Fire Compromises the Recovery of a Managed Forest in Tapajós National Forest, Eastern Amazon, Brazil

Logged forests are more prone to fire, shifts in species composition, and losses in biodiversity. In this work changes in the horizontal structure and species composition of a managed forest in the Tapajós National Forest, Eastern Amazon, Brazil, along 31 years (1981-2012) was evaluated. The disturbances included logging (1982), thinning of non-commercial species (1993/1994), and fire (1997). Data were obtained in 36 0.25-ha permanent plots split in 12 plots per each one of three harvesting treatments. In 1997, 16 plots were reached by an accidental superficial fire. The changes in species composition and diversity between the last measurement after logging and before fire (1995) and the last measurement (2012) were compared. PERMANOVA, considering the relationship between the NMDS axes and the treatment variable (logging / control + unburnt / burnt) differed in species composition, among treatments before fire (1995) and 15 years after fire (2012). The post-hoc test for PERMANOVA showed great similarity among logged forests before and after fire. The forest pre-disturbance conditions were important drivers in forest recovery, since logged forests under heavy thinning presented more losses in basal area and alterations in species composition. Therefore, stronger and more frequent disturbances can compromise the forest resilience.