红树林水生动物栖息地功能及其渔业价值

红树林生长于热带、亚热带海陆交界的生态敏感带,其根系为生活于潮间带高度异质环境下的生物提供了适宜生境:藻类、双壳类、甲壳类等大量附生于红树根部;红树的呼吸根、支柱根、树干、倒落的枝条和残骸等,与沉积物形成的松软基质为大量底栖动物提供栖息地,根部结构间的空隙成为虾类、蟹类和鱼类等游泳动物的优良避难所和索饵场。红树林凋落物以碎屑形式进入食物网,连同浮游植物、附生藻类和底栖微藻等,是红树林生态系统的碳循环重要组成部分,为红树林区水生动物提供了丰富的食物来源。可见,食物来源丰富、隐蔽性强、捕食压力低等特点使得红树林成为水生动物的理想栖息地,许多水生动物选择在其中度过部分或完整生活史。另外,红树林也是重要经济动物(鱼、虾、蟹类)的育苗场,为近岸鱼类种群的补充和渔业活动提供支持。为合理开发红树林区渔业和有效保护红树林湿地生态系统,从生境价值、凋落物在红树林生态系统食物网中的贡献等方面总结了红树林栖息地功能及其渔业价值,提出今后的研究方向应将红树林的栖息地功能从其它河口、近岸栖息地中分离出来,甄别不同栖息地间的动态关系及其对渔业的影响。     

Plant-animal interactions and the structure and function of mangrove forest ecosystems*

Trophic interactions involving plants and animals in tropical mangrove forests have important controlling influences on several population, community and ecosystem-level processes. Insect herbivores remove up to 35% of leaf area from some mangrove tree species and can cause the death of seedlings. Leaf chemistry and toughness and soil nutrient status all appear to be important in explaining the between- and among-species variance in leaf damage. Insects also attack and damage, mainly by boring, a large proportion of mangrove seeds. Shadehouse experiments have shown that such post-dispersal predation can have a significant effect on seedling survival, growth and biomass allocation to leaves, stems and roots. Sesarmid crabs are also responsible for severe post-dispersal seed predation. In field trials, crabs consumed more than 70% of the seeds of five tree species. For four of these five species there was an inverse relationship between seed predation rate and the dominance of conspecific adult trees, while the within-site distribution pattern of one tree species appears to be partially controlled by crabs. The same crab species also consume 30–80% (depending on forest type and intertidal elevation), of the annual litter fall in mangrove forests and, thus, have an important role in controlling the rate of remineralization of detritus within forests and the export of particulate matter from the forests to other nearshore habitats. The other major component of litter in the forests is wood, which is broken down relatively rapidly by teredinid molluscs (shipworms). More than 90% of the weight loss from decomposing trunks of Rhizophora species during the first four years of decay is through ingestion by teredinids. The annual turnover of dead wood mass in Rhizophora forests is equivalent to that of the processing of leaf detritus by crabs. Because of the relatively low species richness of trees and consumers in tropical mangrove forests, they are likely to serve as productive sites for further investigations of the influence of plant-animal interactions on the dynamics of tropical forests.     

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.     

Modern bivalve shell assemblages on three atolls offshore Belize (Central America,Caribbean Sea)

The Belize atolls—Glovers Reef, Lighthouse Reef and Turneffe Islands—show differences in geomorphology, lagoonal depth, bottom sediment, growth of mangroves and sea-grass, exposure to waves and currents as well as in their sedimentation rates and their age. Bivalve shell assemblages in lagoonal areas reflect these geomorphological differences. On each atoll, 32 to 44 recent sediment samples were taken (total number of samples 111) and bivalve shells subsequently identified. The resulting database (32,122 bivalve shells in total) was analysed using Q-mode cluster analyses. Both the distribution of species characteristic of different lagoonal habitats and the distribution of bivalves with different life and feeding habits were investigated. Epifaunal suspension feeders were found particularly on hard-bottom along the reef-crests or clinging to mangrove roots. Infaunal suspension feeders show a more diverse distribution. Deeper lagoonal parts and areas with mangrove growth are often inhabited by chemosymbiont-carrying bivalves, indicating locations of reduced sediment. Deep burrowing detritus feeders are very abundant in shallow-water areas with moderate to high water agitation and were seldom found in Halimeda-rich sediments.     

Feeding mechanisms, and their variation in form, of some adult ground-beetles (Coleoptera: Caraboidea)

The structure of the mouthparts and foregut of some caraboid beetles has been correlated with their type of feeding mechanism. These may be adapted to fragmentary feeding, fluid feeding (where pre-oral digestion is important), or to mixed feeding (a large category which ranges from a mainly fluid to a mainly solid intake). Head structures concerned with feeding have been discussed in relation to these methods; they include the mandibles, maxillae, labrum-epipharynx and anterior foregut, proventriculus, labium-hypopharynx and the head floor. Different types of head floor were denned in relation to gular structure, in particular the presence or absence of the mid-gular apodeme. Convergent evolution of feeding mechanisms was noted amongst both fragmentary feeders and fluid feeders; in the latter group, sucking pumps have been evolved in the Carabitae, Scarites , Cicindelidae, Paussini and some other caraboids. It was suggested that head shape in caraboids may reflect locomotory adaptations more frequently than feeding adaptations.     

SEXUAL DIMORPHISM AND DIVERGENCE IN WINTER FORAGING BEHAVIOUR OF THREE-TOED WOODPECKERS PICOIDES TRIDACTYLUS

Measurements of 48 males and 45 females of Three-toed Woodpeckers shot in Norway revealed that the mean lengths of wing, tail, bill and tarsus of males were significantly greater than those of females. Sexual dimorphism was most marked for the bill and tarsus.
Feeding observations of the species from spruce-dominated mixed forests during the October-March period indicated an intersexual partitioning of the foraging niche. The males exhibited a stereotyped foraging pattern of bark scaling low down on the main trunks of dead spruce, whilst females used a more differentiated feeding technique and utilized a greater variety of trunk and branch sizes of dead, decaying and living trees of several different species. Significant intersexual differences were found in tree height preference and in the diameter of trunks and branches. The males foraged almost exclusively on the trunks of trees over 10 m high and over 15 cm in diameter, whilst females often frequented dead spruce, under 5 m high, and foraged on thinner trunks and branches. Foraging height was significantly lower for males than for females.
The relationship between the sexual dimorphism, the intersexual partitioning of the feeding niche and their biological significance, is briefly discussed.     

THE MANTLE AND SHELL OF SOLEMYA PARKINSONI (PROTOBRANCHIA: BIVALVIA)

The shell of Solemya exhibits considerable flexibility which is further enhanced by the marked extension of the periostracum beyond the calcareous portions of the valves. This fcature, more than any other, has made possible the habit, unique among bivalves, of burrowing deep within the substrate without direct contact with the water above. The inner calcareous layer of tho valves is restricted to a small area near the umbones while the outer calcareous layer is thin and contains a high proportion of organic material. The shell conchiolin consists mainly of protein, varying in composition, but much of it strengthcned by quinone-tanning, and in ccrtain regions probably by the presence of appreciable quantities of chitin. The ligament, although superficially resembling an amphidetic structure, is opisthodetic, the extcnsion anterior to the umbones consisting of anterior outer layer only.
The mantle is characterized by an extension of the outer fold of the mantle margin which has effected equally both the inner and outer surfaces of this fold. The secretory epithelium and the modified pallial musculature, contraction of which results in the intucking and plaiting of the periostracum, is dcscribed. Simple tubular oil glands open at the mantlo margin and are responsible for the water-repellent nature of the periostracum.
The form of the mantlelshell and that of the enclosed body are discussed and compared with those of other bivalves in which elongation of the mantle/shell is achieved in a different way. It is concluded that the mantlelshell of Solemya is of little value in determining its relationships, and that the greatly elongatod ligament, the edentulous hinge and the flexible shell are all adaptations to a specialized mode of life.     

Locomotor behavior and feeding ecology of the panamanian tamarin (Saguinus oedipus geoffroyi,callitrichidae, primates)

The Callitrichidae are a family of New World primates that exhibit a complex of behavioral and morphological characters reputedly similar to those of tree squirrels of the genus Sciurus.In particular, the locomotor behavior of tamarins and marmosets has been described as “squirrel-like. ” In this paper I describe a field investigation of the locomotor behavior and ecology of the Panamanian tamarin (Saguinus oedipus geoffroyi)and the redtailed squirrel (Sciurus granatensis).From January through August 1978, a total of 1200 hr was spent observing freeranging populations of tamarins and tree squirrels in an area of secondary forest on the Pacific Coast of Panama. Observations were made using an instantaneous time sampling technique. Individual activity records were collected on focal animals and recorded at 2.5-min intervals throughout the day. The following information was collected: (a) nature and structure of the substrate exploited, (b) activities on these supports and/or types of resources procured, and (c) body posture involved in the use of these supports. Data presented indicate major differences in substrate preference and positional behavior in tamarins and tree squirrels. Unlike squirrels, tamarins avoid vertical and sharply inclined supports during travel. Movements through the canopy is accomplished by a series of long leaps which begin and end on thin terminal supports. However, the Panamanian tamarin spent numerous hours clinging to large vertical trunks while feeding on plant exudate. Gums comprise 23.O% of the noninsect portion of the tamarin diet. The relationships between small body size, claw-like nails, substrate preference, and positional behavior are discussed. Claw-like nails enable this primate to exploit a food resource that would otherwise be inaccessible. The interrelationship between environment, behaviour, and morphology provides a frameworks from which to understand callitrichid adaptations. These adaptations are not convergent with those of the sciurid rodents. An earlier draft of this paper was presented at the 48th Annual Meeting of the American Association of Physical Anthropologists, San Francisco, April 1979.     

Colonization of a dynamic substrate: factors influencing recruitment of the wood-boring isopod, Sphaeroma terebrans, onto red mangrove (Rhizophora mangle) prop roots.

The isopod Sphaeroma terebrans, which bores into the prop roots of the red mangrove, Rhizophora mangle, can cause death and subsequent breakage of the inhabited root and, debatably, may reduce the support system of the tree. We examined whether different characteristics of a root or its physical setting, both of which may relate to habitat quality, influence the colonization of S. terebrans. A series of in situ experimental manipulations were conducted over 2 years. The first experimental protocol examined colonization of intact root substratum. Free-hanging aerial prop roots which were previously unsubmerged were bent down and anchored underwater at high tide after which the colonization of S. terebrans was monitored. A second manipulation was performed to evaluate the relative roles of submergence depth and plant anatomy in isopod colonization preference. Detached aerial prop roots were oriented either with the root tip directed downward, or upside down with the root tip directed upward but at a constant water depth. Additionally, detached aerial prop roots were oriented so that their tips were in contact with the sediment surface in order to investigate whether colonization on grounded roots was prevented by benthic predators. For all experiments, colonization began within 24 h; juveniles were the predominant colonizers. The submergence depth of a prop root, a characteristic of a root's physical setting, was consistently the strongest component correlated with the abundance of colonizing S. terebrans. The root-quality feature of root diameter was also found to play a significant role in colonization. Biotic influences, such as predation, however, did not influence recruitment of the isopod onto a root. Additionally, the absence of burrowing on grounded roots appeared to be related to intrinsic plant features. Along a root there was a strong preference by S. terebrans to colonize the root tip region (i.e., youngest part of the root) especially when these roots were also the deepest. The results of our experimental manipulation using natural root substratum are the first to identify physical setting as an important feature of habitat suitability for S. terebrans.     

The Grapsidae and Ocypodidae (Decapoda: Brachyura) of Tanzania

Twenty-nine species of the Grapsidae and 15 species of the Ocypodidae were collected from the littoral zone in the area around Dar es Salaam. Nine species of Grapsidae and three of Ocypodidae were new records for the East African area, bringing the total of recorded species for the region to 35 and 26 respectively. The distribution of these crabs indicates a very limited endemism in the western Indian Ocean, with the majority of species forming an attenuated extension of the abundant Indo/West Pacific brachyuran fauna.
The habitat preference of each species is described. Within each subfamily there is a relative uniformity in general habitat preference, mode of life and manner of feeding. The species of each subfamily are then separated by substrate choice and preferred level on the shore. The greatest numbers of species occur in the most diverse habitats—the creek mangrove, the coastal mangrove and the reef flat.     

Branch-fidelity in the tree crab Sesarma leptosoma (Decapoda, Grapsidae)

Sesarma lepzosoma is the only species of crab inhabiting the mangrove swamps of East Africa which can climb to the top of tall mature trees, where it feeds on fresh leaves. Twice daily, in the morning and evening, this crab performs mass migrations towards the canopy and spends about three hours on the tree-tops. At dusk it descends to spend the night among the aerial roots of the tree. Two observation stations were built on a Rhizophora mucronata tree, up to 13 metres above ground level, to observe and record the feeding and spatial aspects of the behaviour of this species during its time in the canopy. Observations on the daily migrations of marked specimens showed that the crabs are faithful to a well-defined feeding site; moreover, the migration paths of the marked specimens were exceptionally constant over the whole of the two-month study period. S. leptosoma was observed to feed on mature fresh leaves by scraping the lower surface of the leaf with its chelae. It was also found to spend most of its time on leaf-buds in a particular stage of development. Water which accumulates among the scales covering these buds represents an important water supply for these crabs, which they prestmably use to reduce physiological stress due to water loss. Feeding-site fidelity in S. leptosoma seems to be related more to the chance of finding suitable leaf-buds, which are relatively rare and patchily distributed, than finding leaves, which are abundant and uniformly distributed all over the canopy.     

Exudates as a fallback food for Callimico goeldii

Fallback foods have been defined as resources for which a species has evolved specific masticatory and digestive adaptations, and are consumed principally when preferred foods are scarce. In the present field investigation, we examine fungi, fruit, and exudate consumption in one group of Callimico goeldii in order to determine the importance of exudates as a fallback food for this species. Based on a total of 1,198 hr of quantitative behavioral data collected between mid-November 2002-August 2003, we found that pod exudates of Parkia velutina accounted for 19% of callimico feeding time in the dry season. This resource was not consumed in the wet season when fruits and fungi were the most common items in the diet. In the dry season of 2005 (July), the same callimico study group did not consume Parkia pod exudates. Instead, the group ate exudates obtained from holes gouged in tree trunks by pygmy marmosets and exudates resulting from natural weathering and insect damage on trunks, roots, and lianas. Pod exudates are reported to contain greater amounts of readily available energy than do trunk and root exudates, and were consumed throughout all periods of the day, particularly in the late afternoon. Trunk and root exudates were consumed principally in the morning. We propose that digestive adaptations of the hindgut, which enable callimicos to exploit fungi (a resource high in structural carbohydrates) year-round, predispose them to efficiently exploit and process exudates as fallback foods when other resources, such as ripe fruits, are scarce.     

Mollusks associated to the submerged roots of the red mangrove,Rhizophora mangle (L.), in the Gulf of Santa Fe,Sucre State,Venezuela

A qualitative and quantitative monthly study of the mollusks community associated to the submerged roots of the red mangrove, Rhizophora mangle (L.), between October of 1998 and September of 1999, in six stations of the Gulf of Santa Fe, (Sucre State, Venezuela). Were collected 4,704 specimens, 45 species of mollusks were identified (22 gastropods, 15 bivalves and 8 chitons). The most abundant species were: Crassostrea rhizophorae, Isognomon bicolar, I. alatus and Brachidontes exustus. The highest values in diversity and evenness, and the smallest dominant values, were in the stations three and four, while the opposed happened in the stations one and two. The analysis of likeness showed that in the first five stations the space variations in the composition of the community are bigger than the temporary variations, while in the station six the temporary differences prevail. They were factors that could be important to determine the structure of the community, as vicinity to other ecosystems and/or specific biological aspects of the species like adaptations to fluctuating conditions, nutritious habits and migration in search of shady and protected atmospheres.     

Vertical clinging, small body size, and the evolution of feeding adaptations in the Callitrichinae.

Primates of the subfamily Callitrichinae (Callimico, Callithrix, Leontopithecus, and Saguinus) are small-bodied New World monkeys (105-700 g) possessing clawlike nails on all manual and pedal digits excluding the hallux. Specialized nails in these genera serve a critical function in feeding by enabling tamarins and marmosets to cling to trunks and other large vertical supports while exploiting food resources. Within the subfamily, there is evidence of at least four distinct large-branch feeding patterns. These include (1) seasonal exudate feeding and occasional trunk foraging (many Saguinus spp.); (2) exploitation of bark surface insects and the use of trunks as a platform to locate terrestrial prey (Saguinus fuscicollis, S. nigricollis, and Callimico); (3) manipulative foraging and bark stripping to locate concealed insects and small vertebrates (Leontopithecus); and (4) tree gouging and year-round exudate feeding (many Callithrix). Large-branch feeding and the use of vertical clinging postures appear to be a primary adaptation among virtually all callitrichines, distinguishing them ecologically from other platyrrhine taxa. Given the anatomy and behavior of extant callitrichines, Saguinus appears to be the most ecologically generalized member of this subfamily, and species of this genus may provide useful models for reconstructing the feeding and foraging adaptations of early callitrichines.     

Sustained high levels of foliar herbivory of the mangrove Rhizophora stylosa by a moth larva Doratifera stenosa (Limacodidae) in north-eastern Australia

The moth larva, Doratifera stenosa (Lepidoptera: Limacodidae), was observed feeding voraciously in great numbers on mature leaves of Rhizophora stylosa in mangroves at Port Curtis in Central Queensland, NE Australia. This behaviour was considered unusual since mangroves, and the Rhizophora species in particular, reportedly harbour few herbivores and have relatively low levels of herbivory, less than 10%. During a two year period (1996–1998), larvae were observed consuming around 30–40% of leaves in the canopy each year, and the mangroves appeared able to sustain these high levels of herbivory. The impact on trees was assessed in conjunction with a study of the herbivore, its behaviour and life history, in an attempt to explain the occurrence. Larvae were 1–2 cm in length, bright green and gregarious, with numerous small, stinging hairs along their upper bodies. Feeding was in small cohort groups of 5–70 individuals that broke up immediately prior to each moult after which they regrouped in much larger numbers of mixed cohorts to form single-file processions across branches, stems and prop roots. In this way, they moved to neighbouring trees with less affected foliage. One of the outstanding characteristics of this herbivore was its ability to desist from killing host trees although it appeared quite capable of doing so had it remained on individual trees. By moving from tree to tree, the herbivore was able to heavily crop Rhizophora foliage in an apparently sustainable manner. These findings demonstrate the role and importance of foliar herbivory in severely affected forests and how such instances best not be ignored or treated as curiosities in future assessments of herbivory and forest turnover in mangrove ecosystems.     

THE WINTER FEEDING ECOLOGY OF WIGEON AT BRIDGWATER BAY, SOMERSET

The feeding ecology of Wigeon wintering in the vicinity of Bridgwater Bay National Nature Reserve is described. The birds roost on mudflats in the Bay during the day and feed, mainly at night, on saltings and wet pastures in the surrounding area. Their food, ascertained from gut analyses, consists largely of grass leaves; with roots, stolons, bulbils and seeds of secondary importance. Analyses including gizzard contents much exaggerated the importance of seeds because they are retained in the gizzard for longer than softer items.
An investigation of Wigeon feeding behaviour and food preferences on salting pasture is described, using the density of the birds' droppings on different vegetation zones to assess usage, and faecal analysis to determine the composition of the selected diet. The technique of faecal analysis is discussed in relation to feeding studies on grazing wildfowl.
Disturbance is a very important factor affecting the availability of feeding habitat, and this can mask the birds' food preferences. Early in the winter, Wigeon select Puccinellia maritima in preference to Agrostis stolonifera and Festuca rubra. They do this initially by selecting the broad zone in which they feed, by selecting feeding sites within zones, and particular plant species from a mixed sward. The birds are more selective when feeding in less preferred zones. The mechanisms and reasons for food selection are discussed in relation to characteristics of the habitat and of the plants. It is concluded that the nutritional value of the plants is important in determining the birds' preference, but that other factors also play a part.
Wigeon are flexible in their feeding habits and are increasingly found on inland habitats. They are adaptable in using new roosts, and in modifying their behaviour in response to changes in food supply and changes in disturbance pressures.     

Changes in hydraulic conductivity, mechanical properties, and density reflecting the fall in strain along the lateral roots of two species of tropical trees

Roots have been described as having larger vessels and so greater hydraulic efficiency than the stem. Differences in the strength and stiffness of the tissue within the root system itself are thought to be an adaptation to the loading conditions experienced by the roots and to be related to differences in density. It is not known how potential mechanical adaptations may affect the hydraulic properties of the roots. The change in strength, stiffness, conductivity, density, sapwood area, and second moment of area distally along the lateral roots of two tropical tree species in which the strain is known to decrease rapidly was studied and the values were compared with those of the trunk. It was found that as the strain fell distally along the roots, so did the strength and stiffness of the tissue, whereas the conductivity increased exponentially. These changes appeared to be related to differences in density. In contrast to the distal-most roots, the tissue of the proximal roots had a lower conductivity and higher strength than that of the trunk. This suggests that mechanical requirements on the structure rather than the water potential gradient from roots to branches are responsible for the general pattern that roots have larger vessels than the stem. In spite of their increased transectional area, the buttressed proximal roots were subjected to higher levels of stress and had a lower total conductivity than the rest of the root system.     

Shell colour polymorphism in a mangrove snail Littorina sp. (Prosobranchia: Littorinidae)

Shell colour polymorphism was examined in populations of a mangrove snail Littorina sp. in Queensland, Australia. Three morphs were recognized, yellow, red and brown, and morph frequencies varied both between widely spaced populations and between islands less than 1 km apart. Morph frequencies also varied with time of year. There was a relationship between shell colour and position on the tree, with yellow snails more often occurring amongst the foliage and brown snails more often on trunks and branches. In some populations yellow snails appeared to survive better than the other morphs, while in other populations there was no difference. The evidence for the maintenance of the polymorphism by natural selection is discussed.     

A comparative study of territory in the Reed warbler (Acrocephalus scirpaceus) and Sedge warbler (A. schoenobaenus)

Various aspects of territoriality were studied comparatively in a marked population of Reed and Sedge warblers at the Attenborough Nature Reserve, Nottinghamshire. Differences in arrival patterns, establishment of territory and particularly territory size were detected. In view of the dynamic nature of territory boundaries, a method is described for obtaining measures of mean territory size for comparative purposes. The sympatric species were largely separated by different breeding and feeding habitats, but there was also a degree of interspecific competition in some areas and interspecific territorialism was found to occur. Adults of both these migratory species were found to exhibit strong site fidelity, and there was some evidence to suggest that early post-fledging experience may influence initial selection of a particular area and territory for first breeding.
The adaptive significance of territory is discussed in relation to the findings presented and current hypotheses. There was some evidence which suggests that reduction of predation pressure and intraspecific interference through spacing out, as well as provision of a nest-site may be important functions of territory in these species, but no evidence that food supply or population regulation are involved. The significance of interspecific territorialism is considered in relation to interspecific competition. The various factors effecting territory size and the patterns of nesting dispersion are also considered in an attempt to account for the striking interspecific differences found between these closely related species. It is concluded that although a multiplicity of factors may well be interacting in complex fashion, the more important of these stem from contrasts in the physical properties of the two habitats.     

Nutrient partitioning and storage in arid-zone forests of the mangroves Rhizophora <Emphasis Type="Italic">stylosa</Emphasis> and <Emphasis Type="Italic">Avicennia</Emphasis><Emphasis Type="Italic">marina</Emphasis>

Mangrove partitioning and storage of macronutrients and trace metals were examined in different arid coastal settings of Western Australia. Total living biomass in three Rhizophora stylosa forests, which ranged from 233 to 289 t DW ha^-1, was significantly greater than biomass in three Avicennia marina forests (range: 79-155 t DW ha^-1). Although prop roots and stems were the largest single tree components for R. stylosa and A. marina, respectively, most nutrients were stored in leaves and living roots of both species. However, only a small fraction of the total nutrient pool was vested in tree biomass; the vast bulk was in soils. A large below-ground pool of dead fine roots was identified at all stands, equivalent to 36-88% DW of total living tree biomass. The amount of Ca, S, Cl, Na, Si, Fe, Mn, Zn, B, Mo and Cu vested in dead roots of both species was greater than in the total living tree biomass. The proportion of Fe and S vested in live and dead roots was exceptionally large, consistent with previous evidence of metal plaques on mangrove roots. Sulphur, iron and zinc in dead roots of both species constituted the bulk of these metals. R. stylosa trees preferentially accumulated more Mg, S, Cl, Na, Si, Fe, Mn, B and Mo than A. marina trees. Proportionally greater storage of P, N, Ca, K, Cu and Zn occurred in two of the three A. marina forests. Foliar concentrations of Mg, S, Mn, B and Mo in mangrove leaves were at the high end of the range reported for other tropical trees, but other elemental concentrations were at the low or mid-range. Nitrogen limitation in these forests is implied by a positive correlation between total tree N and net canopy production and by a lower percentage of ecosystem N in tree biomass as compared with other forests. Unlike terrestrial forests where a large proportion of nutrient capital is vested in floor litter, most elements in these mangrove forests are stored in dead roots. A large reservoir of dead roots below the forest floor may serve as a conservation mechanism, particularly in such arid oligotrophic environments.