Nutrient fluxes and growth of Carapa guianensis Aubl. in two plantation systems in the central Amazon

Abstract

The K, Mg, and P fluxes as well as the growth dynamics of the important timber tree Carapa guianensis Aubl. were compared in a monoculture and in an enrichment plantation on a “terra firme” site near Manaus, central Amazon. During the 7 years experimental period, the K, Mg, and P fluxes and the balance of the soil were quantified for monthly intervals. The nutrient input into the soil was calculated from the wet and dry deposition as well as from litter decomposition. The nutrient output out of the soil was calculated from the net nutrient uptake of the vegetation and the nutrient leaching from the soil. The growth dynamics of the planted trees were studied by means of biomass data obtained from dendrometric measurements and total tree harvesting. After 7 years of growth, the K, Mg, and P balance of the soil of the enrichment plantation was stabilised, whereas a significant deficit of the K, Mg, and P balance of the soil of the monoculture became obvious, caused by high leaching of K and Mg from the soil and low litter decomposition rates. Due to strong competition during the first 5 years of growth, a reduced biomass production of the planted Carapa trees was found in the enrichment plantation compared to trees grown in the monoculture. After that period tree growth was strongly reduced in the monoculture, whereas after 7 years, growth of Carapa grown in the enrichment plantation was still steady. From this study, it was concluded that due to the balanced K, P, and Mg input and output of the soil and more sustainable growth of the planted trees in the enrichment plantation compared to the traditional monoculture, the cultivation of Carapa for timber production is recommended in diverse plantations, such as enrichment plantations on this study site.