KEANEKARAGAMAN DAN KELIMPAHAN FAUNA SEMUT TANAH PADA LAHAN GAMBUT YANG DIALIHGUNAKAN MENJADI KEBUN KELAPA SAWIT DAN HTI AKASIA DI KAWASAN BUKIT BATU, RIAU

Abstract

The aim of this study was to assess the structure of ground-dwelling ant fauna (class Insecta; order Hymenoptera; family Formicidae) as well as the nest abundance and species diversity in peatland that had been converted into oil palm plantation and industrial pulpwood plantation (HTI). This study was carried out in Bukit Batu area, Bengkalis District, Riau Province. Four oil palm plots (all about 5-6 year-old Elaeis guineensis stands) and four HTI plots (all about 5-6 yr-old Acacia crassicarpa stands) were selected as sampling sites. In each selected plot, four separated sampling transects of 25 m x 2 m were established. Ground-dwelling ants occurring within the plots were sampled directly from their nest holes. There were in total only 13 ants species encountered, of which the most frequently-encountered ant species were members of Formicinae and the least one was member of Ectatomminae. Eleven of them (Anoplolepis gracilipes, Anochetus sp., Dolicoderus sp., Gnamptogenys sp., Iridomyrmex sp., Meranoplus sp., Odontoponera transversa, Odontomachus sp., Pheidole sp., Paratrechina longicornis, and Tapinoma sp.) were found in oil palm plots and eight (Anoplolepis gracilipes, Iridomyrmex sp., Odontoponera transverse, Odontomachus sp., Pheidole sp., Paratrechina longicornis, Camponotus sp., and Polyrachis sp..) were encountered in HTI plots. Inter-plot similarity in species assemblages between oil palm plantation and HTI was averagely 53,5% (Sørensen Similarity Index). Similarity between oil palm plots was averagely 75,9% and between HTI plots was 57,9%. Species diversity at plot level was invariable low in both land use types (values of Shannon Weiner Index ranged only 0.22-0.24). Species with highest encounter frequency and most abundant nests in oil palm plots were Odontomachus sp. and Pheidole sp., while in HTI plots Iridomyrmex sp., Paratrechina longicornis and especially Anoplolepis gracilipes were the dominant species. Average overall nest density was 1000 nests/ha and 1112.5 nests/ha in oil palm plantation and HTI, respectively.