Plantations of native-tree species are often recommended for ecological restoration, but the understanding of how these techniques catalyze natural ecological processes is limited. We investigated natural regeneration in five plantations of native trees in the Poço das Antas Biological Reserve (PABR) in the state of Rio de Janeiro, Brazil. The plantations were 9-11 years old, and contained 8-14 native-tree species with different compositions and relative density of species. We analyzed floristic composition, structure (density and basal area) of overstory and understory strata, as well as other ecological attributes (dispersal syndromes, fruit or seed size, and the availability of fruit for frugivores). Zoochorous species comprised 77% of the community, with a prevalence of the two smallest size classes of propagules (<0.6 and 0.6-1.6 cm) in natural regeneration. The density of zoochorous plants in the understory was positively correlated with their density in the overstory, indicating their influence on natural regeneration (r 2 = 0.36; p < 0.0002). Fruit availability for frugivores (density and richness of plants fruiting during the year) was also positively correlated with the density of stems in the understory. Therefore, attributes such as dispersal syndrome and fruiting season should be considered in selecting species to be planted. The differences in natural regeneration observed in each of the native-tree plantations indicated that the performance of plantations as a restoration strategy may differ, depending on initial species composition, planting density, and site conditions.

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Artocarpus heterophyllus Lam. (jackfruit) was man made introduced in Tijuca National Park (TNP) in the mid1800s. Native from Southeast Asia, nowadays densely colonizes the TNP. Here we analyze some jackfruit population parameters that probably allowed the local colonization followed by successful invasion of the new habitat. Based on 20 sample plots, randomly placed inside 5 sites colonized by jackfruit, we described subpopulations hierarchical size diameter structures. Gini's coefficient values turned around 0.64 and Lorenz's asymmetry coefficient around 1.03, indicating that size hierarchies were very similar between sites. The five sites were also compared and do not differ based on jackfruit basal area, number of species, Shannon's index and canopy openness. Jackfruit may, therefore, be considered invasive in all these sites and the low tree diversity values (H' overall mean 0.74) also indicates that this exotic species locally excludes native ones. Keywords: jackfruit, invasive species, biological invasion, population structure, Tijuca National Park, Brazil. ResumoArtocarpus heterophyllus Lam. (Jaqueira) foi introduzida pelo homem no Parque Nacional da Tijuca (PNT), em meados do século XVIII. Nativa do sudeste da Ásia, esta espécie exótica hoje coloniza densamente o PNT. Neste estudo analisamos alguns parâmetros populacionais da jaqueira que provavelmente permitiram a colonização local e conseqüentemente a invasão bem sucedida deste novo habitat. A partir da amostragem de 20 parcelas alocadas aleatoriamente em cinco sítios colonizados por jaqueiras, descrevemos as estruturas de diâmetro das subpopulações. Os coeficientes de Gini oscilaram em torno 0,64 e os de Lorenz 1,03, indicando hierarquia de tamanhos semelhante entre as amostras. Os cinco sítios também foram comparados e não diferiram quanto à área basal de jaqueiras, riqueza total de espécies, índice de diversidade de Shannon e abertura do dossel. A jaqueira pode, portanto, ser considerada invasora em todos estes sítios e os baixos valores de diversidade de árvores (H' em torno de 0,74) também podem indicar que esta espécie exótica exclui localmente as espécies nativas. Palavras-chave: jaqueiras, espécies invasoras, invasão biológica, estrutura de populações, Parque Nacional da Tijuca, Brasil.

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