SUCCESSIONAL DEVELOPMENTS IN SOME HUMAN-IMPACTED AREAS
AT KAMBURUPITIYA FOLLOWING THE NILWALA PROJECT
K.K.L.U. Aruna Kumara and R. Senaratne
Department of Crop Science, Faculty of Agriculture, University
of Ruhuna, Mapalana, Kamburupitiya.
A study on successional development at a human-impacted site was conducted
at Kamburupitiya from June to October 1999. This site was previously maintained
under agroforestry, but has been severely disturbed and its soil has been
removed down to the bedrock in 1987, under the Nilwala project. Three
such sites (12 X 104, 2 X 104, 1 X 104 m2) which are about 500 meters
apart were selected for the study.
The study involved characterisation of the physical and chemical properties
of the soil and assessment of successional development. An undisturbed
site was used as the control experiment. Bulk density, true density and
porosity of the soil were 1.163 gcm-3, 2.14 gcm-3, and 45.6 gcm-3. respectively,
with a water holding capacity of 28.5%. The per cent of organic matter
and N in the soil were 0.451 and 0.0088, respectively, whereas the corresponding
values for the undisturbed site, were 1.214 and 0.095. The cation exchange
capacity of the derelict sites was 4.71 m.e. per 100g of soil and had
a pH value of 4.2. The corresponding figures for the reference site were
7.40 and 5.43, respectively. Plant populations in three sites were 15,902,
21,266 and 98,776 ha-1. Even after 12 years, only about 0.13-0.26% of
plants had a girth exceeding 3 cm at breast height and only about 1% of
plants had a height greater than 1m. Twenty one species occurred in three
sites, which belonged to sixteen families, namely (in order of abundance),
Graminae, Gleicheriaceae, Apocynaceae, Leguminosae, Verbanaceae, Rubiaceae,
Burseraceae, Cyperaceae, Compositae, Malvaceae, Lauraceae, Periplocaceae,
Melastomataceae, Euphobiaceae, Anacardiaceae and Rhizophoraceae. Of these
species, about 75% were herbaceous while the rest were woody. Alstonia
scholaris was by far the most abundant and dominant woody species followed
by Cinnamon verum, Carallia brachita. Even after 12 years of the disturbance,
the biomass production of Alstonia scholaris was only 9.5 gm-2 or 95 kha-1,
showing an extremely successional development.
Ecological implications of such a tardy successional development and human
interventions required to facilitate and catalyse the natural successional
processes are discussed.
Department of Forestry and Environmental Science,
of Sri Jayewardenepura,Sri Lanka. 1995-2000. All rights reserved.