SUCCESSIONAL DEVELOPMENTS IN SOME HUMAN-IMPACTED AREAS AT KAMBURUPITIYA FOLLOWING THE NILWALA PROJECT

Abstract

A study on successional development at a human-Impacted sitl' W;I~ conducted atKurnburupiuya from June to October 1'1\)9. This site was previously maintained underauroforcxtrv. but has been scvcrclv disturbed and its soil has been removed do wn t(l theb~drock in "19~7, under the N i1wala" project. Three such sites ( 12 X H)I, 2 X I ()4, I X 10· me)which are about 500 meters apart were selected for the study, The study involvedcharacterisation of the physical and chemical properties of the soil and assessment ofsuccessional development. An undisturbed site was used as the control experiment.

Bulk density, true density and porosity of the soil were 1,163 gem". 2.14 gcrn', and 45.6gcm'. respectively, with a water holding capacity of 2H.5'11:,The per cent of organic matterand N in the soil were 0.451 and 0,0088. respectively, whereas the corresponding values forthe undisturbed site. were 1,214 and 0.095, The cation exchange capacity of the derelictsites was 4,71 m.e. per IOOg of soil and had a pH value of 4.2. The corresponding figuresfor the reference site were 7.40 and 5.43, respectively, Plant populations in three sites were15.LJ02. 21.266 and LJ~.776 ha I, Even after 12 years. only about 0,13-0.26(1, of plants had agIrth exceeding 3 em at breast height and only about I (I, of plants had a height greater than1111. Twenty one species occurred in three sites. which belonged to sixteen families. namely(in order of ahundance). Grarninac. Gleichcriaccac, Apocynaceac, Lcgurninoxac.Vcrhanaccac. Rubiaccac, Burseraccue. Cyperaccac, Compositac, Malvaccac. l.auraccac.Pcriplocuccac. Mclastomaiaccac. Luphohiuceae, Anacardiaccae and Rhizophoraccac. orthese species, about 75% were herbaceous whilc the rest were woody. Alstonia scholaris\\as by fur the most abundant and dominant woody species followed by Cinnamon VC/'IIII/.Carallia brachita, Even alter 12 years of thc disturbance, the hiomass production ofAlstonia scholaris was only 9.5 gm·2 or 95 kha'. showing an extremely successionaldevelopment. Ecological implications of such a tardy successional development and humaninterventions required to facilitate and catalyse the natural successional processes arediscussed,