Rhizophora stylosa, commonly known as the spotted mangrove, red mangrove, small stilted mangrove, or stilt-root mangrove, is a significant mangrove species found in your region of Caboolture, Queensland, Australia, and across a wide range of the Indo-Pacific.
Here's a breakdown of its key characteristics and habitat:
Characteristics:
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Size: It's a small to medium-sized evergreen tree, typically growing up to 15 meters (50 ft) tall, although it can reach up to 30 meters in more tropical areas. The trunk can have a diameter of up to 25 centimetres (10 inches), sometimes more.
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Stilt Roots: A defining feature is its numerous, arching stilt roots (prop roots) that emerge from the lower trunk and sometimes from lower branches, providing support in the soft, muddy substrate. These roots also have lenticels for gas exchange, allowing the tree to "breathe" in oxygen-poor sediments.
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Bark: The bark is usually dark brown to black and can be fissured.
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Leaves: The leaves are opposite, typically obovate to elliptic in shape, measuring 6-14 cm long and 3-8 cm wide. They are thick, glossy, and hairless (glabrous) with a pointed tip (caducous mucro). The lower surface often has reddish corky dots. The petiole (leaf stalk) is 1-3.5 cm long, and the stipules (small leaf-like appendages at the base of the petiole) are 2-4 cm long and often yellowish.
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Flowers: The small, inconspicuous flowers are typically greenish-cream to pale or dark yellow. They grow in branched inflorescences (2-8 flowers per cluster) that arise from the leaf axils on long, slender, often yellowish stalks. The petals are linear and hairy along the margins, and the calyx lobes are pale yellow and recurved.
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Fruit: The fruit is brown, ovoid to pear-shaped, and relatively small, measuring 2-4 cm long.
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Propagules: Rhizophora stylosa exhibits vivipary, meaning the single seed inside the fruit germinates while still attached to the parent tree. The seedling develops a cylindrical stem called a hypocotyl, which can grow to 20-50 cm (or even up to 65 cm in tropical areas) before falling. This elongated propagule floats vertically and can establish roots quickly when it reaches suitable land.
Habitat and Distribution:
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Geographic Range: Rhizophora stylosa has a wide distribution across the Indo-Pacific region, including:
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Asia: Japan, China, Taiwan, Cambodia, Vietnam, Malaysia, Indonesia, Philippines, Singapore, Thailand, Myanmar (Burma), Brunei, Micronesia, Papua New Guinea, Samoa.
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Australia: Western Australia, Northern Territory, Queensland, New South Wales.
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Pacific Islands: Many areas across the Pacific.
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Specific Habitat: It typically grows in sandy beaches and coral terraces on seashores and in saline mud in river estuaries. It is often found on the seaward side of mangrove swamps and can tolerate more wave action than some other mangrove species. In some areas, it can also extend upstream along tidal waterways that remain brackish.
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Co-occurring Species: In mangrove communities, it is often found growing alongside species like Avicennia marina (Grey Mangrove), Ceriops australis, Ceriops tagal, Rhizophora apiculata, Rhizophora mucronata, and Sonneratia alba.
Ecological Importance:
Like other mangroves, Rhizophora stylosa plays a crucial role in coastal ecosystems:
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Coastal Protection: Its dense stilt roots help stabilize shorelines, reduce erosion, and dissipate wave energy, providing protection against storms and sea-level rise.
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Nursery Habitat: The intricate root systems provide shelter and nursery grounds for various fish, crustaceans, and mollusks, many of which are commercially important.
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Water Filtration: Mangroves help filter pollutants and sediments from coastal waters, improving water quality.
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Carbon Sequestration: They are highly efficient at storing carbon dioxide, playing a role in mitigating climate change.
