for seed-dispersing vertebrates. Conversely, Carrière (1999) and Carrière et al.
(2002) found that the practice of leaving remnant trees accelerates regenera-
tion and produces a landscape that is more hospitable as a habitat for biodi-
versity in the Ntumu agricultural system in Cameroon.
To sum up, it is clear that a significant proportion of the individuals of
woody plant species in any shifting cultivation landscape has regenerated by
resprouting, and it seems highly likely that the agricultural cycle exerts strong
selection for species capable of resprouting after cutting, burning, and weed-
ing. Shifting cultivation landscapes may be generally more favorable to the
maintenance of vertebrate-mediated seed dispersal processes than other
anthropogenic habitats such as pastures. They nevertheless remain landscapes
dominated by pioneer plant species. If the lack of seed sources means that
resprouting is the main or even the only mechanism of regeneration of many
forest-dependent tree species in shifting cultivation landscapes (Denich 1991;
Vieira and Proctor 1998), then the chance that diverse forest with at least
some of the characteristics of the original vegetation will ever be recovered on
shifting cultivation land seems limited. The vigorous regeneration from root
sprouts of exceptionally valuable multiple-use species such as Platonia insignis
(see Shanley et al. 1998) appears to have contributed to some authors’ opti-
mism regarding the potential of secondary succession in shifting cultivation
landscapes for production and forest restoration (e.g., Vieira et al. 1996). On
the other hand, Denich (1991) suggests that fallows should not be viewed as
a stage in the regeneration of primary forest but as a new, wholly anthro-
pogenic vegetation type. If this is the case, it does not mean that farmers can-
not manage fallows for certain products as they have always done (Unruh
1988), but it is a sobering idea in the context of biological conservation.
Successional Dynamics of Fallows and the Factors That
Underlie Successional Change
The successional dynamics of fallows and the secondary forests sometimes
derived from them have been studied in moist forest of Mesoamerica (Mex-
ico, Guatemala, Panama), the Amazon basin, the Guianas, and the South
American subtropics and show successional sequences broadly similar to those
in Africa and Asia (Kenoyer 1929, cited by Richards 1976; Gómez-Pompa
and Vásquez-Yanes 1981; Vieira et al. 1996; Kammesheidt 1998; Vester and
Cleef 1998; Ferguson 2001; Peña-Claros 2001). Reviewers differ in the num-
ber of successional stages they identify within this overall framework of simi-
larity, and the identification of stages in an essentially continuous process is
largely for convenience. At a very general level, Finegan (1996) described three
stages of neotropical lowland rainforest succession during the first century of
the process. Initial dominance by pioneer herbs, shrubs, and climbers often is
followed by stages dominated by short-lived and then long-lived pioneer tree
164 III. The Biodiversity of Agroforestry Systems