Ecologia populacional de espécies lenhosas clonais em savana neotropical
Abstract
The aims of this thesis were: to investigate the heterogeneity of soils and to
evaluate the contribution of clonal growth to the population dynamics of woody species under
contrasting soil conditions. In the Cerrado-Pantanal ecotone (15º43 S; 56º04 W), the soil
possesses typical features from both the soil of Cerrado in the Central Plateau and the soil of
the Pantanal Plain. Given the variability of soil and pluviosity, our hypothesis is that clonal
growth is the demographic parameter that most contributes to the population growth rate ()
of five woody species in this ecotone area. This study was carried out in five Cerrado areas.
We identified four soil categories; three of them typic Litoplinthic Petric Plintosol, typic
Dystrophic Yellow Latosol and Dystrophic Yellow Latosol with plinthite had not yet been
described for the study site. The chemical attributes aluminum saturation, magnesium,
calcium, pH and manganese explained 38.7% of the variability of the soils in the study sites.
The spatial distribution of the edaphic attributes was heterogeneous. These attributes differed
between the soils in the Cerrado Pantanal ecotone and the soils of Cerrado in the Central
Plateau and of the Pantanal Plain. The population dynamics of Curatella americana, a
dominant species with wide geographical distribution, was evaluated in Petric Plintosol (P)
and in Yellow Latosol (L), in the dry and rainy seasons. Sexual reproduction and seedling
growth were higher in P, whereas clonal growth was higher in L. The population growth rate
(λ) was higher in P. The adult survival rate exerted the strongest effect on λ for the two soil
categories and the dry and rainy seasons. The interaction between soil category and pluviosity
exerted the strongest effect on λ. We also analyzed the dynamics of species with small
populations (Bowdichia virgilioides and Roupala montana) and large populations (Curatella americana and Caryocar brasiliense), to determine which demographic parameters characterize woody clonal species with different sizes. For the species with small populations, the rate of sexual reproduction and the density of all life stages were smaller, whereas the clonal growth was higher. Small populations were more susceptible to variations in soil and pluviosity. The rates that most contributed to the λ of Bowdichia virgilioides and Roupala montana in L and P were: respectively, the survival of young ramets and immatures, in the dry season; and for both species, the survival of adults, in the rainy season. For C. americana and C.brasiliense, the survival of adults was the parameter that most contributed to λ, independently of soil category and season. The study indicated an heterogeneity of the superficial layer of the soil and of the soil categories that occur in this area. Soils with contrasting attributes exerted an important effect on the dynamics of woody clonal species.
The survival of young and immature individuals, originated from clonal growth, was the rate
that most contributed to the λ of the small-sized populations of woody clonal species B.
virgilioides and R. montana , whereas the survival of adults was the rate that most
contributed to the λ of the large-sized populations C. americana and C. brasiliense.