Resumo A variação fitofisionômica do Cerrado brasileiro é intensa e estudos fitossociológicos podem fornecer subsídios sobre quais fatores são responsáveis por essa heterogeneidade ambiental. Nesse sentido, esse estudo teve o objetivo de avaliar a estrutura da vegetação lenhosa de três áreas de cerrado sentido restrito, no município de Jataí - GO, buscando discutir os achados com o histórico de perturbação de cada área e aspectos físicos dos solos. Foram alocadas dez parcelas contíguas de 20x50 m em cada área, totalizando três hectares de levantamento no total. Incluíram-se na amostragem todos os troncos com diâmetro ≥ 5 cm, medidos a 30 cm do solo. As áreas apresentaram diferenças quanto à estrutura da vegetação lenhosa com formações mais abertas e outras mais densas (densidade de 991 a 1859 ind.ha-1 e área basal de 10,85 a 17,68 m2.ha-1). A riqueza florística variou de 70 a 82 espécies. Apesar de haver uma mistura de elementos florísticos savânicos e florestais entre as áreas, detectou-se maior domínio de espécies savânicas. Os padrões florístico e estrutural indicaram heterogeneidade nas comunidades em função de diferenças texturais do solo e incêndios. Isso reforça a importância da preservação de formações savânicas no sudoeste do estado para entender variações estruturais e florísticas e, consequentemente, fornecer informações para outros estudos sobre os aspectos ecológicos relacionados a eles.

Abstract The physiognomy variation of Brazilian Cerrado is intense and phytosociological studies can provide subsidies on which factors are responsible for this environmental heterogeneity. Thus, the objective of this study was to evaluate the structure of the woody vegetation of three sites of Cerrado sensu stricto, in the municipality of Jataí, state of Goiás, Brazil, aiming to discuss the findings with the history of disturbance of each site and physical aspects of the soils. Ten 20 x 50 m contiguous plots of were allocated in each area, totaling three hectares of survey in total. We included in the sample all trunks with diameter ≥ 5 cm, measured at 30 cm of the ground. The sites showed differences in wood structure, ranging from more open to more dense areas (density ranging 991-1859 ind.ha-1 and basal area ranging from 10.85 to 17.68 m2.ha-1). The richness in the areas ranged from 70 to 82 as well as the species composition. Although, there is a mix of savanna and forest floristic elements, we detected higher domain of typical savanna species for the three areas. The floristic and structural patterns indicated heterogeneity in the communities, even geographically close, possibly due to soil texture differences. This reinforces the importance of the preservation of savanna formations in the southwest of Goiás state to understand the structural and floristic variations and, consequently, to provide information for other studies on the ecological aspects related to them.

ABSTRACT We evaluated nutrient cycling by measuring leaf litter production and decomposition in the Brazilian savanna (cerrado sensu stricto) on eutrophic (calcareous) and dystrophic (arenitic) Neosols over the same spatiotemporal scale. We installed three transects in the Cerrado with plots in each Neosol type. Areas along the transects were randomly chosen for determining soil chemical properties, and accumulated leaf litter was collected monthly for a year for analysis. We used litter bags to test for a correlation between loss of dry mass and nutrient release. The calcareous cerrado had higher levels of macronutrients, higher pH, and lower Al compared to the arenitic cerrado. The estimated annual release of leaf litter nutrients in kg ha-1 yr-1 was higher in the calcareous cerrado. Nutrient concentration was significantly higher in different months in the calcareous cerrado, except for S and N. In general, the loss of dry mass was not correlated with nutrient release. Calcareous Neosol is unique to the cerrado sensu stricto, and retains more nutrients and facilitates higher leaf litter chemical quality than cerrado of the same physiognomy on dystrophic soils. Nutrient release is not always related to loss of dry mass, regardless of the amount of leaf litter.

The input of particulate and dissolved organic matter (POM and DOM, respectively) from terrestrial ecosystem drainage basins is an important energy and nutrient source in limnic food chains. Studies indicated that semi-deciduous seasonal forests located in drainage areas in Brazil have the potential to produce 7.5 - 10.3 Mg ha−1/year of POM. The global increase in vegetation destruction, such as forests, threatens this allochthonous resource and can have significant impacts on river and lake communities and food chains. Therefore, it is critical that exploitation and occupation protocols are updated to protect the transition areas between terrestrial and limnic ecosystems. This review highlights the existing knowledge of these ecosystem interactions and proposes responsible sustainable methods for converting the vegetation in drainage basins. This was based on Brazilian ecosystem data and the new "Brazilian Forest Code." This study also considers the importance of including flood tracks in permanently protected areas to improve Brazilian legislation and protect hydric resources.

Parâmetros fitossociológicos, como freqüência de classes de altura e de diâmetro, são muito utilizados em inferências sobre sucessão secundária em fitocenoses. Indivíduos abustivo-arbóreos com no mínimo 1,5 m de altura e fuste a 1,3 m, foram amostrados em 2.600 m² de floresta estacional semidecidual do Jardim Botânico Municipal de Bauru (JBMB). Informações sobre as freqüências de classes de diâmetro das cinco espécies com maior índice de valor de importância (Ocotea pulchella, Protium heptaphyllum, Copaifera langsdorffii, Platypodium elegans e Trichilia pallida) e a classificação sucessional das populações mais numerosas também foram analisadas para inferências sobre as características sucessionais da comunidade estudada. As freqüências de classes de diâmetro de Vochysia tucanorum, espécie típica de savana, também foi estudada. As informações obtidas permitiram considerar que a floresta do JBMB encontra-se em estádio sucessional intermediário, e que, embora tenha sofrido com a ação do fogo no passado, algumas dessas populações estão conseguindo renovar-se.

Phytosociological parameters, as the frequency of height and diameter classes, are commonly used to make inferences about secondary succession in given phytocenoses. Shrub and tree individuals higher than 1.5 m and with a bole length of at least 1.3 m were sampled in 2,600 m2 of semideciduous seasonal forest in the Municipal Botanical Garden of Bauru (JBMB). Information on the diameter class frequencies of five species with the highest Importance Value Index (Ocotea pulchella, Protium heptaphyllum, Copaifera langsdorffii, Platypodium elegans and Trichilia pallida) and the more numerous species' successional classification were analyzed to make inferences about the successional features of the studied community. The diameter class frequencies of savannic species Vochysia tucanorum were also studied. The information obtained allowed to consider that the forest of the JBMB is at an intermediate successional stage, and that, although it used to be periodically burnt, some of its populations are able to renew themselves.

Informações florísticas escassas, referentes ao município de Bauru, e a elaboração de hipóteses sobre mecanismos de ocupação de fitocenoses florestais por espécies savânicas, representaram as principais questões motivadoras do presente estudo, desenvolvido em dois fragmentos de floresta estacional semidecidual (5 ha e 7 ha) mantidos pelo Jardim Botânico de Bauru, que abriga também savana florestada. O material botânico foi coletado a partir de caminhadas ao acaso e em parcelas implantadas durante estudo fitossociológico. Foram encontradas 264 espécies arbustivo-arbóreas, pertencentes a 58 famílias. Dessas espécies 126 foram coletadas apenas na fitocenose florestal, e 66 espécies foram coletadas em ambas as fitocenoses. As duas famílias com o maior número de espécies foram Rubiaceae (25 espécies) e Myrtaceae (21 espécies). Foi realizada análise de similaridade florística, a partir do índice de Jaccard (S J), entre a floresta do JBMB e outros 11 remanescentes florestais, alguns dos quais, sob influência florística savânica. A riqueza florística dos fragmentos florestais do JBMB sofreu incremento, pela ocupação de espécies savânicas, oriundas da savana florestada contígua. Incêndios pretéritos, além da ocorrência de microambientes distintos, representaram prováveis fatores de facilitação para a invasão dessas espécies savânicas.

Scarce floristic information for Bauru Municipality and the formulation of hypotheses on occupation mechanisms of forest communities by savanna species represent the main questions that motivated this study. The research was carried out in two seasonal-semideciduous-forest fragments (5 ha and 7 ha) maintained by Jardim Botânico de Bauru - JBMB (Bauru Botanic Garden), which includes forested savanna as well. The plant material was collected during random walks and in plots installed for a phytosociological study. We found 264 arboreal-shrubby species belonging to 58 families. Of these, 126 species were collected exclusively in the forest community, while 66 species were collected in both plant communities. The families Rubiaceae (25 species) and Myrtaceae (21 species) had the highest number of species. A floristic similarity analysis was performed, based on Jaccard's index (S J), between the JBMB forest and 11 other forest remnants, some of which showed savanna floristic influence. The floristic richness of the JBMB forest fragments increased due to occupation by savanna species which came from the adjoining forested savanna. Previous fires plus the occurrence of distinct microenvironments were possibly the factors that facilitated the invasion by savanna species.

A heterogeneidade florística do cerrado pode sofrer influência de espécies florestais oriundas de matrizes vegetacionais próximas, sendo as matas de galeria uma das vias para essa ocupação. A expansão florestal por áreas savânicas pode ser explicada por tal fenômeno. As espécies arbustivo-arbóreas presentes na área estudada, na cidade de Bauru, Estado de São Paulo, e em 14 diferentes localidades abrigando cerrado sensu stricto e cerradão, foram definidas como florestais a partir de listagens florísticas das fitocenoses em questão. As porcentagens de ocorrência de espécies florestais nas localidades analisadas variaram de zero a 4,5%. A proximidade de matrizes florestais, a ocorrência de incêndios e critérios de inclusão utilizados foram alguns dos fatores que podem ter influenciado tal variação.

Based on studies of floristic lists the contribution of forest tree and shrub species in a forested savanna area in the city of Bauru, State of São Paulo, and in 14 different places sheltering cerrado sensu stricto and cerradão in Brazil is defined as the evidence of forest species causing a change of cerrado heterogeneity. The percentages of occurrence of forest species in the locations analyzed varied from zero to 4.5%. The proximity of different forest matrices, the occurrence of fires and the inclusion criteria used were some of the factors that may have influenced such variation.