Central American Successional Crop System
Slash- and- burn (a.k.a. swidden) agriculture (chapter 17) has much in common with ecological succession in that it
mimics the successional process in restoring soil after use for farming. Polycultures (plantings of numerous species in
the same plot) can effectively maximize productivity of a given plot. Instead of only one crop, several surface crops,
such as corn and beans, share the same plot with root crops (such as manioc or sweet potatoes) while the border
of the plot may be planted in peppers and tomatoes. Polycultures are more resistant to insect attack, because crop
biodiversity provides habitat for herbivore predators and reduces the competitive effects of competing forbs (weeds).John Ewel and colleagues have done comparisons of various monoculture crops with mixed- species plots, which
have shown that the more diverse plots had significantly more root surface area, enhancing the plants’ ability
to capture nutrients. They concluded that nutrient uptake and storage of minerals was critical to maintaining
productivity in the plot.
Robert Hart, working in Costa Rica, has suggested that farming can be directly
analogous to succession. He presented a scheme whereby crops are rotated
into and out of plots on the basis of their successional characteristics. Using
such a system, Hart claims, it would be possible to utilize a plot of land
continuously and productively for at least 50 years or more (plates 7- 25– 26;
fig. 7- 1). To quote Hart:
Early successional dominance of grasses and legumes can be assumed to
be analogous to maize (Zea mays) and common bean (Phaseolus vulgaris)
mixtures. Euphorbiaceae, an important family in pioneer stages of early
succession, can be represented by cassava (Manihot esculenta), a root crop
in the same family. In a similar replacement, banana (Musa sapientum) can
be substituted for Heliconia spp. The Palmae family can be represented by
coconut (Cocos nucifera). Cacao (Theobroma cacao) is a shade- demanding
crop that can be combined with rubber (Hevea brasiliensis) and valuable
lumber crops such as Cordia spp., Swietenia spp., or other economically
valuable members of the Meliaceae family to form a mixed perennial
climax. (Hart 1980, p. 77.)
Subsistence farming is discussed further in chapter 17..5 1234567891020304050StructureYears
Beans
Maize
Cassava
Banana
Coconut
Cacao
RubberFigure 7– 1. This diagram, from Robert Hart’s study of farming practices, illustrates
how a sequence of crops would essentially mimic the overall pattern of succession.
Reprinted with permission from Kricher, John. Tropical Ecology. Princeton, NJ:
Princeton University Press, 2011.Plates 7- 25 and 7- 26. Manioc (7- 25),
which yields the root crop cassava,
and bananas (7- 26) are common
components of the types of plots
described by Robert Hart.
Photos by John Kricher.Plate 7- 26.Plate 7- 25.chapter 7 if a tree falls . . . rain forest disturbance dynamics 111