Abstract

Aim of study: To assess responses of the shade-tolerant species Theobroma subincanum in relation to canopy gaps created by reduced impact logging (RIL).Materials and methods: A managed forest in themunicipality ofMoju, Pará state,Brazil, harvested in 1997 through RIL was monitored during 12 years (1998-2010). Nine logging gaps were selected and classified in small, medium, and large. Four 10 m x 50 m strips starting from the gap’s border towards the forest and following the directions of cardinal points were installed. Each strip was divided in five 10 m x 10 m plots. Density, diameter distribution (DBH ≥ 5 cm with intervals = 5 cm), and diameter growth were measured.Main results: No significant changes in seedling density of T. subincanum were found, and its diameter distribution followed the reverse “J” shape during all monitoring time. T. subincanum presented diameter growth of 0.15 cm year-1 with highest Periodic Annual Increment in diameter up to three years, and stabilization in nine years after RIL. The species responded to a growth gradient inversely proportional to the gap’s border distance (p = 0.001) but not to gap size and plots direction in cardinal points around the gap.Research highlights: Shade-tolerant species such as T. subincanum have sensible and positive growth responses to disturbances caused by RIL even when seedlings received low amounts of indirect sunlight. These positive responses should be considered in the management of production forests.Keywords: Ecological group; forest management; diameter distribution; reduced impact logging (RIL).

Highlights

  • Materials and methodsA managed forest in the municipality of Moju, Pará state, Brazil, harvested in 1997 through reduced impact logging (RIL) was monitored during 12 years (1998-2010)

  • Forests under selective logging usually present high­ er dynamics than untouched forests, due to logging op­ erations as infrastructure construction and tree cut and dragging (Yguel et al, 2019)

  • This study, had the objective to assess the effects of forest harvesting and logging gaps size on growth of seedlings belonging to a remnant population of T. subincanum in a forest monitored during 12 years after reduced impact logging (RIL) in the Eastern Amazon

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Summary

Materials and methods

The experiment was carried out in the Experimental Field of Moju, belonging to Embrapa Eastern Amazon and located at Km 30 of the PA 150 highway, munici­ pality of Moju, Pará state, Brazil, between the latitudes 2°07’30”S and 2°12’06”S and longitudes 48°46’57”W and 48°48’30”W. The number of individuals in class 5.0-9.9 diminished as a conse­ quence of mortality and switch of individuals to upper diameter classes (Fig. 3) This distribution pattern is proper of shade-tolerant species. Individuals of T. subincanum were distributed accord­ ing to a reverse “J” shape, the most common distribu­ tion pattern of native tropical forests This curve indi­ cates a population dynamic balance of a shade-tolerant species, where most of the individuals are concen­ trated in smaller diameter classes. Shade-tolerant species are sensible to low quantities of light, as even those plots far 40 and 50 m away from the gaps’ border, two years after RIL, still presented statistical differences from each other. Despite the fact that individuals of T. subincanum grew better in a light gradient, they did not respond to their location in cardinal points

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