Abstract Tijuca National Park (TNP) covers an area corresponding to 3.5% of the city of Rio de Janeiro. It is an Atlantic Rainforest fragment with peaks and watersheds that make this protected area a mosaic of habitats. It is composed of four subunits: Serra da Carioca, Pedra Bonita and Pedra da Gávea Inselbergs, Tijuca Forest, and the Pretos Forros/ Covanca Considering the importance of conserving biodiversity in rainforest fragments, such as those found in Tijuca National Park and its subunits, we analyzed the spatial distribution of species in relation to climatic factors that could impact species richness. In addition to floristic analysis, we provide details of endemism, conservation status, substrate and habitat preferences, as well as data on geographic distribution patterns for each species. Precipitation during the wettest month was shown to be one of the most important climatic features in the study area and may be related to floristic richness and composition. The TNP holds about 38.5% of known species in the state of Rio de Janeiro with 254 taxa distributed in 26 families and 83 genera. Floristic richness can be impacted by environmental variables, including climatic factors. Our results show that relating floristic richness to environmental variables can be a way to understand biodiversity.

Resumo O Parque Nacional da Tijuca ocupa uma área correspondente a 3,5% da cidade do Rio de Janeiro. É um fragmento de Mata Atlântica com picos e bacias hidrográficas que fazem desta área protegida um mosaico de habitats. É composto por quatro subunidades: Serra da Carioca, Pedra Bonita e Pedra da Gávea Inselbergs, Tijuca Forest, e Pretos Forros/ Covanca. As espécies foram analisadas quanto à sua distribuição espacial, relacionando-as com os fatores climáticos que poderiam afetar a riqueza. Além disso, fornecemos comentários sobre o endemismo, estado de conservação das espécies, uma análise florística e dados sobre os padrões de distribuição geográfica. A precipitação do mês mais chuvoso foi uma das características ambientais mais importantes para essas áreas e pode estar relacionada à similaridade florística entre elas. O Parque Nacional da Tijuca detém cerca de 38,5% das espécies conhecidas para o estado do Rio de Janeiro, com 254 taxa, distribuídos em 26 famílias e 83 gêneros. Os nossos resultados mostram que, relacionar a riqueza florística às variáveis ambientais, pode ser uma caminho para o entendimento da biodiversidade..

Fragmentos remanescentes de vegetação natural em paisagens antropizadas sofrem ameaças permanentes, devido aos efeitos de borda e às atividades antrópicas nas áreas limítrofes. Para verificar a hipótese de que o tipo de ameaça ao ecossistema e a sua freqüência dependem do uso da terra no seu entorno, foram analisados 81 fragmentos de Cerrado no estado de São Paulo. Para cada fragmento foram registrados os tipos de perturbação no ecossistema e os tipos de uso da terra no seu entorno. Os usos mais freqüentes foram pastagens cultivadas (registradas em 78% das áreas), plantio de cana-de-açúcar (26%), rodovias (19%), reflorestamento (14%) e culturas anuais (14%). As ameaças mais freqüentemente registradas foram gramíneas invasoras (35% das áreas parcial ou totalmente invadidas), presença de gado (32%), desmatamento (21%) e fogo (21%). A análise da freqüência observada de cada tipo de impacto mediante a freqüência esperada caso não houvesse influência do uso da terra (qui-quadrado), mostrou que as ameaças dependem do uso da terra nas áreas ao redor dos fragmentos, exceto para o desmatamento, que tem ocorrido indiferentemente ao tipo de uso. Gramíneas invasoras e fogo são muito mais freqüentes na vizinhança de rodovias e zonas urbanas, enquanto que o plantio de cana-de-açúcar, silvicultura e fruticultura têm sido os usos da terra menos impactantes para a vegetação de Cerrado, considerando-se apenas a freqüência de ocorrência dos impactos. Esses cultivos envolvem o controle de plantas invasoras e a prevenção e controle de incêndios, e a eliminação do gado, com reflexos positivos para a conservação dos ecossistemas naturais.

Patches of natural vegetation remaining in landscapes occupied by man are continuously under threat due to the edge effects and also to land use types around these remnants. The most frequent threats and land use types in the vicinity of 81 Cerrado (tropical savanna type) fragments in the State of São Paulo, Brazil, were analyzed in order to verify if the frequency of every type of disturbance to the natural ecosystem depends on the neighboring land use. The hypothesis of the study assumes that environmental threats are correlated with land use around protected areas. From the 81 areas, the most frequent human-induced land cover types around the Cerrado remnants were: pasture (recorded in 78% of the areas), sugarcane plantations (26%), roads (19%), annual crops and reforestation (14% each). The most frequent sources of threats were invasive grasses (35% of the areas partially or totally invaded) and cattle (observed in 32% of the areas), followed by deforestation (21%), and fire (21%). The chi-square analysis revealed that, with the exception of deforestation, which does not depend on land use, all other threats are influenced by the neighboring land use. The occurrence of invasive grasses and fires are strongly favored by the presence of roads and urban areas. Sugarcane, reforestation, and permanent crops were the less impacting land use types found in the study area, when only considering impact frequency. These land use types have fire and weed control, and also exclude cattle, indirectly protecting natural ecosystems.

Atualmente vêm sendo desenvolvidas e utilizadas várias técnicas de modelagem de distribuição geográfica de espécies com os mais variados objetivos. Algumas dessas técnicas envolvem modelagem baseada em análise ambiental, nas quais os algoritmos procuram por condições ambientais semelhantes àquelas onde as espécies foram encontradas, resultando em áreas potenciais onde as condições ambientais seriam propícias ao desenvolvimento dessas espécies. O presente estudo trata do uso da modelagem preditiva de distribuição geográfica de espécies nativas, através da utilização de algoritmo genético, como ferramenta para auxiliar o entendimento dos padrões de distribuição do bioma cerrado no Estado de São Paulo. A metodologia empregada e os resultados obtidos foram considerados satisfatórios para a geração de modelos de distribuição geográfica de espécies vegetais, baseados em dados abióticos, para as regiões de estudo. A eficácia do modelo em predizer a ocorrência de espécies do cerrado é maior se forem utilizados apenas pontos de amostragem com fisionomias de cerrado, excluindo-se áreas de transição. Para minimizar problemas decorrentes da falta de convergência do algoritmo utilizado GARP ("Genetic Algorithm for Rule Set Production"), foram gerados 100 modelos para cada espécie modelada. O uso de modelagem pode auxiliar no entendimento dos padrões de distribuição de um bioma ou ecossistema em uma análise regional.

Many different techniques are used today with different objectives to model species geographic distribution. Some of these techniques are based on environmental analysis where algorithms search for environmental conditions similar to those where the species are known to occur, resulting in potential areas where the environmental conditions would be favorable for the growth of these species. The present study is based on predictive modeling of species geographic distribution using genetic algorithm as a tool for plant conservation in modeling the "cerrado" biome of the State of São Paulo. The methodology used and the results obtained were considered satisfactory for the generation of geographic distribution models for plant species, based on abiotic data for the regions studied. The accuracy of the model in predicting the occurrence of species in the "cerrado" is greater if only points that occur within the "cerrado" and not in transition areas are used. In order to minimize problems due to the lack of convergence of the genetic algorithm GARP ("Genetic Algorithm for Rule Set Production"), 100 models were generated for each specie. The use of modeling tools can help understand the distribution patterns of a biome or ecosystem in a regional analysis.

The present study applies a series of new techniques to understand the conservation of Cerrado tree species in the face of climate change. We applied techniques from the emerging field of ecological niche modeling to develop a first-pass assessment of likely effects of climate change on tree species’ distributions in the Cerrado biome by relating known occurrence points to electronic maps summarizing ecological dimensions. Distributional data represent 15,657 records for 162 tree species occurring in Cerrado. By focusing on the trees of one important and highly endemic biome, rather than the biota of a political unit, we were able to focus on developing biome-wide projections. An important limitation of this study is that only those species with more than 30 unique occurrence records were used-hence, the study is limited to those species of relatively broad geographic distribution, and does not take into account those species with narrower geographic distributions. Global climate change scenarios considered were drawn from the general circulation models of HadCM2; we assessed both a conservative and a less conservative scenario of how climates could change over the next 50 year using the (Hadley HHGSDX50 and HHGGAX50 scenarios, respectively): HHGSDX50 assumes 0.5%/yr CO2 increase, whereas HHGGAX50 assumes a 1%/yr CO2 increase. Results of predictions of present and future distributions varied widely among species. Present distributional models predicted areas of 655,211-2,287,482 out of the 2,496,230 km2 core area of Cerrado in Brazil. All models used to represent species’ present geographic ranges were highly statistically significant based on independent test data sets of point localities. Most species were projected to decline seriously in potential distributional area, with both scenarios anticipating losses of >50% of potential distributional area for essentially all species. Indeed, out of 162 species examined, between the two climate change scenarios, 18 (HHGSDX50 scenario) - 56 (HHGGAX50 scenario) were predicted to end up without habitable areas in the Cerrado region, and 91 (HHGSDX50 scenario) - 123 (HHGGAX50 scenario) species were predicted to decline by more than 90% in potential distributional area in the Cerrado region. Bearing in mind the limitations of the method, and considering its explicit assumptions, these results nevertheless should be cause for ample concern regarding Cerrado biodiversity. Since only 2.25% of the Cerrado biome is presently protected, this future scenario presents a pessimistic forecast, which would likely include widespread species loss from the biome, as well as dramatic shifts to the south and east, further complicating conservation planning efforts.