INCOME AND DIVERSITY TRADEOFFS FROM MANAGEMENT OF MIXED LOWLAND DIPTEROCARPS IN MALAYSIA

Abstract

Short-run and long-run effects of current management regimes in Southeast Asia were evaluated for their economic returns and diversity of tree size and species. A two-species (dipterocarp and non-dipterocarp), seven size-class growth model was constructed to agree in the steadystate with data from old-growth lowland dipterocarp forests in Peninsular Malaysia. Three options for Southeast Asian forest management systems were evaluated and compared to constrained optimum regimes. The evaluation criteria were the Shannon-Wiener index to measure diversity, minimum number of trees in any species-size class, soil rent, forest value, internal rate of return, and annual yield. Regimes were compared in the steady-state (long-run) and during convergence (short-run) of stands of different initial conditions to the steady-state. Regimes that gave the highest economic performance or maximum diversity in the steady-state also did so during conversion, for stands with either high or low initial basal area. To a great extent, the ability to harvest heavily and early in the conversion period determined the economic performance of a management regime. Among the regimes studied, a good compromise between economics and diversity was to cut mostly 30- to 40-cm trees of dipterocarps and non dipterocarps every 10 years. This would maintain some trees in all size and species classes. Financial returns would be comparable to those of other investments in Malaysia and similar to the highest yield under current management regimes, but tree diversity would be much higher.