Effects of fire on seedling diversity and plant reproduction (sexual vs. vegetative) in Neotropical savannas differing in tree Density

SALAZAR, A.,; GOLDSTEIN G

BIOTROPICA

WILEY-BLACKWELL PUBLISHING, INC

Lugar: Londres; Año: 2014 p. 287 - 308

0006-3606

Little is known about the effects of fire on the structure and species composition of Neotropical savanna seedling communities. Sucheffects are critical for predicting long-term changes in plant distribution patterns in these ecosystems. We quantified richness and densityof seedlings within 144 plots of 1 m2 located along a topographic gradient in long-unburned (fire protected since 1983) and recentlyburned (September 2005) savannas in Brazil. These savannas differ in tree density and canopy cover. Sites along the gradient, however,did not differ in species composition prior to the fire. In recently burned savannas we also evaluated the contribution of vegetativereproduction relative to sexual reproduction by quantifying richness and density of root suckers. Finally, we tested seed tolerance topulses of high temperatures?similar to those occurring during fires on the soil surface and below?of five dominant savanna tree species.Seedlings were more abundant and diverse in unburned than in burned savannas. Seedling species composition differed among unburned and burned savannas probably reflecting early differences in root: shoot biomass allocation patterns. In recently burned savannas,root suckers were more abundant and diverse than seedlings. Relatively long exposures (>10 min) of temperatures of 90 °C reduced seed germination in all studied species suggesting a negative effect of fire on germination of seeds located at or aboveground level.Because vegetative reproduction contributes more than sexual reproduction in burned environments, frequent fires are likely to causemajor shifts in species composition of Neotropical savanna plant communities, favoring clonally produced recruits along tree density/topographic gradients.