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SUMMARYIn addition to latex and timber, the rubber tree is useful in the alleviation of rural poverty and also in the mitigation of climate change through fixing atmospheric CO2as biomass. For developing any rubber-based carbon projects, protocols for quantifying biomass and carbon fixed are required. In this context, the present study was aimed at building up allometric models using simple growth indicators (i.e. tree diameter and total height) to assess the timber, biomass and carbon in rubber trees and also to quantify their ontogenetic variation under average growth conditions in two major climatic regimes (i.e. wet and intermediate) of Sri Lanka. All models developed were in the accuracy level of over 88%. The mean absolute percentage error in the validation of allometric models was only 12.9% for timber and less than 5% for biomass and carbon. Under average growth conditions, 1 ha of rubber could produce 208 m3timber, 191 MT biomass and fix 78 MT carbon during its 30-year lifespan in the wet zone and ca. 16% lesser values in the intermediate zone. The applicability of the findings in carbon trading is discussed.

The goal of this study was to investigate the social carrying capacity (SCC) of the Horton Plains National Park (HPNP). Crowding is considered as the social norm for estimating the standards for SCC. The 'normative theory' approach was applied in this study and separate social norm curves were prepared for each viewing point. Based on the hypothesis that visitor acceptability or tolerance is infl uenced by 'crowding', scenarios (images) with different numbers of visitors were generated for fi ve main viewing points in the HPNP. The crowding standards for SCC were estimated by asking each respondent whether the presented scenarios were acceptable or not at each viewing point. The average visitor acceptability decreased with increasing number of visitors ('crowding'). The social norm curves were used to determine the standards. It was revealed that view points at the HPNP were crowded beyond the carrying capacity standards during weekends and public holidays. The highest carrying capacity standard was found at the Greater World's End and the least was recorded at the Chimney Pool. Therefore, the results of the present study could be applied in decision making to diversify tourism activities in order to achieve better visitor management.

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