Eucalypt growth in monoculture and silvopastoral systems with varied tree initial densities and spatial arrangements

Brazil has large stretches of degraded land, mainly occupied by pasture. Recently, the Brazilian government created a program providing financial support to recover these lands throughout the country by establishing agroforestry systems, among others. To select the most appropriate initial spatial arrangements and tree planting density for such systems, the plant growth and leaf area index (LAI) of a Eucalyptus camaldulensis clone were evaluated in five spatial arrangements: 3.6 x 2.5 m, and 3.3 x 3.3 m (monoculture), and (2 x 2) + 10 m, (3 x 3) + 9 m, and 9 x 3 m (silvopastoral systems), with 1,111, 918, 833, 556 and 370 plants per hectare, respectively. The arrangement did not affect plant height growth (p > 0.05) up to 50 months. The average diameter was affected by plant proximity in the planting line, being smaller (p < 0.05) in the arrangements (2 x 2) + 10 m, and 3.6 x 2.5 m, and by the number of lines in the rows, as the plants in the single line arrangement (9 x 3 m) attained the highest diameter. Individual volumes of high initial density stand were lower than in the silvopastoral systems. The arrangements (2 x 2) + 10 m, 3.6 x 2.5 m, and 3.3 x 3.3 m did not differ (p > 0.05) in volume per hectare, which was higher (p < 0.05) than for the other arrangements studied. LAI decreased with age and it was higher (p < 0.01) in the monoculture as compared to the silvopastoral systems. The silvopastoral system can be established in the (2 x 2) + 10 m arrangement for high biomass production besides having the additional benefit of financial returns from the pasture, as compared with the monoculture. The 9 x 3 m arrangement is preferable for large diameter log production.