Miguel F.Acevedo
ABSTRACTS
MODELS OF FOREST DYNAMICS BASED ON ROLES OF TREE SPECIES
Ecological
Modelling
87/1-3:267-284. 1996
M.F. Acevedo 1, D.L. Urban 2 and H.H. Shugart 3
1 Institute of Applied Sciences and Department of Geography University
of North Texas, Denton, Texas 76203 and Universidad de Los Andes,
Merida
Venezuela.2 Department of Forest Sciences, Colorado State University,
Fort
Collins, Colorado 80523. 3 Environmental Sciences Department,
University
of Virginia, Charlottesville, Virginia 22903.
Abstract
A linkage between the two major modeling approaches to forest dynamics,
transition markovian models and JABOWA-FORET type simulators, is
generated
by developing a compact model of forest dynamics. This patch transition
model utilizes functional roles instead of species. The roles or types
are based on the regeneration and mortality characteristics of tree
species;
specifically, the requirements of canopy gaps for regeneration and the
capacity to create canopy gaps upon death. A gap-size plot can be
assigned
to each of a set of states defined according to dominance of one of the
roles. Transition probabilities among these states and mean holding
times
in each transition lead to semi-markovian analytical calculations of
the
stationary state probabilities. Forest dynamics, as the proportions of
total canopy space occupied by each role in a collection of gap-size
plots,
can be analyzed and simulated using a chain of first-order differential
equations to emulate the distributed time-delays. Additional fixed
time-delays
in the transition of every pair of states is also included to account
for
long latencies. In addition to simplifying the simulations, the
resulting
model can also utilize available results of the theory of semi-markov
processes;
and therefore, can provide analytical guidance to the simulations, the
feasibility of direct exploration of hypothesis and the possibility of
fast computation from closed-form solutions and formulae. These
advantages
can especially be useful in the simulation of landscape dynamics and
species-rich
tropical forests.
Key words: Markov, semi-Markov, forest succession, gap models.
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