Influence of a common palm, Oenocarpus mapora, on seedling establishment in a tropical moist forest in Panama

Abstract

Plants often modify microsite conditions important for seedling establishment. In tropical moist forest, advance regeneration in the form of shade-suppressed seedlings is a major component of regrowth in new gaps. Tree seedlings may be filtered by the composition and structure of the forest understorey. In a lowland forest in Central Panama, we examined light availability, Utter accumulation and the seedling community (abundance, diversity and composition) under and away from the canopies of a common subcanopy, clonal palm, Oenocarpus mapora, and tested whether seedling abundance varies as a function of changes in understorey light conditions and leaf litter depth. We found evidence that leaf litter was five times deeper and light availability 2 7% lower under O. mapora canopy than where it was absent. The probability of finding a seedling in plots under O. mapora canopies was 33% lower than in plots without the palm. Plots under O. mapora canopies also had 49% fewer species of seedlings and those seedlings came from significantly larger seeds than seedlings in plots not under the palm. Overall, seedling density was positively correlated with light availability and negatively correlated with leaf litter depth. A transplant experiment confirmed that for at least one large-seeded species of dicot, seedlings are negatively affected by the reduction in light availability and increase in leaf litter. Under O. mapora, seedlings of Gustavia superba (Lecythidaceae) had lower survivorship and biomass accumulation than away from the palm. Thus, site conditions produced by large, clonal, multi-layered palms such as O. mapora may reduce establishment of small-seeded and shade-intolerant species, potentially affecting species composition in the understorey seedling pool.

Comparison of seedling recruitment under arborescent palms in two Neotropical forests

“…Density/m 2 and the number of species/m 2 of the study's post-cotyledonous seedlings were not affected by litter depth. This result contrasts with the earlier report that seedling density was negatively correlated with litter depth under Oenocarpus (Farris-Lopez et al 2004). Litter would have its main effect on the earlier life stages of seedling emergence and small cotyledonous seedlings (Molofsky and Augspurger 1992;Vazquez-Yanes and Orozco-Segovia 1992).…”

“…Farris-Lopez et al (2004) demonstrated at BCI that Oenocarpus lowered survival, especially of small-seeded and shade-intolerant species. Therefore, at least at BCI, one species of arborescent palms may selectively favor certain groups of species during seedling establishment.…”

“…Areas with greater arborescent palm density in an oldgrowth forest on Barro Colorado Island (BCI), Panama, had lower seedling density (Denslow and Guzman 2000). Also at BCI, plots under the subcanopy clonal palm species, Oenocarpus mapora, had lower seedling density and lower estimated number of species of seedlings than plots without the palm (Lopez-Farris et al 2004). Furthermore, seedlings under O. mapora were of largerseeded species than seedlings that were not under the palm.…”

The exotic palm Roystonea oleracea (Jacq.) O. F. Cook (Arecaceae) on an island within the Atlantic Forest Biome: naturalization and influence on seedling recruitment

“…Palm leaves and reproductive structures typically decompose slowly, forming a deep litter layer. Litter accumulation modifies microhabitat conditions and affects the recruitment of other plant species, as has been observed by Farris-Lopez et al (2004) for the palm Oenocarpus mapora, in Panama, and by Aguiar & Tabarelli (2010) for the palm Attalea oleifera, in Brazil, both of whom reported reductions in the abundance and richness of seedling species beneath palm crowns. Because R. oleracea is a tall palm with large, heavy leaves, negative effects on seedling recruitment beneath their crowns are also to be expected.…”

Trait-based community assembly of understory palms along a soil nutrient gradient in a lower montane tropical forest

“…Palms (Arecaceae) are a group of plants common in tropical forests that can show morphological, phenological and genetic divergences among closely related species along resource gradients (Henderson et al 1995;Svenning 2001;Savolainen et al 2006). The lower montane forests examined here are a hotspot of diversity for understory palms, which comprise a major component of the understory and have the potential to alter regeneration patterns of woody seedlings (Farris-Lopez et al 2004;Harms et al 2004;Wang and Augspurger 2004). In a previous study, understory palm species composition was related to soil nutrients, particularly available nitrogen and cations (Andersen et al 2010a).…”