**6. Sequential agroforestry systems**

Sequential AFS occurs at a site where there is a chronological succession between a period with annual crops and another with a forest component; that is, annual crops and regeneration of the natural forest or tree plantations follow each other over time. This category includes modalities of migratory agriculture with fallow management and taungya systems, where annual crops are made interspersed between rows of trees in the stage of establishment of a forest plantation until the foliage of the trees is developed (**Figure 3**).

**Figure 3.** *Relation between Net photosynthesis (NP) and Leaf Area Index (LAI). (Russo, R. Agroforestry Course).*

### **6.1 Shifting agriculture**

The migratory agriculture also called itinerant, nomadic, or "*shifting cultivation*" is possibly the oldest of the agricultural systems and consists of the slash and burn of natural vegetation with the option of clearing the land to cultivate. On the other hand, it has been an important source of subsistence for rural populations in the tropics. Its application has varied according to the site and local conditions, but several practices are almost universal; among them is the rotation of cultivation sites or milpas (rotation of trees and crops), the cleaning of land by burning (slash-graveburn in Mexico), the exclusion of chemical fertilizers, the exclusive use of manual labor, planting by hand and short periods of cultivation alternated with long periods of fallow. The system was developed in conditions of low population density, oriented towards subsistence, with a high concurrence of forests and simultaneous production of several crops with different harvest times. Fertility is restored through a long fallow period, and during the first production season little or no weeding is needed [27]. In addition, slash, grave, and burn fallows serve as habitats for wildlife, corridors between patches of forest and as shields against edge effects such as extreme temperatures, desiccation, and fires [28].

#### **6.2** *Taungya* **system**

The *Taungya* system (TS) is a reforestation method that allows the temporary combination of a forest plantation in its establishment phase with the production of shortcycle crops, such as maize and beans, or horticultural crops (**Figure 4**). Under certain conditions, the TS works better than pure reforestation, since there is an intermediate use of the land in agriculture, which if it did not occur could proliferate weeds that compete with the plantation [17]. The word *taungya*, which means "hillside terrain" is Burmese (Burma, today Myanmar from where the system migrated in 1870). In India, that same practice was called "kumri". In Java, the TS was used to plant 40,000 ha

*Agroforestry: An Approach for Sustainability and Climate Mitigation DOI: http://dx.doi.org/10.5772/intechopen.105406*

**Figure 4.**

*Taungya system: a young tree plantation with a short-cycle crop between rows (Russo, Agroforestry Course).*

of *Tectona grandis* (teak) in the late 1800s; in 1920 there was 190,000 ha, in 1952 312,000 ha and currently exceeding 700,000 ha [29, 30]. Annual crop yields in *taungya* combinations are usually lower than in pure crops, but they produce income that covers planting costs and can be considered an added value to reforestation, which would not otherwise be obtained. To be successful, TS must be applied in places where there is a need for land; soils are suitable for producing food crops with reasonable temporary yields, without causing excessive soil deterioration; tree species in demand are of proven adaptability; there is a peasant population, and local staff is trained to operate the system [27]. The TS has been very successful to establish forest plantations under different conditions. In the dry areas of what is now Myanmar, with 450–1100 mm of annual rainfall, communal forests were established using taungya systems for 2–3 years to provide firewood from *Acacia* spp., *Albizia lebbek*, *Senna siamea*, *Dalbergia sissoo*, *Melia azedarach*, *Prosopis* spp. and *Eucalyptus* spp.; and to produce pulpwood. An example is the *Gmelina arborea* plantations in Jari in southern Brazil, established through the *taungya* system; rice and beans have been harvested for 2 years in plantations of *Cunninghamia lanceolata*; rice, cotton, and corn with *Eucalyptus.* In addition, among the ecosystem benefits that TS provides, it is a restoration tool, combining afforestation actions with agricultural activity during the early stages of tree establishment, which represents an economic and social benefit, while preventing the establishment of weeds and contributing organic matter to the soil with crop stubble (**Figure 5**).

#### **Figure 5.**

*Taungya system: Left: Young plantation of Eucalyptus deglupta (eucalyptus) and Araucaria hunsteinii (klinki) intercropped with Zea mays (freshly harvested corn) between rows, in Guácimo, CR; and, Right: New plantation of Swietenia macrophyla (mahogany) intercropped with Eryngium foetidum (coriander) between rows, in Turrialba, CR. Photos: Rolando Camacho.*
