Increases in native woody bamboos affect gap phase regeneration and long term survival of forest canopies insubtropical Atlantic Forest

MONTTI LÍA; PAULA I. CAMPANELLO; GOLDSTEIN GUILLERMO; ZHANG, YJAO

Bangalore, India

Conferencia; 5th International Canopy Conference; 2009

As a consequence of increase in selective tree harvesting of native forests and other man-made interventions in semideciduous Atlantic Forests of North-Eastern Argentina, the abundance of native woody bamboo species has increased substantially during the last 100 years. These forests are the southern limit of the Atlantic forest biome that extends from northern Brazil to Eastern Paraguay and the subtropical portion of Argentina. Even without disturbances, woody bamboo species are common in the understorey and small gaps of forest stands. Chusquea ramosissima is a conspicuous aggressive bamboo after disturbance. This species is monocarpic, flowering at irregular intervals, perhaps every 15–20 years, and forming impenetrable thickets that can inhibit canopy tree regeneration by outcompeting light-requiring species in gaps. The culms connected by rhizomes can be either erect or scandent. The culms can reach the upper canopy of the forest affecting the amount of light that the leaf surfaces of the canopy trees receive, and consequently reducing their growth rates. A manipulative experiment was done to assess the impact of this detrimental effect by removing bamboo from host trees and monitoring growth rates with dendrometers in control plots and in plots where bamboo have been experimentally removed. Results have shown that Atlantic forests with abundant bamboo from northern Misiones have low canopy tree seedling and sapling densities, low species richness, and low relative growth rates of saplings from several native timber species. Consequently bamboo have negative effects on long-term survival of tropical forest canopies by either exploiting light resources in the upper canopy and/or interfering with seedling recruitment of canopy species in the forest floor. This phenomenon appears to be of importance in most subtropical forests around the world.