Atlantic rain forest recovery: successional drivers of floristic and structural patterns of secondary forest in Southern Brazil

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Abstract

Questions:

The growing importance of secondary forests has stimulated research on the patterns of structure, biomass, species diversity and species composition of successional tropical forests. Despite current knowledge, the future of tropical forests and their ability to recover from human impacts are still a challenge for researchers. The Atlantic Forest is one of the most endangered ecosystems on Earth, yet has been reduced in size and distribution due to human disturbance such that most of the remaining fragments are secondary forest at different successional stages. How do these forests recover structure and species composition during succession? What are the main drivers of community assembly during succession?

Location:

Subtropical Atlantic rain forest, South Brazil (29°42′S, 50°11′W).

Method:

Using four replicate chronosequences, we described floristic and structural successional patterns of subtropical Atlantic Forest in Brazil, and investigated causal relationships with environmental, spatial and temporal variables in structuring tree species composition. The chronosequences were described by four successional stages, according to floristic (species composition and richness) and structural (density, basal cover and height of trees) characteristics, tested using ANOVA with randomization tests. Time since abandonment and environmental conditions of topsoil, relief and spatial components were considered as possible successional drivers. Hypotheses about causal relationships in the successional process were tested using path analysis, considering the influence of those variables on the successional forest communities.

Results:

We found that forest stands of 26–45 yr old displayed structural characteristics similar to those of old-growth stands, but that species composition of successional forest was somewhat different from reference areas (old-growth forests). In our study, time since abandonment overcame the influence of environmental and spatial variables on forest assembly patterns in the chronosequences.

Conclusions:

Our study is the first one describing floristic and structural successional patterns of the Atlantic rain forest in a subtropical context and proposing causal relationships between recovery age, environment and community composition of secondary successional forests. We conclude that the dynamic of forest succession is autogenic and not entirely predictable from local environmental conditions of soil, space and relief.

Conclusions:

Our study describes floristic and structural successional patterns of the Atlantic rainforest, looking for causal relationships between recovery age, environment and community composition of successional forests. We conclude that time since abandonment has driven the process of forest succession, since it overcame the influence of soil, space and relief variables on forest assembly patterns in the studied chronosequences.

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