Jh. Vandermeer et al., Growth and development of the thinning canopy in a post-hurricane tropicalrain forest in Nicaragua, FOREST ECOL, 148(1-3), 2001, pp. 221-242
The effect of catastrophic disturbance on forest structure was studied for
10 years subsequent to the landfall of Hurricane joan in 1988. Four sites w
ithin the damage area and one control site outside of the area were establi
shed in the early 1990s and positions and sizes (DBH and crown height) were
measured annually. Results of the study are reported in the context of the
debate between equilibrium versus non-equilibrium models of tropical fores
t dynamics. Equilibrium models imply some sort of niche segregation on a sp
ecies to species basis. whereas non-equilibrium models emphasise chance and
history in the development of canopies. In either case, the details of the
dynamics of building and thinning after a disturbance are key to resolve t
he debate. Physical aspects of the developing canopy began with a severely
damaged forest with effectively no canopy at all. Two distinct canopies had
developed 4 or 5 years after the disturbance; (1) a larger but diffuse can
opy made up of the tress that had survived the hurricane standing and had b
egun resprouting high in their damaged crowns and (2) a 'thinning canopy' o
f very densely packed crowns of small individual trees, resulting from the
growth of surviving saplings and seedlings and trees that had sprouted near
to the ground. Competitive thinning has begun to occur in this dense lower
canopy. Since the disturbance, the increase in number of species has been
great, ranging from 134 to 208% over what would be expected in a mature for
est. Mortality patterns in the thinning canopy suggest that trees are not d
ying at random and thus supports a niche-based model of forest regeneration
. Qualitative analysis of the thinning canopy also suggests that some speci
es have come to occupy the upper position in the canopy (and are thus likel
y to be competitive dominants) while other species have come to occupy the
lower position (and are thus likely to be competitively suppressed). A qual
itative model is proposed illustrating where, during the process of regener
ation, various authors have emphasized either a niche (equilibrium) or non-
niche (nonequilibrium) model. It is suggested that in the building phase of
the post-disturbance forest a non-niche interpretation is most appropriate
while in the thinning phase a niche interpretation may be warranted. (C) 2
001 Elsevier Science B.V. All rights reserved.