Growth dynamics of tropical savanna grass species using projection matrices
Authored by J Raventos, J Segarra, MF Acevedo
Date Published: 2004
DOI: 10.1016/j.ecolmodel.2003.12.044
Sponsors:
United States National Science Foundation (NSF)
Platforms:
No platforms listed
Model Documentation:
Other Narrative
Mathematical description
Model Code URLs:
Model code not found
Abstract
Savannas are very important tropical ecosystems characterized by
co-dominance of herbaceous vegetation and less abundant trees and
shrubs. Models of the dynamics of the spatial distribution of
aboveground components of grass plants can be a useful tool to
understand the dynamics of savanna ecosystems. We developed a model of
grass plant growth as a collection of the individual dynamic behavior of
shoots inspired in data for plants of three species of common grasses in
the Venezuelan savannas. The species are: Elyonurus adustus (Trin.) E.
Ekman., Leptocoryphium lanatum (Kunth) Nees and Andropogon semiberbis
(Nees) Kunth. These species represent various types of architecture and
regeneration response to fire. The individual-shoot model is based on
shoot emergence. mortality, and elongation given by Richards' equation, plus a few simple geometric considerations. Model Output is shoot
density in each cell of a square grid at several vertical levels.
Differences in patterns of shoot density among species are explained by
changing a set of parameter values related to growth form and phenology.
Vertical distribution of shoot density was calculated from the
Simulation results and the field data with the purpose of deriving a
simpler lumped shoot-population model. This simpler demographic model is
based oil a projection matrix that predicts the essential dynamics of
growth in the vertical dimension. The transient and final behavior of
vertical distribution of shoot density are calculated with the matrix
model and compared to field data yielding good fit as assessed by the
root mean square (RMS) error of difference between the field data and
the model results. This error is of the same magnitude as the RMS
difference among the three field data replicates. Sensitivity analysis
of the matrix model for the three species was used to identify those
vertical levels for which the damping ratio is more sensitive to a
perturbation. For early and precocius species (E. adustus and L.
lanatum), the top level is more sensitive whereas the late blooming
species (A. semiberbis) is more sensitive at lower levels. Although
developed for these three species, the matrix model is generic and
therefore can be applied to plants with the basic growth form of
perennial grasses of seasonal savanna ecosystems. Applications include
scaling-up the individual-shoot model to larger areas and analysis of
savanna dynamics subject to fire. (C) 2004 Elsevier B.V. All rights
reserved.
Tags
population
Strategies
Transition
Fire
Responses
Plants
Forest dynamics
Gap models
Phenologies