Because the living environment of the land-sea junction is very special, mangroves have formed some unique characteristics to adapt to this special living environment. The most wonderful feature of mangrove is the so-called "viviparous phenomenon". The seeds of many plants in mangroves have begun to germinate in fruits and grow into rod-shaped hypocotyls before leaving their mothers. When the hypocotyl develops to a certain extent, it leaves the mother tree and falls into the mud on the beach. After a few hours, it can take root in the soil and grow into a new plant. Hypocotyl that fails to take root in the mud in time can drift on the sea for months with the current and take root and sprout on the coast thousands of miles away. The most striking feature of mangroves is dense and developed column roots, many of which grow from the base of tree trunks and firmly plunge into the mud to form a stable scaffold, which makes mangroves stand firm under the impact of waves. The pillar roots of mangroves not only support the plants themselves, but also protect the coast from wind and waves, so mangroves are also called "coast guards". Mangroves are often flooded by tides, and the air is very scarce. Therefore, the respiratory roots of many mangrove plants have thick lenticels outside and spongy ventilation tissue inside, which meets the air demand of mangrove plants. At low tide, all kinds of column roots and breathing roots are exposed to the ground, crisscrossing, making it difficult for people to pass. Tropical beaches are sunny and the soil is rich in salt. Mangrove plants are mostly halophytes and adapt to physiological drought. Plants have secretory glands that can discharge excess salt, and their leaves are bright and leathery, which is beneficial to reflect sunlight and reduce water evaporation.
Mangrove is a biological community developed in a special environment, so there are not many typical mangrove plants, and because mangrove plants can be spread to future generations by ocean currents, as long as the sea areas are connected, mangroves far away can have similar components. The African continent and the American continent separate the tropical Atlantic from the tropical Indian Ocean and the tropical Pacific Ocean, while the tropical Indian Ocean and the tropical Pacific Ocean are connected by seawater. In this way, mangroves formed two formations, the west and the east. The junction of tropical Indian Ocean and tropical Pacific Ocean is the largest archipelago in the world-Nanyang Islands, which has the longest tropical coastline and has become the development center of oriental mangroves. The mangroves in Nanyang Archipelago and its vicinity are the largest, most diverse and most lush in the world. Mangroves grow into towering trees here, up to 35-40 meters high, and are connected with tropical rain forests, so that many islands in Nanyang Islands are covered with dense forests from coast to top. Oriental flora is widely distributed in the vast tropical Indian Ocean and tropical Pacific Ocean, from the Indian Ocean coast in Africa to the Pacific islands in the east, to chatham islands, New Zealand, where the sun first rises in the new century, and to Japan and South China in the north. Mangroves are tall and diverse near the equator, with fewer species in the north-south direction and much lower trees. China is the northern edge of mangroves, and the mangroves in Hainan are the best developed in China, with the highest height of10-15m. The species of mangroves are very similar to those of Nanyang Islands, but the community height is far less than that of Nanyang Islands. Further north to Fujian, most of them are short shrubs, and there are not many kinds. There is also a water coconut community near the mangrove distribution area in Asia and northern Australia, which is only found in the southeast coast of Hainan, China. Water coconut community can be regarded as a semi-mangrove community, which likes to live in brackish water environment, and most often appears in estuaries and floodplains where salt and fresh water meet. The mangrove forests in the western strata are centered on the Caribbean Sea in America, the north coast of South America and the Gulf of Guinea in Africa. Plant species are far less than the eastern strata, but the forest is still tall and lush. Mangroves along the northern coast of South America are connected with the Amazon rainforest and become part of the most extensive tropical forest in the world. Historically, North and South America were separated, so mangroves in the western strata could cross the American continent and reach the east coast of the Pacific Ocean. In the Pacific islands of Fiji and Tonga, some species in the western and eastern strata can coexist.
Although there are not many kinds of plants in mangrove community, mangroves have raised a large number of animals. Mud under mangroves is home to crabs, mudskippers and other animals. The trunks and branches of mangroves are shelters for many crustaceans, and the crown of mangroves is the territory of tropical seabirds. In the mangroves in kalimantan island, Southeast Asia, there is a strange-looking proboscis monkey. Male monkeys have a huge nose, and cynomolgus monkeys are another kind of monkeys that appear in mangroves in Southeast Asia. At the mouth of the Ganges River, the mangrove forest in Sandaban is one of the places with the largest number of tigers, and there is also the only man-eating tiger in the world, forming a wonderful relationship between people and tigers.
Mangrove community is small in the world, but it has high ecological value. Once it is destroyed, it will cause serious consequences. Mangroves in China were severely damaged in the past, and now most of the areas where mangroves are distributed in large areas are classified as nature reserves, and many of them are national nature reserves and are strictly protected.
Marsh community is another kind of biological community developed in a special environment, which is distributed in places where the soil is too wet, the drainage is not smooth and there is often water accumulation. Unlike mangroves that grow in tropical and subtropical areas, swamps are hidden vegetation, which does not form an independent vegetation zone, but scattered in other vegetation zones from the equator to the North Pole. There are many types and classification methods of swamps, which can be divided into woody swamps, herbaceous swamps and sphagnum swamps. Or eutrophic swamp, eutrophic swamp and eutrophic swamp; Or low swamp, middle swamp and high swamp. Marsh communities are most widely distributed in coniferous forests and tundra in the northern Arctic, but coniferous forests are the most typical. The largest swamp in the world grows in coniferous forests in western Siberia. The plants in the swamp community also have some special adaptations to the environment, some of which are similar to mangroves. Swamp plants usually have developed aeration tissue, breathing adventitious roots and strong asexual reproduction ability. The most wonderful thing is the oligotrophic swamp where the soil lacks nutrients. Many plants have insect-eating habits to supplement the lack of soil nutrients. Lauraceae, Utricularia, Venus flytrap and Nepenthes are all famous insect-eating plants. The most spectacular is the swampy forest that was flooded. There are large areas of flooded forests in the Amazon basin, Congo basin and tropical rain forests in Southeast Asia. Trees have developed pillar roots and respiratory roots, which are very similar to mangroves. Even fish that feed on fruits and insects on trees have evolved in forest water. Aquatic vegetation has a certain connection with swamp vegetation, and it also belongs to hidden vegetation. Plants in aquatic vegetation can be divided into four types: emergent plants, floating plants, floating plants and submerged plants, many of which are the same as swamp plants. Marsh community, aquatic community and mangrove community all belong to wetland ecosystem, which is one of the richest ecosystems on earth. Many wetlands, such as the Okavango swamp in Africa and the Everglades in the United States, are world-famous wildlife habitats. The Everglades National Park in the United States has herbaceous swamps, flooded forests and mangroves. It is a famous world natural heritage and has many precious animals, such as Mihe crocodile, snapping turtle, crane, snake sole and manatee.
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