Abstracts (Translations will be available eventually).
Chapter 2. A Theoretical Overview of the Processes Determining Species Richness in Forest Fragments. Og DeSouza, José H. Schoereder, Valerie Brown, and Richard O. Bierregaard, Jr.
A fragmentação de habitats refere-se a qualquer processo que resulte na redução da área original, criando um habitat novo, menor, ou vários habitats menores espalhados. A literatura sobre este assunto vem crescendo muito nos últimos anos, tanto em quantidade quanto em complexidade, o que pode dificultar o entendimento do cenário global dos processos biológicos envolvidos na fragmentação. O objetivo deste capítulo é apresentar uma síntese dos efeitos biológicos previstos após a fragmentação.
A grande maioria das previsões dos efeitos biológicos da fragmentação usa a teoria da biogeografia de ilhas como um ponto de partida, devido à semelhança entre as manchas remanescentes de cobertura vegetal e ilhas verdadeiras. Contrariamente às ilhas, no entanto, deve-se levar em consideração que as áreas entre os fragmentos de habitats podem também fornecer indivíduos que vão colonizar os fragmentos. Uma outra diferença está nos organismos que permanecem no fragmento após a perturbação, e que podem mudar drasticamente a dinâmica prevista pela teoria de biogeografia de ilhas.
Neste capítulo apresentamos uma teia de processos biológicos,
envolvendo mudanças biológicas e estruturais, e que têm três possíveis
resultados: aumento, diminuição ou manutenção da riqueza de espécies
original. A dicotomia mudanças biológicas e estruturais, porém, não é tão
clara, uma vez que processos locais (perda de indivíduos e habitats), em
mesoescala (isolamento, efeitos de borda e de forma) e regionais (imigração) são
ligados. No entanto, não importando os resultados finais da fragmentação (aumento,
diminuição ou manutenção da riqueza), os processos ecológicos envolvidos têm
muitos mecanismos em comum. O resultado final do evento da fragmentação, dessa
forma, será o resultado de um complexo conjunto de caminhos percorridos por
estas cadeias de mecanismos.
Chapter 5. The Hyper-diverse Flora of the Central Amazon: An Overview. William F. Laurance.
In
this chapter I provide an overview of the diverse central Amazonian flora for
the nonspecialist reader.
I describe the forests of the BDFFP study area, place the local flora in
a regional context, and discuss ecological and historical factors that may have
contributed to the remarkably high richness of tree species.
Central Amazonian forests may be an important "crossroads"
where species with varying geographic distributions meet.
Relative to other well-studied Neotropical sites, the central Amazonian
flora is very distinctive, with many species adapted for the acidic, heavily
weathered soils of the central and northern Amazon.
These forests contain many rare plant species, and many taxa with patchy
distribution patterns (at local and landscape scales).
Because of high alpha, beta, and gamma diversity, it will be necessary to
stratify networks of nature reserves across major biogeographic, climatic, soil,
and topographic gradients in order to preserve a high proportion of the
floristic diversity of the Amazon.
Chapter 6. Lecythidaceae of a Central Amazonian Lowland Forest: Implications for Conservation. Scott Mori, Peter Becker, and Dwight Kincaid.
The reserves of the Biological
Dynamics of Forest Fragments Project in central Amazonian Brazil are greater in
numbers of individuals and richer in species of Lecythidaceae (Brazil Nut
Family) than any other place heretofore reported in the literature. Our data for
Lecythidaceae confirm the concept that Amazonia is a center of tree species
richness and support the suggestion that large biological reserves in central
Amazonia would protect considerable Neotropical tree species richness. The 38
species of
Lecythidaceae in a 100-hectare plot surrounded by continuous forest at Reserve
1501 (Km 41) represent 17.6% of all currently described species of
Lecythidaceae. Values for frequency, density, dominance, and species richness
are provided for the Lecythidaceae found in the 100-hectare plot.
This information provides the
baseline data needed to monitor possible future changes in stand composition of
Lecythidaceae as a result of forest fragmentation or climate change. Species
area curves based on samples from the 100-hectare plot indicate that
considerable effort is needed to sample
all species of Lecythidaceae in a large plot. Because the cost of sampling is so
high, careful questions should be formulated before large-scale inventories of
tropical forests are undertaken.
Chapter
10. Effects of Landscape Fragmentation on Palm Communities. Aldicir Scariot.
In
this chapter I describe aspects of diversity and floristic composition of a
central Amazonian palm community in a set of 11 forest fragments and continuous
forest. This area has
high genera and taxa richness of palms, with 11
genera and 36 species (in plateaus only), which represents 32% of the genera and
20% of the palm species and varieties of the whole Amazon region. Adding species
that do not occur in topographically flat areas but occur only in low wet and
swampy areas increases the figures to 41% of the genera and 22% of the species
and varieties. The
mean number of 7,188 palms per ha in the continuous forest in the BDFFP is very
high, even for Amazonian sites. The importance of palms in the Amazonian
landscape is due more to their abundance than to their species richness. In this
site, large reserves more closely resemble the continuous forest in palm
community structure and floristic composition. For younger life stages, the
effects of isolation are more evident. At the critical life stage of seedlings,
fewer species are recruiting seedlings in the small reserves than in the
continuous forest, what may even increase divergence in species composition
between small reserves and continuous forest. Seedling may be the first life
stage to be affected by forest fragmentation. Even a short time after isolation,
the palm community is already showing the consequences of habitat fragmentation,
such as species invasion and reduction in population size. Because none of the
sites in this study had all 36 species of palms, it is clear that an extensive
series of reserves covering a wide range of the habitat heterogeneity is needed
to preserve most of the species. Due to their importance in forest structure and
composition, their high taxa richness, and their use by humans and wildlife, the
palm family must be a primary target of any conservation plan in the Amazon
basin. The best approach to maintain the integrity of this group and other
species directly and indirectly associated with it, is to establish many large
reserves taking in account the geographical distribution of the species to
encompass site heterogeneity. Indeed, any long-term plan of preserving
biodiversity must be designed to preserve the patterns and the ecological
processes of the target species.
Chapter 11. Regeneration in Tropical Rainforest Fragments. Julieta Benitez-Malvido.
To
evaluate the impact of fragmentation on forest regeneration I used the abundance
of naturally occurring shade-tolerant tree seedlings, and the performance
(survival, growth, and herbivory damage) of three transplanted mature forest
seedling species (Chrysophyllum pomiferum,
Micropholis venulosa, and Pouteria caimito). The fragment types studied
were, (1) continuous forest
(control); (2) 100-ha fragments; (3) 10-ha fragments; and (4) 1-ha fragments.
For 100- and 10-ha fragments seedling density and performance were measured at
their centre, edge, and corner, and at 20m intervals up to 100m away from the
fragments edge. The results showed: (1) a significant decline on seedling
abundance from continuous forest to forest fragments; (2) lower seedling density
at corners of 100-ha fragments that in their edge and center; (3) seedling
density increases towards forest
interior; (5) responses of seedlings to forest fragmentation are
species-specific; (6) herbivory declines from continuous forest, to 100-ha
fragment, to 10-ha fragment, to 1-ha fragment; and (7) corners appear to be poor
habitats for seedling establishment. I conclude that fragmentation at this
Amazonian site affects the regenerative potential of the forest and the
interaction of seedlings with other organisms.
Chapter 13. Fragmentation and Plant Communities: Synthesis and Implications for Landscape Management. William F. Laurance.
I provide an overview of known and potential effects of forest fragmentation on Amazonian plant communities. Fragmentation leads to dramatic changes in forest dynamics, principally as a result of elevated tree mortality near forest edges. This in turn promotes a proliferation of disturbance-adapted plant taxa such as pioneer and successional trees and lianas, at the expense of old-growth, forest-interior trees. Large (>60 cm diameter) trees are especially vulnerable to fragmentation. In addition, the floristic diversity of forest fragments may erode over time as many rare species (whose populations are probably maintained my immigration from outside source areas) gradually disappear from fragments. Other plant species, such as certain epiphytes, orchids, and taxa that rely on coevolved pollinators and seed-dispersers, may also be highly vulnerable in fragmented forests. Using empirical data from the BDFFP, I propose some landscape-design principles to help reduce the ecological effects of fragmentation at landscape and regional scales.
Chapter 16. Landscape Modifications and Ant Communities. Heraldo L. Vasconcelos, Karine S. Carvalho, and Jacques H. C. Delabie.
As formigas são um dos invertebrados de maior abundância e diversidade na florestas da região Neotropical, cumprindo um papel chave na dinâmica destes ecossistemas. Este trabalho analisa como as formigas respondem às recentes mudanças na cobertura vegetal e nos padrões de uso da terra na Amazônia central. Coletamos formigas que vivem ou forrageiam no solo, usando armadilhas pitfall, iscas de sardinha, ou extraindo-as de amostras de liteira ou solo. Os resultados mostram que a conversão da floresta em pastagens causa uma perda substancial de espécies. Haviam duas vezes menos espécies de formigas nas pastagens do que na floresta, e poucas das espécies encontradas nos pastos eram espécies florestais. Uma vez que os pastos são abandonados e florestas secundárias se estabelecem, a fauna de formigas da floresta gradualmente se recompõe. Esta recuperação entretanto dependo do histórico de uso da terra, sendo mais rápida em áreas menos impactadas pelo homem. A coleta de formigas nos fragmentos de floresta mostrou que a densidade de espécies (número de espécies por unidade de área) é independente do tamanho do fragmento. A maioria das espécies encontradas na floresta contínua também foi encontrada nos fragmentos. Porém, mudanças na abundância de muitas destas espécies, especialmente próximo à borda dos fragmentos, foram detectadas. Parte da variação na composição de espécies de formigas foi atribuída à variações na profundidade da liteira, que é maior próximo às bordas, embora seja provável que variações no microclima e na estrutura da vegetação também estejam envolvidas.
Chapter 26. Selective Logging in the Brazilian Amazon: Its Relationship to Deforestation and the International Tropical Hardwood Market. Niro Higuchi.
Este artigo trata das questões relacionadas com a exploração seletiva de madeira e sua relação com o desmatamento da região. Com a diminuição das reservas de florestas produtivas do mundo tropical, a Amazônia passa a ser o alvo das grandes madeireiras internacionais, para abastecer um mercado estável de madeira dura tropical. Diante desse novo cenário, a madeira em pé começa a ser usada com pré-investimentos de projetos agropecuários da região amazônica, que sempre foram altamente dependentes de subsídios oficiais. Por conta disso, mesmo com a retirada dos subsídios oficiais aos projetos agropecuários, as taxas de desmatamento na Amazônia continuam fora do controle do Poder Público.
