Biophysical factors associated with radiation use efficiency and productivity of Mimosa scabrella plantations for energy

Forest plantations managed for biomass production play an important role in the transition toward renewable energy systems. However, the biophysical factors underlying biomass production and radiation use efficiency (RUE) in native tree species remain poorly understood. This study evaluated radiation use efficiency, biomass accumulation, radiation interception, and potential energy yield of Mimosa scabrella Benth. plantations established under different planting spacings in southern Brazil. A nine-year field experiment was conducted in a randomized complete block design with three replications and four planting spacings (2.0 × 1.0, 2.0 × 1.5, 3.0 × 1.0, and 3.0 × 1.5 m). Measurements were performed at 1, 3, 5, 7, and 9 years to evaluate leaf area index (LAI), photosynthetically active radiation interception, biomass accumulation and partitioning, and RUE. The relationships among these variables were further investigated using principal component analysis based on treatment means for each spacing × age combination. Planting spacing affected stand development, radiation interception, biomass production, and energy yield. The densest spacing (2.0 × 1.0 m) exhibited the highest RUE (0.0021 kg MJ −1 ), aboveground biomass production (264 Mg ha −1 ), and potential energy yield (1,276.9 MWh ha −1 ), indicating greater biomass production per unit of intercepted radiation. Principal component analysis showed strong associations among LAI, radiation interception, RUE, and biomass accumulation, highlighting the role of canopy development in stand productivity. These findings contribute to understanding the biophysical factors associated with biomass production in M. scabrella plantations and provide a basis for evaluating planting spacing in forest systems intended for sustainable bioenergy production.