| Abstract: |
Short-rotation (3-4 years) and high density (4,500-10,000 trees per hectare) acacia for pulp and paper purpose is one of the most popular forest plantation systems in Viet Nam, including in the Southcentral Coast region. There is a need however to find alternative designs to further improve the economic return and environmental benefits such carbon storage that can be derived from the system, and to develop forest plantation systems for other purposes, such as timber production. We used the Water, Nutrient and Light Capture in Agroforestry Systems (WaNuLCAS) model to assess the performance of eight forest plantation systems for Quang Nam province that could be expected to provide higher and more stable income and higher levels of carbon storage, including timber production. The systems combined different spacings and rotations of acacia with cycles of cassava as intercrop.
Among the different systems, for farmers who largely rely on forest plantation as the source of income, the four-year rotation system with 3 x 3 m tree spacing for pulp and paper purpose and three seasons of cassava is the most feasible option as it leaves no income gap between investment and tree harvesting. In terms of carbon storage however, this system is inferior than the four-year rotation systems and the baseline. Among the systems for timber, the highest income per year, time-averaged carbon storage and timber production were obtained from 3.5 x 3.5 m and 4 x 4 m acacia spacing, in 12-year rotations. For these options, farmers need other sources to cover the income gap between investment and timber harvest and to the loan.
We conclude that the performance of current short-rotation forest plantation system can be improved by selecting appropriate tree spacing and include more cycles of intercrop. Systems with long rotations for timber, however, need to offer other income sources for farmers to maintain cash flow. Furthermore, since smallholder farmers with few resources generally are risk-averse, local authorities need to develop demonstration trials of selected alternative systems with the farmers, whilst improving micro-finance and loan system, and access to markets for other products than pulp and paper. |
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