The stock of biomass and nutrients has been the basis of many studies in the forest area, mainly those that evaluate the nutritional sustainability of the system. The objective of the present work was to evaluate the biomass and nutrients for the hybrid Eucalyptus urograndis and Acacia mearnsii in monospecific and mixed-species stands at the age of 9 years. For this, the study was carried out in an experimental area in South of Brazil, with three treatments: 100% E. urograndis; 100% A. mearnsii; 50% E. urograndis + 50% A. mearnsii. The hybrid E. urograndis showed lower stemwood in mixed-species planting (105.8 Mg ha⁻¹) when compared to monospecific planting (145.5 Mg ha⁻¹), however A. mearnsii, which increased stemwood at planting (213.9 Mg ha⁻¹) relating to its pure planting (143.6 Mg ha⁻¹). The nitrogen concentration in the leaves and stembark (25 and 5 g kg⁻¹, respectively) of A. mearnsii was significantly higher than that found in the respective hybrid E. urograndis components (18 and 3 g kg⁻¹ for leaves and stembark, respectively). A. mearnsii had higher accumulation of biomass and nutrient accumulation in the mixed-species plantation when compared to its monoculture, and the inverse was observed for the hybrid E. urograndis, thus showing that mixed-species planting exerted a competition effect on eucalyptus.

生物量和养分储备一直是森林地区许多研究的基础，主要是那些评估系统营养可持续性的研究。本工作的目的是评估9岁时在单种和混合种林中杂交的桉木和阿拉伯相思的生物量和养分。为此，该研究是在巴西南部的一个实验区进行的，采用了三种处理方法：100％的E. urograndis；100％mearnsii ; 50％urograndis  + 50％mearnsii。杂种E. urograndis在混合树种种植中的材材较低（105.8 Mg ha ^-1）与单种种植（145.5 Mg ha ^-1）相比，然而，A。mearnsii增加了种植时的茎木（213.9 Mg ha ^-1），这与其纯种植（143.6 Mg ha ^-1）有关。在叶片（25和5g公斤的氮浓度和stembark ^-1分别）的A.黑荆树是显著比在各自的混合发现更高E. urograndis部件（18和3g千克^-1为树叶和stembark，分别）。与单一栽培相比，混合物种人工林中的A. mearnsii具有更高的生物量积累和养分积累，而杂种则相反E. urograndis，因此表明混种种植对桉树具有竞争作用。