红树林海岸的沉积物输运和碳沉降特征

Mangroves play an important role in sequestering carbon and trapping sediments. However, the effectiveness of such functions is unclear due to the restriction of knowledge on the sedimentation process across the vegetation boundaries. To detect the effects of mangrove forests on sediment transportation and organic carbon sequestration, the granulometric and organic carbon characteristics of mangrove sediments were investigated from three vegetation zones of four typical mangrove habitats on the Leizhou Peninsula coast. Based on our results, sediment transport was often "environmentally sensitive" to the vegetation friction. A transition of the sediment transport mode from the mudflat zone to the interior/fringe zone was often detected from the cumulative frequency curve. The vegetation cover also assists the trapping of material, resulting in a significantly higher concentration of organic carbon in the interior surface sediments. However, the graphic parameters of core sediments reflected a highly temporal variability due to the sedimentation process at different locations. The sediment texture ranges widely from sand to mud, although the sedimentary environments are restricted within the same energy level along the fluvial-marine transition zone. Based on the PCA results, the large variation was mainly attributed to either the mean grain size features or the organic carbon features. A high correlation between the depth and δ13C value also indicated an increasing storage of mangrove-derived organic carbon with time.     

海南儋州湾红树林区沉积有机质来源及碳储量

本文测定了海南儋州湾南岸柱状沉积物的粒度、总有机质参数(TOC、C/N和δ¹³C)和类脂生物标志物含量,并通过端元混合模型使用红树植物特征标志物蒲公英萜醇含量、长链正构烷烃含量和δ¹³C值半定量区分了海南儋州湾南岸沉积有机质来源,尤其是红树林的贡献。另外,通过估算沉积物的有机碳储量来评估儋州湾红树林区域的储碳能力。在沉积有机质中,陆源、水源和红树植物有机质所占平均比例分别为47%,36%和17%。沉积物柱状样中单位厘米深度沉积物的碳储量范围在0.12~2.90 t/ha。本研究表明,儋州湾地区沉积物中来自于红树林的有机质比例较低,且其碳埋藏量可能低于全球平均水平。修复和保护儋州湾红树林,能够有效提升湿地的碳埋藏效率,从而减缓大气CO₂上升对环境的负面影响。本文应用生物标志物和碳同位素方法,半定量区分了红树林生态系统各种来源有机碳的贡献,将蒲公英萜醇作为红树林特征生物标志物应用在计算模型中,能够量化红树植物来源有机碳的贡献,加深对红树林系统有机碳埋藏情况的了解。     

The exchange of organic carbon in basin mangrove forests in a southwest Florida estuary

The magnitude and seasonality of organic carbon exchange was estimated for two basin mangrove forests in Rookery Bay, Florida. Runoff and tidal inundation in the forests were seasonal with half the annual total of each occurring from August to October. In each forest there were 152 tides yr^?1 with a cumulative depth of about 12 m. Total organic carbon increased in bay waters exporting from the mangroves following a flood tide and peak concentrations were associated with export due to rainfall. The amount of net export from each basin forest was similar, although the concentration of organic carbon in each were different. Monthly net organic carbon export was proportional to the cumulative tidal amplitude within the forest. Total organic carbon export was 64 gC m^?2 yr^?1 and DOC was 75% of the total. A comparison of organic carbon export among riverine, fringe and basin mangroves suggests that tidal hydrology influences the proportion of litter fall that is exported from mangroves; and the magnitude of this organic carbon export from mangroves is related to the cumulative tidal amplitude within the forests.     

雷州半岛红树林边缘效应及其对海岸有机碳库的影响

作为滨海湿地与邻近海区之间物质循环、能量和物种流动及其相互作用的重要界面,红树林的边缘效应对研究海陆生态系统相互作用,滨海湿地生物地貌形成过程以及海岸带有机碳库分布格局等方面的具有重要意义。文章以雷州半岛东岸红树林4种典型地貌分布区为重点,通过调查红树林前缘光滩,林缘及林内植被及土壤理化特征的变化,探讨红树林边缘效应的表现及其对土壤有机碳库的影响。结果表明,不同地貌类型红树林边界区的群落结构及土壤理化因子分布特征有所不同。边界区群落特征表现为林缘的冠层低于林内,叶面积指数低于林内,物种丰富度林内高于林缘(除河口区外),且林缘的植被盖度受风浪影响显著,表现出河口区>内湾区>岛屿区>前沿浪击区。土壤理化性质边缘效应表现为林缘的pH值、粒度低于光滩,氧化还原电位、盐度高于光滩(除内湾区外),而林内的土壤理化性质波动较大,可能受林缘植被演替及地貌双重影响。不同地貌单元红树林边界区的土壤表层有机碳含量,有机碳密度均表现为林内>林缘>光滩。综合影响表层土壤有机碳的主要生物及非生物因子进行主成分分析和相关分析,结果显示土壤表层有机碳密度与环境第一主成分呈显著负相关,即受植被盖度,叶面积指数和土壤pH因子影响密切。红树林土壤有机碳沉积虽然受到不同水文地貌的影响,但总体而言,红树林初级生产输入和土壤酸性环境对红树林林下土壤有机碳库的富存贡献显著。     

A cross-system analysis of sedimentary organic carbon in the mangrove ecosystems of Xuan Thuy National Park, Vietnam

A cross-system analysis of bulk sediment composition, total organic carbon (TOC), atomic C/N ratio, and carbon isotope composition (δ¹³C) in 82 surface sediment samples from natural and planted mangrove forests, bank and bottom of tidal creeks, tidal flat, and the subtidal habitat was conducted to examine the roles of mangroves in sedimentation and organic carbon (OC) accumulation processes, and to characterize sources of sedimentary OC of the mangrove ecosystem of Xuan Thuy National Park, Vietnam. Sediment grain sizes varied widely from 5.4 to 170.2 μm (mean 71.5 μm), with the fine sediment grain size fraction (< 63 μm) ranging from 11 to 99.3% (mean 72.5%). Bulk sediment composition suggested that mangroves play an important role in trapping fine sediments from river outflows and tidal water by the mechanisms of tidal current attenuation by vegetation and the ability of fine roots to bind sediments. The TOC content ranged from 0.08 to 2.18% (mean 0.78%), and was higher within mangrove forests compared to those of banks and bottoms of tidal creeks, tidal flat, and subtidal sediments. The sedimentary δ¹³C ranged from − 27.7 to − 20.4‰ (mean − 24.1‰), and mirrored the trend observed in TOC variation. The TOC and δ¹³C relationship showed that the factors of microbial remineralization and OC sources controlled the TOC pool of mangrove sediments. The comparison of δ¹³C and C/N ratio of sedimentary OC with those of mangrove and marine phytoplankton sources indicated that the sedimentary OC within mangrove forests and the subtidal habitat was mainly composed of mangrove and marine phytoplankton sources, respectively. The application of a simple mixing model showed that the mangrove contribution to sedimentary OC decreased as follows: natural mangrove forest > planted mangrove forest > tidal flat > creek bank > creek bottom > subtidal habitat.     

Sources and distributions of terrigenous organic matter in a mangrove fringed small tropical estuary in South China

The sources and distributions of terrigenous organic matter (OM) were investigated in a small tropical estuary in the Hainan Island, South China. Plants, suspended particulate matter (SPM), and surface sediments samples in the estuary and coast were collected. Bulk properties [organic carbon (OC%), total nitrogen (TN%), stable carbon isotope (δ13C) and grain size] and lignin phenol concentrations were measured. OC% of mangrove plants was (43.4 ± 2.1)%, which is similar to the values reported for mangrove plants in other regions. OC% of sediment samples ranged from 0.07% to 1.42%, and they were related to the sediment texture. Lignin phenols in the sediment ranged from 5.16 mg/100 mg OC in the uppermost station to 0.51mg/100mg OC in the coast. The molar ratio of organic carbon to total nitrogen (C/N) (～7) and δ 13 C (～-31.1×10-3 ) of riverine SPM revealed that the major OM sources of riverine SPM were aquatic OM (phytoplankton and/or bacteria). Moreover, the lower lignin concentration (Λ8) and higher (Ad/Al)v of lignin phenols suggest that terrestrial OM in riverine SPM were mainly from soil. Furthermore, C/N ratio, δ13C and lignin phenols reveal that mangrove plants were the predominant OM sources of mangrove surface sediment. Based on the δ13C and lignin phenols, it can be concluded that the major OM sources in estuarine and coastal surface sediments were marine phytoplankton, riverine SPM and mangrove surface sediment. In addition, the higher (Ad/Al)v of lignin phenols in those coastal sediments indicate that seagrass might be a potential OM source in coastal sediments, however, the lower (Ad/Al)v in the estuarine sediments in turn suggests that seagrass could not be transported to the mangrove fringed region. A three-end-member model which is based on lignin concentrations and δ13C was applied to evaluate the contribution of mangroves to the organic matter preserved in the surface sediments. Around the mangrove fringed region, mangrove could contribute more than 50% to the sedimentary OM, and this value is much higher than riverine OM. Nevertheless, mangrove OM could not be efficiently transported to the coastal region. Our study suggests that mangrove forest is an important OM source in this small estuary.     

Solutions to blue carbon emissions: Shrimp cultivation,mangrove deforestation and climate change in coastal Bangladesh

In Bangladesh, export-oriented shrimp farming is one of the most important sectors of the national economy. However, shrimp farming in coastal Bangladesh has devastating effects on mangrove forests. Mangroves are the most carbon-rich forests in the tropics, and blue carbon (i.e., carbon in coastal and marine ecosystems) emissions from mangrove deforestation due to shrimp cultivation are accumulating. These anthropogenic carbon emissions are the dominant cause of climate change, which in turn affect shrimp cultivation. Some adaptation strategies including Integrated Multi-Trophic Aquaculture (IMTA), mangrove restoration, and Reducing Emissions from Deforestation and forest Degradation (REDD+) could help to reduce blue carbon emissions. Translocation of shrimp culture from mangroves to open-water IMTA and restoration of habitats could reduce blue carbon emissions, which in turn would increase blue carbon sequestration. Mangrove restoration by the REDD+ program also has the potential to conserve mangroves for resilience to climate change. However, institutional support is needed to implement the proposed adaptation strategies.     

2010—2018碳收支的变化分析年海南东寨港红树林湿

红树林生态系统在全球气候变化和碳循环过程中发挥着很重要的作用，准确评估红树林湿地的碳收支，对于保护和恢复海洋蓝色碳汇以及全球气候治理工作具有重要的意义。本研究以海南东寨港国家级自然保护区的红树林湿地为研究对 象，采用 《对 2006 IPCC 国家温室气体清单指南的 2013 增补：湿地》 （简称 《湿地指南》） 中的计算方法，利用野外现场调查数据及已有的研究成果作为参数，评估和量化海南东寨港红树林湿地在 2010—2018 年期间的碳收支情况。研究表明：（1） 2010 年红树林面积为 1 627.21 hm2，全部为成熟红树林，碳储量为 5.85*105t C；2018 年红树林面积为 1 665.42 hm2，其中 1 625.84 hm2为成熟红树林，碳储量为 6.71*105t C，39.58 hm2为过渡期红树林，碳储量为 4.36*103t C，总碳储量为6.75*105t C。 （2） 2010—2018 年期间红树林碳储量增加了 9.0*104t C。另外，有 1.37 hm2的红树林湿地退化为水域，释放了81.36 t 的碳储量。因此，2010—2018 年期间东寨港红树林湿地碳收支为+8.99*104t C，整体上表现为净碳汇生态系统。本研究结果可为气候变化背景下海南红树林湿地的保护与恢复、风险评估以及气候治理提供科学参考。     

百余年来珠江口及邻近西部海域有机碳来源及其埋藏记录

对珠江口外和粤西沿海的两个具百余年沉积历史的柱状样进行了基于支链与类戊二烯甘油四醚(glycerol dialkyl glycerol tetraether,GDGT)化合物比值的BIT(branched and isoprenoid tetraether)指标分析,该指标指示的是沉积有机质中陆源土壤来源有机质的相对输入贡献。结果发现,BIT值在两个柱状样中都小于0.26,显示水生有机质是沉积有机质的主要来源。BIT时间序列在两个柱状样中表现出一致的变化趋势:大约在1940年代以前,BIT保持在相对稳定的高值,此后表现出逐渐下降趋势,1990年以来下降趋势显著。这一下降趋势表明,半个多世纪以来沉积有机质中陆源有机质的相对贡献是持续减少的,或者水生有机质的相对贡献是持续增加的。在分析了陆源和水生有机碳沉积通量变化序列的基础上,认为水生生产力对沉积有机质的相对贡献持续增大是BIT指数持续降低的主要原因。水生有机碳输出通量半个多世纪来的上升趋势及其与广东省GDP变化趋势的相似性表明,陆地人类活动的不断增强导致了沿海水域营养化水平的不断升高。     

江苏盐城滨海盐沼湿地沉积物有机碳含量及碳储量研究

全球范围内有植被定植的海岸带栖息地(红树林、盐沼和海草床)是巨大的沉积物有机碳碳库,同时也是自然生态系统中最密集的碳汇之一,在全球碳循环中发挥着重要作用。针对江苏盐城海岸盐沼湿地沉积物有机碳的研究,区域上的稀疏性和偏向性限制了其作为区域碳汇能力的可靠估计。本研究采用47个100 cm深沉积柱样的现场调查数据,探讨了江苏盐城海岸盐沼湿地沉积物有机碳含量、密度和储量特征。结果表明,0～100 cm深度沉积物有机碳平均含量和平均密度分别为1.68%和23.07 kg/m³,不同盐沼群落沉积物有机碳含量和密度存在一定的差异,其中有机碳平均含量大小排序依次为互花米草>芦苇>盐地碱蓬,有机碳密度排序为芦苇>互花米草>盐地碱蓬。总体而言,3种盐沼群落沉积物有机碳含量的垂向变化趋势与有机碳密度变化趋势具有一致性,芦苇和互花米草表聚性明显。沉积物有机碳含量与其理化性质有关,互花米草群落沉积物有机碳含量具有明显的粒度控制效应,而其他群落不显著。3种盐沼湿地类型0～100 cm深度沉积物总碳储量约为6195.27×10³Mg C。研究成果揭...     

Biomass accumulation and organic carbon stocks of Kandelia obovata mangrove vegetation under different simulated sea levels

Mangrove forests are vulnerably threatened by sea level rise (SLR). Vegetation organic carbon (OC) stocks are important for mangrove ecosystem carbon cycle. It is critical to understand how SLR affects vegetation OC stocks for evaluating mangrove blue carbon budget and global climate change. In this study, biomass accumulation and OC stocks of mangrove vegetation were compared among three 10 year-old Kandelia obovata (a common species in China) mangrove forests under three intertidal elevations through species-specific allometric equations. This study simulated mangrove forests with SLR values of 0 cm, 40 cm and 80 cm, respectively, representing for the current, future ~100 a and future ~200 a SLR of mangrove forests along the Jiulong River Estuary, China. SLR directly decreased mangrove individual density and inhibited the growth of mangrove vegetation. The total vegetation biomasses were (12.86±0.95) kg/m2, (7.97±0.90) kg/m2 and (3.89±0.63) kg/m2 at Sites SLR 0 cm, SLR 40 cm and SLR 80 cm, respectively. The total vegetation OC stock decreased by approximately 3.85 kg/m2 (in terms of C) from Site SLR 0 cm to Site SLR 80 cm. Significantly lower vegetation biomass and OC stock of various components (stem, branch, leaf and root) were found at Site SLR 80 cm. Annual increments of vegetation biomass and OC stock also decreased with SLR increase. Moreover, significant lower sedimentation rate was found at Site SLR 80 cm. These indicated that SLR will decrease mangrove vegetation biomass and OC stock, which may reduce global blue carbon sink by mangroves, exacerbate global warming and give positive feedback to SLR.     

珠江口红树林基围养殖生态开发模式评述

起源于珠江三角洲的红树林基围(land-based enclosure)养殖传统模式是红树林可持续利用和生态开发范例之一。本文介绍了珠江口红树林基围养殖生态开发模式的3个个例: 仅存香港米埔红树林自然保护区的传统基围养殖运作历史和演变, 及其候鸟生境、养殖、观鸟、环境教育综合功能的实现; 珠海淇澳岛大围湾红树林传统和粗放式基围养殖试验和围内水位盐度等环境条件变化对红树林生长影响的研究; 伶仃洋东岸海上田园红树林海水种植-集约式养殖系统试验和红树林净化水质研究。在珠江口红树林保护管理及海域污染防治过程中建议重视红树林可持续利用模式的研究和推广, 建立新的基围养殖示范区, 大力推广红树林基围养殖的生态开发模式, 探索毁林养殖区红树林友好式整治模式, 改善红树林基围养殖技术提高养殖产量, 加强红树林基围养殖系统相关科学研究。     

深圳湾红树林老鼠簕灌丛的光合固碳及其影响因子

红树林(Mangroves)是生长在热带和亚热带海岸潮间带的木本植物群落。老鼠簕(Acanthus ilicifolius)是我国红树林林下灌丛的主要物种,是林下植被碳库的主要构成成分。本研究选取深圳福田红树林区的林下、林窗、林缘和光滩等不同生境下自然生长的老鼠簕植株,测定植株生物量和光合特性等相关指标。研究表明,林窗生境下的老鼠簕植株的光合能力、光合固碳速率和地上生物量累积均达到最大;林下生境最不利于老鼠簕植株固碳;光滩的老鼠簕植株具有较高的地下生物量累积,但由于其蒸腾速率高、水分利用率低下,其固碳较低。光照强度是决定不同生境老鼠簕植株固碳的关键因子。在未来我国红树林造林中,老鼠簕可作为林下植被构建,以提高红树林生物量总碳库,但最适宜老鼠簕固碳的光照约为40%~80%。本文研究结果将为红树林造林实践中的物种选择和林分构建提供理论参考。     

全新世大暖气广西钦州湾红树林衰退的红树林源有机质贡献示踪及其对亚洲季风的响应

The response of mangrove ecosystems to the Asian monsoon in the future global warming can be understood by reconstructing the development of mangrove forests during the Holocene climatic optimum(HCO), using proxies preserved in coastal sediments. The total organic matter in sediments of a segmented core, with calibrated age ranges between 5.6 and 7.7 cal. ka BP and corresponding to the HCO, from the Qinzhou Bay in Guangxi, China, is quantitatively partitioned into three end-members according to their sources: mangrove-derived, terrigenous,and marine phytoplanktonic, using a three-end-member model depicted by organic carbon isotope(δ13Corg) and the molar ratio of total organic carbon to total nitrogen(C/N). The percentage of mangrove-derived organic matter(MOM) contribution is used as a proxy for mangrove development. Three visible drops in MOM contribution occurred at ca. 7.3, ca. 6.9, and ca. 6.2 cal. ka BP, respectively, are recognized against a relatively stable and higher MOM contribution level, indicating that three distinct mangrove forest degradations occurred in the Qinzhou Bay during the HCO. The three mangrove forest degradations approximately correspond to the time of the strengthened/weakened Asian winter/summer monsoon. This indicates that even during a period favorable for the mangrove development, such as the HCO, climatic extremes, such as cold and dry events driven by the strengthened/weakened Asian winter/summer monsoon, can trigger the degradation of mangrove forests.     

Particle size shapes the prokaryotic microbial communities in mangrove sediments: A case study of Sanya,China

The prokaryotic microbial communities in the sediments play crucial roles in the ecological functions of mangrove ecosystems. Therefore, the environmental factors that affect the structures of these prokaryotic microbial communities could indirectly participate in the regulation of mangrove functions, which is of great value for mangrove studies. The particle size (PS) of soils is recently demonstrated as a key environmental factor for shaping the microbial communities; however, this hypothesis has rarely been tested for mangrove environments. A case study of three tropical mangroves from Sanya, China was performed in this work to assess the influence of PS on the prokaryotic microbial community structures of bacteria, archaea, diazotrophs, and denitrifiers in the sediments. Results showed the variability in the spatial scale and the stability in the temporal scale for the prokaryotic communities, indicating that the tropical mangrove sediments could be a versatile but stable environment. Among the collected environmental factors, PS, salinity, and humidity had the greatest impacts, and PS mostly affected the structures of these prokaryotic communities based on its highest R2 values of canonical correspondence analysis, Mental test, and linear fitting (p≤0.05). Furthermore, PS was positively correlated with the diversity and abundance of diazotrophic communities and negatively correlated with the abundances of methanogenic communities including Methanobacteriaceae, Methanospirillaceae, Methanoregulaceae, and Methanosaetaceae. Former studies show the increasing trend of PS caused by the rise of sea level and the intensification of human activities. Therefore, our findings indicate that PS could be a potential intermediate that links climate change and human activities with the possible ecological function migration of mangroves; meanwhile, the increase of PS could in turn release the stress of these environmental changes by increasing the abundance and diversity of the diazotrophic community and decreasing the abundances of methanogens.     

中国西南广西英罗湾红树林近130年来演化指标——沉积物中的红树叶片亚化石

Located in the intertidal zone of the tropical and subtropical coasts, mangrove forests are an important ecosystem in the global carbon cycle and serve as a protector of local seashores. Under the double impacts of climate change,especially sea-level rise, and human activity, mangrove forests around the world have faced degradation, against which the reconstruction of the historical development of mangrove forests using an effective indicator has been regarded as a necessary strategy for designing a predictable model. As the primary product of mangrove forest, it is reasonable that the content of leaf fragments of mangrove(CLFM) buried in sediments in the form of sub-fossils potentially has the same indicative function for the development of mangrove forests as that of widely-used mangrove pollen. In this study, the leaf fragments of mangrove in two sediment cores(YLW02 and YLW03) drilled in the Yingluo Bay in Guangxi, Southwest China were picked out and weighted for calculation of CLFM, which was used as an indicator of mangrove development after examination of parallelism and a statistical correlation of the CLFM with the concentration of mangrove pollen. The results clearly show that the vertical distribution of the CLFM for the core taken from the landward margin of mangrove forests(YLW03) only parallels that of the local mangrove species(Rhizophora. stylosa) with a significantly positive correlation(R=0.56, P=0.05), while the vertical distribution of the CLFM for the core taken from the interface between seaward margin of mangrove forest and the trunk of tidal creeks of the bay(YLW02) parallels the summed concentration of mangrove pollen(SCMP) with a more positive correlation than that of YLW03(R=0.85, P=0.01), indicating that the trunk outlet of tidal creeks must have been the site where mangrove production gathered from the overall forest rather than from local production. The variations in the CLFM of both cores indicate that overall the mangrove forests in the Yingluo Bay have increasingly flourished over the last 130 years except for the interval of 1940–1950 AD in response to an increase in air temperature and decrease in rainfall, which would have resulted in an increase in seawater salinity;while the coupled extreme increases in air temperature and in rainfall in summer, which would have resulted in extreme decreases in seawater salinity, would be responsible for the relative degradation of mangrove forests in the interval of 1940–1950 AD.     

Nutrient fluxes in a semi-arid microtidal mangrove wetland in the Gulf of California

Nutrient (C, N and P) fluxes were monitored in a microtidal semi-arid mangrove system, which links a semi-enclosed shallow coastal lagoon with the Gulf of California. We assessed the role of the mangrove ecosystem as a nutrient sink/source and determined how mangrove litterfall rates, tidal regime and climate factors influence these fluxes. Despite high seasonal differences in DOC, POC, N-NO₃⁻ and TP levels, nutrient concentrations were only marginally influenced by either hydrological variables or the concentration of these fractions in the adjacent lagoon. The carbon budget appeared to be balanced throughout the study. Retention rates in the mangrove system were related to litterfall rates. Export of DIN was observed mainly in the wet season due to the low nitrogen assimilation efficiency of the system. Import of organic nitrogen was related to the high retention efficiency of particulate organic nitrogen. Phosphorus fractions were imported and retained in the mangrove supporting previous findings that mangroves are phosphorus sinks. Finally, through a simple meta-analysis we tested the quantitative importance of main variables (tidal flow, tidal elevation, tidal range, rainfall, mangrove catchment area, litterfall) controlling mangrove nutrient dynamics. Although results suggest that generalizations can be made about factors regulating nutrient export from mangroves, the lack of statistical significance highlights the relative importance of the local environment for the magnitude of nutrient exchange in mangroves. Future research should focus on finding mechanistic models to explain these general patterns, taking into account the main biogeochemical processes and their roles in coastal ecosystem ecology.     

广西沿海不同演替阶段红树群落沉积物粒度分布特征

沉积物粒度分布是影响红树群落演替的重要因素之一。本文对代表广西红树群落演替趋势的白骨壤(Avicennia marina)、秋茄(Kandelia candel)、木榄(Bruguiera gymnorrhiza)3种红树群落沉积物进行了粒度分析。结果表明:3种红树群落沉积物类型均以砂和粉砂为主,随着红树林群落保存状况的逐渐变差,砂的含量逐渐上升,粉砂和黏土含量逐渐下降;沉积物粒径分布趋势均为砂粉砂黏土砾。木榄和秋茄2个群落底床沉积物不同深度沉积物粒径分布规律一致,但与白骨壤群落存在差异;3种红树群落的沉积物粒度频率曲线均呈现为双峰或多峰形态。     

厦门湾红树林生境适宜性评估及修复潜力分析

为定量评估多元环境因子对红树林分布的影响,探索区域红树林生境适宜性和修复潜力的空间分布格局,本研究应用最大熵模型评估厦门湾红树林生境适宜性,叠加土地利用/覆被数据分析红树林修复潜力。结果表明,在生物气候、地形、水质、沉积物、水文等5组环境变量中,影响厦门湾研究区内红树林分布的主要环境变量类型为温度、地形和水质。在单项环境因子中,离岸线距离、营养盐浓度、盐度等对厦门湾红树林生境适宜性的贡献度最大。适宜性和修复潜力较高的区域主要分布于九龙江河口、翔安下潭尾、海沧东屿等区域。与现存红树林的分布相对照,理论上还有约406.4 hm^2的高修复潜力区和1001.2 hm^2的中修复潜力区可考虑用于未来红树林修复。现有的保护区和修复工程已基本覆盖了上述大部分区域,未来厦门湾内的红树林修复选址可考虑泉州市安海湾沿岸、龙海市九龙江河口、漳州港沿岸和附近岛屿。本研究尝试采用新兴模型方法判断红树林的综合适生条件,并实现空间化、定量化的评估,其结果可为红树林修复选址提供重要的科学依据,并为区域红树林保护与修复管理提供决策支持。     

The role of pneumatophores in sedimentary processes

The role pneumatophores play in affecting sedimentation patterns is investigated by a series of rods set up as grids of different sizes placed in front of the mangroves on Magnetic Island, north Queensland. Average pneumatophore spacings were noted for Avicennia eucalyptifolia and Sonneratia alba. The effect of a 10-cm grid was negligible. However, grids of 5-cm, 2.5-cm and 1-cm spacings had a profound effect. Erosion was initiated soon after the grids were inserted in March 1975. A cycle of cut and fill prevailed during the wet and dry seasons of 1975 and 1976. The effect of a 2.5-cm grid placed in the mangrove fringe was significantly less than that of a similar grid placed in the bare mud in front of the mangroves. Thus the mechanical role of pneumatophores is seen as one of binding and stabilizing the intertidal sediment rather than necessarily producing a quiet environment for sediment deposition.