Effects of bamboo dominance and mortality on population structure and phytosociology of timber species in Southwestern Amazonian forests

Abstract

Timber forest management is an important activity in Acre, but in the eastern portion of the state the forests present a high density of bamboo culms (Guadua spp.), which leads to lower diversity, high tree mortality, and reduced biomass and carbon accumulation. This study analyzed and compared the population structure of timber species across three forest typologies: (1) areas without bamboo dominance, (2) with dominance, and (3) post-mortality of bamboo (Guadua spp.) in the southwestern Amazon. In the study area, three distinct forest typologies were identified: non-dominance, dominance, and post-mortality of Guadua spp. In each typology, three 0.5-ha plots were installed, and commercial individuals with DBH ≥ 10 cm were recorded. Dendrometric parameters (basal area, basal area per hectare, and over-bark stand volume) and phytosociological metrics (relative density, relative dominance, relative frequency, and importance value) were assessed. In areas without bamboo dominance, basal area, volume, and density of commercial species were significantly higher than in areas where bamboo was present or had died. In the same typology, early secondary and climax species showed high importance values, whereas in the other typologies a reduction in the importance of these species was observed. The changes caused by bamboo, especially after its mortality, can negatively affect the population structure and dynamics of timber species, compromising sustainable forest management.