Contribution of harvest residues to nutrient cycling in a tropical Acacia mangium Willd. pantation

Harvest residues can play a crucial role in conserving nutrients for recycling in forests, but little is known about the rates of decomposition and nutrient release from these residues following logging in tropical acacia plantations. In this study, we examined the biomass and nutrient content of harvest residue components (bark, leaves, and branches) using the litterbag technique for a 1.5-year-period following harvest of a seven-year-old Acacia mangium plantation in Northern Vietnam. At harvest, the total dry biomass of harvest residues was 18 t ha^-1 comprising bark (8.9 t ha^-1), branches (6.6 t ha^-1), and leaves (2.5 t ha^-1). The retained bark on site conserved 51% N, 29% P, 32% K, 64% Ca, and 24% Mg content from harvest residues for recycling. Decomposition rate of the leaves was the most rapid (k = 1.47 year^-1; t_0.5 = 0.47 year), then branches (k = 0.54 year^-1; t_0.5 = 1.29 year), and bark (k = 0.22 year^-1; t_0.5 = 3.09 year). During decomposition, the loss of nutrients from harvest residues was K ≈ Ca > N > P > Mg. Decomposition of harvest residues and the associated rate of nutrient release can potentially supply a significant amount of nutrients required for stand development in the next rotation.