Interannual variation in rainfall, drought stress and seedling mortality may mediate monodominance in tropical flooded forests

Abstract

Flood tolerance is commonly regarded as the main factor explaining low diversity and monodominance in tropical swamps. In this study we examined seedling mortality in relation to seasonally, i.e., flooding versus drought, of the dominant tree species (Prioria copaifera), and three associated species (Pterocarpus ojficinalis, Carapa guianensis and Pentaclethra macroloba), in seasonally flooded forests (SFF) in Darien, Panama. Seedling mortality differed among species, years and seasons. Prioria seedlings experienced the lowest overall mortality, and after 3 years many more Prioria seedlings remained alive than those of any of the associated species. In general, within species, larger seedlings had greater survival. Seed size, which can vary by close to 2 orders of magnitude in Prioria, had a confounding effect with that of topography. Large-seeded Prioria seedlings experienced 1.5 times greater mortality than small-seeded seedlings, as large-seeded Prioria seedlings were more likely to be located in depressions. This finding suggests that seed size, plant size and topography are important in understanding SFF regeneration. For all species, seedling mortality was consistently greater during the dry season than during flooding. For Prioria, dry season seedling mortality was correlated with drought stress, that is, high mortality during the long El Nino dry season of 1998 and the normal dry season of 2000, but very low dry season mortality during the mild dry season of 1999. Prioria's ability to dominate in seasonally flooded forest of Central America is partly explained by its low drought-related mortality in comparison to associated species.

Biogeochemical processes along a nutrient gradient in a tropical ombrotrophic peatland

“…Low diversity tree communities are typical of Central American wetlands (Keogh et al 1999;Ellison 2004;Ramberg et al 2006;Lopez and Kursar 2007). For example, the low diversity in San San Pond Sak is similar to that in forested wetlands in Mexico (Shannon index 1.95; Moreno-Casasola et al 2009) and lowland forest swamp in Costa Rica (Shannon index 1.99-2.56; Webb and Peralta 1998).…”

“…However, many wetlands in the region are not calcareous and the nutrient status of these systems remains poorly understood. Links between vegetation diversity and peat properties have been found in wetlands in both Southeast Asia (Page et al 1999) and Central and South America, including Belize, Mexico, and Venezuela (Johnson and Rejmankova 2005;Vegas-Vilarrubia and Laseras 2008;MorenoCasasola et al 2009), which suggests that edaphic properties, in conjunction with hydrological processes, can drive diversity in tropical wetlands (Ferreira and Stohlgren 1999;Lopez and Kursar 2007;Rodriguez-Gonzalez et al 2008). This is likely to have important implications for the carbon cycle, because peat properties (Bachoon and Jones 1992;Bridgham and Richardson 1992;Keller et al 2006) and vegetation type (Chimner and Ewel 2004) exert strong controls on carbon storage and greenhouse gas fluxes from tropical and subtropical wetlands.…”

Wetland-Dryland Vegetational Dynamics in the Pennsylvanian Ice Age Tropics

“…Based on modern tropical analogues (Gentry 1982;Valencia et al 1994;Condit et al 1996Condit et al , 2002Condit et al , 2005Wright 2002;Hubbell et al 2008;Lamarre et al 2012), habitat quality is higher in terra firma lowland environments than in swamps (Prance 1979(Prance , 1989Terborgh et al 2002, fig. 1.2; Koponen et al 2004;Lopez and Kursar 2007). That is, they have higher nutrient availability, better oxygenation of soils, and lower levels of physical stress.…”

Hydrological modification, saltwater intrusion, and tree water use of a Pterocarpus officinalis swamp in Puerto Rico

“…Despite evident stress related to increased flooding and salinity, Pterocarpus remains the most successful colonizer of flooded landscapes in the Caribbean (L opez and Kursar, 2007;Migeot and Imbert, 2011). Analysis of stem water d values can provide additional insights to this success.…”