A regeneração de uma floresta tropical montana após corte e queima (São Paulo - Brasil)

Abstract

Regeneration of a neotropical montane forest following slash-and-burn (São Paulo-Brazil)Slash-and-burn has been the main kind of disturbance in the Atlantic montane forest. We analyzed the change in vegetation structure, woody species composition, species richness and diversity and plant guild composition after the cutting and burning of a mature forest. According to our results the rate of vegetation change is related to the forest attribute analyzed. In the first moment, the disturbed forest had the species richness and diversity restored, followed by plant guild composition, species composition and finally its physical structure. A forty year old forest site showed between 38.8% and 117.1% of the values recorded in the mature site, suggesting that this forest regenerates following patterns observed in other tropical forests. In addition to disturbance intensity, this montane forest has particular features as the average size of diaspores and tree species richness, which are thought to provide this forest higher resilience. Changes in woody species composition can be described by successional models formed by three or four stages, depending on the disturbance intensity. Models are characterized by pioneer species of Imperata, Pteridium, Baccharis, Tibouchina and Alchornea genera.Key words: Atlantic montane forest, forest regeneration, resilience, slash-and-burn. RESUMOO corte e queima são um dos tipos de perturbação predominante na floresta Atlântica montana no Sudeste do Brasil. A análise de uma cronosseqüência de regeneração (10, 18, 40 anos e floresta madura) corrobora a hipótese de que as características da floresta se transformam em diferentes velocidades em direção aos valores observados na floresta madura. Em ordem decrescente de velocidade, a floresta, após corte e queima, restaura a riqueza e a diversidade de espécies arbóreo-arbustivas, a composição de guildas, a composição florística (importância relativa das famílias) e, por último, os atributos da estrutura física, com exceção da densidade de indivíduos. A floresta com 40 anos apresentou entre 38,8% e 117,1% dos valores observados na floresta madura, sugerindo que esta se regenera dentro do padrão observado para o conjunto das florestas tropicais. Além da intensidade de perturbação, determinadas características dessa floresta montana, como o tamanho médio de diásporos e a importância relativa de grupos dispersores, podem conferir-lhe maior resiliência. As transformações florísticas direcionais, observadas durante a regeneração, podem ser descritas através de modelos sucessionais compostos por quatro ou cinco fases, dependendo da intensidade de perturbação. Nesses modelos, as espécies dominantes pertencem aos gêneros Imperata, Pteridium, Baccharis, Tibouchina e Alchornea.Palavras-chave: corte e queima, floresta Atlântica montana, regeneração, resiliência.

Diversity and structure of the tree community of a fragment of tropical secondary forest of the brazilian Atlantic Forest domain 15 and 40 years after logging

“…The typical pattern of species diversity in tropical secondary forests is the accumulation of species, approaching that of a mature forest within a time span of up to 80 years (Brown & Lugo 1990, Tabarelli & Mantovani 1999. In accordance with this, the older stand yielded a higher number of species than did the younger stand.…”

“…They could be both continuing to accumulate biomass, though at lower rates. Tabarelli & Mantovani (1999) recorded figures of basal area and volume in secondary Atlantic rain forests aged 40 years considerably below those of nearby mature forests, although the regeneration started from pastures without live tree remnants.…”

“…Species classification based on regeneration and stratification guilds have been successfully used in the analysis of tropical forest dynamics and regeneration in a number of studies, yielding similar patterns (e.g. Manokaran & Kochumenn 1987, Whitmore 1989, Lieberman et al 1990, Oliveira Filho et al 1997, Tabarelli & Mantovani 1999). …”

“…There are, however, few studies of forest regeneration in the Brazilian Atlantic Forest domain and most that have been done are in the coastal rainforests (e.g. Klein 1980, Mendonça et al 1992, Pessoa et al 1997, Tabarelli & Mantovani 1999. In the present contribution we compared a number of characteristics of two adjacent tracts of hinterland semideciduous forest of the Atlantic Forest Domain.…”

“…However, the 'complete' restoration of many characteristics of the original mature forest is dependent upon many factors, particularly regeneration time, distribution and size of forest fragments, the history of land use and disturbance, and the existence of preserved mature forests on the landscape (Whitmore 1990, Saldarriaga & Uhl 1991, Guariguata & Dupuy 1997, Parthasarathy 1999. Important forest characteristics, such as species richness and diversity, species composition, and tree density and biomass, are affected differently by these factors and are restored at different rates (Uhl et al 1982, Saldarriaga et al 1988, Saldarriaga & Uhl 1991, Tabarelli & Mantovani 1999.…”