Pinus caribaea will it be an another invader in knuckles grasslands ?

| by Dr. Lalith Gunasekera

Pinus caribaea is growing in Central Mountains
(November 21, Melbourne, Sri Lanka Guardian) The knuckles Mountain Range display the highest number of different climatic and vegetation zones in any area in Sri Lanka. The vegetation type of utmost interest to the expedition is the upper montane cloud forest, considered the most endangered ecosystem on the island. As of the 5th May 2000, an area of 17500 hectares of the Knuckles range was declared a conservation forest by Gazette Notification. Areas above 1067 meters in altitude are now protected. After introduction of the Forest Policy 1970 large areas of land were put under plantation forestry. The Forest Department implemented a large scale reforestation program to grow over 7500 hectares per year. Most of the Eucalyptus and Pinus caribaea were planted in the hilly area from 1966 to 1976. The Forest Department has converted more than 25000 ha of abandoned, highly eroded unproductive tea lands to plantations of P. Caribaea in the Wet and Intermediate lowlands and montane areas including some parts of Knuckles Mountain Range. Since its introduction, the natural spread of P. Caribaea has not been reported in Sri Lanka but this alien plant species has been listed in the Global Invasive Species database. But recent studies carried out by the Botany Department of University of Peradeniya found that populations of seedlings, saplings and mature trees have been established in grasslands nearby P. Caribaea plantations in the Knuckles Mountain Range. This plant has several values other than timber production. Some of the other benefits are fibre for the paper industry and tapping for resin which distilled to produce Turpentine and Gum resin. P. Caribaea that is the most common Pinus species available in Sri Lanka has both these factors on and economically acceptable level.

Pinus caribaea plant
This species grow best in frost free areas up to about 700 m in more fertile sites with good subsoil if drainage and annual rainfall of 2000 – 3000 mm. 

P. caribaea is a fine tree up to 20-30 m tall often 35 m with a diameter of 50-80 cm and occasionally up to 1 m. Bark grey to reddish brown, fissured and shed in large, wide flat plates. Trunk generally straight and well formed lower branches large, horizontal and drooping. Upper branches often ascending to form an open rounded to pyramidal crown. Distinguished yellowish green leaves (needle like) mostly 15-25 cm long, crowded and spreading at ends of twigs and remaining attached for 2 years. Young plantations usually start bearing female cones when they are 3-4 years old but these do not produce fertile seed owing to the inadequate supply of pollen at this age unless older plantations adjoin in the site. Male and female flowers are borne on the same plant. The female cones are the equivalent of needle bundles (short shoots). The seeds are black to grey or brown in colour about 6 mm long with wing about 2.5 cm long. There are 35 to 40 seeds per cone. Seeds spread by wind.

Research carried out by the Botany Department of Sri Lanka found that the P. Caribaea trees grown on the perimeter of plantations produced higher number of cones per tree than the interior plants. Then they spread into grasslands in the knuckles Mountain Range. The results of that study clearly showed that P. Caribaea is invading grasslands around Knuckles.

(The writer, Invasive Plants Specialist based in Melbourne, Victoria )

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