Maryland Sanchez

Phenology of a tree community in a cerrado sensu stricto, Barra do Garças, Mato Grosso State, Brasil

We observed leaf and reproductive phenology and analyzed the relationship among phenophases and abiotic variables (rainfall, temperature and photoperiod) and investigated the occurrence of seasonality. The local climate is characterized by marked wet (October-April) and dry seasons (May-September). From October 2005 to September 2007, 1221 individuals of 84 species were observed monthly for changes in leaf fall, leaf flush, flowering and fruiting. Deciduous (44%) and brevideciduous (16%) species were predominant in the area. The leaf fall was negatively correlated with rainfall and photoperiod, with mean date in August. Leaf flush was positively correlated with temperature. Flowering and fruiting were observed in both years for 69 species. Flowering occurred mainly at the dry season (July-August) and was inversely correlated with rainfall. The zoochorous species were predominant in the community. Fruiting of anemochorous species was inversely correlated with rainfall. Fruiting of zoochorous species occurred continually throughout the year and was negatively correlated with rainfall and positively with temperature. Our results suggest overall seasonal patterns with peaks of vegetative and reproductive activity occurring between dry and wet seasons. These phenological patterns have been demonstrated to be common in Brazilian savanna, and suggest that the timing of seed dispersal, germination and young seedling development is a major factor responsible for synchronized ripening of fruits at the beginning of the rainy season.

Florestas de restinga e de terras baixas na planície costeira do sudeste do Brasil: vegetação e heterogeneidade ambiental

It was evaluated the floristic similarity between two Atlantic Rainforest physiognomies in Brazilian coast area, herein called Restinga and Lowland forests. The hypothesis was that, due the differences in geomorphologic processes, these forests would differ on soil physical and chemical properties, floristic composition, live above-ground biomass and litterfall production. It was sampled 1 ha (100 × 100 m) for each site located in Ubatuba, Sao Paulo state, SE Brazil. Within each hectare it was recorded trees with DBH > 4.8 cm in all 10 × 10 m contiguous plots, and collected soil and litterfall samples. The cluster and ordination analyses indicated the two communities as distinct groups considering soil and floristic composition, agreeing with the initial hypothesis. Species diversity was higher (p 0.05) between the two forests. This apparent paradox could be explained assuming that, since different species establish themselves in the Restinga or Lowland forests and find a favorable spectrum of conditions and resources, they would tend to persist and to develop in that place; even so the edaphic conditions differ between the Restinga and Lowland forests, each species could respond in a particular way to these variations, and then both forests could reach similar values of biomass and litterfall production. It is probable that the environmental filter conditioned by soils has being important for the strong floristic segregation between these two forests.

Fogo e dinâmica da comunidade lenhosa em cerrado sentido restrito, Barra do Garças, Mato Grosso

Studies on the dynamics and structure of woody vegetation after natural fires in Parque Estadual da Serra Azul have shown that fire affects plant survival and growth. The response of vegetation to fire depends on intensity, frequency and duration of burning. Ten plots (20 × 50 m) (Area 1) were burned in 2002 and 2005. Another ten plots (Area 2) were burned in 2002, 2005 and 2007. In January 2009, in Area 1, tree mortality was lower (2.0%) and recruitment (3.7%) higher than that observed Area 2 (4.3% and 0.05% respectively). Plant mortality decreased with increasing size class. In Area 2, there was a reduction in plant size (height and diameter). The resprouting pattern after fire was related to plant size. Smaller size classes had higher proportions of resprouting at the base of the stem while the larger size classes had more resprouts at the tree crown. In Area 2, species richness was reduced (estimated by Jacknife and Chao 2). Our results suggest that the tolerance of adult trees and smaller plants due to resprouting may explain the persistence of the woody cerrado community submitted to a fire regime interval over five years.

Spatial and seasonal variation in the species richness and abundance of ferns and lycophytes in gallery forests of Cerrado in Central Brazil

This study investigated the relationship between environmental factors and the spatial and seasonal variations in the species richness and abundance of ferns and lycophytes in four gallery forests in the Cerrado savanna biome of central Brazil. The species composition, diversity, and similarity of the assemblages were analyzed, along with the influence of environmental factors on the spatial–seasonal variation found in these parameters. A total of 72 species was recorded. Species richness was affected by the rockiness of the substrate in both the rainy and dry seasons. Abundance was affected by the presence of bamboos and Marantaceae in both seasons. Many species occurred in plots with reduced exposure to sunlight, and plots with the highest soil humidity had the highest species richness, including species found only in these plots. The seasonal variation in species richness and abundance was related primarily to the reduction in humidity during the dry season. Two highly similar groups were detected. For the first group, the factors that most influenced species richness (rockiness in the soil) and abundance (presence of bamboos and Marantaceae) are also related to the greater environmental heterogeneity of the streams. On the other hand, in the second group the highest levels of similarity in species composition were related to the environmental homogeneity of the streams.