Produção de eucalipto em alto fuste e talhadia e de braquiária em sistemas silvipastoris com diferentes arranjos espaciais

Abstract

The aim of this study was to subsidize the choice of spatial arrangements and eucalypt clones for silvopastoral systems (SSP's) and monoculture based on growth, yield and leaf area index (LAI) of the tree component, and braquiaria dry matter production, in the region of cerrado. The clones 02, 58, GG100, 62 and 19 were studied in the spatial arrangements (2x2) + 10 m, (3x3) + 9 m e 9x3 m, in consortium with Brachiaria brizanta Stapf cv. Palisade, managed as high forest and coppice, and in monoculture, in the arrangements 3.6x2.5 m, 3.3x3.3 m. The experiment was conducted in a completely randomized design with three replications. The LAI was measured along a transect starting from the tree planting line to half of the distance of the interplanting lines, at 30, 50 and 62 months after planting. Crown projection was measured in eight positions every 45°, at 38 months. The brachiaria dry weigth production was obtained at the age of 50 months after planting, at different distances between tree)planting lines. The diameter of 1.3 m height (dbh) and average tree height were measured between 10 and 62 months after planting. The number of sprouts per stump and their survival were evaluated at 62 months after planting. There was a reduction in LAI with stand increasing age and with decreasing tree planting density for most spatial arrangements and clones, for the high forest and coppice systems. The LAI was negatively correlated with the tree spacing and brachiaria dry weight. Positive correlation between spacing and tree projection for all clones was observed. The highest brachiaria dry weight production was obtained in wider spacings. It was observed some increase in brachiaria dry weight in the central part of the interplanting line, for the high forest system, and in the south face for the coppice systems for most clones and tree planting spatial arrangements. The spatial arrangement influenced height growth (p<0.05) for clones 58 and GG100 in the high forest system, and the coppice system always presented lower height as compared to high forest system for all clones. The diameter growth was influenced by the proximity of the plants (p<0.05). The growth in volume per plant was higher in arrangements with lower planting density, highlighting the arrangement 9x3 m (p<0.05). The volume per hectare was influenced by genotype, spatial arrangement, dbh and basal area, with different responses among clones. In some spatial arrangements and clones coppice yield were equal to that achieved in the high forest system (p>0.05). The capacity of eucalypt to maintain sprouts in the stump influenced the final production of coppice forest stand. In general, for higher wood production of small dimensions in silvopastoral systems, the spatial arrangement of planting (2x2) + 10 m is the most suitable, but the (3x3) + 9 m is the most suitable for the GG100 clone, the most productive one. The 9x3 m arrangement can be recommended for producing large dimension logs, with higher aggregation value. The overall results suggest the possibility of using juvenile plants coppice to produce small dimension wood without compromising the production of forage in silvopastoral systems. Some clones are more suitable for the silvopastoral systems due to their low density canopies and, or, due the the high wood production. The choice of the spatial arrangement of the tree component should be performed for each genotype, in order to obtain high yields of the tree component and forage.