The Indian Ocean tsunami sounded the alarm for the world. Experts here pointed out that we must learn lessons, raise awareness of disaster prevention, and restore coastal mangroves as soon as possible in addition to strengthening the construction of breakwaters in coastal areas. Mangroves are recognized as "natural coast guards", and trees play a great role in resisting waves. It is a woody plant community growing in intertidal zone of tropical and subtropical coast. Mangroves are distributed in 70% tropical and subtropical coasts around the world. The species composition is mainly mangrove plants, and the bark is rich in tannins. Including mangrove plants: mangrove plants are woody plants in intertidal zone, which grow specially on mangrove beaches and can often be infiltrated by tides, including ferns; Semi-mangrove plants: Semi-mangrove plants are amphibians, which can grow and develop on land and sea only in Hong Chao; Associated plants: non-woody plants that grow in mangrove areas and are often infiltrated by tides, such as some palm plants and vines (derris); Mangroves: Mangroves belong to mangroves in classification. Mangroves are mainly composed of mangroves, such as Bruguiera gymnorrhiza, Lotus, Kandelia candel, Mangrove and Hedysarum hedysari. However, there are still many mangrove plants that are not members of mangroves, such as some growing on land and some growing on mountains, which are non-mangrove plants of mangrove family; Non-mangrove plants: Mangroves include not only mangroves, but also halophytes, Verbenaceae, Rubiaceae, Sonneraceae, Euphorbiaceae and so on. These are non-mangrove plants. In fact, Guangdong, Fujian, Guangxi, Hainan and other provinces and regions are the areas with the most frequent typhoon disasters in China, and there are also many rainstorms and tsunamis. Liang Guozhao, a researcher at Guangzhou Institute of Geography, Guangdong Academy of Sciences, believes that in order to prevent the tsunami, coastal areas such as Guangdong should not only strengthen the construction of breakwaters, but also restore coastal mangroves as soon as possible. Unfortunately, there used to be more than 500,000 mu of natural mangroves in Guangdong, and now there are only less than 6.5438+10,000 mu left.
★ Know mangroves
"Trees or shrubs that grow below the highest tidal level and above the average tidal level on tropical or subtropical coasts are called mangroves", which is a narrow definition of mangroves. Mangroves are very interesting plants, such as viviparous, respiratory roots and supporting roots. Mangroves have certain functions, such as maintaining the rich ecology of coastal wetlands, windbreaks and resisting tidal erosion. Where does the middle name of mangrove come from? The answer is that red dye can be extracted from its bark, so it is called "mangrove". Unfortunately, red eggplant and thin-core mangrove called "mangrove" no longer exist.
mangrove
On the beach in the southeast of Qiongshan City, a dense tree grows, just like a green fairy, bathed in light green sea water. At the high tide, I only saw part of her graceful crown, full of interest in "hiding half a face behind her guitar in front of us"; At low tide, her trunk with the smell of sea mud shyly emerged from the sea. What a sight this is, "However, before she came to us, we had called for it a thousand times and urged it a thousand times"! This is the world-famous mangrove forest, which is nicknamed "undersea forest".
Mangrove is a unique plant community on tropical and subtropical coastal beaches, which has vitality that many other plants do not have. Mangrove is an evergreen shrub of mangrove family with reddish-brown bark and dark green leaves. Its roots and branches are like interlaced cobwebs, which are very developed. Mangroves have a special function. Their roots and leaves can filter out the salt water that kills plants, so they are the only green shrubs that can grow in coastal silt and seawater in tropical areas. There are 82 species of mangroves in 24 families all over the world, among which 16 species are viviparous plants, which is the only plant in the plant world that thrives in viviparous way. Because viviparous mangrove is one of the special landscapes in the plant kingdom, several countries with mangroves in the world have listed mangroves as ecological reserves and protected them as valuable natural resources. The mangrove association has been established internationally, and academic exchanges are held regularly to promote the protection and development of mangroves.
The viviparous way of mangroves is very special. Mangrove seeds do not fall off after maturity, but germinate on the mother tree, the young roots extend downward, the young roots explode into stems, and two leaves are produced at the upper end to become young trees. Once the young trees grow up, they will fall off their mother trees. Because the stems and roots are heavy, the young trees fall vertically, and the young roots are well inserted into the beach mud and continue to grow independently. After a year or two, they can grow into small shrubs. From seed maturity to full maturity, mangrove forest, a series of life-creating processes, can be compared with mammals' behavior of raising offspring. Viviparous saplings and mangroves are unique among plants because of their adaptability to seawater, so scientists and people in many countries in the world attach great importance to them.
Mangroves in Qiongshan City have a long history of growth and are still in a primitive state. Hainan people have long known the value of mangroves. As early as the 25th year of Qing Daoguang (A.D. 1845), the local government of Qiongdao in Qing Dynasty had taken measures to prohibit the felling of mangroves, and once erected a monument in Shangshan Village of Yanfeng Town. 1980, Guangdong Provincial People's Government re-established the mangrove nature reserve in the waters of Dongzhaigang, Qiongshan City. This is the first mangrove reserve in China. Donggangzhai Mangrove Reserve stretches for more than 50 kilometers with a total area of more than 60,000 mu. Thousands of mangroves, with staggered roots, climbing branches and covered leaves, form a confusing array. There are 29 mangrove species in China, of which 16 family and 18 family are distributed in Donggang village, accounting for more than 60% of mangrove species in China.
The main mangrove species in Donggang Village are Hong Kong orchid, Bruguiera gymnorrhiza, hawthorn, Kandelia candel, Solanum lyratum, sea bone root, sea lacquer, tung tree, rat's joy, willow, Cassie Wang, sea mango and so on.
The mangroves in Donggang Village have various forms and beautiful scenery. Looking up from the coast, I saw a green crown in the endless green ocean. These mangroves are flourishing, with high and low levels and distinct colors. If you look around the branches of the harbor, you can clearly see that there are dozens of twisted air roots around each tree head, up to one meter Fiona Fang, which cross into the mud and look like a chicken coop. Locals call it "chicken cover". The roots of mangroves are amazing! Some are as lifelike as the head of the leading monkey; Some are like fairy Weng in myth, senile and poetic. The best time to enjoy the mangrove landscape is to row into the mangrove area after the high tide. Surrounded by strange and beautiful green crowns, there is a long winding forest waterway in the middle. The surging tide pushed the boat leisurely along the waterway, twitching from side to side. Visitors only see the blue sea water and the green crown, and feel the magical charm like fog in mangrove trees, which permeates the sea. ...
Donggangzhai Mangrove Reserve not only has high scientific research value and ornamental value, but also has very important practical value. Mangroves, like the Great Green Wall on the sea, have effectively prevented tsunamis and strong winds from invading farmland and cottages. Their roots are deeply rooted in the soil, which can not only protect the soil from being washed away by the tsunami, but also prevent the soil from being washed down by the rain. Its fallen leaves fall into the sea, and after a period of decay, they are transformed into nutritious food for fish, shrimp, shellfish and crabs.
Mangrove coast with a variety of customs
Nothing can make you fantasize more than this scene: you drive a motorized boat into a coastal area in the south. Under the boat is emerald water, surrounded by lush green forests, and thousands of equally emerald waterways crisscross the green forests. White seagulls pass by when your boat passes by. For this reason, you will marvel at the beauty and magic of nature. This is the mangrove coast.
Mangrove coast is a biological coast. Mangrove is a general term for trees and shrubs growing in intertidal zone. Intertidal zone refers to the zone between high tide level and low tide level. There are many species and genera of mangrove plants, but from a global perspective, they can be divided into two types: western flora and eastern flora. The mangroves in China, like those in Asia, Oceania and the east coast of Africa, belong to the Oriental flora. Due to the influence of geographical latitude, heat and rainfall decrease from low latitude to high latitude, and the species diversity of mangrove gradually becomes relatively single from south to north, and the height of planting branches from high to low, from lush trees to relatively short shrubs.
Mangrove plants are mainly distributed in tropical and subtropical areas along the south China and southeast coast. There are 37 species of mangrove plants in Hainan Island, China. Followed by Guangxi, Guangdong and Taiwan Province provinces; Fujian is second; In Zhejiang, there is only one species left, which is artificially introduced and planted. The northern boundary of natural growth of mangrove plants is about 27 20' north latitude, which is Ding area in Fujian Province. But it seems to be bounded by Xiamen, Fujian at 24 27' north latitude, where the mangrove coast is well developed; In the north, there are few mangrove coasts. Although Taiwan Province Province and Fujian Province have the same geographical latitude, there are more mangrove species along the coast of Taiwan Province Province than Fujian Province, which is due to the influence of the Kuroshio warm current in the Pacific Ocean in Taiwan Province Province.
The growth and development of mangrove plants are closely related to geographical latitude, temperature and rainfall. Mangrove plants are flourishing in Wenchang area on the east coast of Hainan Island, with an altitude of 12m- 13m. Near the mountain pass in Guangxi, the latitude is high, 2137' north latitude, and the mangrove forest is 3-5 meters high; In Quanzhou Bay, Fujian, the highest mangrove forest is only 2.2 meters; In Shacheng Port, Fuding, Fujian, at 27 20' north latitude, the height of mangrove forest is only 0.8m- 1.0m, which is shrub-like.
Changes of mangroves
Shantou City is located in the southeast of Guangdong Province, with a total population of 4.49 million and a coastline of 298 kilometers. At present, the mangrove greening project along the coastal beach is under way here.
Mangrove is an extremely tenacious plant community, which can easily take root and survive on the subtropical coastal beaches. Because this community is mainly composed of mangrove plants, biologists have given them a beautiful name-mangrove, which is commonly known as "Ding" by local people. For residents living in southern coastal areas, it is definitely not a simple plant.
Zhong Xiaoqing, an associate professor at the School of Life Sciences, Sun Yat-sen University, told the reporter that for ordinary plants, because the concentration of soil solution in seawater and beaches may be greater than that in plants, they can not only absorb water and nutrients in the soil, but will be regenerated by soil solution, resulting in plants being burned to death. Mangroves do not have this phenomenon, because they have a very peculiar function-reverse concentration gradient absorption. This unique function enables mangroves to effectively prevent and reduce the occurrence of red tides and promote the growth and reproduction of marine life. At the same time, mature mangroves are flourishing and have developed roots, which can also form a natural wind and wave barrier to protect seawalls.
However, since the early 1970s, mangrove forests with extremely tenacious vitality have been distributed less and less in the coastal areas of Shantou. Due to the artificial reclamation of land and roads, the growth environment of mangroves has been damaged to some extent. The natural secondary mangrove forest is only 160 mu from the previous 50,000 mu. And this only 160 mu is still curled up in a remote harbor in Dahao District, Shantou City.
The reporter found the shadow of a mangrove forest at the foot of the mountain opposite Nanbin Road in Shantou City. How did this natural mangrove survive? According to Li Xuyi, chief of forestry administration department of Shantou Forestry Bureau, there is a culvert here, from which seawater can enter at high tide and be discharged at low tide. Culverts transport seawater to this mangrove forest to make it survive.
Professor Zhong Xiaoqing told reporters that mangroves have strong reproductive capacity, and now its area is gradually shrinking, because people's destructive capacity is far greater than the growth capacity of mangroves.
During the period of 1998, a large-scale red tide occurred in the southern coast, and the algae reproduction in the coastal waters increased abnormally, resulting in a large number of fish deaths and huge economic losses to the aquaculture industry in Shantou. Although the occurrence of red tide is directly related to the pollution in the offshore area, there is a unique phenomenon in the area where red tide occurs. After the occurrence of red tide, the places with mangroves in Zhanjiang are basically unaffected.
As a result, mangroves, which are almost forgotten by people, have attracted the attention of Shantou municipal government and forestry departments. 1998, Shantou forestry system began to artificially plant mangroves in Chenghai coastal beach.
Although the trial planting is only three years, the unique mangrove ecosystem has gradually begun to take shape. In Fengxi, the largest mangrove planting area in Chenghai City, the reporter saw hundreds of crabs sunbathing together. Lin Ruimin, deputy director of Chenghai Forestry Bureau, said that this kind of crab is very popular as fiddler crab. Originally, the muddy land here stinks, and fiddler crabs can't survive at all. Since planting mangroves, the muddy land no longer stinks, and fiddler crabs began to live here. At the same time, many birds, fish and shrimp often come here to live, and marine life is gradually diversified.
On the riverbank of Fengxi, the reporter met Zhang Minggui, a professional goose farmer, who raised 1200 large and small geese by the riverbank. There are dozens of farmers like Zhang Minggui on the Yifeng River, and their farming methods have realized a three-dimensional cycle-pond culture, where geese and ducks are raised on the water and bananas are planted at the base. Because ducks and geese only eat aquatic plants and plankton on the water surface, it not only does not affect the growth of underwater fish, but also the feces of ducks and geese can be used as feed for fish. At the same time, the feces cleared from the shore and pond can be used as organic fertilizer for cash crops such as bananas. When the opposite mangrove grows up, these ducks and geese can play and feed in the mangrove and participate in a larger food chain cycle. This three-dimensional circulation farming method not only saves the cost of farmers, but also makes the eggs laid by ducks large and nutritious because of the high calcium content of marine organisms such as shellfish gathered in mangrove ecosystem.
Professor Zhong Xiaoqing also told reporters that the bait fed by general farming is very expensive and may not grow naturally. This kind of three-dimensional circulation farming method forms a food chain with their own responsibilities and interdependence through the collocation of producers, consumers and decomposers in mangrove ecosystem.
At present, Shantou plans to invest more than 30 million yuan. By 20 10, mangroves will be planted on more than 90,000 mu of coastal beaches suitable for planting. Shantou people once put forward a new slogan to the important place in the sea-to want forests to the sea. Perhaps, when the reporter comes to Shantou again, coastal residents will become better friends with mangroves.
Mangrove ecosystem
Mangrove is a woody plant community in intertidal zone of tropical and subtropical harbors. In a region dominated by mangroves, the whole composed of animals, plants and microorganisms is collectively called mangrove ecosystem. Its habitat is coastal salt marsh wetland, and the forest environment formed by alternating tides is different from the terrestrial forest ecosystem. 60%-70% beaches in tropical waters have mangrove patches or scattered distribution.
(1) Habitat characteristics
1. Geology and landform
Mangroves are mainly distributed in the hidden coast, mostly because of the small wind and waves and slow water flow. Therefore, it is a "landmaker" like a coral reef. The naturally developed beach surface is flat and wide, which can often extend inland for several kilometers along the estuary bay, delta area or estuary. Mangroves are mostly distributed in intertidal zone, and intertidal beach is the most lush area.
The growth of mangroves is also related to geological conditions, because geological conditions may affect the deposition of beaches. If the estuary coast is granite or basalt, its weathering products are fine and sticky, depositing estuary silt, which is suitable for mangrove growth. If it is sandstone or limestone strata, beaches will be formed at the outlet of rivers, and mangroves will not grow in most areas.
2. Matrix
Mangroves are suitable for growth in fine alluvial soil. In alluvial plains and deltas, soil (alluvial layer) is composed of silt and clay, which contains a lot of organic matter and is suitable for mangrove growth. Mangrove soil is generally native soil, with a salt content of 0.2% ~ 2.5% and a pH value of 4-8, which is rarely lower than pH 3 or higher than pH 4-8.
3. Temperature
The annual average seawater temperature in the central area of mangrove distribution is 24 ~ 27℃, and the temperature is between 20 ~ 30℃. The annual average seawater temperature in Haikou, Hainan Island, China is about 25℃, while that in Xiamen Port is 265,438+0,7℃, with an average temperature of 20.9℃. There are only five mangrove species in the latter, much less than the 25 species in the former.
4. Seawater and tides
Salt water is very important to mangrove plants, which have the characteristics of salt tolerance and become the dominant species in seawater with a certain salinity. Although some species, such as paulownia and Avicennia marina, can grow in both seawater and fresh water, they grow better in seawater. Another important condition is tide, and mangrove plants can't grow well without the daily interval change of high tide and low tide in intertidal zone. After long-term flooding, mangroves died quickly; Mangroves will not grow well after a long drought.