Production and Nutrient Cycling in Mixed Plantations of Eucalyptus and Albizia in Hawaii

Abstract

Abstract Experimental plantations of pure Eucalyptus saligna (Sm.), pure Albizia falcataria (L.) Fosberg (a nitrogen-fixing species), and five proportions of mixtures of these species were examined at age 6 for biomass, production, nutrient cycling in litterfall, and resource-use efficiencies. Biomass was greatest in the 34% Eucalyptus/66% Albizia treatment, averaging 174 Mg/ha, compared with 148 Mg/ha in the fertilized pure Eucalyptus treatment and 132 Mg/ha for the pure Albizia treatment. The 34% Eucalyptus/66% Albizia treatment also showed the greatest aboveground net primary production (52 Mg ha-1 yr-1) and annual increment (39 Mg ha-1 yr-1). The N and P content of above-ground litterfall ranged from 35 and 3.5 kg ha-1 yr-1 in pure Eucalyptus to 240 and 9.5 kg ha-1 yr-1 in pure Albizia. Nutrient-use efficiency, defined as Mg of ANPP/kg of nutrient in fine litterfall, was greater for Eucalyptus (1.1 for N, 13.4 for P) than for Albizia (0.2 for N, 5.7 for P). Light-use efficiency ranged from about 14 kJ/MJ of intercepted light in the pure Albizia treatment, to 17 kJ/MJ in the pure Eucalyptus treatment, to 18 in the 34% Eucalyptus/66% Albizia treatment. The patterns of productivity across the mixtures resulted from the combination of (1) greater nutrient use efficiency of Eucalyptus, (2) greater nutrient cycling under Albizia, and (3) greater light capture and high use efficiency in mixed stands. For. Sci. 38(2):393-408.