What is the Long-Term Effect of Bamboo Dominance on Adult Trees in the Araucaria Forest? A Comparative Analysis between Two Successional Stages in Southern Brazil

Abstract

Bamboos are opportunistic species that rapidly colonize open areas following forest disturbance, forming dense clusters that alter the regenerative processes and maintain lower levels of tree diversity. Widespread forest degradation, especially in Latin America and Asia, and human-induced introduction have allowed native and non-native bamboo species to thrive, hindering successional pathways that would otherwise lead to more diverse forests; such a large-scale phenomenon is a key concern in the conservation of forest resources around the globe. Despite previous research on this phenomenon, little is known about the long-term effects of bamboo dominance on forest structure and composition and the corresponding interaction with natural regeneration. As such, we sought to evaluate the long-term effects of bamboo dominance on the dynamics of adult forest populations considering two forest types (Bamboo Forest—BF and Araucaria Forest—AF) over an 11-year period in the Embrapa Research Station in Caçador, Brazil. We monitored 20 plots (15 × 15 m) in each forest type where we tagged, identified, and measured the height and diameter of all the trees taller than 1.5 m (H) and diameter at breast height (DBH) greater than 3.18 cm. Comparisons were based on forest species diversity and structure parameters. In BF, diversity of species increased after the bamboo die-off that occurred in 2006 with a subsequent reduction in the number of pioneer species overtime. However, secondary species remained stagnant demonstrating that recruitment and transition into higher size classes is restricted to the immediate die-off aftermath. On the other hand, plant diversity and structure in the relatively bamboo-free AF were stable with secondary species accounting for the most richness. Our results confirm that BF maintains significantly lower levels of diversity that are restricted to pioneer species; AF structure and diversity are not significantly affected by bamboo die-off and recolonization; and BF tree species are caught in a closed cycle of arrested successional development. The widespread presence of bamboos as dominant species in the region should become a part of the conversation pertaining to forest management and conservation in Brazil and other countries in south America and Asia.