The growth of Kandelia candel seedlings in mangrove habitats of the Zhangjiang estuary in Fujian, China

Propagules of Kandelia candel collected from the Zhangjiang estuary were planted in mangrove habitats along the intertidal gradient. The rooting rates of K. candel propagules varied spatially. The lowest rate occurred in Avicennia marina forest (69.7%). The rates were higher in K. candel forest (90.0%), at the fringe of the mangrove forest (89.3%) and on the bare tidal flat outside the mangrove forest (82.7%). After one year, the survival rates of seedlings planted under A. marina forest, K. candel forest, at the fringe of the mangrove forest, and on the bare tidal flat were 13.7%, 54.7%, 76.0%, and 34.7%, respectively. Among the surviving K. candel seedlings, those at the fringe of the mangrove forest and on the bare tidal flat had greater height, stem diameter, leaf number, leaf area, and biomass than those under A. marina and K. candel forests. These results demonstrated that establishment and growth of K. candel seedlings occurred successfully at the fringe of the mangrove forest, but were the worst under A. marina forest. The performance of K. candel seedlings was independent of physico-chemical characters of sediment. However, interspecies competition, propagule predation by insects and crabs, and the incident light had significant effects on seedling survival and growth.     

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。     

Wetland changes and mangrove restoration planning in Shenzhen Bay, Southern China

Mangrove forests and associated gei wai (excavated ponds used for shrimp and fish farming) provide important ecosystem services in Shenzhen Bay. Much of the mangrove and gei wai wetlands, however, have been lost because of intensified human activities in the past 30 years. Using five-phase remote-sensing images, we describe the recent history of the spatial–temporal dynamics for the wetlands in the bay. From 1986 to 2007, mangrove area increased from 1.8 to 4.8 km², while the area of gei wai decreased from 36.6 to 17.2 km². Reclamation of gei wai mainly occurred in western and northern Shenzhen Bay, and changed the tidal water environment. The bay has five typical mangrove communities: Avicennia marina + Kandelia candel + Aegiceras corniculatum, Kandelia candel + Aegiceras corniculatum + Acanthus ilicifolius, Bruguiera gymnorrhiza + Excoecaria agallocha, Aegiceras corniculatum, and Sonneratia apetala + Sonneratia caseolaris. The distribution of these communities and their dominant species in the bay exhibit a spatial pattern and temporal (successional) sequence. We describe a mangrove restoration program based on the mangrove successional sequence and the interaction of mangrove and gei wai in the bay. We have planned six mangrove protection and restoration projects in closed areas, semiclosed areas, and open areas to reconstruct the ecological integrity of the entire Shenzhen Bay.     

Standing crop and aboveground biomass partitioning of a dwarf mangrove forest in Taylor River Slough,Florida

The structure and standing crop biomass of a dwarf mangrove forest, located in the salinity transition zone ofTaylor River Slough in the Everglades National Park, were studied. Although the four mangrove species reported for Florida occurred at the study site, dwarf Rhizophora mangle trees dominated the forest. The structural characteristics of the mangrove forest were relatively simple: tree height varied from 0.9 to 1.2 meters, and tree density ranged from 7062 to 23 778 stems ha^–1. An allometric relationship was developed to estimate leaf, branch, prop root, and total aboveground biomass of dwarf Rhizophora mangle trees. Total aboveground biomass and their components were best estimated as a power function of the crown area times number of prop roots as an independent variable (Y = B × X^–0.5083). The allometric equation for each tree component was highly significant (p<0.0001), with all r² values greater than 0.90. The allometric relationship was used to estimate total aboveground biomass that ranged from 7.9 to 23.2 ton ha^–1. Rhizophora mangle contributed 85% of total standing crop biomass. Conocarpus erectus, Laguncularia racemosa, and Avicennia germinans contributed the remaining biomass. Average aboveground biomass allocation was 69% for prop roots, 25% for stem and branches, and 6% for leaves. This aboveground biomass partitioning pattern, which gives a major role to prop roots that have the potential to produce an extensive root system, may be an important biological strategy in response to low phosphorus availability and relatively reduced soils that characterize mangrove forests in South Florida.     

The importance of mangrove species association to the population biology of the sesarmine crabs Parasesarma affinis and Perisesarma bidens

The population biology of two sesarmine crabs, Perisesarma bidens andParasesarma affinis, was studied over a two-year period in twomangrove forests, one dominated by Kandelia candel and the other by Avicennia marina. Despite the fact that the mangrove forests werecontiguous, shared the same water supply and were less than 20 cmdifferent in tidal position, significant differences in population biology ofboth crab species were recorded. Individuals of both species associated withthe topographically higher Kandelia candel forest were more abundant,had a higher tissue organic content, higher gonosomatic and hepatosomaticindices than their counterparts in the Avicennia marina forest. Femaleindividuals of both species were also larger in size in the Kandeliaforest. These differences result in higher secondary production of the crabsat the Kandelia forest. By contrast, association with different mangrovespecies did not result in significant differences in the sex ratio, growth andreproductive periodicity, and size-specific reproductive output of the crabs.The results suggest significant influence by the associated mangrove specieson the population biology of the crabs, through processes such asmodification of the physical habitat fabric and/or provision of trophicresources of different quality and quantity by the mangroves. This influencefurther reiterates the bi-directional nature of mangrove-crab interactions andthe need to consider these intricate interactions in future studies on tropicalmangrove structure and function.     

Relationships between height and girth of mangroves and soil-water conditions in the Mary and Hawkesbury River estuaries,eastern Australia

Abstract The height and diameter at breast height (DBH) of mangroves on the Hawkesbury River, New South Wales and the Mary River, Queensland were related to soil-water salinity, soil-water content and distance from the mouth of the estuary. On the Hawkesbury River, both Avicennia marina and Aegiceras corniculatum declined in height and DBH with increasing soil-water salinity and soil-water content, and increased in height with distance from the mouth of the estuary. Both species showed an extensive range of all variables. On the Mary River, where species diversity was higher, no relationship was found between the height and DBH of A. marina and A. corniculatum and soil-water salinity and soil-water content. Both species increased in height with increasing distance from the mouth of the estuary, a characteristic shared with all other species studied (Excoecaria agallocha, Ceriops tagal var. australis, Rhizophora stylosa). The results suggest that growth characteristics of mangroves are not a simple response to salinity gradients in diverse systems and that other variables such as nutrient availability may be important controls on mangrove growth.     

Isolation and characterization of chloroplast microsatellite markers in four mangrove species,Aegiceras corniculatum,Avicennia marina,Acanthus ilicifolius and Lumnitzera racemosa

One, three, seven, and six of polymorphic chloroplast microsatellite (cpSSR) markers were developed from four mangrove species, Acanthus ilicifolius, Aegiceras corniculatum, Avicennia marina, and Lumnitzera racemosa, respectively. Characterization of 229, 509, 369, and 216 individuals of A. ilicifolius, A. corniculatum, A. marina, and L. racemosa, collected from different natural mangrove populations (A. ilicifolius, 6; A. corniculatum, 14; A. marina, 10; L. racemosa, 6) in the southern coastline of China showed that these loci provide cpSSR markers with polymorphisms ranging from two to four alleles per locus and gene diversity between 0.005 and 0.675. Combining the polymorphic cpSSR loci of each species, 3, 5, 11, and 4 of cpSSR haplotypes were separately detected in populations of A. ilicifolius, A. corniculatum, A. marina, and L. racemosa in the southern coastline of China. These cpSSR markers will be useful for analyzing the maternal lineage distributions and population genetic structures of these four species.     

Forest structure and biomass of mangroves in the Mgeni estuary,South Africa

Forest structure and biomass were determined in a mangrove stand dominated by Bruguiera gymnorrhiza (L.) Lam. Trees in 5 m² sample plots were harvested at ground level and then further cut into 1 m strata for separation into living wood, dead wood, leaves, reproductive material and pneumatophores. Mean above-ground living biomass was calculated at 94.49±7.83 t dry matter ha^–1, while dead wood contributed a mean mass of 7.63±0.89 t dry matter ha^–1. Excavations of roots yielded a below-ground biomass of 9.67 t dry matter ha^–1 which represented only 9.8% of the above-ground value. There was a mean density of 4700 living stems ha^–1 with plant heights ranging from 0.57 m to 5.80 m. Mean LAI was 4.95±0.80. As a basis for estimating standing biomass, regression lines were fitted to biomass values from individual trees of B. gymnorrhiza and Avicennia marina (Forssk.) Vierh. of various sizes. A comparison of these relationships with methods used by previous workers for estimating biomass suggests that most other methods cannot be applied without modification for local stands of mangroves.     

Structure of a unique inland mangrove forest assemblage in fossil lagoons on the Caribbean Coast of Mexico

Scrub mangrove wetlands colonize the intertidal zone of fossil lagoons located in carbonate continental margins along the Yucatan Peninsula of Mexico. These unique ecological types were investigated in October, 1994, by locating transects in several mangrove forests along the Caribbean coast of the peninsula. Four species of mangrove occurred at these sites including Rhizophora mangle, Avicennia germinans, Laguncularia racemosa, Conocarpus erecta. This is one of the first examples of a species rich scrub forest. The mangroves fell into three height categories: short scrub less than 1.5 m, tall scrub to 3.0 m, and basin forests between 4.5 and 6 m. Average height, diameter (dbh), basal area, and complexity index generally increased from short scrub to basin forests. Basal area, ranged from 0.16 m² ha^–1 in a short scrub forest intermixed with Cladium jamaicense to 12.9 m² ha^–1 in a basin forest. Density ranged from 1520 trees ha^–1 to over 25,000 trees ha^–1 in a short scrub forest dominated by R. mangle. The complexity index ranged from 0.01 to 8.3. Height, dbh, basal area, and complexity index were positively related. A number of trees were growing as sprouts from larger downed trunks, suggesting that hurricanes, such as Gilbert that occurred in 1988, are important in controlling the structure of these forests. These forests appear isolated from the sea, but are influenced by groundwater exchange occurring at the land-margin zone.     

Diversity and distribution of the mangrove forests in Taiwan

In a survey of 1992 to 1994, mangrove forests withfour species of true mangroves, Kandelia candel(L.) Druce, Avicennia marina(Forsk.) Vierh.,Rhizophora stylosaGriff., and Lumnitzera racemosaWilld., were found at 22locations in the west coast of Taiwan. The northernrange of their distribution was at Tanshui Estuary(Latitude 25^°11N) and the southern range atTapen Bay (22^°28N). The total area wasestimated to be 286.95 ha. There was an obvious changein species composition and a decrease in speciesnumber of true mangroves from south to north: the fourspecies dominated by A. marinain thesouth and K. candelas thesole species in the north. Air temperature associatedwith sea surface temperature and oceanic currents inwinter, but not soil property, was found to be theprimary environmental factor, affecting the diversityand distribution of true mangroves in Taiwan as wellas in the northeast region of Asia.     

Variation in the δ<Superscript>13</Superscript>C of Two Mangrove Plants is Correlated with Stomatal Response to Salinity

To better understand the relationship between salinity and the carbon stable isotope composition (expressed as δ¹³C) of mangrove plants and to test whether the patterns of variation in δ¹³C of mangrove plants differ from those of nonhalophytes as response to salinity, the effect of salinity on leaf δ¹³C in two dominant mangrove species, Aegiceras corniculatum and Kandelia candel, was studied. Furthermore, to determine whether the variation in δ¹³C of mangrove species is adjusted by stomatal conductance, K. candel was selected as an example, and leaf gas-exchange characteristics of the seedlings were measured. It was observed that both mangrove species had a lower leaf δ¹³C under their optimum salinity (1.50% for Ae. corniculatum and 2.00% for K. candel). This variation in δ¹³C of mangrove plants was attributable largely to stomatal adjustment as for nonhalophytes in which a strong correlation between δ¹³C and relevant photosynthetic properties is observed. This result suggests that the different response pattern in δ¹³C was a consequence of the variation in stomata in relation to the different tolerance to salinity. The optimum salinity inferred by leaf δ¹³C provides a feasible method for comparing salt tolerance between mangrove plants belonging to different species, which is useful for mangrove restoration.     

Structural properties of two types of mangrove stands on the northwestern coast of Sri Lanka

Mangrove stands in Puttalam lagoon and Dutch bay, two interconnected lagoons situated on the northwestern coast of Sri Lanka have been classified broadly into two groups, i.e., estuarine and island/mainland-fringing stands. Structural diversity of six mangrove stands, representing the two types was studied in terms of floristic composition, density, basal area, mean stand diameter, tree height, standing above-ground biomass and leaf-area index.Rhizophora mucronata andAvicennia marina were the dominant species. Higher mean stand diameters for the mangrove stands in Puttalam lagoon indicated greater maturity than the estuarine mangrove stands in Dutch bay. Nevertheless, estuarine stands in Dutch bay were structurally more complex (complexity indices 8.11–22.7) than the island/mainland-fringing mangrove stands (complexity indices 1.38–6.78). Higher number of species present in the estuarine mangrove stands is the major element that contributes to the higher values for the complexity indices for those stands. This appears to mask the contribution of stand-age to the complexity of a mangrove stand. Therefore complexity indices alone may not be used to explain adequately the structural diversity among mangrove stands.     

Changes in the functional feeding groups of macrobenthic fauna during mangrove forest succession in Zhanjiang,China

Understanding the relationships between mangrove forest succession and the functional diversity of mangrove fauna could facilitate the restoration of mangrove ecosystems, which have been severely damaged in recent decades. The current report describes changes in macrobenthic functional diversity in a mangrove chronosequence that included a primary community (unvegetated shoal), an early community (Avicennia marina), a middle community (Aegiceras corniculatum), and a late community (Bruguiera gymnorrhiza?+?Rhizophora stylosa) in Zhanjiang, China. Phytophages were the dominant macrobenthic functional feeding group regardless of mangrove succession stage, sampling season, or macrobenthic faunal parameter (species richness, abundance, and biomass). As mangrove succession progressed, the proportions of macrobenthic species richness, abundance, or biomass represented by omnivores significantly increased (except for biomass and in the late stage; ranged from 0.065 to 0.230 and 0.033 to 0.368, respectively in wet season, and 0.000 to 0.192 and 0.000 to 0.396, respectively in dry season), while the proportions significantly decreased for detritivores during the dry season (ranged from 0.156 to 0.056, 0.107 to 0.019, and 0.066 to 0.005, respectively). Non-metric multi-dimensional scaling and PERMANOVA also indicated that the structure of macrobenthic faunal functional feeding groups was significantly affected by mangrove succession. Further analyses indicated that the changes in the relative dominance among macrobenthic faunal functional feeding groups during mangrove succession were mainly associated with changes in plant density, coverage/canopy density, and total nitrogen content of sediment, i.e., they were mostly associated with changes in food sources. The results increase our understanding of the relationship between benthic functional diversity and mangrove succession and could help guide mangrove restoration in China and around the world.     

The suitability of non-target native mangroves for the survival and development of the lantana bug <Emphasis Type="Italic">Aconophora compressa</Emphasis>, an introduced weed biological control agent

Aconophora compressa (Hemiptera: Membracidae), a biological control agent introduced against the weed Lantana camara (Verbenaceae) in Australia, has since been observed on several non-target plant species, including native mangrove Avicennia marina (Acanthaceae). In this study we evaluated the suitability of two native mangroves, A. marina and Aegiceras corniculatum (Myrsinaceae), for the survival and development of A. compressa through no-choice field cage studies. The longevity of females was significantly higher on L. camara (57.7 ± 3.8 days) than on A. marina (43.3 ± 3.3 days) and A. corniculatum (45.7 ± 3.8 days). The proportion of females laying eggs was highest on L. camara (72%) followed by A. marina (36%) and A. corniculatum (17%). More egg batches per female were laid on L. camara than on A. marina and A. corniculatum. Though more nymphs per shoot emerged on L. camara (29.9 ± 2.8) than on A. marina (13 ± 4.8) and A. corniculatum (10 ± 5.3), the number of nymphs that developed through to adults was not significantly different. The duration of nymphal development was longer on A. marina (67 ± 5.8 days) than on L. camara (48 ± 4 days) and A. corniculatum (43 ± 4.6 days). The results, which are in contrast to those from previous glasshouse and quarantine trials, provide evidence that A. compressa adults can survive, lay eggs and complete nymphal development on the two non-target native mangroves in the field under no-choice condition.     

Diurnal gas exchange characteristics and water use efficiency of three salt-secreting mangroves at low and high salinities

Continuous measurements of gas exchange characteristics were made on two to nine year old hydroponically grown Avicennia germinans (L.) Stearn, Aegialitis annulata R. Br. and Aegiceras corniculatum (L.) Blanco maintained at 50 or 500 mol m^–3 NaCl. In Avicennia germinans and Aegialitis annulata, CO₂ assimilation rates were initially higher at 500 mol m^–3 NaCl and decreased gradually towards the end of the photoperiod when rates were similar to those at the lower salinity. In Aegiceras corniculatum, assimilation rates were higher at 50 mol m^–3 NaCl and about 55% lower at the higher salinity. In all three species, leaf conductance and transpiration exhibited trends similar to those for CO₂ assimilation. Intercellular CO₂ concentrations were similar at both salinities in Avicennia germinans and Aegialitis annulata, but considerably higher at the lower salinity in Aegiceras corniculatum. Water use efficiencies (WUE), although similar between salinity treatments in Avicennia germinans and Aegialitis annulata, were greater at the higher salinity in Aegiceras corniculatum. Data obtained from CO₂ response curves indicated that assimilation at high salinity in Aegiceras corniculatum was limited by conductance, and to a lesser extent, by photosynthetic capacity. In Avicennia germinans and Aegialitis annulata, assimilation was greater at the higher salinity as indicated by increase in both the initial slope and the upper plateau of the CO₂ response data. Greater assimilation at high salinity in Avicennia germinans and Aegialitis annulata may be attributed to lower carbon losses via photorespiration and to efficient salt excretion and sequestration.     

中国红树林生态系统保护空缺分析

红树林作为海岸带重要的生态系统类型,具有维持海岸生物多样性、防风固岸、促淤造陆等重要的生态功能,在气候变化和快速城市化背景下认识红树林受保护状况具有重要意义。以基于遥感解译的红树林分类数据为基础,通过空缺分析,分析了我国红树林的就地保护状况,结果显示我国分布的红树林总面积为264 km~2(尚不含我国港、澳、台的统计数据),其中61.4%在自然保护区内受到保护。从红树林分布的主要省份来看,在海南省分布的红树林面积较少但保护比例高,广西和广东省分布的红树林面积大但受保护面积比例相对较低。在3种红树林类型中,红树-木果楝林和红海榄-木榄林分布面积较小,但受保护的面积都在90%以上,秋茄-桐花树-白骨壤林分布的面积最大,但受保护的面积为52.6%。研究提出自然保护区外红树林分布的关键区域,并建议通过划定生态保护红线等方式来进行保护。     

Differential Distribution of Metals and Enzymes in Quanzhou Bay Estuarine Wetland Soils under Three Mangrove Species

This study aimed to investigate the effects of three dominant mangrove species (Avicennia marina, Aegiceras corniculatum, and Kandelia obovata) on the distribution of the metal elements Fe, Mn, Cu, and Zn and the enzymes urease, phosphatase, polyphenol oxidase, and catalase. Concentrations of the metallic elements and enzymatic activities were quantified in soils under the three mangrove species in the Quanzhou Bay estuarine wetland, a typical coastal wetland in China. Results showed that A. corniculatum promoted aggregation of Mn, urease, and phosphatase, while K. obovata contributed to accumulation of Cu, urease, and phosphatase. Furthermore, A. marina induced activation of Zn and accumulation of urease, phosphatase, and catalase. The characteristic enzyme and metal distributions induced by the different mangrove species are likely to result from different planting times, root systems, and soil pH and salinity. Moreover, the three mangrove species were found to influence the diversity of elemental and enzymatic stoichiometry through differences in the soil microenvironment, which can promote biodiversity in wetland ecosystems. These findings provide a useful guideline to develop strategies for restoration of estuarine wetlands.     

Differences in regeneration between hurricane damaged and clear-cut mangrove stands 25 years after clearing

The effect of human disturbance on mangrove forest may be substantially different from the effects of natural disturbances. This paper describes differences in vegetation composition and structure of five vegetation types in two mangrove areas near Darwin, Australia, 25 years after disturbance. The vegetation in clear-felled forest showed more adult Avicennia marina than in the hurricane-affected forest, and a virtual absence of A. marina juveniles and saplings. This indicates that A. marina will be replaced by other species in the canopy, showing a multi-phase vegetation development in mangrove forest after human disturbance. The mechanism of disturbance and the conditions after clearing therefore affects the vegetation composition for at least 25 years after this disturbance took place.     

Nutrients and heavy metal contamination of plants and sediments in Futian mangrove forest

An ecological survey was carried out to determine the levels of nutrients and heavy metals in the sediments and leaf tissues of two dominant mangrove plant species, Kandelia candel and Aegiceras corniculatum, in Futian mangrove forest, Shenzhen, the People's Republic of China. The spatial and seasonal variations of these elements were also investigated. The results show that there was no major difference between two sampling sites 150 m apart. In both sites, the sediment concentrations of total and NH₄ ⁺-N, total and extractable P, total and extractable K, total organic carbon were consistently higher in the landward locations and decreased gradually towards the sea. The sediment sample collected at the seaward edge of the mangrove plant community had the lowest levels of nutrient and organic matter. The vertical variations (from the land to the sea) of sediment heavy metals were less obvious and no particular trend could be identified. Extremely high contents of Cu, Cd, Pb, Cr and Zn were found at certain locations, suggesting the occurrence of some local contamination. The mean total metal concentrations in sediments decreased in the order Mn > Zn > Cu > Cr = Pb > Cd for the sample locations. Most of the heavy metals were not in a bioavailable form as the concentrations of extractable metals were relatively low (< 1% of total metals). Pb, Cr and Cd were not detected in leaf samples. Leaf C, N, P and K contents were similar between the two species and no significant difference was found among locations, although A. corniculatum seemed to have lower Mn concentrations than K. candel. With reference to temporal variations, no significant difference in sediment concentrations of some nutrients and metals was found between the spring and autumn seasons.