Spatial analysis of the natural regeneration of Candeia (Eremanthus erythropappus (DC.) MacLeish) as influenced by non-Candeia tree layer composition

Abstract

Background: Tree regeneration in native stands harvested for wood is essential to guarantee sustainability of the practice. Understanding how forest species spatially establish themselves in exploited areas enables the verification of ecological processes and possible interactions among ecological variables. For instance, tree species that are light demanding must be managed in a way that ensures that the canopy of the stand is opened enough to permit direct sunlight to reach the seeds, otherwise stand regeneration is not obtained. This is the case of native candeia stands located in southern Minas Gerais State, Brazil. This species is managed for wood used in essential oil extraction. Being a species that occurs in transition zones from forest formations to open fields, this species tends to form monodominant stands in areas that have low fertility soils. Objective: The main objective of this study is to determine how candeia regeneration establishes itself after wood harvest under varying intensities of canopy cover. Results: We analyzed the influence of uncut mature trees on candeia natural regeneration, by means of spatial dependence analysis and mapping of the natural regeneration of candeia and the tree layer in areas subjected to exploration. The variables analyzed included the number of regenerated individuals of candeia and noncandeia trees present in the tree layer, obtained from circular sample plots. Both variables showed structured spatial continuity, varying only in terms of the degree of spatial dependence. Results showed that there is a spatial relationship between the intensity of candeia that was naturally regenerated and the number of individual trees of other species present in the tree layer in all forest fragments subjected to management. This represents a limiting factor in candeia natural regeneration in areas with high noncandeia tree layer incidence. Conclusion: Sustainability of the management practiced in terms of natural regeneration is attained in areas of high candeia dominance (at least 64% of occurring individuals).