FOREST REGENERATION IMMEDIATELY, AFTER TRADITIONAL SHIFTING CULTIVATION IN THE NORTHERN DRY ZONE OF SRI LANKA

Abstract

The forest regeneration immediately after traditional shifting cultivation wasstudied in an abandoned shifting cultivation field at Sigiriya in the northern dryzone of Sri Lanka. Biotic and abiotic factors that are responsible for the forestregeneration process were also identified.

The vegetation and the soil seed bank (both surface and sub-surface) wereenumerated before clearing the land for shifting cultivation and one month afterthe abandonment. In addition, the soil seed bank was investigated 15 hours afterburning of the land (i.e. a 12-15 year old secondary forest) prior to cultivation.Some physical environmental parameters were recorded after the abandonment ofthe land.

Regeneration after traditional shifting cultivation was mainly by roots and stembases of woody plants, which existed before cultivation. Thus, many early andlate survivalspecies were regenerated. The ground of recently abandoned shiftingcultivation land was very open (% canopy opennes = 69.39±4.80 and this resultsin to have high soil temperatures and low soil moisture contents. Wind dispersedseeds of grass and agricultural weed species frequently disperse into the burntland. Few seeds of some pioneer species are capable of withstanding fire and mayoccur as a soil seed store. However, seeds in the soil seed bank may not involvein forest regeneration at this early stage. Underlying reasons for that are alsodiscussed.