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.

Birds of Humaitá Forest Reserve, Acre, Brazil: an important forest fragment in south-west Amazonia

“…Prior to 2001, 150 bird species had been recorded in the Zoobotanical Park (Guilherme 2001), an area of c.100 ha (Meneses-Filho 1995), although this total increased to 196 species over the next 15 years (Guilherme 2016). In the Catuaba Experimental Farm fragment of 1,200 ha (Medeiros et al 2013), 257 bird species were recorded by Rasmussen et al (2005), and this number rose to 275 over the next 11 years (Guilherme 2016). Despite the increasing inventory, total richness at both sites is still lower than at HFR.…”

Recuperation of theTerra FirmeForest Understory Bird Fauna Eight Years after a Wildfire in Eastern Acre, Brazil

“…The variation in the primary axis of the PCA was determined by the number of bamboo stems. These plants take advantage of clearings in the forest produced by tree-fall or deforestation [77] and may colonize large areas of forest in a short time [77,78], and they may also mask edge effects and tree mortality [79]. Bamboos and palms are also important pioneer plants in the succession of forests impacted by fire [24,26].…”

Life cycle of bamboo in southwestern Amazon and its relation to fire events

“…Even though, the tree cover percent of bamboo-dominated forests was slightly smaller than the bamboo-free areas. We believe this might be 10 related to (i) an increased gap opening associated with faster forest dynamics and tree mortality of these areas influenced by bamboo Medeiros et al, 2013), or (ii) artifacts of the tree cover computation method that uses the pixels' reflectance from Hansen et al (2013).…”

“…Thus, these forests support up to 40% less tree species diversity than nearby bamboo-free forests and from 30 to 50% less carbon stored as a consequence of the lower woody tree density (Silveira, 2001;Rockwell et al, 2014). Bamboo-dominated forests also have elevated tree mortality rates (3.6 ± 2.5 % yr −1 ) Medeiros et al, 2013) when compared even to the typically fast-turnover forests in western Amazon (2.62 % yr −1 ) (Johnson et al, 2016). In the region, 74 different bamboo populations, that is, patches having individuals of the same internal 2017-2028 period.…”