Phenology of the herbaceous layer in a campo sujo community in the fazenda água limpa, Federal District, Brazil

O objetivo deste trabalho foi avaliar a influência das mudanças sazonais sobre a fenologia vegetativa (foliação) e reprodutiva (floração e frutificação) do componente herbáceo-subarbustivo de uma comunidade de campo sujo (15º55’478”S e 47º54’225”W) naFazenda Água Limpa, Brasília, DF. O clima da região é do tipo Aw, segundo a classificação de Köppen, com precipitação média anual de 1.500 mm. Foram selecionados 3 a 10 indivíduos de 61 espécies distribuídas em 23 famílias, resultando em 519 indivíduos marcados. Osindivíduos foram observados quinzenalmente, de outubro/1999 a fevereiro/2001. O fogo ocorrido na área dois meses antes do início doestudo estimulou a floração e a frutificação das espécies amostradas. A floração na comunidade apresentou-se distribuída por todo operíodo estudado, com concentração na estação chuvosa. O período de produção de frutos foi similar ao de produção de flores e a maioriadas espécies amadureceu seus diásporos do meio da estação chuvosa até o fim da seca. Na estação seca houve grande percentagem deespécies com folhas secas. No entanto, nem todas as espécies secaram completamente suas folhas nesse período, sendo que 3,2%produziram folhas novas e 31% mantiveram suas folhas verdes. Os eventos vegetativos e reprodutivos das plantas da camada herbáceosubarbustivamostraram-se dependentes da pluviosidade.The objective of this study was to analyse the phenological events in the herbaceous and sub-shrub layer of a campo sujo (15º55’478”S and47º54’225”W) community in relation to rainfall. The climate is Aw by Köppen classification with a mean annual precipitation of 1,500 mm. Three to ten individuals belonging to 61 species were studied totaling 519 individuals. The individuals were observed quarterly, from October1999 to February 2001. An accidental fire happened in the area two months before the beginning of this study. It stimulated flowering and fruiting of the species. Flowering occurred continuosly over the study period but, with a concentration in the rainy season. Fruiting presented a similar pattern with most species maturing their diaspores from the middle to the end of the rainy season. During the dry season there wasa higher production of dry leaves. However, some species did not have all leaves completely dried in that period, 3.2% produced new leaveswhile 31% remained with mature green leaves. The vegetative and reproductive events of the plants in the herbaceous layer were dependenton the precipitation

Floristic of the herbaceous and subshrub layer of a moist grassland in Brasília, Brazil.

A riqueza florística do estrato herbáceo-arbustivo de campo limpo úmido, uma vegetação campestre do bioma Cerrado, é pouco conhecida, embora as ervas e subarbustos sejam o maior componente na vegetação de Cerrado. O presente trabalho teve por objetivo caracterizar a riqueza florística da camada herbáceo-subarbustiva de um campo limpo úmido, com aproximadamente 16 ha, localizado na Fazenda Água Limpa (FAL), Brasília, DF (15º56’ a 15º59’ S e 47º55’ a 47º58’ W), além de comparar a sua flora herbáceo-arbustiva com a de outras áreas do bioma Cerrado no Brasil central e sudeste. Material botânico fértil foi coletado quinzenalmente, de setembro de 1999 a fevereiro de 2001, ao longo de trilhas distribuídas de modo a percorrer a maior extensão da área possível. Foram registradas 197 espécies, distribuídas em 105 gêneros e 41 famílias, tendo sido provavelmente descoberta uma nova espécie de Syngonanthus (Eriocaulaceae). As oito famílias com maior número de espécie foram Poaceae (39 espécies); Cyperaceae (24); Asteraceae (21); Polygalaceae (15); Eriocaulaceae (12); Xyridaceae e Melastomataceae (8) e Fabaceae (7). A similaridade florística, medida com índice de Sørensen, entre o campo limpo úmido estudado e as outras 12 áreas de Cerrado foram baixas variando de 3,3% a 37,4%. As baixas similaridades entre as áreas comparadas podem estar relacionadas com as diferenças de saturação hídrica do solo ou diferenças no tamanho das áreas de Cerrado remanescentes. A ordenação separou claramente as áreas úmidas das áreas secas e sugere que a distância geográfica entre as mesmas também pode ter influenciado a heterogeneidade florística no componente herbáceo-subarbustivo. ____________________________________________________________________________________ ABSTRACTLittle is known on the floristic richness of the herb-subshrub layer of the moist grassland, a grassy field vegetation within the Cerrado biome, although herbs and subshrubs are the major components of the Cerrado flora. The objective of this work was to characterize the floristic richness of the herb-subshrub layer of a moist grassland, in 16 ha in Fazenda Água Limpa (FAL), Brasília, DF (15° 56’ to 15° 59’ S and 47° 55’ to 47° 58’ W) and to compare with it with other Savana-like vegetations in central and southeastern Brazil. Vouchers were collected at quarterly intervals, from September 1999 to February 2001 along transects established in order to cover most of the study-area. A total of 197 species in 105 genera and 41 families was recorded. A species of Syngonanthus (Eriocaulaceae), probably new to science was found. The richest families were Poaceae (39 species); Cyperaceae (24); Asteraceae (21); Polygalaceae (15); Eriocaulaceae (12); Xyridaceae and Melastomataceae (8); and Fabaceae (7). Similarities between this moist grassland and 12 other sites, measured with the Sorensen index, were low, varying from 3.3% to 37.4%. The low similarities between the compared sites may be related to the differences in soil water saturation or differences in the size of the area covered by grasslands in each site. The ordination analysis readily distinguished dry from humid sites and suggested that geographic distance between the sites can also affect floristic heterogeneity in the herbaceous subshrub-component

Variáveis ambientais e a distribuição de espécies do estrato herbáceo-subarbustivo emuma área de campo limpo úmido no Distrito Federal, Brasil

O solo é sazonal ou permanentemente saturado nas savanas campestres úmidas, localmente conhecidas como Campo Limpo Úmido. A variação na umidade do solo parece determinar a distribuição espacial desta comunidade. O objetivo deste estudo foi analisar a relação entre as variáveis ambientais e o padrão de distribuição espacial das espécies do estrato herbáceo-subarbustivo em uma área de Campo Limpo Úmido na Fazenda Água Limpa, Brasília, DF (15° 56 a 15° 59 S e 47° 55 a 47° 58 WGr.). Uma área de 400 x 400 m foi subdividida em quatro porções de 200 x 200 m onde foram sorteadas as linhas de amostragem. No levantamento, fitossociológico adotou-se o método de inventário por interseção na linha. Foram coletadas amostras de solo superficial (0-20 cm) para análise química e textural. A umidade gravimétrica do solo foi obtida quinzenalmente durante o ano de estudo. Foram amostradas 85 espécies incluídas em 67 gêneros e 24 famílias. A diversidade da área segundo o índice de Shannon foi de H = 2,60 nats.cobertura–1. A composição florística dos transectos em solos com alta umidade gravimétrica, altos teores de matéria orgânica e areia diferiu da dos transectos em solos com menor umidade gravimétrica e com variação sazonal na umidade. Uma análise de correspondência canônica (CCA) mostrou correlações significativas entre a textura e a umidade do solo e a distribuição das espécies. As variáveis ambientais mais fortemente correlacionadas foram umidade gravimétrica, matéria orgânica, argila, silte e areia, que foram preponderantes na determinação da distribuição das espécies do campo limpo úmido da FAL, determinando a formação de mosaicos na vegetação. _______________________________________________________________________________ ABSTRACTThe soils are seasonally or permanently saturated in the moist grassland savanna, locally known as Campo Limpo Úmido. Soil moisture variation seems to determine spatial distribution of communities. The objective of this study is to analyse the relationship between environmental variables and the patterns of spatial distribution of species in the herbaceous-subshrub layer of an area of moist grassland at the Água Limpa Farm, Brasília, DF (15° 56 to 15° 59 S and 47° 55 to 47° 58 W Gr.). An area of 400 x 400 m was divided into four sections of 200 x 200 m where four transects were randomly sampled. A line intercept method was adopted for the phytossociological study. Superficial soils samples (0-20 cm) were collected for chemical and textural analyses. Gravimetric soil moisture was measured quarterly during the study-year. A total of 85 species in 67 genera and 24 families were found. The diversity was high, Shannon s index, H , was 2.60 nats.cover-1. Floristic composition of the transects in soils with a high gravimetric soil moisture and high content of organic matter and sand differed from those transects in soils with a lower gravimetric soil moisture indicating seasonal variation. A Canonical Correspondence Analysis (CCA) showed significant correlations between soil texture and soil moisture features and species distribution. Gravimetric soil moisture, organic matter, clay, silt and sand were significantly correlated to species distribution in the moist grassland determining mosaics in the vegetation

Germination and growth of Magonia pubescens A. ST.-HIL seedlings

This study aimed to analyze the germination, growth and development of Magonia pubescens A. St.-Hil. (tinguí ortimbó), a typical species of the deciduous forest. The germination of seeds of four matrices was evaluated at different treatments: directsowing in greenhouse (50% of shade), direct sowing under full sunlight and moistened paper at laboratory condition and underfluorescent light with photoperiod of 12 hours in ambient temperature. The germinated seeds under laboratory conditions weretransplanted to polyethylene bags with soil under full sunlight and 50% of shade. The variables evaluated were: time of the first andlast germination, germinability; average time and the rates of speed of germination index. In addition there were evaluated the seedlingheight, stem base diameter, number of leaf and leaflets were monitored at 30, 60, 90 and 120 days. The species presented highgerminability at laboratory conditions (G> 90%) and under full sunlight (96%>G>56%), however, the germinability in 50% shadepresented inferior result (G< 36%). The highest average values of seedling height (78.52 ±19.90mm) were obtained with 50% ofshade treatement. The diameters presented no significant statistical differences among treatments (highest diameter of 3.35mm;p>0.05). The leaf and leaflets number varied among treatments, with highest average for seedling under full sunlight. Suggesting thatMagonia pubescens A. St.-Hil. is a useful species for rehabilitation of degraded areas

Edaphic filters and plant colonization in a mine revegetated with sewage sludge

We evaluated the recruitment of plant species and their relation with edaphic attributes in a mine revegetated with sewage sludge in the Brazilian Federal District. Plant species in the revegetated mine and in remaining portions of Cerrado (savanna) within the mined landscape were sampled and identified. Then, samples of revegetated substrate and soils from Cerrado portions were collected, analyzed for chemical attributes and submitted to statistical tests. Results indicated that the remaining portions of Cerrado were colonized by 91 species (22% allochthonous species), and the revegetated substrate housed 62 species (55% allochthonous species). Multivariate tests showed that the edaphic condition built from the incorporation of sewage sludge into the mining substrate acted as filter on the assemblage of plant species. Despite the two study sites shared the same landscape, the Cerrado portions and the revegetated substrate did not share similar plant communities after a decade from mine rehabilitation works

Vascular flora in dry-shrub and wet grassland Cerrado seven years after a fire, Federal District, Brasil

ABSTRACTStudies of temporal dynamics for grassland sites report that fire suppression plays a crucial role in floristic changes. The objective of this study was to verify whrther after seven years without fire, communities showed variations in terms of composition, life forms pollination and dispersal syndromes. The first survey (T0) was conducted from September 1999 to October 2000, while the second (T1) took place from August 2006 to August 2007. The floristic results in T1 were compared with the survey in T0 through the Sorensen similarity index and Chi-square tests. Over time, there were differences in the composition,life forms and pollination and dispersion syndromes. The evidence of changes suggests that the frequency of the regime can be considered the fire regime can be considered the main agent for change in the flora of these communities