Tree mortality, recruitment and growth in a bamboo dominated forest fragment in southwestern Amazonia, Brazil

Abstract

Forest fragmentation affects the structure and dynamics of plant communities, leading to biodiversity loss in forest remnants. In this paper we show that in a bamboo (Guadua weberbaueri Pilger) dominated forest fragment in southwestern Amazonia edge effect may be confounded by bamboo effect, which also occur inside the forest. We measured growth, mortality and, recruitment rate of trees with DBH ≥ 10 cm, in a fragment of bamboo dominated open forest in southwestern Amazonia, state of Acre, Brazil, in 15 plots at the forest edge and 15 plots inside the forest fragment, 500 m away from the border. Time interval between censuses was 1.8 years. The average diameter growth rate differed significantly between edge (3.82 ± 0.10 mm a-1) and interior (2.39 ± 0.18 mm a-1); but there were no differences in annual mortality rate (edge = 3.8 ± 2.5 % a-1 CV = 65.7%; interior = 3.6 ± 2.6% a-1 CV = 72.2%) or in annual recruitment rate (edge = 7.1 ± 3.2% a-1 CV = 45%; interior = 8.9 ± 7.9% a-1 CV = 88.7%). Diameter growth rate, particularly of pioneer and fast-growing trees, is favored by the environmental conditions of the edge, where bamboo abundance is higher. However, the absence of an edge effect on mortality and recruitment could be due to the particular dynamics of bamboo patches, which could be mimicking forest edges and therefore masking possible edge effect in this fragment. We speculate that the mortality and recruitment patterns in fragmented forests of southwestern Amazonia is different from other areas in Amazonia and that bamboo is one of the key controllers of successional processes in these fragments.