考洲洋人工种植红树林湿地大型底栖动物群落环境响应

2017年以来,广东省惠州市在考洲洋潮间带开展了大规模人工种植红树林生态修复工程,但考洲洋人工种植红树林湿地大型底栖动物群落的环境响应未见报道。根据2018-2019年四个季节在考洲洋盐洲大桥附近红树种植1-2年（X断面）和5-6年（Y断面）的两处湿地的大型底栖动物定量取样数据,分析了人工红树林湿地大型底栖动物的时空格局及其环境响应。方差分析表明,Y断面冬季的大型底栖动物群落的物种数、栖息密度、生物量、多样性指数（H''）和丰富度指数（d）,以及夏季的栖息密度均随潮高（海平面高程）降低而增加;而Y断面冬季的均匀度指数（J）、夏季的H''和J则是随潮高降低而减少。聚类（Cluster）和非度量多维尺度（nMDS）分析表明冬季和夏季X断面和Y断面大型底栖动物群落相似性较低,而春季和秋季X断面和Y断面大型底栖动物群落相似性较高。冬季和夏季最大潮高、潮差、大型底栖动物物种数、栖息密度、H''和d较春季和秋季的高。红树种植1-2年的X断面大型底栖动物物种数、H''和J低于种植5-6年的Y断面。上述结果证实潮汐和红树种植年限影响考洲洋红树林湿地大型底栖动物的群落结构,研究结果可为大型底栖动物多样性保护和生态修复提供基础资料。     

Mangrove leaf litter decomposition under mangrove forest stands with different levels of pollution in the Niger River Delta,Nigeria

Nutrient cycling often moves between litter fall and decomposition. It is hypothesized that hydrocarbon pollution will slow down mangrove litter decomposition because of the reduction in microbial activities. We studied decomposition rates at different levels of pollution (i.e. high and low) and amongst different mangrove species (i.e. red, white and black). For the first experiment, fresh leaves of Rhizophora racemosa were collected, sealed in a litter bag and placed on the mangrove floor for 1.24 years at which all the leaves had completely decomposed to humus and were oven‐dried and weighed to calculate the decomposition rate constant (k) of mass loss. Although there was no significant difference in the rate of decomposition (P > 0.05), leaves at the highly polluted plot had lower rate of decomposition (6.58 × 10^?4) when compared to leaves at the lowly polluted plot (1.75 × 10^?3). In the second experiment, there was a significant difference in decomposition rates amongst species (P < 0.05). Red mangrove leaves (0.41) decomposed more than white (0.28) and black (0.28) mangrove leaves. This implies that hydrocarbon pollution slowed, but did not stop the decomposition of mangrove leaves.     

Sulphur‐oxidizing and sulphate‐reducing communities in Brazilian mangrove sediments

Mangrove soils are anaerobic environments rich in sulphate and organic matter. Although the sulphur cycle is one of the major actors in this ecosystem, little is known regarding the sulphur bacteria communities in mangrove soils. We investigated the abundance, composition and diversity of sulphur‐oxidizing (SOB) and sulphate‐reducing (SRB) bacteria in sediments from three Brazilian mangrove communities: two contaminated, one with oil (OilMgv) and one with urban waste and sludge (AntMgv), and one pristine (PrsMgv). The community structures were assessed using quantitative real‐time polymerase chain reaction (qPCR), polymerase chain reaction‐denaturing gradient gel electrophoresis (PCR‐DGGE) and clone libraries, using genes for the enzymes adenosine‐5′‐phosphosulphate reductase (aprA) and sulphite reductase (Dsr) (dsrB). The abundance for qPCR showed the ratio dsrB/aprA to be variable among mangroves and higher according to the gradient observed for oil contamination in the OilMgv. The PCR‐DGGE patterns analysed by Nonmetric Multidimensional Scaling revealed differences among the structures of the three mangrove communities. The clone libraries showed that Betaproteobacteria, Gammaproteobacteria and Deltaproteobacteria were the most abundant groups associated with sulphur cycling in mangrove sediments. We conclude that the microbial SOB and SRB communities in mangrove soils are different in each mangrove forest and that such microbial communities could possibly be used as a proxy for contamination in mangrove forests.     

真红树和半红树植物叶片性状的比较研究

红树植物是一类生长在热带、亚热带海岸潮间带的乔木、灌木或草本植物,根据其分布特征可分为真红树植物植物和半红树植物。为了探究两者对海岸潮间带高盐、高光和缺氧等环境的生态适应策略的异同,该文选取5种真红树植物植物[卤蕨(Acrostichum aureum)、木榄(Bruguiera gymnorrhiza)、老鼠簕(Acanthus ilicifolius)、桐花树(Aegiceras corniculatum)、秋茄(Kandelia candel)]和4种半红树植物[银叶树(Heritiera littoralis)、水黄皮(Pongamia pinnata)、黄槿(Hibiscus tiliaceus)、杨叶肖槿(Thespesia populnea)]为研究对象,对叶片解剖和功能性状进行了对比研究。结果表明:(1)9种红树植物叶片的共同特征表现为均具有角质层、叶肉具有栅栏组织和海绵组织分化、气孔下陷等。(2)不同之处在于真红树植物植物叶片有蜡质层和内皮层、无表皮毛、气孔仅分布在下表皮,而半红树植物的叶片则较少有蜡质层,部分有表皮毛,无内皮层,气孔在上下表皮分布不完全一致。(3)真红树植物植物的气孔密度和比叶面积显著小于半红树植物(P<0.05),而叶片厚度、含水量、比叶重和鲜干重比则显著大于半红树植物(P<0.05)。以上结果说明真红树植物植物的叶片性状使其在维持盐度平衡及贮水保水能力方面强于半红树植物,从而能更好地适应海岸潮间带高盐环境。     

Detrital traits affect substitutability of a range‐expanding foundation species across latitude

Climate‐driven range shifts of foundation species could alter ecosystem processes and community composition by providing different resources than resident foundation species. Along the US Atlantic coast, the northward expanding foundation species, black mangrove Avicennia germinans, is replacing the dominant salt marsh foundation species, marsh cordgrass Spartina alterniflora. These species have distinct detrital attributes that ostensibly provide different resources to epifauna. We experimentally examined how detritus of these species affects decomposition and community composition in different habitat contexts at regional and local scales. First, we manipulated detritus identity (Avicennia, Spartina) at 13 sites across a 5° latitudinal gradient spanning mangrove, mixed marsh‐mangrove and salt marsh habitats. Across latitude, we found that Avicennia detritus decomposed 2–4 times faster than Spartina detritus, suggesting that detrital turnover will increase with mangrove expansion. Epifaunal abundance and richness increased 2–7 times from south to north (mangrove to salt marsh) and were equivalent between Avicennia and Spartina detritus except for crabs, a dominant taxonomic group that preferred Spartina detritus. Second, to examine the whether changing habitat context affected regional patterns, we manipulated detritus identity and surrounding habitat type (mangrove, salt marsh) at a single mixed site, also including inert mimics to separate structural and nutritional roles of detritus. Epifaunal richness was similar between the two detrital types, but crabs were 2–7 times more abundant in Spartina detritus due to its structural attributes. Surrounding habitat type did not influence decomposition rate or community patterns, which suggests that latitudinal influences, not surrounding habitat, drove the regional community patterns in the first experiment. Overall, mangrove expansion could alter epifaunal communities due to the lower structural value and faster turnover of mangrove detritus. As species shift with changing climate, understanding foundation species substitutability is critical to predict community change, but we must account for concomitant environmental changes that also modify communities.     

Extremely low genetic diversity across mangrove taxa reflects past sea level changes and hints at poor future responses

The projected increases in sea levels are expected to affect coastal ecosystems. Tropical communities, anchored by mangrove trees and having experienced frequent past sea level changes, appear to be vibrant at present. However, any optimism about the resilience of these ecosystems is premature because the impact of past climate events may not be reflected in the current abundance. To assess the impact of historical sea level changes, we conducted an extensive genetic diversity survey on the Indo‐Malayan coast, a hotspot with a large global mangrove distribution. A survey of 26 populations in six species reveals extremely low genome‐wide nucleotide diversity and hence very small effective population sizes (N_e) in all populations. Whole‐genome sequencing of three mangrove species further shows the decline in N_e to be strongly associated with the speed of past changes in sea level. We also used a recent series of flooding events in Yalong Bay, southern China, to test the robustness of mangroves to sea level changes in relation to their genetic diversity. The events resulted in the death of half of the mangrove trees in this area. Significantly, less genetically diverse mangrove species suffered much greater destruction. The dieback was accompanied by a drastic reduction in local invertebrate biodiversity. We thus predict that tropical coastal communities will be seriously endangered as the global sea level rises. Well‐planned coastal development near mangrove forests will be essential to avert this crisis.     

八种红树植物幼苗的叶片可溶性蛋白和抗氧化酶活性对光强的响应

红树林湿地生态系统的恢复与重建是我国南方海岸带生态恢复研究的重点领域之一。为明确红树植物光适应的生理生态策略，该文选取无瓣海桑(Sonneratia apetala)、秋茄(Kandelia obovata)、木榄(Bruguiera gymnorhiza)、桐花树(Aegiceras corniculatum)、老鼠簕(Acanthus ilicifolius)、卤蕨(Acrostichum aureum)、银叶树(Heritiera littoralis)和黄槿(Hibiscus tiliaceus)作为研究对象，通过遮荫控制试验，探究这8种红树植物一年生幼苗在不同光照强度(自然光强的100%、45%、30%、10%)处理下的叶片可溶性蛋白含量和抗氧化酶活性的响应特征。结果表明：(1)随光照强度下降，木榄、老鼠簕和卤蕨的叶片可溶性蛋白含量受到的影响较小，而无瓣海桑、秋茄、桐花树、银叶树和黄槿的叶片可溶性蛋白含量则表现出下降趋势。(2)木榄、老鼠簕和卤蕨的超氧化物歧化酶(SOD)和抗坏血酸过氧化物酶(APX)等抗氧化酶活性在10%光照强度处理下的活性与对照无显著差异，而无瓣海桑、秋茄...     

Mangrove ecosystem changes during the Holocene at Spanish Lookout Cay, Belize

Mangroves are halophytic plants living at the land–sea interface and are therefore natural trackers of sea-level. Multiple proxies of a continuous (8 m) mangrove peat core (BT-79) from Spanish Lookout Cay, Belize illustrate mangrove ecosystem changes during the Holocene. Radiocarbon measurements show this site was colonized by mangroves ~ 8000 cal. yrs BP, with a significant decrease in the peat accumulation rate from ~ 6000 to 1000 cal. yrs BP. Stratigraphic characteristics of this peat core such as bulk density, magnetic susceptibility, and loss on ignition show relative uniformity, inferring an uninterrupted mangrove ecosystem during a majority of the Holocene. This is supported by pollen data from BT-79 that show that the site has been consistently dominated by Rhizophora mangle (red mangrove), with Avicennia germinans (black mangrove) and Laguncularia racemosa (white mangrove) present as well. Subfossil R. mangle leaves are used for stable nitrogen, carbon, and oxygen isotope (δ¹⁵N, δ¹³C, and δ¹⁸O) analyses. δ¹⁵N and δ¹³C values provide a proxy of this plant's past physiology and stand structure showing that dwarf (δ¹⁵N < − 3‰) and tall (δ¹³C < − 27‰) R. mangle stands were previously present at the site, which are a result of nutrient limitations that we equate with seawater inundation. δ¹⁸O values show differences in source water of R. mangle, with higher values attributed to the source water being composed of a greater proportion of seawater relative to precipitation. A decrease in inundation at the site is shown by lower δ¹⁸O values (< 19‰) from ~ 7000 to ~ 1000 cal. yrs BP that covary with the decreased sedimentation rate. Existing Caribbean sea-level data do not show evidence of a decrease in the rate of relative sea-level rise or fluctuations that we take to be the major causes of environmental changes at site BT-79.     

红树林沉积物中天然多聚有机物厌氧降解菌多样性与细菌新类群分离

[目的]红树林沉积物中有机物丰富,通过研究认识参与难降解天然有机多聚物的微生物降解过程及其环境作用,并获得新颖的难培养厌氧微生物。[方法]对漳州九龙江河口红树林沉积物中降解纤维素、几丁质和木质素的厌氧细菌定向富集和平板分离纯化,并对其多样性进行分析。[结果]共筛选分离获得202株厌氧细菌(82株专性厌氧细菌,120株兼性厌氧细菌),包括4个疑似新属(Lachnotalea sp.MCCC 1A16036、Varunaivibrio sp.MCCC 1A15903、Clostridium sp.MCCC 1A15884、Caminicella sp.MCCC 1A17445)和4个疑似新种(Sunxiuqinia sp.MCCC 1A15904、Pseudodesulfovibrio sp.MCCC 1A16040、Pseudodesulfovibrio sp.MCCC 1A16038、Mangrovibacterium lignilyticum MCCC1A15882)。不同天然有机多聚物富集菌群分离到的优势可培养细菌主要属于变形菌门、拟杆菌门和厚壁菌门,但种群略有差异。在纤维素和几丁质富集菌群中,变形菌门和拟杆菌门菌株是纤维素和几丁质富集菌群的优势菌群,拟杆菌门的Prolixiacer bellariivorans、Mangrovibacterium lignilyticum和变形菌门的Desulfovibrio salexigenes、Vibrio alginolyticus分别在纤维素和几丁质富集菌群可培养细菌中占绝对优势。但降解实验表明,放线菌门细菌Demequina salsinemoris MCCC 1A15890和Brevibacterium celere MCCC 1A17451对纤维素降解活性最高。梭杆菌门细菌Propionigenium maris MCCC 1A15874和Ilyobacter polytropus MCCC 1A15889对几丁质降解活性最高。在木质素富集菌群中,拟杆菌门的Mangrovibacterium lignilyticum和厚壁菌门的Clostridium amygdalinum都具有较高的相对丰度。变形菌门细菌Desulfomicrobium apsheronum MCCC 1A15932和拟杆菌门细菌Mangrovibacterium lignilyticum MCCC 1A15882对木质素降解效果显著。[结论]红树林沉积物中存在丰富多样且新颖的厌氧难培养细菌,且多数具有纤维素、几丁质或木质素厌氧降解能力。该研究结果为探究红树林沉积物原位环境天然有机多聚物碳的生物地球化学循环机制提供了相关理论基础和纯培养微生物资源。     

红树植物功能性状对盐和铜胁迫的响应

目前,室内通过人工控制方式开展红树林对环境胁迫的响应研究,忽视了不同红树植物物种的生长习性,且以单一胁迫为主。通过野外生长与人工控制相结合方式,研究5个时期(2018.6-2020.8)盐和铜胁迫对3种红树植物(秋茄、拉关木和木榄)11种功能性状的影响,使用单因素和双因素方差分析研究不同时期不同树种下盐和铜胁迫对叶片功能性状的影响,回答红树植物功能性状对盐和铜单一及复合胁迫响应的科学问题。结果表明,不同时期下,三种红树植物功能性状具有明显差异。随着时间增长,三种植物的碳含量和冠层高度均呈升高趋势,其他功能性状因物种不同而表现出不同趋势;与乡土红树植物(秋茄和木榄)相比,外来入侵物种(拉关木)具有更快的生长速度。不同时期下,拉关木比秋茄和木榄具有更好耐盐性,三个物种的植物生长发育对铜胁迫的响应均不敏感。大部分时期下,单一盐胁迫对拉关木的植物功能性状无显著影响(P < 0.05),对秋茄和木榄的碳含量、冠层高度和比叶面积有显著影响(P < 0.05);单一铜胁迫对三个物种的绝大多数功能性状无显著影响。另外,盐-铜复合胁迫对秋茄叶片碳、磷、氮磷比及冠层高度有显著影响(P < 0.05),对拉关木叶片碳、铜含量、冠层高度、比叶面积有显著影响(P < 0.05),仅对木榄SPAD值有显著影响(P < 0.05)。在红树林保护修复工作中,研究成果可为红树林退化原因和机理阐释、红树林生长监测评估、生境治理以及树种选择提供一定的理论依据。     

Biodegradation of nonylphenol in mangrove sediment

This study investigated the biodegradation of nonylphenol (NP) in mangrove sediments collected at five sites along the Tanshui River in northern Taiwan. NP biodegradation rate constants (k₁) and half-lives (t_1/2) ranged from 0.039 to 0.139 day⁻¹ and 5.0 to 17.8 days, respectively. The biodegradation of NP was enhanced by the addition of yeast extract, hydrogen peroxide, brij 35, sodium chloride, or cellulose. However, NP biodegradation was inhibited by the addition of humic acid, heavy metals, or phthalic acid esters (PAEs). Of the microorganism strains isolated from the mangrove sediment, we found that strains A9, A10 and A13 (all identified as Bacillus sp.) expressed the best biodegrading ability. NP biodegradation rate constants (k₁) and half-lives (t_1/2) by the three strains ranged from 0.291 to 0.630 day⁻¹ and 1.1 to 2.4 days, respectively. The highest NP biodegradation rate was found in the sediment with the inoculation containing strains A9, A10 and A13, whereas the sediment without any inoculation had the lowest biodegradation rate.     

广东省中山市2种红树林有害生物风险分析及防控策略

【目的】了解红树林有害生物风险及其防控,维护红树林健康生长,发挥红树林的生态功能。【方法】2018—2019年,连续2年对广东省中山市红树林有害生物种类进行系统调查监测,并对薇甘菊和星天牛2种有害生物在中山市的分布状况、定殖和扩散的可能性、潜在危害性、受害对象的重要性、防控难度等进行分析,结合红树林的生态效益,参照国际有害生物风险性分析方法对两者在中山市红树林的危害风险性进行综合分析评估。【结果】调查发现,中山市红树林主要有害生物有23种,其中薇甘菊、星天牛最为严重,评估风险性R值分别为1.63和1.61,属中度危险的林业有害生物。【结论】薇甘菊和星天牛目前仅在中山市红树林局部地区发生危害,但具有明显扩散蔓延趋势,应该建立以应急除治、生物防治、生态修复等多种技术相结合的生态控制技术体系。     

Seed predation by insects in tropical mangrove forests: extent and effects on seed viability and the growth of seedlings

Summary Although insects are known to be important seed predators in most terrestrial forests, their role in marine tidal (mangrove) forests has not been examined. Surveys at 12 sites in tropical Australia showed that between 3.1 and 92.7 percent of the seeds or propagules of 12 mangrove tree species had been attacked by insects. Seeds/propagules of six species (Avicennia marina, Bruguiera gymnorrhiza, B. parviflora, Heritiera littoralis, Xylocarpus australasicus and X. granatum) showed consistently high (>40%) levels of insect damage. Greater than 99% of H. littoralis seeds were attacked by insect predators. The survival and subsequent growth in height and biomass of insect-damaged and non-damaged control seeds/propagules of eight mangrove species were compared in shadehouse experiments. Mangrove species fell into 4 groups with regard to the effect of insect predators on their seeds and seedlings. Xylocarpus australasicus and X. granatum had significantly decreased survival (X 48 and 70%) and growth in height (X 61 and 96%) and biomass (X 66 and 85%). Bruguiera parviflora showed decreased survival (X 59%), but there was no effect of insects on the growth of surviving propagules. In contrast, there was no effect of insect damage on the survival of seedlings of Avicennia marina and Bruguiera exaristata, but decreased growth in height (X 22 and 25%) and biomass (X 22 and 26%). Survival and growth of seedlings of Rhizophora stylosa and Bruguiera gymnorrhiza were not affected. The influence of insect seed predators on the survival and growth of seeds of mangrove species in forests will depend on the relative abundance of seed-eating crabs and intertidal position in mangrove forests.This is Contribution No 499 from the Australian Institute of Marine Science     

广西北部湾典型海岛红树林的结构特征、空间格局及种间种内关联性

为研究广西北部湾茅尾海自然保护区海岛红树林群落的空间点格局和演替规律,在典型红树林海岛设置调查样地,以样地内的桐花树(Aegiceras corniculatum)、秋茄(Kandelia obovata)、白骨壤(Avicennia marina)等红树植物为研究对象,构建单变量函数的完全空间随机模型、异质泊松模型与双变量函数的环形转变模型,分析3种红树林种群的结构特征、空间格局及种内种间关联性。结果发现：(1)桐花树种群的小树和中树的个体数目较多,种群年龄结构呈金字塔型,种群处于增长状态;秋茄种群的中树个体数目较多,种群结构呈钟型,种群数量处于稳定状态;白骨壤个体数相对较少,且幼树较少老树较多,种群更新受阻,种群结构呈纺锤型,属于衰退型种群。(2)红树林群落整体上呈现出空间集聚的分布特征,从不同种群的集聚程度来看：桐花树>白骨壤>秋茄。(3)随着空间尺度的增大,红树林群落在空间分布上依次表现出聚集、随机和均匀3种特征。(4)桐花树与秋茄、白骨壤的种间关系随着尺度增加均表现为空间无关联性-空间负关联性-空间无关联性的演变特征,秋茄与白骨壤的种间关系则为全尺度的空间无关联性。(5)桐花树种内不同龄级之间存在空间正关联性、空间无关联性和空间负关联性,秋茄种内不同龄级之间均表现出空间无联性,白骨壤种群则在不同龄级之间均出现空间正关联性。(6)红树植物种群的空间格局受到自身繁殖特性、生境异质性、种内和种间竞争、病虫害等多种因素的影响。红树林人工种植和恢复需要结合沿海地区的自然生态条件,按照红树林种群的适应形态学特点、群落类型和自然演替规律,种植乡土红树植物,适当引进外来物种,研制出近似天然的人工红树林林分结构,提高群落的生物多样性和群落稳定性,发挥红树林湿地生态系统的生态环境效应。     

Protein and enzymes regulations towards salt tolerance of some Indian mangroves in relation to adaptation

Elevated substrate salinity and anthropogenic impulse are the major threat to the mangrove ecosystem. In the Indian subcontinent, Sundarbans have the richest mangrove species diversity. Due to geomorphic characteristics and unplanned management, the elevated salinity prevails in the western part and that has direct impact on vegetation. Seven mangrove taxa were examined, of which four (Aegialitis rotundifolia, Heritiera fomes, Xylocarpus granatum, and X. mekongensis) were considered as degrading and three (Bruguiera gymnorrhiza, Excoecaria agallocha, and Phoenix paludosa) were considered as natural control. The targeted taxa were collected from five different islands and were selected on the basis of increasing salinity gradient. As salinity increased from site I to V (11.76–15.2 ppt), the amount of total leaf proteins decreased in all the targeted species and ranged between 5.67 and 25.23%. The percentage of protein depletion was less in Aegialitis, Heritiera, and Xylocarpus than the other three taxa in higher salinity that pointed out their less adaptability, as degradation of protein may be essential for efficient stress management. Two antioxidative (peroxidase and superoxide dismutase) and two hydrolyzing (acid phosphatase and esterase) enzymes showed a positive correlation with salinity. In four degrading taxa, the percentage of enzyme increment was less than those of their natural control taxa. Salinity imposed increment of antioxidant enzymes facilitate ROS scavenging, which is an inevitable elevated byproduct during photo-inhibition. Lower amount and number of isoforms in higher salinity indicated towards less suitability of Aegialitis rotundifolia, Heritiera fomes, Xylocarpus granatum, and X. mekongensis in increased salinity level of western Sundarbans.     

Length–weight relationships of fish species caught in a mangrove swamp in the Gulf of California (Mexico)

The relation between length (L) and weight (W) was estimated for 33 species representing 14 families of fishes from El Conchalito mangrove swamp, Gulf of California (Mexico). The parameter b estimated by nonlinear least squares of weight and length data, ranged from 1.41 to 3.68. Length ‐ weight parameters can be used for several biological or fishery purposes to enable the derivation of weight estimates from given a value of length or vice versa.     

Diatoms from Indonesian mangroves and their suitability as sea-level indicators for tropical environments

We collected modern diatom samples from two mangrove environments of Sulawesi, Indonesia to provide a much needed dataset for the reconstruction of sea level from tropical environments. The diatom assemblages are dominated by mesohalobous species (e.g. Amphora coffeaeformis, Amphora turgida, Achnanthes delicatula, Nitzschia sigma and Tryblionella balatonis) and oligohalobous (e.g. Amphora veneta, Diploneis ovalis and Progonoia didiomatia) taxa. Both study sites show strong vertical zonations, which suggests that duration and frequency of intertidal exposure are important factors in controlling the relative abundance of diatoms. The assemblages can be generally divided into a mixed assemblage of mesohalobous, oligohalobous–halophilous and oligohalobous-indifferent diatoms that are found from the dense mangrove vegetation towards the landward edge of the transects, and mesohalobous diatom assemblages that are located within the fringing Rhizophora and tidal flat environments. We subsequently developed a diatom-based transfer function, which is a quantitative approach to sea-level reconstruction. The relationship between observed and diatom-predicted elevations suggests accurate and precise reconstructions are possible. The error estimate (± 0.15 m) is comparable to diatom-based transfer functions from temperate marshes.     

Assessing fine beam RADARSAT-1 backscatter from a white mangrove (Laguncularia racemosa (Gaertner)) canopy

To determine whether spaceborne Synthetic Aperture Radar (SAR), specifically fine beam RADARSAT-1 C-band, could be used to provide quantitative data on white mangrove (Laguncularia racemosa (Gaertner)) forests, backscatter coefficients (σ°) were examined in relation to structural parameter data collected from plots located in a mangrove forest of the Mexican Pacific. Significant coefficients of determination were recorded between the backscatter coefficients and the logarithms of both Leaf Area Index (LAI) and mean stem height at two incident angles for both the dry and wet seasons. The highest coefficients of determination for LAI (r ² = 0.60) and mean stem height (r ² = 0.72) were observed using the shallower (~40°) and steeper (~47°) incident angles, respectively. No significant relationships were recorded between the backscatter coefficients and either stem density, basal area or mean DBH. Given the results of this investigation, it is recommended that for cloud covered regions, fine beam RADARSAT-1 data could be used by resource managers when they require a quick method for surveying structural damage to mangroves resulting from both natural and anthropogenic causes.     

Valuing mangrove benefits: contribution of mangrove forests to local livelihoods in Bhitarkanika Conservation Area,East Coast of India

The consumptive benefits of mangrove forests to subsistence economy receive little recognition. This paper quantifies the value of provisioning services of mangrove forests to local livelihoods in terms of forestry and fishery products. To examine the use of mangrove products, 324 households from 36 villages in the Bhitarkanika Conservation Area located in East Coast of India were surveyed using structured questionnaires. For estimating the contribution of mangrove forests to fish productivity, fish production was evaluated in three stages—inshore fishery, offshore fishery and the role of mangrove forests as nursery ground for fish and shellfish. The findings revealed that 14.2% of the fuel need of each household was being met by the forests. Other forestry products used were timber, honey and thatch grass. During the study, 14 species of fish and three of shellfish were recorded. The total catch for inshore fishery was estimated as 3.77 kg h⁻¹ having market price of US2.25. In offshore fishery the number of species caught as well as income from the catch was higher in areas with mangroves (US 2.25. In offshore fishery the number of species caught as well as income from the catch was higher in areas with mangroves (US 44.61 h⁻¹) than in those without mangroves (US$ 2.62 h⁻¹). The market price of the forestry and fishery products used by the people was estimated as US$ 2.62 h⁻¹). The market price of the forestry and fishery products used by the people was estimated as US 107 household⁻¹ annum⁻¹. The resources extracted from mangrove forests contributed to more than 14.5% of the total income of the household. This was around 30% for the households residing in the immediate vicinity of the forests. This study suggests that provisioning services provided by the mangrove forests are of significant importance to the coastal communities as they increase the resilience and sustainability of the local economy.     

Long-Term Growth and Succession in Restored and Natural Mangrove Forests in Southwestern Florida

We compared colonization, growth and succession from 1989 to 2000 in a restored mangrove site and in gap and closed canopy sites in a natural mangrove forest. The restored site was created in 1982 and planted with Rhizophora mangle (≈2 m⁻²) propagules. By 1989, Laguncularia racemosa, with densities up to 12.9 tree m⁻², was a dominant in all plots, although densities were greater at edge plots relative to inner plots, and near open water (west plots) relative to further inland (east plots), and in tall mangrove plots relative to scrub plots. Rhizophora mangle (1989 tree densities about 2 m⁻²) was a codominant in inner and scrub plots, while Avicennia germinans had the lowest densities (<1 tree m⁻²) in all plots. From 1989 to 2000 L. racemosa experienced reduced recruitment and apparent density-dependent mortality of canopy individuals in plots with high initial densities. Scrub plots experienced high rates of colonization by R. mangle and L. racemosa, rapid growth in height of all species (1989–1996), followed by a dieoff of L. racemosa in later years (1997–2000) as the canopy came to resemble that of tall mangrove plots. Colonization and growth rates were lower in gap and closed canopy regions of the natural forest relative to rates in the restored site. After 11 years, densities of L. racemosa were 10–20× lower and R. mangle slightly less in the gap relative to densities in tall mangrove plots in the restored site at the same age. Although the restored stand had converged with the natural forest by 2000 in terms of some factors such as species richness, vegetation cover, litterfall, and light penetration, trees were still much smaller and stem densities much higher. Full development of mature structure and ecological function will likely require decades more development.