Wednesday, March 18, 2009 5:54 AM
Article 3
Mangrove forests are a type of tropical wetland forests, which include brackish-water, freshwater and peat swamp forests. It is directly influenced by seawater, existing in an intertidal zone between mid-tide level and the highest spring tides. At high tide, the roots of the mangroves are fully immersed in sea water, while at low tide, rain or river water may wash out the salt, or evaporation concentrates the roots further. Mangrove soils are fine-grained and rich in organic matter (detritus). They are alluvium, transported as sediment and deposited by rivers and the sea. Mangrove soils are made up of sand, silt and clay in different combinations. The soil is typically anaerobic or lacking in oxygen. Soils are usually soft and unstable, and become semi-fluid when flooded. Mangroves have special adaptations to survive the extreme environmental conditions of high and fluctuating salinity, submergence in inter-tidal seawater and fine silt that is deficient in oxygen. In order to adapt to the high saline conditions, mangroves are especially salt-tolerant. All species secrete salt to some extent through their roots. Some mangrove species, such as Api-Api (Avicenna) and Sea Holly (Acanthus) secrete salt through their leaves, through special glands. Salt crystals form on the leaf surface which are then removed by the wind and rain. The saline condition also makes this a 'physiologically' dry environment. Thus, to reduce water loss, most species have thick walled and waxy leaves. The root systems of mangroves have special features to adapt to the unstable anaerobic soils. Specialised aerial breathing roots, known as pneumatophores, provide air supply for the underground root system. Pencil or finger-like breathing roots of the Avicenna and Sonneratia protrude up through the soil surface, from the base of the plant. Some trees, such as Bruguiera and Ceriops have "kneed-roots", horizontal roots growing just below the soil surface grow vertically upwards and then immediately loop downwards to resemble a bent knee. To anchor the trees to the unstable soil, stilt roots are developed in bakau (Rhizophora) trees, with branched, looping roots that arise from the trunk and lower branches. Nyireh bunga (Xylocarpus granatum) trees grow plank roots. These are horizontal roots which grow vertically upwards on its upper side above ground.
Article abstract from http://infopedia.nl.sg/articles/SIP_412_2005-01-03.html Reflection 3
After reading the article, I have learn that at high tide, the roots of the mangroves are fully immersed in sea water, while at low tide, rain or river water may wash out the salt, or evaporation concentrates the roots further. Mangrove soils are made up of sand, silt and clay in different combinations. Mangroves even have special adaptations to survive the extreme environmental conditions of high and fluctuating salinity, submergence in inter-tidal seawater and fine silt that is deficient in oxygen, and to adapt to the high saline conditions, mangroves are especially salt-tolerant. . Some mangrove species, such as Api-Api (Avicenna) and Sea Holly (Acanthus) secrete salt through their leaves, through special glands. Salt crystals form on the leaf surface which are then removed by the wind and rain. The saline condition also makes this a 'physiologically' dry environment. Thus, to reduce water loss, most species have thick walled and waxy leaves. I even learn that the root systems of mangroves have special features to adapt to the unstable anaerobic soils, such as breathing roots, known as pneumatophores, provide air supply for the underground root system. Pencil or finger-like breathing roots of the Avicenna and Sonneratia protrude up through the soil surface, from the base of the plant. Some trees, such as Bruguiera and Ceriops have "kneed-roots", horizontal roots growing just below the soil surface grow vertically upwards and then immediately loop downwards to resemble a bent knee.
(239words) ( Some of the information in my reflective journal is taken from the article)
