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Fire, growth and survivorship in a Neotropical savanna grass Andropogon semiberbis in Venezuela

Published online by Cambridge University Press:  10 July 2009

Juan F. Silva  and
Fernando Castro
Juan F. Silva
Affiliation:
Centro de Investigaciones Ecologicas de los Andes Tropicales (CIELAT), Departamento de Biologia, Facultad de Ciencias, Universidad de los Andes, Merida, Venezuela
Fernando Castro
Affiliation:
Centro de Investigaciones Ecologicas de los Andes Tropicales (CIELAT), Departamento de Biologia, Facultad de Ciencias, Universidad de los Andes, Merida, Venezuela
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Abstract

This study was conducted in a woodland savanna in western Venezuela exclosed from grazing and burnt once a year towards the end of the dry season. Mean annual rainfall is 1500 mm, with a strong seasonality.

Two cohorts of seedlings of Andropogon semiberbis were tagged and monitored for up to three years. Several variables such as survivorship, plant size, seedling density, fire damage and distance to the nearest adult were measured or estimated. Two burning experiments to measure survivorship before and after fire, and two seedling-growth experiments to assess competitive interference from adult plants of three grass species were performed.

The highest mortality takes place during the dry season and is due to fire. This decreases as the plants get bigger due to increasing structural complexity of the clump by growth which gives added protection to the meristems. Other mortality factors such as desiccation, uprooting and shading seem to be important during the wet season, when mortality rate is relatively constant. Survivorship during the first year and after three years is strongly correlated to the size attained by the end of the first growing season.

Seedling densities are rather low and do not seem to play any role in survivorship in this population. Adult interference with seedling growth decreases with distance and seems to be due to root competition, although there is a tendency toward increased foliage interference related to the canopy structure of adult plants.

Keywords

densityfiregrassesNeotropicsplan demographysavannasizeVenezuela
Type
Research Article
Information
Journal of Tropical Ecology , Volume 5 , Issue 4 , November 1989 , pp. 387 - 400
Copyright
Copyright © Cambridge University Press 1989

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