Assessing the sustainability of Sengon ( <i>Falcataria moluccana</i> ) community forests in West Java, Indonesia: insights from litter dynamics and nutrient contributions

Sengon (Falcataria moluccana)-based community forests are widely promoted in Indonesia for their rapid growth and economic value. However, understanding of their litter dynamics and nutrient contributions to soil fertility remains limited. This study aimed to evaluate litter production, decomposition rates, and nutrient (C, N, P, K) returns across an altitudinal gradient and varying planting distances in West Java, Indonesia. Research was conducted over 12 months, encompassing both dry and wet seasons, using litter traps and litterbags combined with laboratory analyses. Results showed that lower elevations (200–500 m a.s.l.) and wider planting distances (2 m × 4 m) produced the highest litterfall (up to 7.5 t/ha/year) and fastest decomposition rates (k = 3.17 year⁻¹), driven by favorable microclimatic conditions. Annual nutrient returns reached 2.8 t C/ha, 98 kg N/ha, 6 kg P/ha, and 78 kg K/ha, translating into potential fertilizer savings of up to 13,990 kg manure, 212 kg urea, 40 kg SP-36, and 156 kg KCl per hectare per year. These findings underscore the importance of optimizing Sengon site selection and planting configurations to enhance nutrient cycling and reduce dependence on external fertilizers. This approach supports the long-term sustainability of community forest and provides a model for similar tropical agroforestry landscapes.