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Determining equations to estimate with precision the volume of commercial trees is relevant for decision taking on the use of the forest and on the establishment of public policies for the monitoring and control of natural resources, their valorization and investments. Current paper develops volume equations for the Dense Ombrophilous Forest in Ipixuna, northeastern region of the state of Pará, Brazil. The real volume of 296 sample trees was determined according to the Smalian method. Forty-six trees were selected for a database for the validation of the equations. Twelve mathematic models were tested, of which six had simple entrance and six had a double entrance. Simple entrance models proved to have the best adjustment quality for the Hohenald & Krenn model, with equation v = 5.29918-0.1374d+0.00010d² (R²aj. = 0.84, Sy.x% = 19.81; DMP% = -3.63). In the case of double entrance, the best was Schumacher & Hall model, with equation Logv = -3.7657+1.9242.logd+0.7540.logh, (R²aj. = 0.96, Sy.xr% = 10.46, DMP% = -0.34). After validation of selected equations, the Schumacher & Hall was recommended to estimate the volume of commercial trees in the municipality of Ipixuna due to high precision adjustment. [ABSTRACT FROM AUTHOR]

Managed forests are important landscape components in tropical regions and may contribute to biodiversity conservation. Yet, managing tropical forests sustainably requires an understanding of ecosystem responses to silvicultural interventions. We investigated how silvicultural intervention intensity affects tree species composition and diversity over 30 years in the Brazilian Amazon by comparing them to pre-logging conditions and to an unlogged control. The interventions comprised logging in 1982 and thinning in 1993–1994 and ranged in intensity from 19 to 53% reduction in the original basal area (BA). Trees with a diameter at breast height (DBH) ≥ 5 cm were measured on eight occasions in 41 permanent sample plots of 0.25 ha each. Silvicultural intervention intensity influenced both tree species composition and its trajectory within 30 years. In contrast, tree species diversity was not impaired. High intervention intensities (with BA reduction > 6.6 m 2 ha − 1 ) had a substantial influence on the community of trees (DBH ≥ 10 cm), which did not show signs of return to pre-logging species composition. The reduction of BA through harvesting damage and thinning had a stronger effect on species composition than logging of mature trees itself. Thus, damage should be kept to a minimal level and strong thinning interventions should be avoided. This may enhance ecosystem recovery and maintenance of biodiversity at other trophic levels. Since current permitted harvesting intensities in the Brazilian Amazon are lower than the lowest intensity examined in our study, legal harvesting practices are unlikely to cause substantial, long-term changes in tree species composition. [ABSTRACT FROM AUTHOR]