Optimizing forest residue management after harvesting: nutrient export scenarios in Eucalyptus plantations across high forest and coppice systems

Abstract

Abstract In tropical regions, biomass from forest residues in Eucalyptus plantations, particularly belowground, are increasingly recognized as a vital energy source; however, harvesting this biomass can deplete soil nutrients, potentially reducing wood productivity in subsequent rotations. This study estimates biomass and nutrient content across various compartments (trunk, branches, leaves, and roots) within high forest (originated from planted seedlings) and coppice systems. Six nutrient export scenarios were established, each varying by the compartments removed: Scenario 1 (S1-W) exports wood only; Scenario 2 (S2-WT) exports wood and the topwood; Scenario 3 (S3-WTS) adds the stump; Scenario 4 (S4-WTB) incorporates bark; Scenario 5 (S5-WTBC) includes the canopy; and Scenario 6 (S6-WTBCS) combines all compartments. This methodology assesses how the selective removal or retention of these compartments influences nutrient availability and soil fertility across successive rotations. The obtained biomass distribution revealed that wood constituted 67%–72%, while leaves accounted for only 2%–3%, with the coppice system yielding 64% more coarse roots than the high forest system. Nutrient exports varied significantly among scenarios, with S3-WTS indicating a 64% nitrogen loss in high forest and 96% in coppice, while S6-WTBCS demonstrated substantial exports of calcium, nitrogen, and sulfur, highlighting a negative nutrient balance that jeopardizes long-term soil health and productivity. Although applying fertilizers may address nutrient deficits, biomass decomposition can also adversely affect soil structure and organic matter. This study offers critical insights for forest managers to better understand nutrient balance in soil for future rotations.