Accumulation and distribution of aboveground biomass and nutrients in pure and mixed stands of guachapele and eucalyptus

The biomass accumulation and the distribution of nutrients in the different components of the aerial parts (leaves, branch, bark, and wood) of pure and mixed stands of guachapele [Pseudosamanea guachapele (Kunth) Harms] and eucalyptus (Eucalyptus grandis W Hill ex Maiden) were quantified in Seropedica, Rio de Janeiro State, Brazil. Mixed stands had the highest production of stem tissue (204 m(3)/ha), in contrast with the pure plantations of each species (78.1 m(3)/ha for guachapele and 199 m(3)/ha for the eucalyptus). Total dry biomass of eucalyptus was 1.6 times more than that of guachapele in monoculture and 6.8 times larger than that in the mixed stands. The eucalyptus had 10% less biomass in mixed stands than in pure stands. Despite production of less biomass, the guachapele had more nutrient uptake, accumulating, as a pure stand, 484.68 kg/ha of nitrogen (N), 35.0 kg/ha of phosphorus (P), 274.5 kg/ha of potassium (K), 223.8 kg/ha of calcium (Ca), and 40.7 kg/ha of magnesium (Mg). The eucalyptus plants were more efficient in the utilization of N, P, K, Ca, and Mg than the guachapele and this efficiency was increased in the mixed stands. Among the treatments the litter layer, in the pure stand of guachapele contained the highest quantities of N (273.1 kg/ha) and P (8.2 kg/ha), while the pure stands of eucalyptus of K (22.6 kg/ha), Ca (163.8 kg/ha), and Mg (28 kg/ha).