ABSTRACT
When traditional shifting cultivation becomes unsustainable because of population pressure and scarcity of land, the adoption of agroforestry systems can be an alternative. These systems often start with the introduction of trees into cleared swidden land during or after food crops have been harvested. The trees grow to partly replace the natural vegetation of the shifting cultivation system and are then known as an “improved tree fallow.” Typically, continuing population pressure forces an evolution from low- to high-intensity management of planted tree fallows. The final stage of this enrichment of shifting cultivation is referred to as an agroforest. It is a major land use in Sumatra (de Foresta and Michon 1991), where important tree crops such as rubber (Hevea brasiliensis) and cinnamon (Cinnamomum burmannii, known as cassiavera) have begun in this fashion. This transformation of farming systems, driven by population pressure, has been summarized by Tomich (1994) and appears in Table 65-1. Farming System Transformations https://www.niso.org/standards/z39-96/ns/oasis-exchange/table">
Rotation (years)
Increasing Population Density
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Sustainable Shifting Cultivation
Unsustainable Shifting Cultivation
Agroforests
Agroforestry
Tree Monoculture
0
Slash–and–burn
Slash–and–burn
Slash–and–burn
Slash–and–burn
Slash–and–burn
1–2
Food
Food
Food
Food
Trees
3–5
Fallow
Food
Trees
Trees
Trees
5–10
Fallow
Weeds
Trees
Trees
Trees
10–19
Fallow
Weeds
Trees
Trees
Trees
20
Slash–and–burn
Weeds
Trees
Trees
Slash–and–burn
21–22
Food
https://s3-euw1-ap-pe-df-pch-content-public-p.s3.eu-west-1.amazonaws.com/9781936331840/48b765c4-3d4e-4e38-af52-cc179e7b7975/content/fig65_2_B.tif" xmlns:xlink="https://www.w3.org/1999/xlink"/>
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Trees
Trees
23–24
Fallow
Trees
Trees
25
Fallow
Slash–and–burn
Trees
26–27
Fallow
Food
Trees
28–39
Fallow
Trees
Trees
40
Slash–and–burn
Trees
Slash–and–burn
Infinity (?)
Infinity (?)
