Assessing woody plant encroachment by comparing adult and juvenile tree components in a Brazilian savanna

Abstract

Woody plant encroachment (WPE) is a process that lead to the transformation of savanna environments into forests, and in the threatened Central Brazilian savanna (locally called Cerrado) it is a result of inadequate conservation policies. Here, we compared the floristic and functional attributes of the adult (trees with diameter at ground level ≥ 5 cm) and juvenile (trees with diameter at ground level < 5 cm) components in a Cerrado sensu stricto to assess changes in a plant formation under a process of woody encroachment. We found that the adult and juvenile components had a mean Jaccard similarity index of 19% and PERMANOVA analysis showed a separation of two clusters (species of the adult component and species of the juvenile component), indicating high species dissimilarity between both components. We also found a higher percentage of forest species, with lower bark thickness and dispersed by animals in the juvenile component compared to the adult component. Our results indicate that under a process of WPE, forest species less adapted to stressful conditions and fire can establish in the juvenile component and may reflect environmental changes as increasing shade, reduced fire and lower temperatures. Considering that Cerrado is becoming hot and drier, our results alert that WPE can make Brazilian savanna ecosystems more vulnerable to global climate changes, since it selects species less resistant to fire. Our sampling approach is useful to detect further encroachment in Cerrado throughout short-term plant inventories.