Can debarking affects sex ratio, population structure and spatial segregation?: insights of unsustainable harvesting in a Mesoamerican tropical tree

Abstract

The ecological mechanisms that contribute to maintaining plant populations have been exhaustively examined around the world, but the relative quantification of the effect of anthropogenic processes on these mechanisms in tropical dioecious tree species has not been revealed yet. The aim of this study was to analyze the effect of debarking on the sex ratio, population structure, distribution and spatial correlation between the sexes and growth stages of Amphipterygium adstringens (Anaciardiaceae), a dioecious tree species that is highly exploited for its medicinal bark. We found differences in plant density between harvested and non-harvested stands. The sex ratio was 1.33♂:1♀ in harvested stands while the opposite was true for non-harvested stands (1.27♀:1♂), which suggest that selective debarking drives androic-skewed and has an impact on reproductive performance. However, despite the dominance of a certain sex in the relative frequencies under each condition, we did not register spatial sex segregation since the analysis suggests that the spatial independence pattern does not differ between sites. In contrast, facilitation requirements (spatial attraction) between androic plants and seedlings, and between seedlings and saplings were found in non-harvested areas, while spatial uniformity patterns on a population level suggest strategies to avoid competition over space and finite resources in stressful environments. These novel findings point out that debarking constitutes a factor that not only modifies the spatial and population structure of a Mesoamerican tropical tree, but it can also influence sex ratio, consequently affecting the long-term conservation of A. adstringens stands.