Tropical Forest Community Ecology

378 Chris J. Peterson and Walter P. Carson

100

Intact

Cut

80

60

% Survival

Psychotria berterianaPsychotria brachiataTabebuia heterophylla

Jacaranda copaia

Palicourea croceoides

Vochysia ferruginea

Cedrala odorata

Engelhardia spicata

Annona spraguei

Swietenia macrophylla

Manilkara chicleGuarea guidonia

Ormposia macrocalyx

Posoqueria latifoliaPrestoea montanaDacryodes excelsa

Sterculia apetalaSpondias mombin

Calophyllum calabaVirola surinamensisHymenaea courbaril

Beilschmiedia sp.

Andira inermis

Calophyllum longifolium

Dipteryx panamensis

Carapa guianensis

40

20

0

Species (in order of increasing seed size)

Figure 22.3 Survival of tree seedlings transplanted into or germinating in intact grassland or pasture vegetation,
and into plots where vegetation had been cut, for 27 species. Pooled from Gerhardt (1993), Hardwicket al.(1997),
Zimmermanet al.(2000), and Hooperet al.(2002). Species are arranged in order of increasing seed size, from left
to right.

IS THE NUCLEATION MODEL A

VIABLE CONCEPTUAL FRAMEWORK

FOR TROPICAL SUCCESSION?

Relative to succession followin ga griculture in
temperate regions, facilitation appears to play a
more prominent role in the tropics. The colo-
nization of woody species beneath both remnant
trees and early colonizin gshrubs and within
plantations (Vieira et al. 1994, Slocum and
Horvitz2000,Slocum2001,ZanneandChapman
2001, Carriereet al. 2002, Holl 2002) are clear
examples of facilitation operatin gto produce
expandin gpatches as predicted by the nucle-
ation model. Thus, much of the variation in the
woody species composition, richness, and rate
of succession may be explained by the initial

abundance and diversity of trees that extend

above the herbaceous layer. In addition, favorable

microsites such as rottin glo gs may also provide

foci for woody species establishment and thus the

formation of distinct patches where woody veg-

etation becomes established. Early successional

communities with few or no remnant trees or a

paucity of key microsites may have very slow rates

of succession. This strongly supports predictions

of the nucleation model where patches of woody

vegetation become established within a matrix of

graminoids and eventually coalesce. Thus, while

it is incomplete as a full conceptual framework,

the nucleation model does describe the gen-

eral dynamics of early post-agricultural succes-

sion, though more research is clearly needed.

Combinin gthe nucleation model with realistic