Search

Euterpe precatoria Mart. is the most abundant plant species in the Amazon basin, and one of the main non-timber forest products on the continent. A thorough understanding of the ecology of this species is needed to support sustainable management initiatives. Resource availability, disturbance regime, and human management are some of the main factors influencing population structure. We described the species’ life stages, evaluated its allometric relationships, and assessed the effects of habitat type (floodplain and upland) and proximity to human settlements on population size distribution in the Central Amazon near the Purus River. The height:diameter ratio increased from Seedlings to Juvenile 2, but decreased from Juvenile 2 to Reproductive 2, indicating changing height investment for any given diameter along these life stages. There was a marked habitat dependency in both the density and population size distribution, with populations in upland forests dominated by juveniles, whereas populations in the floodplains were dominated by reproductive palms. Proximity to human settlements was not related to population structure parameters. Our results suggest that the disturbance regime may have opposite meanings in várzea forests, where it limits recruitment under increased light levels, and in terra firme forests, where it may stimulate recruitment under limited light conditions.

Our understanding regarding the demography of adult conifers in forest–grassland mosaics is still limited. I studied the landscape-scale demography and spatial distribution of the conifer Araucaria angustifolia (Bertol.) Kuntze in a subtropical forest–grassland mosaic over a 24-year period. Araucaria angustifolia is a long-lived pioneer that is expected to thrive in grasslands and forest edges better than in forest patches. I used the position of trees in aerial photographs taken in 1984 to analyze spatial patterns and a 2008 satellite image to estimate individual survivorship. Spatial distribution of trees in the grassland was aggregated and was not related to the distribution of trees in forest patches. Survivorship was higher in forest patches than in grasslands, where it showed density dependence. In forest patches, survivorship was positively related to both patch area and distance from forest edge. Crown breakage was more common in the grassland than in forest patches. In forest patches, it was positively related to crown size, number of conspecific neighbours, and patch area. Adult Araucaria angustifolia seem to benefit from angiosperm-dominated neighbourhoods relative to isolation in grasslands. Density-dependent effects, known to be widespread among seeds and seedlings, were shown to be important to adult trees as well.

We investigated the patterns of growth and reproduction of the understory clonal palm Geonoma brevispatha based on the identification of post-germinative ontogenetic stages, over a 3-year period. Genets were monitored in 100 5 × 5 m plots and 100 2 × 2 m subplots, in a 1-ha area of swamp forest in São Paulo state, southeastern Brazil. Ramets pass through four ontogenetic stages (bifid-leafed juveniles, pinnatifid-leafed stemless immatures, stemmed nonreproductive virgins, and reproducers). Leaf size, leaf number, and leaf production rate increased during ontogeny, but diameter growth rate was higher among immatures. Stem length, number of nodes, and leaf rachis length were positively correlated across ontogenetic stages, but crown height was smaller than stem length in adult palms because of frequent leaning. Leaf number and sexual fecundity increased with ramet size, but declined in larger, senescent ramets. Clonal fecundity preceded sexual fecundity, and sexual and clonal fecundity increased continuously with genet size. No relationship was found between sexual and clonal fecundity. Growth and survival strategies of G. brevispatha were consistent with the patterns found in other tropical clonal palm species. Sexual fecundity and cloning seem to be two integrated processes favored by environmental conditions that also support the growth of existing ramets.Key words: stage-structured populations, ontogenetic stages, swamp forest, Brazil, Atlantic forest, senescence.

A study of the ontogenetic stages of the acaulescent palm Attalea humilis Mart. ex. Spreng was conducted in three fragments (1.6, 6.4, and 9.9 ha) of the Atlantic forest in southeastern Brazil. The fragments were damaged by fire during the study period (1996-1999). External macromorphology and quantitative measures of leaf number and length of the newest leaf's rachis allowed the distinction of five ontogenetic stages. Seedlings were attached to buried fruit remains and presented entire leaves. Juveniles possessed incomplete segmentation of the blade. Pinnatifid-leafed, non-reproducing individuals were morphometrically divided in two groups: immature, with fewer leaves and smaller but highly variable youngest leaf length, and virginile, with more and larger leaves, but more constant youngest leaf length; the critical crown size by which immature and virginile stages could be identified varied according to fragment and year. Reproductive palms bore identifiable reproductive structures. Seedlings, juveniles, and immatures had fewer leaves than virginile and reproductive individuals. Leaf length was similar between seedlings and juveniles but increased in later stages. The characteristics of each stage were fairly constant throughout the study years in the three fragments and were little affected by fire, indicating that the stages we define in this study are important in the developmental program of A. humilis.Key words: stage-structured populations, ontogenetic stages, forest fragments, fire, leaf size, leaf number.

A study of the ontogenetic stages of the acaulescent palm Attalea humilis Mart. ex. Spreng was conducted in three fragments (1.6, 6.4, and 9.9 ha) of the Atlantic forest in southeastern Brazil. The fragments were damaged by fire during the study period (1996-1999). External macromorphology and quantitative measures of leaf number and length of the newest leaf's rachis allowed the distinction of five ontogenetic stages. Seedlings were attached to buried fruit remains and presented entire leaves. Juveniles possessed incomplete segmentation of the blade. Pinnatifid-leafed, non-reproducing individuals were morphometrically divided in two groups: immature, with fewer leaves and smaller but highly variable youngest leaf length, and virginile, with more and larger leaves, but more constant youngest leaf length; the critical crown size by which immature and virginile stages could be identified varied according to fragment and year. Reproductive palms bore identifiable reproductive structures. Seedlings, juveniles...