Physiological Aspects of Acacia and Eucalyptus in Competition with Brachiaria

Competition between plants results in the reduced availability of certain resources essential for the species, leading to deficiencies that culminate in changes in their physiological characteristics. In the intercropping systems the species in the study grew under competitive conditions. The competitive potential of plants for environmental resources was dependent upon the other species present in the area, as well as the competitive characteristics of the individuals concerned. Therefore, this study was conducted to evaluate the physiological characteristics of Acacia mangium and Eucalyptus urophylla × grandis in the early stages of development when grown intercropped with forages of the genus Brachiaria. An experiment was set up using a randomized complete block design, in which the treatments consisted of a factorial arrangement of 2 × 4, being respectively, two tree species (acacia and eucalyptus) and the forage species, Brachiaria brizantha cv. Marandu and cv. Piata, Brachiaria decumbens cv. Basilisk grown together with the tree species, plus two additional controls with acacia and eucalyptus grown in monocrop. The coexistence of the forages negatively affects the photosynthetic characteristics of both the tree species. B. decumbens was the species that promoted a negative effect on most of the variables in both acacia as in eucalyptus, presenting a greater competitive capacity among the brachiaria studied.