As the name suggests this forest type can be seen in the dry zone of the country, where the annual rainfall is between 1400 – 2000 mm. This forest type is also known as the semi-evergreen forest; it is the dominating forest type in the lowland, dry areas of the country. This forest type can occur up to 600m from the sea level. Today as much as 75% of the remaining intact forest cover in the island is categorized under dry-zone forest.
Sri Lanka summer monsoon from May to October
Sri Lanka has 6 months changing weather pattern. 6 months of the year from May to October, northern and eastern Sri Lanka coming under the influence of monsoon. The monsoon from May to October is known as summer monsoon.
Sri Lanka winter monsoon from November to April
Sri Lanka winter monsoon soaks up southern Sri Lanka, west coast and central mountain range. Therefore, the large part of Sri Lanka is benefitted from the winter monsoon (May to October).
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Summer monsoon Vs Winter monsoon
The major difference between winter monsoon and summer monsoon is the amount of rainfall. The winter monsoon (from May to October), brings fairly heavy rain on a large area of Sri Lanka. Some areas get as much as 5000 mm of rain per year. But places under the influence of Summer monsoon get about half of the rainfall of winter monsoon.
Sri Lanka’s dry zone
Dry-zone forests are to be found in the areas that are under the influence of summer monsoon, where the rainfall is lower. Rainforest is to be found in the areas where the rainfall is high due to the south-west or winter monsoon.
Sri Lanka’s wet zone
Dry zone forest grows from the beaches of the island and spread up to 600 meters above the sea level in the direction of the central mountain range. This is the leading forest type in the dry zone region – means that freshly cleared lands can be turned into a forest of this type with forest regeneration.
Distribution of rain forests
Sinharaja rain forest, Kannliya rain forest, Horton plains national park, are some of the popular patches of forests fed by south-west monsoon, and all of them are coming under rain forests.
Distribution of dry zone forests
Most dry-zone forests are scattered in deep south Sri Lanka, north-central province, northern Sri Lanka and east coast. The primary water source for these places is the north-central monsoon, which brings rain from May to October. Most wildlife reserves of Sri Lanka such as Wilpattu national park, Yala national park, Minneriya wildlife reserve and Galoya national park coming under dry zone forest type.
Dry zone forests are grown in broad northern and eastern flanks of the island. The areas with Dry zone forests are flooded in the months of October, November, December and January, through the heavy monsoonal rain. This is the main rainy season of this region while these forests are not blessed with the South-West monsoon (April to October).
Central mountain range Sri Lanka
The central mountain range that stretched from north to south, in the middle of the island, barricades the South-West monsoon reaching North-East part of the country. Dry monsoon wind that prevails in the region during the South-West monsoon resulted in scorching heat and dry weather in the area.
Trees and plants of dry zone forests of Sri Lanka
Dry monsoon forest across the country covers a wide range of flora species and these forests consist of more than 100 different tree species and 40-60 in any given forest patch depending on the area.
The dry zone forests with riverine areas show much wider species diversity than the forest without riverine vegetation. Drypetes sepiara, which known as wira in Sinhala and virai in Tamil is a medium-sized tree that grows up to 5 meters average, dominates the sub-canopy of these forests and the most notable characters of the tree are the gnarly trunk and small purplish fruit.
Vitex altissima produces hardwood that needed for manufacturing furniture and the tree is called Milla in Sinhala language and Kaaddamanakku in Tamil. One distinct character that makes this tree so popular is the termite resistant capability of its wood.
The trees can be easily recognized by its trifoliate or three-leaf arrangements. Cassia species such as Cassia fistula (English: Indian laburnum, Sinhala:Ehela, Tamil:Tiru kontai) and Cassia roxburghii (English: red cassia, Sinhala: ratu wa, Tamil:vakai) are two main cassia species show a wide distribution in the dry zone forests.
Red cassia with attractive, large paired leaves, brilliant yellow flowers and cylindrical fruit pods that appears like giant black beans, is the most attractive ornamental tree in the dry zone forests. The fruit of the tree attracts the toque macaque monkeys (Macaca sinica). Both these cassia species are very common in the dry zone including areas such as Anuradhapura, Polonnaruwa, Sigiriya and Dambulla.
Diospyros ebenum (English: ebony, Sinhala:kaluwara,Tamil: kurungali) is the rarest indigenous flora species with highest economic value in these forests. It is being ranked as the best quality wood for carving. Dark black coloured, hardwood is so dense that is sinks in water; the harder part of the tree is covered with a soft, pale-coloured outer layer.
This had been the most favourite wood for making pianos, black pieces of chess and harpsichord keys largely due to the exceptional shine it produces after polishing. Today it is a protected flora species and is restricted to any form of usage. Deforestation, overexploitation plus slow growth rate, has led it to almost extinction in the jungle.
Berrya cordifolia (English: Trincomalee word, Sinhala: halmilla, Tamil:chavandalai), is a water-resistant wood used in the boat construction and manufacturing casks. Satin wood Chloroxylon swietenia (Sinhala: burutha, Tamil mutirai), is one of the giant trees in the dry zone forest that grows up to 30 meters, and it is most famous for making cabinets. Manilkara hexandra (Sinhala: palu, Tamil palai) is another popular hardwood for manufacturing purposes. The sweet, yellowish, delicious seasonal fruit is loved by the bear and many other animal species in the forest.
Fauna species of Sri Lanka dry zone forest
Most notable animal species in these forests is the Elephant (Elephaus maximus), that inhabits the dry zone evergreen forests. Leopards (Panther pardus kotiya), sambhur (Cervus unicolour), wild boar (Sus scrofa), and grey langurus (Presbytis entellus) are the other most common animals in the forest. Dry zone forests are also very rich in birdlife and attract a large number of migrants bird species, especially during the winter season in the northern hemisphere.
Dry zone is closely related to the early history of Sri Lanka and the ancient Sri Lankan culture flourished in this part of the country. Even the first capital (Anuradhapura 4th century BC) was in the heart of the dry zone vegetation in the northern plain while the southern capital (Ruhunu Rata) was housed in the dry zone in southern Sri Lanka.
These civilizations expanded in the areas for thousands of years making them most populated areas in the country. Today dry zone is also densely populated like most parts of the country and makes huge pressure by the human for resources on this green cover.
Most of the national parks are located in the dry zone lowland in the island and these parks generate huge income for the country by providing the possibility to observe wild animals. Today strict rules and regulation keep the forests in safe at large. Yala, Wilpattu is the most famous national parks and both are located in the dry zone in the country. People have easy access to most of the dry zone and a visit to one of them will make a most memorable occasion in life.