Approximating spatial interactions in a model of forest dynamics as a means of understanding spatial patterns
Authored by Nicolas Picard, Nicolas Verzelen, Sylvie Gourlet-Fleury
Date Published: 2006
DOI: 10.1016/j.ecocom.2006.03.001
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Abstract
Understanding the behaviour of individual-based models of forest
dynamics becomes difficult as their complexity increases. A useful
strategy consists in simplifying parts of the model, then scrutinizing
for possible differences between the original model's predictions and
those of the simplified version. This strategy is adopted to understand
the role of space in a complex individual-based space-dependent model of
tropical rain-forest dynamics in French Guiana. The model is made of
three components: growth, recruitment and mortality. Two aggregation
techniques are used to simplify space-dependent interactions into
space-independent interactions: the mean-field approximation and an ad
hoc approximation that considers pair interactions. Each technique is
applied to one of the components of the model, the other two being left
untouched, or to all components. Nine versions of the model (including
the original one) are thus compared on the basis of the predicted
diameter distribution at stationary state. The fully
distance-independent models are consistent with the original one, whereas growth and recruitment significantly modify the model's
predictions when simplified by the aggregation techniques. The interplay
between the spatial distribution of trees at the population level and
the dynamic processes at the individual level is thus understood, and
the excessive impact of the mortality component that favours the
establishment of clusters of big trees is diagnosed. (c) 2006 Elsevier
B.V. All rights reserved.
Tags
Competition
individual-based models
Simulations
ecosystems
Aggregation
Populations
Ecological theory
French-guiana
Moment equations
Point process