depth decreased in the landward direction (i.e. mud flats > 30cm, Spartina alterniflora 11cm, mangroves 4cm). Along with this decrease in sediment mixing depth was a shift from physical to biological mixing. The Barra de Guaratiba core had a sediment mixed layer of 13cm as a result of physical and intense biological activity. 相似文献
8.
不同潮带红树林空间结构比较研究 总被引：5，自引：0，他引：5
通过对广东廉江市高桥红树林保护区不同潮带红树林林分混交度、大小比数及角尺度等空间结构参数进行分析比较,结果表明:红树林几种优势树种在不同潮带其空间分布格局多呈均匀分布和中弱度混交,低潮带的红树林呈随机分布的概率较高,而高潮带中红树林均匀分布的比例相对较高,空间大小分化和大小组合的差异不大。重构林分空间结构应以恢复到天然红树林结构为目标。 相似文献
9.
T. Dittmar 《Mangroves and Salt Marshes》1999,3(3):185-195
During the dry season, dissolved inorganic nutrients and organic carbon (DOC) in a mangrove tidal creek (Bragança, North Brazil) presented a clear tidal signature: silicate, phosphate, ammonium and DOC covaried with salinity, with minima at high tide and maxima at low tide. Hydrodynamical calculations explained most diel variability as dilution of nutrientrich groundwater input by estuarine water. Creek nutrients tended to lower concentrations towards the end of the dry season, probably due to changes in groundwater dynamics. Ammonium was about 44% higher in the night than during the day, while silicate, phosphate nitrate + nitrite showed differences < 5%, indicating preferential autotrophic uptake of ammonium as nitrogen source. Nitrification and/or nitrogen fixation are probably sources of nitrate + nitrite, which contributed only 12% to the dissolved inorganic nitrogen pool. Dissolved oxygen (7%) and DOC (11%) were lower during the night, suggesting the existence of a labile, algalderived DOC pool. There is a loose coupling between aquatic primary production, groundwater dynamics and tidal regime. 相似文献
10.
Abu Hena Mustafa Kamal Mohammed Muzammel Hoque Mohd Hanafi Idris Osumanu Haruna Ahmed Md.Khurshid Alam Bhuiyan Md.Masum Billah Md.Nesarul Hoque Zamri Rosli 《林业研究》2020,31(2):613-623
Decaying mangrove detritus plays a significant role in nutrient cycling and fueling in both the forests and aquatic habitats where the detritus stems from estuarine and coastal food webs.Detrital decay rates partly depend on the type of detritus,but most studies have thus far focused on leaf litter decay and decomposition,whereas other detrital sources(except for roots)have largely been ignored.We compare the decay rates of Rhizophora apiculata and Xylocarpus granatum non-leafy detritus(flowers,propagules,stipules,and twigs)with mangrove leaf litter in field studies,using litter bags during the dry and the wet seasons in the tropical mangrove forest of Sibuti,Sarawak,Malaysia.We observed higher microbial decay rates of stipules,flowers,propagules,and twigs for both the R.apiculata and X.granatumduring the wet months.By contrast,leaf decay rates were higher during the dry months.Decay rates depended on the lignin content of the detrital sources of both species,both during dry and wet months.Accordingly,the half-life(T0.5)and 95%lifespan(T0.95)of non-leaf materials(flowers,propagules,stipules and twigs)for both species were remarkably longer than those of leaf litter.Slowly decaying non-leafy detritus may play a significant role in nutrient and carbon cycling over longer time,when leaf litter is either being decomposing rapidly and/or being washed away by tidal flush and river runoff.Hence,non-leafy(flowers,propagules,stipules and twigs)detritus should be taken into account when budgeting organic matter turnover in mangroves. 相似文献
11.
12.
Ayukai Tenshi Miller Diane Wolanski Eric Spagnol Simon 《Mangroves and Salt Marshes》1998,2(4):223-230
In Coral and Conn Creek, northeastern Australia, the variations in concentrations of nitrate, phosphate, silicate, dissolved organic carbon (DOC) and particulate organic carbon (POC) were measured over tidal cycles on five occasions and along each creek on four occasions. The fluxes of these five properties were then estimated using two methods. The first method is the socalled Eulerian method, whereby water flow and material concentration are measured at a fixed station near the creek mouth and the net flux is calculated by adding up flux increments over a tidal cycle. The second method first derives the longitudinal eddy diffusion coefficient from the salt mass balance equation and then calculates material fluxes from their observed gradients along the creek. The use of the latter method is permitted only in the absence of freshwater inputs.The Eulerian method was not sensitive enough to examine whether there was any statistically significant difference in fluxes of nutrients, DOC and POC between ebb and flood periods. This casts some doubt over the meaning of individual flux estimates. It is, however, worth mentioning that 17 out of 25 flux estimates were positive (= import) in Coral Creek, whereas only eight positive flux estimates occurred in Conn Creek. In Coral Creek, the average flux values for nitrate, phosphate and DOC were positive, but negative for silicate and POC. In contrast, the average flux values for all properties were negative in Conn Creek. This may be due to the difference in amount of freshwater input between Coral and Conn Creek.The presence of freshwater inputs from upstream sources restricted the use of the salt mass balance equation to the Coral Creek data collected in September, 1996. However, the study of the variability of nutrient, DOC and POC concentrations along the creek could provide valuable insight into their behavior in Coral and Conn Creek. For example, the concentrations of silicate and DOC were consistently higher upstream than downstream and the distance–concentration relationship was statistically significant in seven out of eight measurements. The concentrations of nitrate and POC also decreased from upstream to downstream, but the trend was statistically significant in only 2–3 measurements. The concentration of phosphate was higher downstream than upstream in four measurements and in two of these four measurements, the trend was statistically significant. These results suggest that in Coral and Conn Creek, silicate and DOC are usually exported to adjacent coastal waters, whereas the import and export of nitrate, phosphate and POC are often finely balanced. 相似文献
13.
Tidal freshwater forests in coastal regions of the southeastern United States are undergoing dieback and retreat from increasing tidal inundation and saltwater intrusion attributed to climate variability and sea-level rise. In many areas, tidal saltwater forests (mangroves) contrastingly are expanding landward in subtropical coastal reaches succeeding freshwater marsh and forest zones. Hydrological characteristics of these low-relief coastal forests in intertidal settings are dictated by the influence of tidal and freshwater forcing. In this paper, we describe the application of the Sea Level Over Proportional Elevation (SLOPE) model to predict coastal forest retreat and migration from projected sea-level rise based on a proxy relationship of saltmarsh/mangrove area and tidal range. The SLOPE model assumes that the sum area of saltmarsh/mangrove habitat along any given coastal reach is determined by the slope of the landform and vertical tide forcing. Model results indicated that saltmarsh and mangrove migration from sea-level rise will vary by county and watershed but greater in western Gulf States than in the eastern Gulf States where millions of hectares of coastal forest will be displaced over the next century with a near meter rise in relative sea level alone. Substantial losses of coastal forests will also occur in the eastern Gulf but mangrove forests in subtropical zones of Florida are expected to replace retreating freshwater forest and affect regional biodiversity. Accelerated global eustacy from climate change will compound the degree of predicted retreat and migration of coastal forests with expected implications for ecosystem management of State and Federal lands in the absence of adaptive coastal management. 相似文献
14.
Root respiration uses a significant proportion of photosynthetically fixed carbon (C) and is a globally important source of C liberated from soils. Mangroves, which are an important and productive forest resource in many tropical and subtropical countries, sustain a high ratio of root to shoot biomass which may indicate that root respiration is a particularly important component in mangrove forest carbon budgets. Mangroves are often exposed to nutrient pollution from coastal waters. Here we assessed the magnitude of fine root respiration in mangrove forests in Belize and investigated how root respiration is influenced by nutrient additions. Respiration rates of excised fine roots of the mangrove, Rhizophora mangle L., were low (4.01 +/- 0.16 nmol CO(2) g(-1) s(-1)) compared to those measured in temperate tree species at similar temperatures. In an experiment where trees where fertilized with nitrogen (N) or phosphorus (P) in low productivity dwarf forests (1-2 m height) and more productive, taller (4- 7 m height) seaward fringing forests, respiration of fine roots did not vary consistently with fertilization treatments or with forest stature. Fine roots of taller fringe trees had higher concentrations of both N and P compared to dwarf trees. Fertilization with P enhanced fine root P concentrations in both dwarf and fringe trees, but reduced root N concentrations compared to controls. Fertilization with N had no effect on root N or P concentrations. Unlike photosynthetic C gain and growth, which is strongly limited by P availability in dwarf forests at this site, fine root respiration (expressed on a mass basis) was variable, but showed no significant enhancements with nutrient additions. Variation in fine root production and standing biomass are, therefore, likely to be more important factors determining C efflux from mangrove sediments than variations in fine root respiration per unit mass. 相似文献
15.
We evaluated photosynthetic gas exchange and the accumulation of iron, manganese and sulfur in seedlings of five mangrove species (Aegiceras corniculatum (L.) Blanco, Avicennia marina (Forsk.) Vierh., Bruguiera gymnorrhiza (L.) Lamk., Hibiscus tiliaceus L. and Rhizophora stylosa Griff.) growing under anoxic soil conditions at low irradiance. Seedlings of the viviparous mangroves showed no significant responses to root anoxia. The presence of ferrous sulfate or manganous sulfate had a smaller effect on CO(2) assimilation, transpiration rate and stomatal behavior than the presence of sodium sulfide. Sodium sulfide inhibited photosynthetic gas exchange and caused complete stomatal closure in all species. Stomatal closure was probably the result of the damaging effect of sulfide ions on root cell membranes. Some leaf epinasty and wilting were also observed in response to the Na(2)S treatment in all species. A combination of FeSO(4), MnSO(4) and Na(2)S had a smaller effect on photosynthesis than Na(2)S alone, especially for Avicennia marina and Rhizophora stylosa seedlings, which maintained appreciable rates of CO(2) assimilation (2.49 and 3.84 &mgr;mol m(-2) s(-1), respectively) in the presence of all three phytotoxins. Roots of phytotoxin-treated seedlings of all species accumulated significant amounts of the corresponding toxin compared with roots of the control plants. The FeSO(4) or MnSO(4) treatments had no effect on foliar concentrations of iron or manganese, whereas the Na(2)S treatment resulted in an accumulation of S in the leaves of all species. Interactions between Fe(2+) and Mn(2+) and sulfide in the culture medium appeared to reduce their uptake by the seedlings. We conclude that high concentrations of sulfides in mangrove sediments may adversely affect both growth and survival of mangrove seedlings at low irradiances. 相似文献
16.
以珠海市淇澳岛红树林引种园23个主要红树林引进树种(2年生)为研究对象,建立涵盖生长适应性、抗逆性、景观价值等多因子的综合评价指标体系,选用层次分析法(AHP)对引进树种进行适应性评价。根据综合评价将红树林引进树种分成4类,表现良好的有拉关木、黄槿、杨叶肖槿和木榄等7种,表现较好的有尖叶卤蕨、海漆等4种,表现一般的有尖瓣海莲、海莲和木果楝等6种,最差的有角果木、正红树和白骨壤等6种。研究认为,拉关木适宜作为低潮滩的先锋造林树种,木榄为中高潮滩的造林树种,而黄槿、杨叶肖槿和海漆可作为高潮滩及堤岸的造林树种,海滨猫尾木、银叶树、海芒果和玉蕊则在滨海城市绿化中更具推广应用价值。 相似文献
17.
研究了Mo、Mn对七子花 5种生理生化指标 (叶绿素含量、净光合速率、暗呼吸速率、可溶性糖含量和硝酸还原酶活性 )的影响 ,结果表明 ,两者对七子花的上述性状都产生了较大的影响。当七子花处于缺Mo缺Mn状态 ,上述各项生理指标都处在最低水平 ,随着Mo或Mn质量浓度的升高 ,各指标都呈现上升趋势 ,当Mo的质量浓度为 0 .5mg·L- 1或Mn的质量浓度为 0 .0 5mg·L- 1时 ,七子花的叶绿素含量 (分别为 2 .0 2 ,1.36mg·g- 1)、净光合速率 (分别为 1.79,0 .90 1mg(CO2 )·dm- 2 ·h- 1)、暗呼吸速率(分别为 2 .2 5 ,2 .95 μmol(CO2 )·m- 2 ·s- 1)都达到最高水平 ;Mo或Mn的质量浓度为 5mg·L- 1时 ,七子花叶片的可溶性糖含量 (分别为 5 .4 5 ,4 .2 6g·kg- 1)最高 ;当Mo的质量浓度为 5mg·L- 1或Mn的质量浓度为 0 .0 5mg·L- 1时 ,硝酸还原酶活性 (分别为 2 79.31,4 6 5 .2 4 μmol(NO- 2 )·g- 1·h- 1)最高 ,高于上述各最高值的质量浓度时 ,七子花上述生理指标都呈下降的趋势。七子花对高Mo的忍耐力大于对高Mn的忍耐力。Mo和Mn的关系较为复杂 ,本试验检测的七子花多数生理指标显示 ,当Mo和Mn在较低质量浓度时 (ρ <0 .0 5mg·L- 1) ,Mo和Mn在七子花体内呈现相互促进作用 ,当Mo和Mn在较高质量浓度时 (ρ≥ 0 5m 相似文献
18.
Fasheng Zou Hanhua Zhang Tom Dahmer Qiongfang Yang Junxin Cai Wei Zhang Chaoyu Liang 《Forest Ecology and Management》2008,255(11):3813-3818
Twenty-two species shorebirds were recorded on mangrove wetlands surrounding Leizhou Peninsula, Guangdong Province, China. One recorded species, Spoon-billed Sandpiper (Eurynorhynchus pygmeus), is listed as endangered in the IUCN Red List (World Conservation Union) and this was the first record of the species at Leizhou in this study. Most recorded species are listed in the Sino-Japan or Sino-Australia Agreement on Conservation of Migratory Birds. Dunlin (Calidris alpina), Kentish Plover (Charadrius alexandrinus), and Greater Sand Plover (Charadrius leschenaultii) were dominant, accounting for 34%, 32%, and 12% of total individuals, respectively. Five survey sites were designated by habitat type. There was no significant difference in species, but total abundance differed significantly among survey sites. More species were recorded in winter and spring than in summer. One hundred and sixty-five species of benthos were recorded. Total mean biomass and density of benthos was 223.3 ± 74.8 g/m2 (±S.E.), density 210.97 ± 67.6 ind./m2, respectively. Mollusks accounted for 83.4% of total biomass, and 75.6% of total density. Both biomass and density of benthos varied significantly among survey sites. There was no significant difference between spring and autumn on biomass or density of benthos. There was a significant and negative correlation between number of shorebirds and densities of polychaetes on mudflats. Shorebird species richness (F1,3 = 13.14, p = 0.036) and abundance (F1,3 = 12.59, p = 0.037) were significantly and positively correlated with mudflat area. Stopping losses of mangrove habitat and tidal flats is the top priority measure for shorebird conservation. Reducing the impacts of human disturbance on both habitats and birds is an urgent necessity for mangrove wetland conservation management. 相似文献
19.
红树植物生长在热带、亚热带海岸滩涂上。健全的红树植物生态系统是人类持续利用红树林的必要条件。如何保护、维持红树林的生态系统及其遗传健全性已成为红树林生态学家最关心的问题。红树植物当前的地理分布格局及形成原因是生态学家和保护生态学家的研究重点。文中介绍了近些年来红树植物亲缘地理学研究概况,包括地理隔离对红树植物分布格局的影响、基因交流受阻隔以及引起红树群体遗传结构变化的原因等内容;阐述了地质历史引起地形地貌变化、地理隔离、繁殖体扩散及生境环境等因子影响红树群体遗传演化的机制;探讨了红树植物亲缘地理学未来研究的重点,以期为红树植物保护和相关研究提供参考。 相似文献
20.
海桑自1994年引种到深圳湾,1999年出现天然更新,在海桑林、天然林和裸滩上均有分布,更新频度达45 0%,幼苗密度最多达69株·m-2,幼苗的扩散距离至少达90m。充足的种源和温暖的气候条件是海桑出现天然更新的前提条件,冬季的低温是决定海桑更新能否成功的关键因素。海桑更新的状况与所接受的光照、种子散播地的隐蔽程度、潮水淹浸深度、潮汐动力作用、人为活动的影响、水禽的取食活动及边缘效应等存在相关关系。海桑幼苗扩散的数量随着距人工海桑林距离的增加而减少,二者符合相关模型:y=58 866 25 741log101 717x。 相似文献