Resumo Os domínios fitogeográficos são estruturados por diferentes fatores geoclimáticos (abióticos) tais como altitude, temperatura e precipitação. Assim, nosso objetivo foi investigar quais os possíveis fatores abióticos que estão relacionados à riqueza florística do componente arbóreo-arbustivo em remanescentes de Chaco, ao longo de sua extensão. O estudo é baseado em dados de presença e ausência de espécies em diferentes remanescentes relacionados com dados geoclimáticos. Somado a isso, foram utilizados shapes da World Wildlife Fund para diferir o Chaco seco do úmido. O banco de dados agregou 36 áreas e 522 espécies. A afinidade florística entre os grupos foi relacionada principalmente à temperatura, altitude e sazonalidade da precipitação. Em remanescentes onde a sazonalidade da precipitação e a altitude foram mais evidenciados, há maior dissimilaridade na composição da vegetação arbóreo-arbustiva. Por outro lado, o gradiente de temperatura explicou a homogeneidade florística no Chaco úmido. Assim, a riqueza do componente arbóreo-arbustivo do Chaco é atribuída principalmente a três fatores geoclimáticos. O Chaco seco apresenta maior dissimilaridade florística comparado ao Chaco úmido. Ainda, a sazonalidade da precipitação e a altitude têm papel preponderante na estruturação de árvores e arbustos no Chaco seco e a temperatura nas formações mais homogêneas que integram o Chaco úmido.

Abstract The phytogeographic domains are structured by different geoclimatic (abiotic) factors, such as altitude, temperature and precipitation. Thus, our goal was to investigate the possible abiotic factors that are related to the floristic richness of the tree-shrub component throughout the Chaco remnants. This study is based on data of the presence and absence of species in different remnants related to geoclimatic data. In addition, World Wildlife Fund shapes were used to differentiate dry and wet Chaco. The database aggregated 36 areas and 522 species. The different clusters obtained by floristic affinity between groups in Chaco was mainly related to temperature, altitude and seasonality of precipitation. In remnants where the seasonality of precipitation and altitude were more evident, there is greater dissimilarity in the composition of the tree-shrub vegetation. On the other hand, the temperature gradient explained the floristic homogeneity in the humid Chaco. Thus, the richness of the tree-shrub component of the Chaco is mainly attributed to three geoclimatic factors. Dry Chaco presents greater floristic dissimilarity compared to Humid Chaco. Still, the seasonality of the precipitation and the altitude play a dominant role in the structuring of trees and shrubs in the Dry Chaco and the temperature in the most homogeneous formations that integrate the humid Chaco.

ABSTRACT We characterized taxonomic and functional differences between two vegetation physiognomies in the Brazilian Chaco, namely chaco woodland (CW) and chaco forest (CF), in order to understand which abiotic and biotic mechanisms underlie the establishment of different physiognomies. We characterized the vegetation physiognomies by comparing woody species composition, richness and diversity and functional diversity between CW and CF plots. We also measured soil variables to characterize abiotic factors related to the different physiognomies. Species richness and diversity and soil nutrient values were higher in CF. Leaf succulence and nitrogen content were higher in CW, while height, leaf area, and specific leaf area were higher in CF. The standardized effect size (SES) of functional richness was higher in CW, but the SES of functional dispersion did not differ between CF and CW. We observed a diversity gradient related to soil fertility. Traits of species in CW were related to adaptations to poor soils, while in CF floristic composition showed a prevalence of species with more attributes related to competition for light. Thus, the structure of the floristic community in CW is likely related to an environmental filter, while competition for resources prevails in CF.

ABSTRACT The distributions of species of Fabaceae are strongly related to the soil. Their presence can alter restrictive conditions and favour the establishment of other species. However, it is still not known how the relationship between species of Fabaceae and edaphic factors interact in structuring woody Chaco vegetation. In this context, we aimed to test the hypothesis that restrictive edaphic conditions can explain the difference in floristic patterns of two types of vegetation through their species representativeness of Fabaceae. We analysed floristic consistency between wooded and forested Chaco to address how spatial and environment components might explain differences between them along with the effects of the interaction between Fabaceae and the soil. We observed that the association between environmental and spatial variables was more important than any individual factor in explaining the structuring of the communities. Both the percentage of species of Fabaceae present and the soil influence the structure of the two types of vegetation. Species of Fabaceae have greater potential as indicators in the wooded Chaco. Therefore, we suggest the interaction between soil types and species of Fabaceae plays a role during the structuring of the communities through the establishment of these species in more restrictive soils.

O Cerrado é o segundo maior domínio morfoclimático brasileiro. O Cerrado é o segundo maior domínio morfoclimático brasileiro. Esta formação é rica em espécies, recebe influência dos domínios fitogeográficos circunvizinhos. O Cerrado, particularmente o cerradão, é vulnerável às mudanças de clima, solo e queimadas. Com base na avaliação da riqueza do estrato herbáceo do cerradão de uma RPPN urbana pretende-se responder as seguintes questões: Qual o hábito de crescimento, forma biológica e síndrome de dispersão predominantes? As espécies avaliadas são exclusivas do domínio fitogeográfico do Cerrado? As coletas foram realizadas de maio de 2007 a junho de 2008 em um remanescente de cerradão da RPPN/UFMS, Campo Grande, MS. Encontramos 59 espécies, 49 gêneros e 17 famílias. As famílias mais representativas foram Fabaceae (15 espécies), Poaceae (12) e Asteraceae (sete). Predominaram as herbáceas eretas (83%), hemicriptófitas (59%) e autocóricas (61%). Em relação à distribuição nos domínios fitogeográficos brasileiros observamos que 12% das espécies são exclusivas de Cerrado e 16% ocorrem no Cerrado, Amazônia, Caatinga, Mata Atlântica e Pampa.

The Cerrado is the second largest Brazilian morphoclimatic domain. It very rich in species, many endemic but it is also influenced by surrounding phytogeographic domains. The Cerrado, particularly cerrado woodland, is vulnerable to changes in climate and soil and to wildfires. Based on the avaliation of the richness of the herbaceous of the cerrado woodland of an urban RPPN want to answer the following questions: What is the growth habit, biological form and dispersal syndrome predominant? These species are exclusive of Cerrado phytogeographical domain? Samples were collected from May 2007 to June 2008 in a remnant of cerrado woodland on the RPPN/UFMS, Campo Grande, MS. We found 59 species, 49 genera and 17 families. The families most representative were Fabaceae (15 species), Poaceae (12) and Asteraceae (seven). Predominated the erect herbs (83%), hemicryptophyte (59%) and autochorich (61%). About distribution of species in Brazilian phytogeographic domains, 12% are exclusive to Cerrado and 16% are in Cerrado, Amazônia, Caatinga, Mata Atlântica and Pampa.