The Effect of Different Levels of Inclusion for Forest Restoration Assessment

Abstract

Aim: The aim of this work is to compare two sampling methods (called survey A and B) with different inclusion criteria to evaluate floristic composition, species richness and horizontal structure of a five-year-old forest restoration area. Methodology: The area with a total of 32.21 ha is located in a Tropical Rainforest region. Survey A included individuals with circumference at breast height (cbh) ≥ 6 cm while in survey B, the minimum cbh was ≥ 15 cm. Results: Forty-six species have been found in survey A belonging to 40 genera and 21 families. In survey B, only 33 species were found, belonging to 30 genera and 15 families. Regarding species richness, method B did not reach the theoretical asymptote in relation to A, leading to underestimation. The number of individuals and absolute density of survey A and B, we found 891 individuals or absolute density of 1,782 ind. ha-1 and 166 individuals or absolute density of 332 ind. ha-1, respectively, representing a difference of 81.4%. Also, significant differences have been observed for cbh, height and crown projection, where method A presented higher potential to express the data. Conclusion: The present study confirmed the hypothesis that the inclusion limit cbh ≥ 15 cm, commonly used for assessing forest restoration processes in recently established areas, provides biased estimates about different ecological processes, such as floristic composition, species richness and forest structure. It is therefore recommended to use a lower cbh for tree measurements in assessments of low-aged tropical rainforest restoration areas.