G. Weerakoon1, S. Somaratne2, P.A. Wolseley3 and S.C. Wijeyaratne1
1Department of Botany, University of Sri Jayewardenepura, Sri Lanka
2Department of Botany, The Open University of Sri Lanka
3Department of Botany, The Natural History Museum, United Kingdom
Lichens have been widely considered as bioindicators of forest health and ecological continuity as well as atmospheric pollution. The use of lichens as bioindicators in tropical zones has been hampered by the lack of taxonomic and ecological knowledge. The purpose of the study was to assess the variation of lichen diversity in different forest management regimes under different environmental conditions on the basis that their potential uses as bioindicators of environmental alterations in different habitats in the Knuckles mountain range. The sampling sites were chosen to include pristine forest of montane and sub-montane and six different disturb vegetation types. Lichen species, their frequency and cover values were recorded together with environmental parameters in 20 sites of 100 m2 plots. Ten trees were sampled randomly in each plot. The collected data were analyzed to assess the relationship between lichen diversity and environmental conditions in different forest management regimes using one-way analysis variance, least significant difference- LSD (mean comparison) and Regression tree analysis.
There were 192 lichen species recorded from the natural vegetations, where as 148 lichen species present in the disturbed vegetation types. The results of the study have shown that there is a considerable variation in the lichen diversity along different vegetation types and their degree of disturbance. The statistical analysis revealed a significant variation in lichen diversity between the disturbed and undisturbed vegetation in the area (F = 6.213, df = 1; p ≤ 0.05). Similarly, lichen diversity in different vegetation types also indicated a remarkable variation (F =3.21, df = 7; p ≤ 0.05). The results obtained from regression tree analysis indicated that there were three important variables that determined the lichen diversity of the study area; type of vegetation, altitude and association with other cryptogamic communities.
There are distinct lichen communities associated with tree boles in disturbed forests including weedy taxa and low diversity with few forest lichen species. The analysis of epiphytic lichen diversity showed significant difference in the natural vegetation and disturbed vegetation.
This may be due to the heterogeneity of microclimatic conditions and specialist lichen communities associated with pristine tropical forests. Thus, there is utmost importance to identify lichen communities that can be use as indicators of reflecting forest health for the purpose of sustainable management.