Swidden-fallow agroforestry in Amazonia: diversity at close distance
W. DE JONG Center for International Forestry Research, Julan Gunung Batu 5, Bogor 16001, Indonesia
Key words: diversity, Peruvian Amazon, ribere~os, terra firme
Abstract. Swidden-fallow agroforestry among riberefio farmers in the Peruvian Amazon has been reported to show important regional variation. In this paper diversity in terrafirme swidden- fallow agroforestry is described for a single village, Santa Rosa, located at the lower Ucayali river, Peru. Local forest gardens differ in managed species composition, weeding patterns, and yield levels. Most of the produce from Santa Rosa forest gardens is locally consumed; only little is traded. Many forest species are actively tended for planted in forest gardens. These systems have the function of suppliers of a range of products. Variation in forest garden management is a result of farmers' individual perception of the need for such products.
Resumen. Informas sobre agroforesteria de chacra y barbecho en la Amazonia Peruana men- tionan la variabilidad de tales sistemas, segun la Iocalidad de donde se encuentran. En el presente articulo se describe diversidad de agroforesteria de chacra y barbecho en un solo pueblo, Santa Rosa, ubicado en el bajo rio Ucayali, Peru. Los jardines forestales alli se distinguen por la composicion de especies, frecuencia e intensidad de deshierbo, y cantidades de productos obtenidos de ellos. La mayoria de los productos de los jardines forestales de Santa Rosa son consumidos localmente; solamente unos pocos son comercializados. Muchas especies forestales son cuidados o sembrados en los jardines forestales. Estos sistemas tienen la funcion de prover una seria de productos. Variacion en el manejo de jardines forestales son el resultado de la percepcion individual de agricultores para la necesidad de estos productos.
I n t r o d u c t i o n
Shif t ing cu l t iva t ion is again rece iv ing increased a t tent ion from scientists . Agroforestry is considered to be one of the important al ternat ives for slash and burn agr icul ture (Raint ree and Warner , 1986; Wiersum, 1983). Many
studies on ind igenous agriculture (Denevan and Padoch, 1987; Gordon, 1982;
Irvine, 1987; Wiersum, 1983) have demonstra ted that del iberately c ombi n i ng crops and trees is c o m m o n in much of the swidden-based agr icul ture , a
swidden being an agricultural field that is slashed and planted for one or a few years and than left fal low for var ious years.
Managemen t of swidden-fa l lows, or swidden-fa l low agroforestry, is par-
t icularly p rominen t among many farmers from the A ma z on i a n basin. In this swidden-based land-use system, the tree vegetations of older fields are actively
managed. The agroforestry component of swidden-fal low agroforestry includes
species which were left from the original forest, planted tree species, and tended or merely harvested species which were spontaneously present in the fallow vegetation. Such management of fallow vegetation increases economic returns from agricultural fields while soil fertility is restored, and biomass is accumulated. In this way, if required, the field can be slashed again and planted with staples and other annuals. It is also not unusual that managed fallow fields become permanent tree gardens.
Swidden-fallow agroforestry as reported from the Amazon is not a uniform practice, but shows important regional variation. For instance, Denevan an Padoch (1987), and Irvine (1987) describe low intensity fallow management among Bora and Runa Indians. Hiraoka (1986) and Padoch et al. (1985) describe cases in which the older swidden-fallow fields have been developed into important cash generating tree gardens. Padoch and de Jong (1987) explain the factors that influence the management of the fallow phase of swidden-fallowers.
In the present article the diversity of swidden fallow agroforestry in Santa Rosa, a riberefio community located at the lower Ucayali river, Peru, is inves- tigated. Diversity in forest gardens is demonstrated to be a characteristic not only at a regional, but also at a single village level. Furthermore, attempt will be made to explain why Santa Rosa agroforestry is different from that in other parts of the Peruvian Amazon, as well as the main factors that cause variations within a single village.
Ribere~o swidden-fallow agroforestry
Ribereaos are the rural population of the Peruvian lowland Amazon. They are detribalized Amazonian natives and their descendants, immigrants or their descendants from neighboring Peruvian regions from other South American countries or from oversees, and the descendants of any unions between members of the above groups (Padoch and de Jong, 1989). They live mostly along the major rivers (Aramburu, 1984) in small villages called caserios. Most ribereaos make a living as agriculturists, but many also extract forest products, work as wage laborers, or as traders to obtain cash income (Padoch, 1987).
Swidden-fallow agroforestry is reported to be widespread and varied among ribere~os (Padoch and de Jong, 1987). Managed swidden-fallows provide a mix of products used in daily subsistence (Denevan and Padoch, 1987; Padoch and de Jong, 1987, 1989), but may also be oriented toward market produc- tion (Hiraoka, 1986). Market opportunities, individual needs, and other pro- ductive activities of farmers are the most important socioeconomic factors which influence the variation in agroforestry practices (Padoch and de Jong, 1987).
Swidden-fallow agroforestry is characterized by a change in the manage- ment pattern of a swidden after several years of farming. Farmers do not
continue the intensive use of a field for more than two to four years because decreasing returns and increasing weed invasion make it less profitable than changing the field to a forest garden and making a new swidden elsewhere (Hoekstra, 1987). Older fields continue to be economically important, and are not simply abandoned. Products may be harvested from planted or naturally occurring species (Denevan and Padoch, 1987; Gordon, 1982; Irvine, 1987).
The change in management from a swidden to a forest garden is antici- pated by most ribere~os long before it actually happens. While the field is still a swidden, several perennial species are planted which will only yield products once the field has become a forest garden. The final decision on the specific management of the forest garden is often postponed, and can be taken without much considerations of the perennial species that have been planted. The structure of a forest garden may vary not only from field to field, but also from year to year (Alcorn, 1990).
Studying managed swidden-faliows
The present study was conducted among riberefto farmers in Santa Rosa, a village on the right bank of the Ucayali river of the Peruvian Amazon. The village is approximately 30 years old and was founded by a group of farmers who used to work on a large agricultural estate just south of its current location (Padoch and de Jong, 1990). In 1986, the village had 350 inhabitants from 60 households. The village center is located on terrafirme, but farmers have agricultural fields both on upland and in the varzea. Santa Rosa farmers produce both for the market and for household consumption. Their daily staples, manioc and plantains, are mostly produced in terra firme fields (de Jong, 1994), which are made both in mature or secondary forest. After two to four years of intensive cultivation they are tended mainly for a large number of perennial species.
According to Fresco (1988), management and labor are the most impor- tant inputs of cropping systems among shifting cultivators. If management of an agricultural field is defined as purposely influencing the development of its vegetation (de Jong, 1994), than differences in management should be reflected in different ways of influencing the vegetation. Cultivation activi- ties which most influence the vegetation of a forest garden are planting and weeding. The densities and diversity of tended species, which are the results of earlier planting or of deliberate species protection, and weeding patterns are primarily responsible for the differences in the management of Santa Rosa forest gardens.
A total of seven Santa Rosa terra firme agroforestry fields were surveyed. In each field the densities of actively tended species was counted, the pro- duction levels estimated, and the weeding patterns recorded. Fields were selected which differed as much as possible in species composition, age, and weeding pattern. The main characteristics of these forest gardens are provided
in Table 1. Fields were sampled using 30 m wide transects which crossed the fields from one side to the other. Each transect included major ecological gradients, in most cases the maximum slope of the field. Transects were sub- divided into 10 x 10 m 2 subplots.
Only the actively tended vegetation was sampled. Each adult individual of a domesticated plant species was considered as tended (Cavalcante, 1976, 1978, 1990). If natural regeneration of a domesticated tree species occurred, and there was no clear indication as to which plants were actually tended, then only individuals larger than 1 m were considered. In addition to domesti- cated plant species, riberefio farmers tend many native forest species. Individuals of non-domesticated species were considered as tended if plant individuals appeared to be recently cleared from the surrounding vegetation, or to be in an unusual habitat. The latter occurs, for instance, when species from the floodplain are grown in terrafirme fields. In several cases the owner of the field was asked if specific plants were tended or not.
An important characteristic used for the comparison of the management of forest gardens in Santa Rosa is the weeding pattern of fields. To estimate this, a Non-managed Vegetation Index (Inmv) was used. The weeding pattern of any terra firme agricultural field is reflected by the state of the non- managed or weed vegetation. Every three months the non-managed (weed) vegetation in each 10 × 10 m 2 subplot was estimated by giving it an index value ranging from 1 to 5. The Inm v 1 indicated that the 10 x 10 m 2 subplot was cleared recently, while a value of 5 indicated that the subplot had a well developed secondary forest. Weeding patterns of four of the nine forest gardens were compared by estimating the state of the non-managed vegeta- tion every three months for a total period of 18 months. The meaning of Into v
values are summarized in Table 2. While surveying the subplots to estimate the Into v the amount of products
which could be harvested in the following three months was estimated as well in each 10 x 10 m 2 subplot. The method used varied for different species. For example, when estimating the yield of fruit trees, the number of fruits which would ripen within the following three months were counted, or esti-
Table 1. Characteristics of six forest gardens.
Forest Age when Weeding Field last garden surveyed intensity made in
A 2 yrs 10 mth high primary forest B 20-25 yrs high primary forest C 20-25 yrs high primary forest D 6 yrs medium primary forest E 9 medium Primary forest F 6 yrs low secondary forest G 25 yrs low primary forest
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Table 2. Non-managed Vegetation Index (I,mv) values used to estimate weeding patterns in Santa Rosa forest gardens.
Inm v Definition
Weed vegetation less than 20 cm high in more than 50% of the subplot Weed vegetation between 20 cm and 50 cm covering more than 50% of the subplot Weed vegetation between 0.5 and 1.5 m for more than 50% of the subplot Weed vegetation between 1.5 to 2.5 m for more than 50% of the subplot Weed vegetation exceeds 2.5 m for more than 50% of the subplot
mated if their numbers were too large. Similar methods were used for other species. These observations were repeated five times during a 15-month pro- duction period.
Diversity of managed species
The total number of tended species in the seven terra firme fields was 92 (Table 3). Only 47 of these are domesticated plant species, common in many Amazonian agricultural systems (Hiraoka, 1986; Denevan and Padoch, 1987; Cavalcante, 1976, 1978, 1980). The other 45 are native species from the forest which were either planted in these fields or they appeared spontaneously and were then tended. Sometimes trees of the original forest cover were spared while slashing the field. Such tending of native forest species is common in many agroforestry systems (e.g. Michon et al., 1986). The number of tended plant species per single forest garden ranged from 14 to 48.
Out of the 92 species recorded in the thirteen fields surveyed, only seven, all cultivated fruit species, were present in all seven forest gardens (Table 3). They are Rollinia sp., Pouteria caimito, Inga edulis, Bactris gasipaes, Musa paradisiaca, Poraqueiba sericea, and Pourouma cecropifolia. A total of 63 species, however, were found in only three or less forest gardens, and 28 were found in only one of the fields sampled. Notably Miconia pilgeriana ranked number nine in the total number of plant individuals. This species is a secondary forest tree which is used for construction purposes. It was actively managed only in forest garden A. Other forest species ranking high in total number of plant individuals were Calathea sp., Cedrela odorata, Vismia angusta. The case of the Calathea sp. is, for instance, special since it occurs naturally only in the varzea. The leaves of this species are used as a food wrap. It had been introduced on terra firme by the owner of forest garden D. According to the owner 's account this species reproduced easily and became very abundant. Forest garden D is a source of Calathea sp. leaves for many people of Santa Rosa.
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Table 3. Densities (individual/ha) of managed plant species in seven forest gardens in Santa Rosa.
Total No plants 2157 1009 719 785 2042 Total No species 40 38 48 26 28
0 0 0 3 0 0
0 0 0 0 0 0
517 I9
0 I 0 3 0 5 0 48 0 8 0 50
0 7 0 4 0 92 0 11 0 3 0 5
678 I4
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Weeding patterns
Forest garden A showed a regular weeding pattern which was uniform throughout the entire field (Figure 1). During the first observation it was just being slash-weeded. The largest part (83%) had very little weed vegetation (Inm v 1) while a smaller part (17%) was covered with somewhat larger weeds (I,rnv 2). During the second observation this slash-weeding had been completed and the entire field had a cover of only very small weed vegetation. During observations 3, 4, and 5, this field showed a gradual increase in cover up to Into v 3. But between the fifth and sixth observation the field was slash-weeded again completely, resulting in an Into v of 2 for the whole field during obser- vation six.
The weeding pattern in forest garden B was much more irregular than in the previous field. During the first observation, the larger part of the field (67%) had a very low weed c o v e r (Into v 1) , while in the rest of the field the weed vegetation was quite developed (Inm v 2 and 3). The second and third observations showed an increase in area exhibiting higher Inm v. During the third observation the larger part of the field was covered with medium to high weeds (Inm v 3 and 4). At the fourth observation this tendency was reversed, and the area with a n Inm v 2 increased again. However, during the third and fourth observation 22% of the field had a cover of a person's height vegetation, reflected by an Inm v of 4. Between observation four and five, parts of the mixed orchard which had Inm v of 2 and 3 were slash-weeded again, while other areas with index values of 4 were left untouched. During the last observation, however, the area with well developed weed vegetation (Into v 4 )
had decreased, and a larger area showed a n Inm v of 2. During the first observation of forest garden D, a large area (60%) was
covered with weed vegetation represented by a Inm v of 4 or 5. During all six observations the areas with tall weed vegetation did not fall below 47%. However, the other half of the field was slash-weeded following a regular schedule, similar to that of forest garden A. Between the first and second observation a smaller area was slash-weeded, resulting in a slight increase in area with a Inm v of 2. The next two observations showed an increase in area with a larger I . . . . but during the fifth and especially during the sixth obser- vation the area with lower index values increased again as a result of slash- weeding.
In forest garden F much less weeding was carried out than in any of the previous fields. Only during the second and third observations did a small area show a Into v of 3. The rest of the field had values of 4 or 5. At observa- tions five and six, 100% of the field had a Inm v o f 5 , reflecting a dense and high cover of secondary forest.
285
Observation: 1 2 3 4 5 6
forest garden A
iL ..1. .... L ! ._!,.. . . . . -o forest garden B
a (D
> forest garden D 0
°it
forest garden F
J d ...I l , | • • • , s • ° • , i • . • , • • • m ~ s • • • , t • •
Inmv value
Figure 1. Non-managed Vegetation Index (l.mv) in four forest gardens. Each single graph indi- cates the percentage of the total area of a single field covered with weed vegetation represented by a certain I.m v at a single observation• Observations were repeated six times at quarterly inter- vals. Into v values: 1 = field recently cleared; 2 = non-managed vegetation up to 0.5 m; 3 = between 0.5 and 1.5 m; 4 = between 1.5 and 2.5 m; 5 = area covered with secondary forest.
286
Yield levels
Yield levels of economically important products were estimated in the same forest gardens in which weeding patterns were evaluated. A total number of 42 different plant species, or 67% of all the managed species yielded har- vestable products in at least one forest garden. In forest garden A, 24 species yielded harvestable products, or 60% of all managed species. In forest garden B there were 23 managed species (61%) which yielded harvestable products. In forest garden C only 13 managed species (50%) and in forest garden F only seven species (37%) yielded harvestable products. Other amounts of har- vestable products per species are presented in Table 4.
Diverse management of ribere~o forest gardens
The results presented above showed differences in the composition of the studied managed species and weeding patterns of the forest garden. Forest garden A and B had 38, 40 and 48 species, although they only had 12 species in common. Forest garden A showed a regular weeding pattern of one complete slash-weeding per year. The larger part of forest garden B was kept fairly clean, but other parts were only cleared when the weed vegetation began to turn into dense forest. The difference in weeding patterns can be explained as a result of the difference in the field ages. Forest garden A, which was not yet three years old when the survey began, required a more thorough weeding in order to achieve the desired vegetation composition and structure. In the older forest garden B, which had a well established forest vegetation, less effort was necessary to maintain the existing composition and structure. As a consequence the amount of labor recorded by the owner of forest garden A in a diary during one year, was 13.5 work days, while the owner of forest garden B recorded only 0.75 work days spent on the same activity during the same year (Padoch and de Jong, 1990).
Forest garden D, and forest garden E had respectively 26 and 28 managed species. Forest garden D also had a one year slash-weeding schedule, but only half of the field was cleared. This is consistent with the lower number of managed species in this field. Only the tended species areas were kept under control, while in other areas the vegetation was allowed to develop freely. The slash-weeded area in forest garden D increased piecemeal during the obser- vation period, as a consequence of more trees reaching production age. Once the tended vegetation of forest garden D becomes fully grown, this field may well be managed in the same way as field number B. Such a strategy is logical, since a more intensive management of the field requires higher labor inputs at younger stages, than when the field is older.
Forest gardens F and G had relatively few tended species, and subsequently were virtually never cleared at all. The low density of tended species does
287
Table 4. Yield levels per hectare of four forest gardens in Santa Rosa, during fifteen months of data collection. Yield levels are in number of fruits unless otherwise indicated.
not justify the investment of more labor. The owner of forest garden F stated that he would make a new field on the same site once the secondary forest was dense enough to suppress the understory weed vegetation. This field and forest garden G are most closely related to the abandoned swidden, which is often considered typical of shifting cultivation practices. Forest garden F, con- served a total of 19 tended species, and forest garden G, 14 tended species.
Intensification of ribere~o agroforestry in Santa Rosa
Increased population pressure among upland farmers had often resulted in a shortened fallow period for swidden-fallow systems (Clarke, 1966). However, other examples demonstrate that higher population densities can also lead to intensification of homegardens or forest gardens (e.g. Michon et al., 1986; Wiersum, 1983). The latter examples are, in most cases, responses to short- ages of forest resources, rather than to land shortages. Agroforestry intensi- fication can also be the result of new market opportunities, as demonstrated with examples from the Amazon (Hiraoka, 1986; Padoch et al., 1985).
In general, Santa Rosa farmers practice more intensive agroforestry than farmers like the Bora Indians who live in remoter areas of Peru (Denevan and Padoch, 1987) or the Runa Indians of Ecuador (Irvine, 1987). The inhab- itants of Santa Rosa do not sell large amounts of products from agroforestry fields to the market, but use most of it for home consumption (Padoch and de Jong, 1989). It can be concluded that agroforestry intensification in Santa Rosa is a result of increased pressure on forest resources and of a higher demand for family labor. The increased pressure on forest resources is a result of the sedentary lifestyle of the Santa Rosa inhabitants. The distance to high forest increases every year, and therefore forest resources near the village are harvested faster than they regenerate. Since Santa Rosa farmers engage in commercial agriculture, they have to minimize their labor expenditures. Producing forest resources in agroforestry fields, therefore, becomes an eco- nomically attractive option.
The focus on subsistence production in Santa Rosa agroforestry also explains in part the diversity in agroforestry practices. Since no obvious increase in monetary income is to be gained from single-crop intensification, farmers value the economic benefits from agroforestry fields in a different way. It becomes a question of individual circumstances and personal prefer- ence as to which crops are to be produced and how much effort they are worth. For instance, farmers in Tamshiyacu, close to Iquitos, obtain financial gain for the larger part from Poraqueiba sericea (Hiraoka, 1986, Padoch et al., 1985). As a result, agroforestry intensification is much more uniform in this village. Since such market stimuli are minimal in Santa Rosa, farmers make forest gardens in accordance with their personal circumstances and desires, resulting in their diversity as discussed above.
The research on ribere~o resource management was conducted in collabora- tion between the Instituto de Investigaciones de la Amazonia Peruana (IIAP), and the New York Botantical Garden (NYBG). Funding came from Suisse- Aid to IIAP and the Exxon Corporation to the New York Botanical Garden. I thank Dr C. Padoch and Dr R. A. A. Oldeman who both reviewed earlier versions of this article, Elysa Hammond who gave constructive comments, and Maria Potess who corrected the English. Mostly, however am I indebted to my friends in Santa Rosa, who shared their time and knowledge with me.
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