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Light use efficiency and productivity of 16 genotypes of Eucalyptus along a 6-year rotation in Brazil

Le Maire G., Guillemot J., Campoe O., Stape J.L., Laclau J.P., Nouvellon Y.. 2019. Pesquisa Florestal Brasileira (39) : p. 314-314. IUFRO World Congress 2019 "Forest Research and Cooperation for Sustainable Development". 25, 2019-09-29/2019-10-05, Curitiba (Brésil).

Forest stemwood productivity depends on the amount of absorbed light and on the Light Use Efficiency (LUE), i.e. the amount of stemwood produced per amount of absorbed light. Other growth limiting factors than absorbed light are for instance water and nutrients, carbohydrates allocation processes, and management practices. In fertilized eucalyptus plantations in Brazil, a shift in the main factor limiting growth is expected, from light at the beginning of the rotation (not limited by water because soil has been recharged during the interval between rotation) to other factors such as water in the subsequent years. Changes of allocation patterns and foliar traits also occur along the rotation. These trends may differ between genotypes. These hypotheses were tested along a 6-year rotation, with 16 contrasted genotypes planted in 10 randomized repetitions in São Paulo Region, Brazil. Absorbed light was estimated using the MAESTRA 3D model precisely parameterized at tree scale for each plot. Stand growth was computed based on allometric relationships calibrated on regular destructive biomass measurements. Results at stand scale showed that 1) LUE increased with stand age for all genotypes, from 0.15 to 0.70 gdry_matter/MJ on average; 2) light was the main limiting factor during the first year of growth (R2 between 0.5 and 0.95). Subsequently, the variability of wood production explained by light was variable among genotypes (R2 of 0.25 on average; 3) The effect of genotype on stemwood production remains high and significant along the rotation. These results and their implications for plantation management are discussed.

Mots-clés : eucalyptus; croissance; lumière; absorption; génotype; fertilisation; brésil

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