shading and soil improvement (several species of the genus Inga[Lawrence
1995], Erythrina, Gliricidia, Albizia,or Ficusspp. [Cook 1901]), a timber
tree (e.g., Cordia alliodorain Costa Rica or Grevillea robustain the highlands
of Guatemala [Villatoro 1986]), or a second commercial crop (e.g., bananas,
oranges, Macadamiaspp., cinnamon, clove, or avocados). In these systems,
species richness is low, vertical structure is simple, and management is inten-
sive.
•Two-layered shade canopies, such as the common Erythrina poeppigiana–
Cordia alliodoracoffee systems in midelevation Costa Rica. The E. poeppi-
gianashade layer is kept short by heavy pollarding to facilitate shade regulation;
the timber layer (C. alliodoraeither planted or selected from natural regen-
eration) is left to grow unchecked, but tree density is carefully regulated to
avoid excessive shading. Popular variations of this system are obtained by
replacing the service tree with bananas or other perennial crops (coffee-
banana-timber or coffee-oranges-timber) or by replacing the timber tree
with a tall service legume tree (nonpollarded Ingaor Erythrinaspecies)
and underplanting with bananas or other perennial crops (e.g., coffee-
banana-Inga).
•Multistory coffee polycultures with three or more species and three or four
vertical strata. Usually the shade canopy is dominated by a planted shade
species (a “backbone species” such as Ingaor Erythrinaspp. sensuRice and
Greenberg 2000) and enriched by planting a mixture of fruit trees, useful
palms, timber trees (often selected from the abundant natural regeneration),
and, in some cases, trees remnant of the original natural forest. With the
exception of the backbone species, which are commonly planted at 50–300
trees ha–1depending on the pollarding and pruning regime, all remaining
species are kept at low densities in the shade canopy.
•Rustic coffee plantations in which the understory of the natural forest is
cleared to plant the coffee bushes while the forest canopy is thinned (to
reduce shade) and enriched with the planting (or favoring) of useful plants.
Rustic coffee systems are rich in tree species and have a structure resembling
that of the original forest; however, coffee yields are low.
Examples of the aforementioned coffee shade systems have been described
for Costa Rica (Lagemann and Heuveldop 1983; Espinoza 1985; Salazar
1985), Nicaragua (Rice 1991), Colombia (Chamorro et al. 1994), Venezuela
(Escalante et al. 1987), Ecuador (Mussak and Laarman 1989), Guatemala
(Villatoro 1986), Mexico (Jimenez-Avila 1979; Granados and Vera 1995;
Moguel and Toledo 1999), Puerto Rico (Weaver and Birdsey 1986), Uganda
(Odoul and Aluma 1990), Ethiopia (Teketay and Tegineh 1991), Indonesia
(Michon et al. 1986; Godoy and Bennett 1989), Kenya (Njoroge and
Kimemia 1993), India (Rao 1975; Awatramani 1977; Reddy et al. 1982;
204 III. The Biodiversity of Agroforestry Systems