vary between regions. For instance, in small coffee holdings in a suboptimal
dry area in Venezuela, fruit production from the shade trees accounted for
55–60 percent of total gross revenues from the coffee plantations, timber 3
percent of total gross revenues, and coffee the remaining 37–42 percent
(Escalante et al. 1987). In Puriscal, Costa Rica, sales from oranges and other
fruits from coffee shade canopies account for 5–11 percent of total sales from
the coffee plot (Lagemann and Heuveldop 1983). Aside from these products
with easily quantifiable market values, shade trees and other plants in the
canopy have other, less easily assessed values. The use of plant parts in tradi-
tional or home remedies is a common cultural practice found in shaded cof-
fee systems throughout the tropics. For example, bark-cloth is made from
Ficus natalensis(a common coffee shade tree species) in Uganda, and plant
parts are used in ceremony, ritual, or as adornment in other places.
The Ground Cover of Coffee Systems
Coffee plantations commonly have 20–90 plant species in the ground cover
plant layer. The diversity of this layer in a given field depends on the prior land
use and within-field variability in soil, drainage, tree canopy distribution,
species composition, and ground cover management practices. Goldman and
Kigel (1986) listed 24 species in a 600-m^2 shaded coffee field in Mexico
grouped in two distinct weed associations: one in microhabitats with more
than 75 percent canopy coverage and the other in microhabitats with less than
25 percent canopy cover. Weed species richness was greater in sunnier places.
This response of weed associations to different shade, soil, and management
history was also recorded in a study of ground cover by plant growth habit in
five coffee fields in northern Nicaragua: perennial broadleafs varied between
fields from 2 to 26 percent of the between-row area, grasses from 12 to 47 per-
cent, and sedges from 0 to 9 percent (Staver 1999).
In a comparison of ground cover plant families in coffee systems in open
sun and with single- and multiple-species shade (Nestel and Altieri 1992),
weed families were similar in the three systems but varied in their abundance.
Asteraceae were more common in open sun coffee, whereas Commelinaceae
were more common in shaded coffee. Similar results have been reported for
Mexico (Jimenez-Avila 1979). In Andhra Pradesh, India, 74 dicotyledonous,
8 monocotyledonous, and 1 fern species were recorded in the ground layer of
coffee plantations; extensive differences were observed depending on the
degree of shading and season. Acanthaceae, Amaranthaceae, Asteraceae,
Cucurbitaceae, Fabaceae, Gentianaceae, Malvaceae, Poaceae, and Rubiaceae
were well represented in the weed complexes (Reddy and Reddy 1980). At
least 28 main weed species have been reported for small coffee holdings in
Papua New Guinea (de Silva and Tisdell 1990), and in Venezuela, prevalent
210 III. The Biodiversity of Agroforestry Systems