What Kind of Tree Is a Mangrove? An Analysis of Its Role and Special Features

Mangroves are called “coast guards”, and in recent years protecting mangroves has become an urgent matter. So what kind of tree is a mangrove? What is its role? What are its special features?

1. What kind of tree is a mangrove

Mangroves refer to the woody biological community of tidal flat wetlands composed mainly of mangrove plants, evergreen shrubs or trees, growing in the upper intertidal zone of low-energy coasts in tropical and subtropical regions, inundated by periodic tides. The species that make it up include herbaceous and vine mangroves. They grow on the shoals of tidal flats at the junction of land and sea, and are a special ecosystem in the transition from land to sea. At the edges near mangrove communities there are also some associated so-called semi-mangrove components, all of which have a certain salt tolerance, such as sea mango, sea hibiscus, silver-leaf tree, pandanus, Malay apple, Derris indica, and coral tree.

2. The role of mangroves

1. Ecological benefits

Mangroves are one of the few most species-diverse ecosystems in the world to date, with extremely abundant biological resources. This is because mangroves, by way of litter, provide a good environment for the growth and development of marine animals through food chain conversion; at the same time, the well-developed tidal creeks within mangrove areas also attract animals to come here to feed, inhabit, and reproduce, forming a good ecological cycle. Because mangroves grow in subtropical and temperate zones and have abundant food resources for birds, mangrove areas are wintering grounds and migration stopover sites for migratory birds, and moreover are places for various seabirds to feed, inhabit, and reproduce. Mangroves can absorb 150 to 250 kg of nitrogen and 15 to 20 kg of phosphorus per hectare per year, playing a role in purifying water bodies.

2. Coast guards

Another important ecological benefit of mangroves is their functions of windbreak and wave dissipation, promoting siltation and preserving beaches, stabilizing shores and protecting embankments, and purifying seawater and air. The intricate and well-developed root system can effectively retain sand from land and reduce the sand content in nearshore waters; the dense and tall branches are like green Great Walls, effectively resisting wind and wave attacks.

In the coastal shelterbelt system of our country, the wave-dissipating forest belt is the first coastal defense line in building the shelterbelt system. Tree species for the wave-dissipating forest belt are required to have strong resistance to salt and alkali, resistance to waterlogging, resistance to intermittent seawater scouring, and wind resistance and soil stabilization capabilities, which requires trees with well-developed root systems and tough branches and trunks, so mangroves naturally become the ideal choice.

3. Medicinal value

Some varieties in mangroves can be used to produce daily health care products. For example, the fruit peels of Bruguiera and sea holly types can be used for stopping bleeding and seasoning, and after the roots are squeezed for juice they can be made into spices. The leaves are often used to control blood pressure; the leaves of Excoecaria mangrove trees can relieve toothache; the fruit juice of some mangrove varieties can relieve the pain of rheumatism; a mouthwash made from the bark of the large red tree can treat sore throat; the fruits of mangroves can be pressed for oil, which can be used for lighting oil lamps, and can also repel mosquitoes and treat insect bites and dysentery fever.

3. The special features of mangroves

1. Vivipary

The most wonderful characteristic of mangroves is the so-called “vivipary”. The seeds of many plants in mangroves begin to germinate in the fruit before they have left the parent plant, growing into rod-shaped hypocotyls. After the hypocotyl develops to a certain extent, it separates from the parent tree and falls into the mud of the beach, and within a few hours it can take root and grow in the mud to become a new plant. Hypocotyls that fail to take root in the mud in time can drift on the sea with ocean currents for several months, and take root and grow on coasts thousands of miles away.

2. Special root system

The most striking feature of mangroves is the dense and well-developed prop roots. Many prop roots grow out from the base of the trunk, firmly rooted in the mud to form a stable support, enabling mangroves to stand unmoved under the impact of sea waves. Mangroves are often in a state of being submerged by tides, and air is very scarce, so many mangrove plants have breathing roots. The breathing roots have thick lenticels on the outside and spongy air-conducting tissue inside, satisfying the air needs of mangrove plants.

3. Salt secretion

Tropical beaches have strong sunlight and soil rich in salt. The morphological structure of mangrove plants gives them the characteristics of being halophytes and adapted to physiological drought. The plants have secretory glands that can excrete excess salt, and the leaves are leathery, which helps reflect sunlight and reduce water evaporation.

Mangroves are strong; they can withstand the high-salinity intertidal environment, but at the same time they are also fragile. Any pollution or felling may destroy the ecological environment and biodiversity they try their best to maintain. So protecting mangroves is the responsibility of each and every one of us.