Silvicultural intensification in natural forests in Indonesia: Consequences for timber yields, carbon dynamics, tree species composition, and profits

• Main Author: Ruslandi
• Format: Dissertation
• Language: English
• Published: ProQuest Dissertations & Theses 01-01-2016
• Subjects: Economics; Sustainability; Wood sciences
• ISBN: 1369655428; 9781369655421

Nature conservation through sustainable forest management in the tropics is challenged by diminishing timber yields. Silviculture treatments beyond logging are recommended to increase timber stocking, growth, and profits. Indonesia embarked on large scale silviculture intensification without solid scientific evidence for the approach. To fill this information gap, I assessed the timber, carbon, tree species composition, and financial implications of different silvicultural practices in dipterocarp forests in Kalimantan, Indonesia. With data from 30 one-ha sample plots monitored for up to 20 years after silvicultural intervention coupled with a new forest growth and yield model simulation (“SILFOR”), I evaluated the long–term consequences of four silvicultural practices. The practices were: once logged with a minimum cutting diameter (MCD) of 60 cm (L60); once logged followed by under-planting with seedlings of commercial timber species (L60UP); twice logged with MCDs of 60 cm and then 40 cm (L60L40); and, twice logged followed by strip planting along cleared lines (L60L40SP). Autocorrelations in the growth data were accounted for with mixed-effect models that also improved model fit compared to a fixed-effect approach. Nevertheless, for projections beyond the field data, fixed-effect models were used for developing diameter increment, mortality and recruitment models. The results indicate that timber yields will not be sustained by L60 or L60L40, even with 60-year cutting cycles. In contrast, yields from enrichment planted loggedover forests will recover to levels higher than the first cut if cutting cycles are extended to 50 years for L60UP and to 40 years for L60L40SP. Under these intensive silvicultural regimes, biomass carbon stocks recover to primary forests levels, with increased representation of commercial species. Strip planting after logging was also more profitable than logging only with annual discount rates of up to 8%. Given that planted trees have better boles and shorter buttresses than naturally regenerated trees, timber yields and profits from strip planting will likely be even higher than predicted. Nevertheless, strip planting should be used to complement low intensity logging to sustain timber yields, to increase financial viability of natural forest management, and to maintain conservation values in managed natural forest.