PHYSIOGNOMY AND NATURAL REGENERATION OF DRY DECIDUOUS FORESTS AT SIGIRIYA, SRI LANKA

Abstract

Although, poor natural regeneration of tropical dry forest has been observed in Sri Lanka.India. Africa and in Latin America. the factors affecting this have not been well studied.In this paper. the physiognomy of dry deciduous forests at Sigiriya in the northern dry zoneof Sri Lanka and some major factors which affect their natural regeneration wereestimated.

The vegetation was enumerated in six 20x20m experimental plots. The diameter 01' trees25cm at breast height (dhh) was measured. Seed rain was detected hy collecting seedsusing wooden trays. allowing them to he germinated and enumerating the germinants overa period of eleven months. The seed bank was examined by collecting ten soil samplesfrom each plot three times within a year. Seedlings were recorded in 2x2m quadrates ineach plot and their growth and survival was recorded throughout an year. Soiltemperature, soil moisture and the canopy openness were also detected.

The species composition and dominant species were identified for dry deciduous forest inthe arca. The beta diversity of forests is high implying the importance of conserving largeareas of dry forests. Seasonality of seed production. seed predation. lack of a persistentseed bank, unfavourahle environmental factors arc found to be affecting the regeneration ofdry deciduous forest. Possibilities of sustainable timber production in dry deciduous forestand the participation of local people in forest management arc also discussed.