Enhancing the sustainability of smallholder timber production systems in the Gunungkidul region, Indonesia

Smallholder farmers who grow trees as part of their farm enterprise face many challenges in optimising returns from their farming systems. This research evaluates a range of silvicultural options that can be applied by smallholders in central Java, Indonesia, in their integrated tree and crop growing systems. The research was conducted in the Gunungkidul region, where planting timber trees on smallscale farms has been promoted as a way to restore degraded farmland and produce forest products for household consumption and commercial markets. Corresponding to the decline in the natural forests of Gunungkidul, the demand and prices for timber has increased, leading to perceptions that farm-based forestry could be an important enterprise for smallholders. However, the typical silvicultural practices applied by farmers result in low levels of production and quality, severely restricting the profitability of teak-based forestry. This research contributes to a better understanding of the context of the farming and forestry systems developed by smallholders in Gunungkidul, and how changes to silvicultural practices could improve the returns to smallholders from timber-based forestry. This research revealed both on-farm and off-farm income, and the total farm area, affect the farming and forestry systems. Farmers with a higher income and larger farm area were more likely to adopt smallholder timber production systems. The research also analysed the effects of tree and site quality factors on tree growth, with results indicating that teak (Tectona grandis) and acacia (Acacia auriculiformis) grew faster on steeper slopes, while mahogany (Swietenia macrophylla) grew best on slight slopes. Acacia grew best where soil Cation Exchange Capacity and bulk density were lower, and mahogany and acacia grew better under lower annual rainfall conditions. Functional Branch Analysis allometric calculations were used to estimate above-ground biomass for teak, mahogany and acacia trees, using models that were consistent with the common tree size and branching patterns for these species. Validation was good for total above-ground biomass, but need further refinement for the branch and twig components. Using the WaNuLCAS model, the research evaluated the feasibility of different silvicultural systems for mixed teak and acacia planting with a maize intercrop. Treatments that combined a wide initial spacing at 4 metres x 4 metres, light pruning of branches (40% of total stem height) and heavy thinning (75% of all standing trees removed) produced the largest diameter and highest timber volume for teak, and also highest net profits and returns on labour. The thesis concludes with a synthesis of the implications of these results for Indonesian smallholders seeking to optimise the performance of tree crops as part of their farming system, and for further research to support this