Search

The Araucaria Mixed Forests (AMF) are subtropical conifer-hardwood mixed forests that are part of the Atlantic forest floristic dominion in Brazil and Argentina. The AMF is dominated by the conifer...

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.

Understanding the effects of disturbance on seed rain is critical to predict changes in forest species composition and diversity. Logging effects on seed rain in a mixed conifer-hardwood forest complex in southern Brazil were evaluated. One year of seed rain data were collected from a large-scale observational experiment in logged and protected forests and quantity and average seed size weighted by species abundance (CWM) were compared between old-growth and logged stands 55 years after logging activities. Using these data, variations in frequency of functional groups of species in the seed rain were examined to see if they could be attributed to logging. Results show that the number of seeds per trap was highly right-skewed, ranging from 13 to 12,788 seeds per trap in one year. Seed rain was affected by logging history, with seed traps in old-growth plots receiving significantly less seeds than traps in logged plots. All species included mean seed size weighted by species abundance were significantly smaller in logged than in old-growth forests. This difference persisted after the exclusion of Araucaria angustifolia, a large-seeded pioneer which was intensively logged, although the difference of seed size between the two forest classes was greatly reduced. Species abundance in the seed rain differed significantly from the established tree community, between logged and old-growth stands. The composition of the seed rain was much more variable than the composition of the established tree community and its points more scattered over the ordination space than the points corresponding to the protected forests. The number of collected seeds across different functional groups of species significantly differed between logged and old-growth plots. The seed rain of logged forests reflects their arrested succession as indicated by reduced abundance of functional groups such as pioneers, large seeded pioneers and Araucaria, as well as reduced functional diversity. Seed rain differences between logged and old- growth stands reflect the intensive logging of A. angustifolia.

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 evaluated the frequently assumed but rarely tested hypothesis that in tropical and subtropical forests species form discontinuities along gradients in trait variation, which can be detected to classify species into ecologically meaningful and statistically defined groups. We also tested the hypothesis that the dominant conifer Araucaria angustifolia have a contrasting trait syndrome from the pool of angiosperms. Data were collected in subtropical mixed conifer-hardwood forests in southern Brazil. Eleven trait variables (relative growth rates, growth rates under favourable conditions, annual mortality rates, seed length, seed dispersal mode, wood density, maximum height, crown depth, stem slenderness, specific leaf area, and leaf blade length) were measured for 66 large tree species. The conifer Araucaria angustifolia differed significantly in most traits and vital rates from the angiosperm distributions. The Simple Structure Index criterion was used to identify the optimum number of non-hierarchical k-means groups. This index was largest for a solution with five groups. Non-hierarchical groups were more strongly related with the resource capture and height gradients than groups formed by hierarchical clustering. We propose the recognition of seven ecological species groups in the studied forests depending on growth rates, leaf size, wood density, height, stem slenderness, dispersal, and crown depth: Conifers, Palms, Pioneers, Large-seeded Pioneers, Wind-dispersed Large trees, Large shade-tolerant trees, and Small Shade-tolerant trees. The classification produced was coherent with the ecological strategies present in the community and represents a subdivision of Westoby’s leaf-height-seed plant strategy scheme.

Temporal variation in seed crop size of the long-lived pioneer conifer Araucaria angustifolia was studied in subtropical South America. We evaluated the expectations that: 1) A. angustifolia presents highly variable seed production (mast seeding behavior); 2) A. angustifolia has endogenous cycles of reproduction of two or three years; 3) There is a tendency for a high seed production year to be followed by an unusually low production year; 4) populations show synchrony in seed production at a geographical scale; 5) seed crop size is influenced by distinct climatic factors occurring during “key” reproductive stages and 6) as an expression of plant productivity, seed crop size should depend on integrated resource availability during the reproductive cycle. We obtained data from two distinct sources: 1) seed harvesting records from a private forest (14 years), and 2) commercial data from 22 municipalities in the Rio Grande do Sul State. Expectations 1, 2, 3 and 5 were not met, while expectations 4 and 6 were supported by the data. A. angustifolia showed environmentally triggered, continuous, moderately fluctuating, and regionally synchronous reproduction. Seed set seems to track variations in resource abundance as well as respond continuously to improved opportunities for successful regeneration.

The regeneration ecology of the long-lived conifer Araucaria angustifolia was studied in Sao Francisco de Paula, southern Brazil. We evaluated the expectations that: (i) size distribution of populations of Araucaria angustifolia, a large conifer that dominates southern Brazil's mixed forests, is left-skewed in old-growth forests but right-skewed in logged forests, indicating chronic recruitment failure in the first kind of habitat as well as a recruitment pulse in the second; (ii) seedlings and juveniles are found under more open-canopy microsites than would be expected by chance; and (iii) reproductive females would be aggregated at the coarse spatial scales in which past massive recruitment events are expected to have occurred, and young plants would be spatially associated with females due to the prevalence of vertebrate and large-bird seed dispersers. Data were collected in the threatened mixed conifer-hardwood forests in southern Brazil in ten 1-ha plots and one 0.25-ha plot that was hit by a small tornado in 2003. Five of these plots corresponded to unlogged old-growth forests, three to forests where A. angustifolia was selectively logged ca. 60 years ago and two to forests selectively logged ca. 20 years ago. For the first time, ontogenetic life stages of this important conifer are identified and described. The first and second expectations were fulfilled, and the third was partially fulfilled, since seedlings and juveniles were hardly ever associated with reproductive females. These results confirm the generalization of the current conceptual model of emergent long-lived pioneer regeneration to Araucaria angustifolia and associate its regeneration niche to the occupation of large-scale disturbances with long return times.

In this paper I examined the usefulness of tree population size distributions in evaluating the conservation status of populations of an endangered tree species. I set expectations derived from two complimentary views of the ecology of rainforest trees and examined whether they were met by size distributions of populations of the South American dominant conifer Araucaria angustifolia and its relationship with forest structural characteristics. Specifically, I evaluated the expectations that (i) A. angustifolia trees have larger diameter than average angiosperm trees and form a higher monospecific canopy layer above the shorter angiosperm canopies; (ii) A. angustifolia populations are characterized by size distributions with many large individuals and a long tail of relatively rare, small individuals (have symmetry coefficient

The morphology of Eugenia dysenterica DC. (Myrtaceae) seeds and post-seminal development was studied and its germination response investigated in relation to temperature, desiccation under different drying regimes and storage under three temperatures. The seeds are elliptical, varying from globose to half-globose and seedlings are cryptogeal with long and slender axial roots. High germination percentages were achieved at temperatures ranging from 15° to 30°C and the thermal optimum was about 24°C. Seeds presented high moisture contents on shedding (47-53%) and completely lost viability when moisture contents were reduced to values below 18-22%; a straight-line relationship was observed between the probit of germination and moisture content percentage. These characteristics provide evidence of a recalcitrant storage behaviour of this species. Storage at near 45% moisture content enabled seed survival for 175 days with over 50% viability, in spite the storage temperature.

The morphology of Genipa americana seeds and post-seminal development was studied, and its germination response investigated in relation to storage in water, substrate water volume, osmotic potential and temperature and light regimes. The seeds are flattened and seedlings are phaneroepigeal with leafy cotyledons. Seeds stored in water kept viable for up to 6 mo, but germination and seedling emergence were reduced after 4 mo. Germination was not affected under water-logged conditions, but seedling emergence was reduced at the water volume corresponding to a water column two times deeper than the seeds' mean thickness (70 ml). When seeds were osmotically stressed, a reduction in the rate and germination percentage occurred at −0.2 MPa and germination was drastically inhibited at −0.6 MPa. Seeds germinated in a wide range of temperatures (15–40 °C), with optimum at continuous temperatures of 25 and 30 °C. Light was not required for germination, and no dormancy mechanisms were observed. The seed and seedling morphology and the germinative responses of the species may permit its regeneration in periodically flooded lowland forests and riparian habitats and are probably key factors in explaining the species' wide distribution.

O presente trabalho teve por objetivo descrever a estrutura e composição do estrato arbóreo de uma Floresta Ombrófila Mista na Floresta Nacional de São Francisco de Paula, Rio Grande do Sul utilizando métodos analíticos mistos de fitossociologia tradicional e de rarefação por unidades amostrais. Os dados, amostradas 29 parcelas de 10x10 m, são apresentados através de critérios de inclusão de diâmetro à altura do peito (DAP) mínimo de 5,0 cm e 10,0 cm, curvas de rarefação baseadas em amostras e estimadores não paramétricos de diversidade, de modo a ampliar seu potencial comparativo com outras comunidades. Segundo o critério de inclusão DAP > 5,0 cm, foram identificadas 41 espécies (índice de Shannon-Wiener (H’) = 1,2 nats.ind ') distribuídas em 32 gêneros, pertencentes a 18 famílias. Segundo o critério de inclusão DAP > 10,0 cm, foram identificadas 35 espécies (índice de Shannon-Wiener (H’) = 1,2 nats.ind') distribuídas em 26 gêneros, pertencentes a 17 famílias. Araucaria angustifolia foi a espécie dominante em densidade e freqüência segundo ambos os critérios de inclusão. Os estimadores não-paramétricos estimaram a riqueza mínima da comunidade variando entre 41,1 e 48,7 espécies (DAP > 5,0 cm) e 35,4 e 47,4 espécies (DAP > 10,0 cm). Devido à abordagem analítica utilizada, estes resultados podem ser diretamente comparados aos resultados obtidos em outros estudos que empreguem a mesma abordagem, o que não é possível com a maioria dos estudos similares feitos no Brasil. In this paper we describe tree community structure and composition of a Mixed Ombrophilous Forest in São Francisco de Paula National Forest, Rio Grande do Sul, using both traditional phytosociological analyses and plot-based rarefaction methods. Data were collected in 29 1 Ox 10 m plots. Results are presented according to the inclusion criteria of diameter at breast height (dbh) of 5.0 cm and 10.0 cm, through sample-based rarefaction curves and non-parametric richness estimators, in order to make quantitative comparisons with other studies valid in the future. Considering individuals with minimum dbh > 5.0 cm, there were 41 species (Shannon-Wiener (H’) = 1.15 nat.ind') distributed in 32 genera and 18 families. There were 35 species with minimum dbh > 10.0 cm (Shannon-Wiener (H’) = 1.22 nat.ind-1) distributed in 26 genera and 17 families. Araucaria angustifolia was the dominant species according to both inclusion criteria. The non-parametric richness estimators yielded minimum estimates of species richness for the whole community varying from 41.1 to 48.7 species (dbh > 5,0 cm) and from 35.4 to 47.4 species (dbh > 10,0 cm). Dueto the analytical approach we used, these results can be directly compared to results obtained in other studies and presented in similar analytical ways, which is not possible in the majority of related results reported in Brazil.

O presente trabalho teve como objetivos definir o tipo de substrato e a temperatura mais adequados à germinação de sementes de jenipapo (Genipa americana L.), conhecer a morfologia das sementes e seu desenvolvimento pós-seminal, caracterizando as plântulas normais, o tipo de germinação e os padrões de anormalidade. Para tanto, realizou-se um experimento colocando-se as sementes sobre os seguintes substratos: papel, vermiculita e solo, nas temperaturas constantes de 20°C, 25°C, 30°C, e 35°C e alternada de 20°C-30°C. O delineamento estatístico empregado foi o inteiramente casualizado (5 x 3), com quatro repetições de 50 sementes. Foram analisados os parâmetros germinação normal (%) e velocidade de germinação. Os melhores resultados foram obtidos nas temperaturas constantes de 25°C, 30°C e 35°C, e nos substratos vermiculita e solo. This study aimed to define the best substrate and temperature for germination of genipap (Genipa americana L. - Rubiaceae) seeds, and to describe the morphology of its seeds, post-seminal development, normal and abnormal seedlings. The experiment was designed according to a 5 x 3 factorial with constant temperatures of 20°C, 25°C, 30°C and 35°C and alternated 20°C-30°C in filter paper, vermiculite and soil substrates. The following parameters were analyzed: normal percentage germination and speed of germination. The 25°C, 30°C and 35°C temperatures and vermiculite and soil substrates were the best conditions for seed germination.

Six-month-old seedlings of Cytharexyllum myrianthum and Genipa americana, two common tree species in different flood-prone areas in Brazil, were flooded for up to 90 days to compare their survival and growth responses under these conditions. Seedlings of both species were found to be relatively tolerant to flooding but growth responses changed according to treatment and plant species. Growth of G. americana was reduced by flooding, showing a decrease in root and leaf dry mass, root/shoot ratio and height, without showing any adaptive morphological changes. On the other hand, growth of C. myrianthum seedlings was stimulated under flooding conditions, showing an increase in root dry mass, root/shoot ratio, height, stem diameter and some morphological changes in roots and stems, i.e., development of new roots and stem base hypertrophy. These results could be regarded as an experimental corroboration of the field observations, showing that these species could be indicated for restoration programs of some Neotropical wetlands. Plântulas com seis meses de idade de Cytharexyllum myrianthum e Genipa americana, duas espécies comuns em áreas sujeitas a inundações em diferentes regiões do Brasil, foram submetidas à inundação do solo durante 90 dias visando conhecer suas respostas em relação à sobrevivência e ao crescimento de plântulas. As duas espécies mostraram-se relativamente tolerantes à inundação, embora as respostas de crescimento variem em função do tratamento e da espécie. O alagamento do solo reduziu o crescimento de plântulas de G. americana, diminuindo a massa seca foliar e do sistema radicular, a relação raiz/parte aérea e a altura da planta, não apresentando qualquer alteração morfológica. Por outro lado, o crescimento de plântulas de C. myrianthum foi estimulado sob condição de inundação, apresentando um aumento na massa seca, na relação raiz/parte aérea, na altura, no diâmetro do caule e algumas alterações morfológicas do caule, como a hipertrofia do colo da planta. Estes resultados vêm confirmar observações de campo indicando que ambas as espécies poderiam ser indicadas para programas de revegetação de áreas neotropicais sujeitas a inundações.