Spatial patterns of tree community dynamics are detectable in a small (4 ha) and disturbed fragment of the Brazilian Atlantic forest

Abstract

The dynamics of the tree community of a fragment of tropical semideciduous forest was investigated in south-eastern Brazil. Surveys were carried out in 2000 and 2005 in 29 20 × 20 m plots. The main purpose was to assess the possibility of detecting spatial patterns of dynamics that could be related to the heterogeneity of both the environment and disturbance history in a small forest area (4.0 ha). Rates of mortality and recruitment of trees and gain and loss of basal area were obtained for the whole sample, four pre-defined soil habitats, diameter classes and twelve tree populations. The tree community was rather unstable in the period, once mortality rates surpassed recruitment rates and loss rates of basal area surpassed gain rates all-over the area denoting the prevalence of a degradation process, possibly triggered by a clear felling in 1985 that reduced the area of the fragment in 26%. The tree community dynamics showed no spatial autocorrelation but was not evenly distributed throughout the fragment. This spatial heterogeneity was chiefly determined by the disturbance history of each site while environmental heterogeneity played a secondary but significant role. The main causes of disturbance heterogeneity were the extension of the adjacent felled area, cattle trampling and selective logging. The environmental variables that most strongly correlated with the variations of the dynamics rates were those related to the availability of light, water and mineral nutrients. In contrast with the overall trends, three understory species expanded in the period, possibly at the expense of the steeply declining density of mid-sized trees.

Tree Component Demography in an Upper Montane Mixed Ombrophilous Forest Under Chronic Anthropogenic Disturbances

“…The fact that there was no structural degradation process, which is characterized by a reduction in the number of trees and basal area, as once observed in other areas with chronic disturbances similar to those occurring in the forest under study (Machado and Oliveira Filho, 2010;Silva et al, 2011), suggests that disturbances intensity may be a determining factor and/or that forest formations may have different levels of resilience and resistance to disturbances. Considering the studies published by Orihuela et al (2015) and Reis et al (2014), one can indeed inferred that MOF is mainly formed by a group of stresstolerant species with Araucaria angustifolia as one of its representatives.…”

“…On the other hand, it is possible to observe a degradation process, synthesized by the reduction of individuals and basal area, in forests subject to intense or chronic disturbances. Some authors have observed these patterns in forest remnants subject to cattle presence and selective logging in Minas Gerais, Brazil (Machado and Oliveira Filho, 2010); in a transition forest between the Brazilian Cerrado and the Amazon, suggesting the influence of a strong drought as a determining factor (Mews et al, 2011); and in alluvial forest remnants subject to anthropic disturbances, after a heavy flood in the south of Minas Gerais, Brazil (Silva et al, 2011). Moreover, studies carried out in transformed landscapes have shown that disturbances caused by selective logging without planning and/or cattle grazing have negatively influenced richness by favoring pioneer species rather than late ones and therefore either slowing the process of succession down or limiting it (Clark and Covey, 2012;Zamorano-Elgueta et al, 2014;Arroyo Rodríguez et al, 2015).…”

Variações temporais na comunidade arbórea de uma floresta decidual sobre afloramentos calcários no Brasil Central: composição, estrutura e diversidade florística

“…As taxas de mortalidade e recrutamento registradas estão dentre as mais elevadas em relação a outras fl orestas tropicais úmidas (Phillips et al 1994;Lewis et al 2004 a,b;Phillips et al 2004), matas de galeria (Felfi li 1995a(Felfi li , 1997Lopes & Schiavini 2007), fl orestas estacionais semideciduais (Guilherme et al 2004;Paiva et al 2007;Higuchi et al 2008;Silva & Araújo 2009;Machado & Oliveira-Filho 2010) e fl orestas estacionais deciduais (Hubbell & Foster 1990;Swaine et al 1990;Sukumar et al 1992;Werneck & Franceschinelli 2004;Marín et al 2005), cujos maiores valores, encontrados para fl orestas estacionais, giram em torno de 4,0%.ano -1 (Hubbell & Foster 1990;Marín et al 2005;Paiva et al 2007). As elevadas taxas e o forte balanço em favor do recrutamento resultaram em baixos tempos de meia-vida (25,0 anos) e de duplicação (15,6 anos), implicando em uma das mais baixas rotatividades (tempo de reposição dos indivíduos; 20,3 anos) dentre as fl orestas supracitadas, sendo menor, inclusive, do que a encontrada para uma fl oresta decidual com elevada mortalidade natural na Nicarágua (21,5 O balanço positivo em favor do recrutamento na comunidade sugere tratar-se de uma fl oresta em fase de construção, padrão normalmente atribuído a fl orestas estruturalmente instáveis e que sofreram distúrbios pretéritos (Chazdon et al 2007).…”

Dinâmica De Populações De Espécies Arbóreas Em Fragmentos De Floresta Aluvial No Sul De Minas Gerais, Brasil

“…2016. Nunes, M. H. et al ISSN eletrônico 1982 10.5380/rf.v46i1.34782 HIGUCHI et al, 2008b;MACHA DO;OLIVEIRA FILHO, 2010). De forma geral, esses trabalhos demonstram instabilidade nas taxas de dinâmica, que são influenciadas pelo histórico de perturbação (OLIVEIRA FILHO et al, 1997) e pelo efeito de borda (OLIVEIRA FILHO et al, 2007).…”