Tree and stand light use efficiencies over a full rotation of single- and mixed-species Eucalyptus grandis and Acacia mangium plantations G. le Maire a,⇑ , Y. Nouvellon a,b , M. Christina a , F.J. Ponzoni c , J.L.M. Gonçalves d , J.-P. Bouillet a,d , J.-P. Laclau a,e a CIRAD, UMR Eco&Sols, 2 Place Viala, 34060 Montpellier, France b University of São Paulo, IAG, Atmospheric Science Department, São Paulo, Brazil c National Institute for Space Research, INPE, Remote Sensing Department, São José dos Campos, Brazil d University of São Paulo, ESALQ, Forest Department, Piracicaba, Brazil e University of São Paulo, Ecology Department, São Paulo, Brazil article info Article history: Available online 6 April 2012 Keywords: MAESTRA Radiation use efficiency Eucalypt Light capture Canopy structure abstract Understanding the light absorption and light use efficiency of each species at the tree scale is essential to disentangle the effects of intra- and inter-species interactions on productivity in mixed-species forest plantations. A complete randomized block design was set up using Eucalyptus grandis (E) and Acacia mangium (A), which is a N 2 -fixing species, planted in monospecific stands (100A, 100E) and in additive (25A:100E, 50A:100E, 100A:100E) and replacement (50A:50E) mixtures. Tree size and biomass were monitored over the complete rotation (6 years). The absorbed photosynthetically active radiation (APAR) for each tree in the experiment was simulated over the full rotation with the MAESTRA model. Measure- ments of tree leaf area, leaf angle distributions, leaf area density, and leaf and soil optical properties were performed to parameterize this model. The APAR and the ratio of stem biomass increment divided by the APAR (which is a measure of the Light Use Efficiency [LUE] for stem production) were calculated at tree and plot scales for each year of the rotation. The LUE of the 100E stand increased with age until stabilizing at 4 years of age, while the LUE of the 100A stand decreased between 2 and 4 years of age and increased between the two last years of the rotation. Eucalyptus trees dominated Acacia trees in mixed plantations. The stratification of the canopy led to an increase of stand Leaf Area Index (LAI) and APAR compared to monospecific plantations. However, both Eucalyptus and Acacia LUE decreased at the end of the rotation in the mixed-species stands, with the decrease occurring more markedly in Acacia, and the final stem bio- mass of the stand was not enhanced in mixed-species plantations compared with the average of the pure stands. Our results indicate that a stratified canopy may offer the potential benefit of capturing more light in mixed-species forests, but this may be negated if another resource deficiency prevents trees from con- verting intercepted radiation into dry matter. Mixed-species plantations should be established at suffi- ciently rainfed sites to maximize LUE, and appropriate fertilizer regimes should be applied. Ó 2012 Elsevier B.V. All rights reserved. 1. Introduction Most forest plantations are currently grown as monocultures. In tropical countries, highly productive Acacia mangium (Willd.) and Eucalyptus grandis Hill ex Maid. monospecific plantations are man- aged over several million hectares (FAO, 2006; Yamashita et al., 2008). Mixed-species plantations can be used to increase the over- all stand productivity through complementarity and/or facilitation processes (Forrester et al., 2006; Kelty, 2006). Species with comple- mentary rooting traits, contrasting vertical growth rates, different crown structures or foliar phenology may increase resource cap- ture by taking advantage of complementary niches (Kelty, 2006; Cardinale et al., 2007). Resource use efficiency is estimated as the quantity of gross or net production per unit of resource used (e.g., water use efficiency, light use efficiency, nutrient use effi- ciency). While resource use efficiency may increase with resource use (Binkley et al., 2004), mixed-species plantations may also use the resource more efficiently through facilitation mechanisms (Kelty, 2006). For example, planting N 2 -fixing tree species with non-N 2 -fixing tree species may enhance N soil availability and in- crease the growth of the non-N 2 -fixing trees (Kaye et al., 2000; Richards et al., 2010). Many studies have shown that N-fixing spe- cies may have a positive effect on the overall productivity of mixed forest plantations (e.g., Binkley et al., 1992; Khanna, 1997; Bauhus et al., 2000, 2004; Forrester et al., 2006). However, inter-specific interactions depend on species associations (Forrester et al., 2006), soil fertility (Boyden et al., 2005), site climatic characteris- tics, abiotic stress factors (Forrester et al., 2011; Moore et al., 2011), and stand ages (Forrester et al., 2011). While many of these 0378-1127/$ - see front matter Ó 2012 Elsevier B.V. All rights reserved. http://dx.doi.org/10.1016/j.foreco.2012.03.005 ⇑ Corresponding author. E-mail address: guerric.le_maire@cirad.fr (G. le Maire). Forest Ecology and Management 288 (2013) 31–42 Contents lists available at SciVerse ScienceDirect Forest Ecology and Management journal homepage: www.elsevier.com/locate/foreco