Ecologia e dinâmica de plantas daninhas em cultivos de eucalipto, em diferentes relevos

Abstract

In the present study aimed to evaluate the dynamics of weeds in crops of eucalyptus and identify in these communities species of importance to the environment and to the use of man. They were realized floristic and phytosociological surveys in homogeneous stands of eucalyptus in Forestry projects of Celulose Nipo Brazilian (CENIBRA) in the mineira cities of Santana do Paraíso and Guanhães. In two areas evaluated prior to planting, it was realized desiccation of the weeds as an operation of area preparation. After the desiccation, the areas were prepared with lime with 700, 1000 and 1500 kg ha-1 of limestone in the lowland, slope and in the upper area respectively, 30 days before planting. After liming, the areas were subsoiled and grooved, with distribution of 700 kg ha-1 of natural phosphate in the groove. In Santana do Paraíso the planting, seedlings of clone 837C were planted in January 2010, with the spacing of 3X2, 5 m. Six months after planting, increased the fertilization of reinforcement with 100 kg ha-1 NPK (6-30-6), distributed in the vicinity of the seedlings in all reliefs. Subsequent to planting, there were two chemical weeding with 2,5 L of glyphosate ha-1, with application in the entire area, at 60 and 180 days after planting (DAP). In Guanhães, planting occurred in December 2009 using the clone 213C99, with spacing of 3.0 x 3.33 m. Eight months after planting there was reinforcement of NPK (6-30-6), being 100 kg ha-1 in all reliefs. Subsequent to planting, there were two chemical weeding with glyphosate at the rate of 2.5 L ha-1 at 60 and 210 DAP. The total area sampled for each location was approximately 10 hectares, comprised of three types of relief: lowland, slope and upper area, being sampled 10 plots of 1m2 each, chosen randomly in zig zag, corresponding to 30 parcels per municipality. The taxonomic identification was made in two times, concerning to the months of March and November for two consecutive years, including four assessments by municipality. The weeds were identified through consultations to herbaria, experts and comparison of the specialized literature. The samples were georeferenced, ensuring a sample in the same plot at different times. It was identified in the municipality of Santana do Paraiso, a total of 3,893 individuals, distributed in 18 families and 61 species, with 17 of them considered as medicinal, 4 food , 5 with potential in nitrogen fixation, 18 forage , 3 toxic and 4 ornamental. In Guanhães, we identified 1,166 individuals, being 13 families and 58 species, with 17 of them medicinal, 4 food, 7 nitrogen-fixing, 12 forage, 2 toxic and 4 ornamental. Poaceae and Asteraceae were the richest families for the two areas evaluated.The group of eucotiledôneas had emphasis on both localities. Diversity indices showed an increase during the crop cycle, especially in the slope and upper area. The highest values of similarity were found between the reliefs of lowland / slope and slope / upper area.