光照条件对蒙古栎幼苗生长及形态特征的影响

对生长于不同光照环境(林内和林外)下的蒙古栎幼苗的形态特征进行了比较.结果表明,光照条件对蒙古栎幼苗的生物量及其分配具有明显影响,林外幼苗单株生物量为林外的4.48倍,其中以根系生物量的差别为最大,林外为林内的6.23倍;林外与林内幼苗根冠比分别为2.70和1.11.在不同的光照条件下,蒙古栎幼苗的叶片形态表现出明显不同,林外叶片比叶面积明显低于林内,分别为139.55cm2/g 和284.94cm2/g,林内约为林外的2.04倍;一次生长叶面积林外明显低于林内,总叶面积则高于林内.二次生长使蒙古栎幼苗的叶面积有明显增加,但是经过二次生长后,幼苗的单株生物量没有明显增加,说明二次生长叶片对于蒙古栎幼苗生物量的积累没有明显贡献;光照对于蒙古栎主干及根系的形态具有明显影响,林外幼苗高(包括二次生长)明显低于林内幼苗,而地径则相反,林外幼苗根系的长度和直径则明显高于林内幼苗;林外幼苗顶芽体积明显大于林内幼苗.同时,林外幼苗的二次生长导致顶芽体积明显下降,从而对翌年的高生长量和未来干型产生影响.认为,蒙古栎幼苗通过形态上的一系列可塑性变化来适应不同的光环境以获取最大的碳收益.     

土壤结构与光照水平对秋茄某些生长和生理参数的影响

在香港的３个红树森样地即黄竹湾（沙土）、西径（沙壤土）和米埔（粘壤土）进行了土壤结构对秋茄（Kandelia candel(L.)Durce)生长和生理影响的研究,并在米埔比较了林内和林外秋茄幼苗的生长和生理参数以观察光照水平的效应。在沙土和沙壤土生长的１．５年秋茄幼苗比粘壤土具有较粗的基径的较高的总生物量,说明秋茄幼苗在沙土和沙壤土中比在粘壤土中生长更好。沙土１．５ 茄幼苗的叶片厚度分别为沙壤土和粘壤土的１．７５和２．０５倍,表明沙土中的秋茄幼苗具有旱生结构以维持体内水分。然而,沙土和沙壤土４．５年秋茄幼树的叶片厚度无显著差异,沙土和沙壤土中１．５年秋茄幼苗分配于根系的生物量比例约为５０％,高于粘壤土的值（约４０％）。沙土和沙壤土中１．５年的秋茄比粘壤土具有较低的叶绿素含量、根系活力、硝酸盐还原酶活性、过氧化物酶（ＰＯＸ）活性、超氧化物歧化酶（ＳＯＤ）活性及较高的丙二醛（ＭＤＡ）含量。米埔１．５年秋茄幼苗在红树林外比林内有更好的长势,具有更大的叶面积、特殊叶面积、叶片数量及生物量。林内幼苗具有较高叶绿素含量,较低叶绿素a/b比值,较高硝酸盐还原酶活性和较强的根系活力,林外幼苗的叶片ＰＯＸ和ＳＯＤ活性比林内的值稍高,ＭＤＡ含量比林内显著要高。     

深圳湾引种红树植物海桑的幼苗发生和扩散格局的生态响应

海桑（Sonneratia caseolaris）是我国华南沿海主要红树林造林树种,在深圳湾引种造林15年后,在天然红树林和光滩中出现了大面积的扩散。为了研究深圳湾红树植物海桑的幼苗扩散及其与生态因子的关系,作者采用样线和样方调查法于2006年9月至2007年9月对深圳福田红树林内天然扩散的海桑幼苗的密度、高度和盖度及其相关生态因子（包括种间竞争、群落类型、光照、扩散距离与滩面高程）进行了6次调查。天然红树林和人工海桑林林下海桑幼苗密度在调查初期分别为24．7棵/m^2和19．7棵／m^2,到2007年9月林下的一年生海桑幼苗全部死亡,说明林下的弱光生境显著抑制了海桑幼苗的早期生长和自然更新。不同林型下（包括天然白骨壤林和秋茄林、人工海桑林）的海桑幼苗的密度、高度、盖度差异不显著（P〉0．05）;而林中空地各指标显著高于林下（P〈0．05）。虽然深圳福田红树林滩面高程介于1．12—2．10m（黄海平均海平面）之间,海桑幼苗自然扩散分布的最适滩面高程是1．40-1．60m,属于深圳湾红树林的中高潮滩,但幼苗密度与滩面高程之间相关性较小。海桑具有一定的长距离扩散能力,天然白骨壤林和秋茄林下海桑幼苗密度与其扩散距离（距最近母树的距离）之间呈显著负相关。天然白骨壤林和秋茄林下海桑幼苗密度与光照强度相关性不显著（P〉0．05）,而人工海桑林林下的海桑幼苗密度与光照强度呈显著正相关,且相关系数逐次增大,说明海桑幼苗的早期生长受到光照强度的影响极为显著。因此,深圳湾引种海桑的繁殖体在天然白骨壤林和秋茄林下的扩散主要受与母树距离的影响,但在海桑人工林下光照强度是影响幼苗分布的最重要生态因子。     

广东湛江红树林国家级自然保护区优势乔木群落的物种组成及结构特征

针对湛江红树林自然保护区的优势乔木群落, 根据优势种重要值大小对群落类型进行了划分, 进一步从立木、苗木和幼苗3 个层次对群落物种组成及结构特征进行了研究。结果显示: 4 科6 种红树植物组成11 个优势乔木群落。无瓣海桑群落分布最广, 平均胸径、高度和冠幅面积显著大于红海榄、秋茄、桐花树和白骨壤优势群落, 但无瓣海桑群落物种多度较低, 群落内无瓣海桑对秋茄有显著抑制作用; 白骨壤和秋茄优势乔木群落的多样性指数较高。红树林优势乔木群落林下层植被组成贫乏、结构简单, 以桐花树、秋茄和白骨壤为主; 林下苗木数量多于幼苗; 白骨壤幼苗占总量的67.1%。未来红树林恢复仍要重视本地红树物种, 建议加强白骨壤作为恢复物种的研究。     

模拟海平面上升对红树植物秋茄的影响

研究了壤质沙土 (粗质土 )和粘土 (细质土 )条件下红树植物秋茄 (K andelia candel)对水位上升和淹水时间延长的反应。模拟海平面上升 30 cm导致红树林土壤的酸化 ,且细质土的酸化比粗质土严重 ;秋茄繁殖体的萌苗速度明显加快 ;促进秋茄的早期生长 ,尤其是导致最初 2个月茎高生长的增加 ,然而 ,后 2个月秋茄的相对生长率并不因水位的升高而增加 ;地下部 /地上部生物量比减小 ,在粗质土中尤为如此 ;幼苗粗根比例明显增加 ;叶片叶绿素 a/ b比值下降。在微型盆栽试验条件下 ,无论是高水位还是低水位 ,所有的秋茄繁殖体均成功萌发且幼苗在整个试验期间均成活。在野外条件下 ,秋茄幼苗成活率在高水位和低水位条件下均高达 90 %以上。野外条件下 ,无论是经胚轴萌发还是幼苗移栽的幼苗 ,最初 4个月的茎高生长均为低潮区高于高潮区 ,与微型试验结果相同。微型盆栽试验和野外种植试验均表明 ,海平面上升 30 cm对秋茄的萌发和早期生长具有促进作用     

拉关木小苗在白骨壤林内及林缘生长实验研究

探讨引进的红树植物拉关木(Laguncularia racemosa)是否对本土红树植物白骨壤林(Avicennia marina)造成入侵风险。通过野外种植实验, 将1年生拉关木苗种植在成熟白骨壤林的林内和林缘, 每月观察记录并测量其生长指标。结果表明: 白骨壤林内和林缘的1年生拉关木苗的月均苗高增量变化趋势相似, 均表现为夏季高, 冬季低; 月均基径增量表现为林内低于林缘, 且随着种植时间的延长而降低。白骨壤林内和林缘的拉关木苗野外种植13个月后的苗高增量仅为14.1 cm和13.5 cm, 基径增量仅为1.0 mm和1.5 mm, 叶片数增量均为负值, 分别为-0.4片和-0.7片, 可见外来种拉关木苗在厦门海沧湾的白骨壤林内及林缘生长速度缓慢, 不具有速生快长特性, 因此, 外来红树植物拉关木只有在其适宜生长的环境才能表现出速生的特性。种植13个月后, 白骨壤林内和林缘拉关木苗的存活率仅为4.7%和5.3%。表明由于光照强度、低温等环境因子的限制, 引进种拉关木小苗很难通过自然扩散在厦门本土红树植物白骨壤林内自然更新生长。     

两种红树植物白骨壤(Avicennia marina )和桐花树(Aegiceras corniculatum)的耐淹性

以两种红树植物白骨壤（Avicennia marina（Forsk.）Vierh.）和桐花树（Aegiceras corniculatum （L.） Blanco）幼苗为材料,在梯度海面高程的野外人工平台上开展了为期1a的淹水胁迫实验。3座平台作为重复,每座设置8个梯度,相邻梯度间高度相差10cm,幼苗立地基质平面的海面高程320~390cm。实验1a后测定1a幼苗的生长状况及与一些生理指标。结果表明：小高程生境对两种幼苗茎的纵向生长均有显著促进作用,但白骨壤幼苗茎生长高度是桐花树的7.5倍。与白骨壤相比,桐花树幼苗有较高的叶片保存率。白骨壤幼苗生物量在各器官分配为：茎〉根〉叶,3个器官平均所占比例分别为56.7%,25.7%和17.6%;桐花树则为：叶〉根〉茎,3个器官平均所占比例分别为49.6%,33.0%和17.4%。小高程生境对白骨壤幼苗全株生物量有较强的促进效果,桐花树幼苗则在中等高程生境中有较大生物量。在任一高程组,桐花树幼苗叶片叶绿素含量均大于白骨壤幼苗,但两种幼苗叶绿素a/b比值差异不显著。无论在叶片还是根系中,桐花树幼苗的活性氧清除酶类活性均高于白骨壤幼苗,表明在相同高程生境中桐花树幼苗比白骨壤幼苗面临更大的困难。综合实验结果和野外观察,可看出白骨壤耐淹水能力高于桐花树;仅从植物本身的生理特性考虑,可确定北部湾沿海白骨壤造林滩面高程不宜低于平均海面30cm,桐花树不应低于当地平均海面。     

福建亚热带红树林生态学的研究

福建亚热带红树林种类计有五科五属六种,即木榄、秋茄、海漆,老鼠簕、桐花树和白骨壤。主要群落类型有秋茄+木榄-桐花树群落、秋茄+桐花树群落、秋茄群落和白骨壤群落。秋茄高生长与土壤含氮量(%)的关系呈半对数线性正相关,回归公式为log y=0.9397+3.124x(y为树高、x为含氮量)。树高与土壤含盐量呈抛物线相关。红树林生态系统中,生物因子的作用是明显的。藤壶附着于叶面或树干上,严重危害秋茄生长发育。林下相手蟹等造穴活动,有利于林下土壤通气性。浒苔、颤藻等藻类繁殖,也会影响红树生长。引种栽培要选择适当的生境和适合本地的种类、才能保证较高的成活率。     

福建亚热带红树林生态学的研究

福建亚热带红树林种类计有五科五属六种,即木榄、秋茄、海漆,老鼠簕、桐花树和白骨壤。主要群落类型有秋茄+木榄-桐花树群落、秋茄+桐花树群落、秋茄群落和白骨壤群落。秋茄高生长与土壤含氮量(%)的关系呈半对数线性正相关,回归公式为log y=0.9397+3.124x(y为树高、x为含氮量)。树高与土壤含盐量呈抛物线相关。红树林生态系统中,生物因子的作用是明显的。藤壶附着于叶面或树干上,严重危害秋茄生长发育。林下相手蟹等造穴活动,有利于林下土壤通气性。浒苔、颤藻等藻类繁殖,也会影响红树生长。引种栽培要选择适当的生境和适合本地的种类、才能保证较高的成活率。     

广西英罗湾红树植物群落的研究

 对广西英罗湾红树植物群落的种类组成、类型、外貌、结构、物种多样性和演替等进行了较系统的探讨。组成群落的优势红树植物有木榄、红海榄、秋茄、桐花树、白骨壤和海漆6种,隶属6属4科。主要的群落类型有木揽群落、木榄+红海榄群落、红海榄群落、红海榄+秋茄群落、秋茄群落、秋茄+桐花树群落、秋茄+白骨壤群落、桐花树群落、白骨壤群落、白骨壤+桐花树群落和海漆群落等11个群系。群落外貌由单叶、革质、全缘、中型叶的高位芽植物决定。群落层次结构简单．单层或两层。和陆地植物群落相比较,组成群落的红树植物的物种多样性较低。受潮滩土壤质地、养分状况、环境盐度和潮淹程度以及红树植物自身对盐渍生境的适应性等因子制约,群落的分布形成了明显的生态系列。随着海平面的相对降低和土壤理化性质的改善,群落具有向陆生植物群落演化的趋势。     

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.     

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.     

Global Patterns of Pre-Dispersal Propagule Predation in Mangrove Forests1

Mangroves in disparate families produce viviparous seedlings (propagules) that are attacked by many crab and insect predators both before and after dispersal. While post-dispersal predation is viewed as an important factor in structuring many mangrove communities, pre-dispersal predation rates and agents have been characterized for few species. Ten species of mangrove and 3299 propagules were surveyed for pre-dispersal propagule predation at 42 sites around the world. Pre-dispersal predation rates were variable among sites and species, ranging from 0 to 93 percent within sands, with a global total predation rate of 23.3 percent (across all propagules examined) and a mean level of 28.3 percent across sites. Grapsid crabs, Coleoptera and Lepidoptera were the primary predators identified. Forests near human population centers and stands occurring at high intertidal sites exhibited higher levels of propagule predation than those in unpopulated or low-intertidal sites. Predation rates on a species were weakly, negatively correlated with conspecific seedling density at a site. To explore temporal variation in, and ramifications of pre-dispersal predation for propagule growth and abscission dynamics, Rhizophora mangle propagules were monitored over two years at three sites in Belize, Central America. Predation did not significantly reduce hypocotylar growth of germinated propagules on the parent tree, but nearly doubled the abscission rate of premature propagules. Pre-dispersal propagule predation is a ubiquitous feature of mangrove forests world-wide, and must be accounted for in estimates of reproductive output, stand health, and propagule availability for forestry and restoration efforts.     

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     

The intertidal distribution of the grey mangrove (Avicennia marina) in southeastern Australia: The effects of physical conditions,interspecific competition,and predation on propagule establishment and survival

Abstract The upper and lower limits of the distribution of mature Avicennia marina lie between mean high water and mean sea level in open estuaries in southeastern Australia. Newly established seedlings are highly variable in abundance, but are rarely found in the saltmarsh or on mudflats. Their distribution is unlikely to be limited by dispersal because propagules disperse into the saltmarsh and to intertidal mudflats, but their establishment may be limited by physicochemical conditions, interspecific competition and predation. The model that physicochemical conditions control the intertidal limits of establishment of seedlings was accepted for propagules stranding in the saltmarsh but rejected for those stranding on mudflats. No seedlings established on saltmarsh sediments but similar numbers of seedlings established within light gaps in adult mangrove stands and on intertidal mudflats. The model that interspecific interaction with freeliving macroalgae (Hormosira banksii) reduces the establishment of seedlings on mudflats covered with macroalgae or in stands with a ground cover of macroalgae was accepted. Under controlled conditions five times as many propagules established on cleared ground compared with ground covered with macroalgae. Predators also reduce seedling establishment, but the model that they preferentially act on propagules stranding on the mudflat was rejected. The low number of seedlings found on mudflats without macroalgae appears to relate to wave and current effects on establishment and the effects of waterlogging or fouling on survival.     

木榄和秋茄对水渍的生长与生理反应的比较研究

研究了不同水渍时间对两种红树植物木榄(Bruguiera gymnorrhiza(L.)Lam)和秋茄(Kandelia candel(L.)Druce)的生长与生理的影响.随着淹水时     

Factors limiting the intertidal distribution of the mangrove species<Emphasis Type="Italic"> Xylocarpus granatum</Emphasis>

The tree species Xylocarpus granatum is commonly described as occurring in the upper intertidal zone of mangrove forests, but mature trees are occasionally found at lower elevations. In the Utwe River basin, on the Pacific island of Kosrae, we investigated the relative importance of several biotic and abiotic factors that may control the intertidal distribution of X. granatum. Factors we evaluated included differential seed predation across the lower, mid, and upper intertidal zones and seedling responses to salinity, tidal flooding, and shade. Seed predation was 22.4% over the first 34 days and varied little among zones or in gaps versus under the forest canopy. By day 161, there were still no differences in seed mortality, but a significant difference was found in seedling establishment, with much greater establishment in the upper intertidal plots. X. granatum seedlings in a greenhouse experiment exhibited greater growth in freshwater than seedlings in 23 ppt salinity, which is typical of salinity levels found in the mid intertidal zone in our field study sites in Micronesia, where mature X. granatum trees are generally absent. Seedlings grown in 23 ppt salinity, however, exhibited few visible signs of stress associated with patterns in growth. Seedlings grown in a simulated tidal flooding treatment (with 23 ppt salinity) also showed few signs of stress. Growth declined dramatically under 80% shade cloths, but there were few interactions of shading with either 23 ppt salinity or simulated tidal flooding. Differential seed predation is not likely to be the primary factor responsible for the intertidal distribution of X. granatum on Kosrae. However, seedling tolerance of flooding or salinity may be more important, especially relative to a potential contribution to secondary stress mortality. Other factors may ultimately prove to be more critical, such as physiological effects of salinity on seed germination, effects of tides on seed dispersal and rooting, or differential herbivory on seedlings.     

Dispersal,establishment and survival of Ceriops tagal propagules in a north Australian mangrove forest

Studies of the ecology of mangroves show that a wide variety of factors, including salinity, desiccation, disturbance, competition and predation, may affect the distribution and abundance of species. Field studies were done to examine the relative importance of several of these factors in the establishment and early survival of Ceriops tagal, a species common in mid-to high-shore regions of mangrove forests in northern Australia. The fate of marked and tethered propagules was followed to estimate the range of dispersal and the intensity of predation. Propagules were artificially planted under different thicknesses of shade cloth (none, 30%, 80%) and in different habitats (clearing, forest, clearing-forest fringe) to examine the effects of light and soil conditions on survival and growth. Results suggested that dispersal was very limited: only 9% of marked propagules were ever found more than 3 m from the parent tree. Losses to predators were great, with 83% of tethered propagules being damaged or consumed within 3 months. On average, 56% of planted propagules survived for at least 6 weeks and 76% of these initiated growth. Survival in clearings was lower than in other habitats, with 29% fewer surviving six weeks and 48% fewer surviving 15 months. The growth of seedlings was correlated with soil temperature, but the effects of treatments were complex. Overall, results indicated that poor dispersal and establishment were the main factors likely to limit the colonisation and population growth of this species. Received: 12 September 1995/Accepted: 14 June 1996     

厦门地区秋茄幼苗生长的宜林临界线探讨

2003年5月在厦门大屿岛白鹭自然保护区西面滩涂上试种秋茄幼苗,研究秋茄的宜林临界线.结果表明,滩涂高程为黄零0.99 m处,每个潮水周期的平均淹水时间高达8 h,幼苗成活率低于50%,生长缓慢,不适合用秋茄造林;在滩涂高程为黄零1.62 m处,秋茄幼苗成活率达90%,生物量积累最大,光合同化作用较高,生长良好,为厦门沿海秋茄的最适生长区;而在高程为黄零1.31 m处,秋茄幼苗仍能正常生长.故厦门地区秋茄造林的宜林临界线应不低于黄零1.31 m (即厦零4.55 m),平均每个潮水周期淹水不高于5.6 h.     

Differential predation on mangrove propagules in open and closed canopy forest habitats

Amounts of seed predation by grapsid crabs (Brachyura: Grapsidae) on two species of mangroves (Aegiceras corniculatum and Avicennia marina) were compared among different habitats in an Australian mangrove forest. For Avicennia, comparisons were between canopy gaps and the adjacent forest understory for six, mid intertidal, gaps of different sizes. For Aegiceras the comparisons were among canopy gaps in the high intertidal; open, accreting mud/sand banks where mangroves were colonizing in the low intertidal; and in the forest understory in both the high and low intertidal zones. These were repeated in the high salinity (35\%) downstream portion and the low salinity (0–5\%) upstream portion of a tidal river.Predation on Avicennia was significantly higher in the understory than in adjacent canopy gaps. Within a canopy opening, predation was greatest in the smallest gaps and lowest in the largest gaps. Predation on Aegiceras was greater in the high intertidal compared to the low intertidal, but no differences were found between river mouth and upstream locations. In the high intertidal zone of the forest, there were no differences in predation between canopy gap or forest understory sites for Aegiceras. In the low intertidal zone, however, significant differences in amount of predation were found between habitats. More Aegiceras propagules were consumed in the understory than on adjacent accreting sandbanks.Frequency of tidal inundation, which in turn affects the amount of time available to forage, is hypothesized to account for differences in predation between low and high intertidal forests and between small and large canopy gaps. Our results also suggest that shade intolerance in these two species may actually reflect an escape from predators, successful when the seeds are dispersed into open areas such as canopy gaps or mud banks.