DISTRIBUTION OF Zanthium indicum AROUND GIRITALE TANK

Abstract

The area around Giritale tank is the main grazing ground of wild and domestic animalswithin the naturc reserve and thcre has been an increase in the population of Xanthiuntitulicurn (Agada) in this area. In the Flora of Ceylon Trimen recorded this as a rare plantprohably introduced from India. Today, it is reported to be present in more than 7 districtsof the country, mostly in moist areas periodically inundated. It reduces the grazingcapacity and the hooked involucres are reported to cause damage to the internal organs ofthe grazers. Studies are heing carried out to find the distribution and suitable controlmeasures.

Area around the tank was sampled at 100m intervals. The plant is capable of producingflowers and fruits irrespective of the time of the year and the size of the plant. When lessthan .'i()(Yr; of the area was covered hy the plant the abundance was taken, as low and whcnit was more than .'i0%, as high. .'i3% of the total area has been identified as highabundance and only 9% as free

The species has already spread from the edge of water towards the forest. Although thefruits are found, the plant has not established in the forest. Soil moisture, texture and thelight intensity determine the growth of this plant. Fruits get embedded in the mud andalter decomposition two achenes arc released which germinate later. There are reports ofXcmtliitun sp. producing two types of achencs, germinating in consecutive years. Studiesarc heing carried out to investigate this.

To improve the grazing capacity of the area it is necessary to control the growth of thisplant. Controlled hurning seems to he the best. Ten other species have heen recordedgrowing with Agada. Crotalaria pallida competes with X. lndicum. reducing itspopulation. The possibility of use of Cuscuta chinensis in the control of Xanthiumindicum is being tested.