Phenology, seed dispersal and difficulties in natural recruitment of the canopy tree Pachira quinata (Malvaceae)

Abstract

Life history and recruitment information of tropical trees in natural populations is scarce even for important commercial species. This study focused on a widely exploited Neotropical canopy species, Pachira quinata (Malvaceae), at the southernmost, wettest limit of its natural distribution, in the Colombian Amazonia. We studied phenological patterns, seed production and natural densities; assessed the importance of seed dispersal and density-dependent effects on recruitment, using field experiments. At this seasonal forest P. quinata was overrepresented by large adult trees and had very low recruitment caused by the combination of low fruit production, high seed predation and very high seedling mortality under continuous canopies mostly due to damping off pathogens. There was no evidence of negative distance or density effects on recruitment, but a clear requirement of canopy gaps for seedling survival and growth, where pathogen incidence was drastically reduced. In spite of the strong dependence on light for survival of seedlings, seeds germinated readily in the dark. At the study site, the population of P. quinata appeared to be declining, likely because recruitment depended on the rare combination of large gap formation with the presence of reproductive trees nearby. The recruitment biology of this species makes it very vulnerable to any type of logging in natural populations. Rev. Biol. Trop. 59 (2): 921-933. Epub 2011 June 01.

Ecology, distribution and population status of Elaeocarpus venustus Bedd. (Oxalidales: Elaeocarpaceae), a threatened tree species from Agasthiyamalai Biosphere Reserve, southern Western Ghats, India

“…Clearing the forests in this site, for cardamom plantations, could have paved the way for more light thus enhancing seed germination. Similar observations have been made for a number of endemic species in tropical forests (Baskin & Baskin 1998;Ganesan 2001;Ganesan et al 2001;Castellanos & Stevenson 2011). There has been little anthropogenic interference in this region after declaring it as a biosphere reserve in 2005 (MoEF 2012).…”

Consequences of Seed Dispersal for Plant Recruitment in Tropical Forests: Interactions Within the Seedscape

“…). Several Neotropical studies have experimentally shown reduced pathogen‐induced mortality of seeds dispersed to gaps as these fungal associations shifted from detrimental to neutral in drier, high‐light environments (Augspurger & Kelly , Augspurger , Wenny & Levey , Castellanos & Stevenson ).…”

“…For plants relying on dispersal to particular microsites, such as light gaps, overharvesting of reproductive trees, disperser loss, or even alterations in disperser behavior can increase seed limitation and may decrease the probability of seeds reaching habitats necessary for recruitment (Brodie et al . , Castellanos & Stevenson , Tang et al . ).…”

“…). Overharvesting of a gap‐dependent, wind‐dispersed species, Pachira quinata , in the Colombian Amazon is hypothesized to have caused population declines due to the combination of seed limitation and specific habitat requirements (Castellanos & Stevenson ). Large‐seeded species tend to be most affected by declines in the frugivore community because the large frugivores are often the most affected by harvesting and habitat fragmentation (Stoner et al .…”

“…In a hurricane-impacted forest in Puerto Rico, the effect of conspecific seedling densities weakened with canopy openness (Comita et al 2009). Several Neotropical studies have experimentally shown reduced pathogen-induced mortality of seeds dispersed to gaps as these fungal associations shifted from detrimental to neutral in drier, high-light environments (Augspurger & Kelly 1984, Augspurger 1984, Wenny & Levey 1998, Castellanos & Stevenson 2011.…”