Dinâmica de reflorestamentos anuais em áreas e mineradas na Amazônia visando a restauração da paisagem florestal, Porto Trombetas, Pará

Abstract

Since the 1970s, Mineração Rio do Norte-MRJN has extracted bauxite in the Saracá-Taquera National Forest, Porto Trombetas, Oriximiná, Pará. After mining, it becomes necessary to restore the original forest landscape by adopting the reforestation technique with the use of tree species, especially those native to the Amazon. The present work aims to provide a diagnosis of the annual reforestations, carried out by the company in the years 1997 to 2002. Two plots were used for each planting year, with dimensions of 10 m x 25 m (250 m'), in which all planted individuals were registered, plotted and identified, measuring the diameter at ground level (DAS), diameter at 30 m (DAP), when possible, and the total height of the individuals. The dynamics of the permanent plots was assessed through parameters such as density, richness, diversity, abundance, mortality, and the average annual increment (AAI) of diametric growth. A total of 493 individuals were recorded, totaling 112 species distributed in 34 families. Mimosaceae and Fabaceae were the most diverse (35 and 31 species, respectively) and most abundant (104 and 95 individuals, respectively. Six families had a single individual in the entire sampling and, consequently, a single species. The most abundant species were Licania tomentosa - Oití (30 individuals. ), Parkia multijulga - Paricá grande (25), Parkia gigantocarpa - Visgueiro - (18), Dipterix odorata - Curnaru (16), üitoria escamosa - Palheteira (15), Dalbergia spruceana - ]acarandá-do-Pará (14), Tapirira guianensis - Tatapiririca (14), Euterpe oleracea - Açaí (13), Enterolobium schomburgki - Fava orelha (12) and Lopbantbera lactescens - Lantern (12). It was also observed that there was higher mortality in the 2000 plantings (79.2%) and lower in 1998 (7.2%). The largest basal area was 2.7 m'/ha observed in the 1998 reforestation and the smallest in the 2002 (0.042 m'/ha). The highest mean annual increment as a function of DBH was 0.215 milha/year for the year 1998 c the lowest 0.05 m'/ha/year for the 2001 planting. It was observed that there is a high species richness - average 92 species planted per year; total of 112 species for the period analyzed. Fabaceae and Mimosaceae, because they grow quickly and occur frequently in the Amazon, are widely used in reforestation and therefore had the greatest diversity and abundance. Diametric growth was very irregular between the years analyzed.