Economic value of secondary succession species in Amazonia: Taking into account age and land use history

Regions Altamira Ponta de Pedras Bragantina Tomé-AçuPonta de Pedras 62%Bragantina 43% 49%Tomé-Açu 45% 47% 58%Yapu 4.7% 5.8% 4.2% 2.9%

Figure 3. Similarity indices between regions and multi-dimensional scaling output using these indices

Figure 4. Jaccard similarity indices across land use types and multi-dimensional scaling output using these

Forest Logging PastureLogging 29%Pasture 15% 15%Swidden 23% 28% 14%

The increasing extensiveness of secondary succession in Amazonia necessitates the assessment of the value of these lands in supporting human populations. Understanding the processes of regrowth can enhance knowledge of agronomic practices and other land-use forms and the landscapes that these eventually create.

Table 3. Average number of species plot within each land use for each plant use categoryLand use # of sites cash construction cultivated food timberForest 7 11 15 3 13 22Logging 8 10 13 1 13 23other 7 14 9 3 12 17Swidden and pasture 7 8 9 2 11 17Swidden agriculture 47 7 10 2 10 17Pasture 3 4 8 1 8 11

Sources Place or groupAnderson, A.B., and D.A. Posey 1989 Management of a Tropical Scrub Savanna …Gorotire Kayapó Anderson, A.B., and E.M. Ioris 1992 Valuing the Rain-Forest …Combu IslandBalée, 'W. 1994 Footprints of the Forest Ka'aporBennett, Bradley C. 1992 Plants and People of Bergman, Ronald W. 1990 Economica Amazonia …Ucayali Bodmer, Richard E., Pablo E. Puertas, Juan E. Garcia, Doris R. Davis, and Cesar Reyes 1999 Game animals, palms, and … Boom, Brian M. 1989 Use of Plant Resources … Chácobo Boom, Brian M. 1990 Useful Plants of the Panare Indians of the Venezuelan Guayana. in prag90nd. Boster, J. 1983 A Comparison of the Diversity …JívaroChibnik, Michael 1994 Risky Rivers. Cooke, Richard, and Dolores Piperino 1993 Native American Adaptations to the Tropical Davis, E. W., and J. A. Yost. 1983. The ethnobotany of the Waorani of eastern WaoraniDenevan, W. M., and C. Padoch. 1987. Introduction: The Bora Agroforestry … Denevan, W. H., and J. M. Treacy 1987. Young managed fallows Brillo NuevoEden, M. J., and Andrade, A. 1987 Ecological Aspects of Swidden …Andoke and WitotoEden, M.J. and Andrade, A. 1988 Colonos agriculture and adaptation …ColombiaFearnside, Philip M. 1985 Agriculture in Amazonia. Ferraz, Joao 1995 Rehabilitation of Capoeiras, Degraded … FIBGE 1988. Produçaô de extração vegetal … Flores-Paitán, Salvador 1987 Old Managed Fallows at Brillo …Brillo NuevoHammond, D.S., Dolman, P.M., Watkinson, A.R. 1995 Modern Ticuna Swidden-Fallow Management …Las PalmerasHiraoka, Mario 1986 Zonation of Mestizo Riverine Farming Systems in Northeast …TamshiyacuHiraoka, Mario 1989 Agricultural Systems on the Floodplains of the Peruvian Amazon. Padoch, C., J. Chota Inuma, W. De Jong, and J. Unrub. 1985. Amazonian agroforestry: A market-orientedTamshiyacuPadoch, C. 1987 The Economic Importance and Marketing of Forest and Fallow Products in the Iquitos RegionIquitosPadoch, C. and W. de Jong. 1987. Traditional agroforestry practices of native … TamshiyacuPadoch, C. and 1989 Production and Profit in Agroforestry Practices …Sta. RosaPadoch, C., and De Jong, W. 1991 The house gardens of Santa Rosa: Diversity, and variability…Sta. RosaPeters, C. M., Balick, M. J., Kahn, F, and Anderson. A. B. 1989 Oligarchic forests of economic plants … Peters, C., A. Gentry, and R. Mendelsohn 1989 Valuation of an Amazon …Rio Nanay, PeruPinkley, H. V.1973 The ethnoecology of the Kofan … Posey, D. 1985 Indigenous Management of Tropical Forest Ecosystems … Prance, G.T. 1984 The pejibaye, Gulielma gasipaes (HBK) Bailey, and the papaya, … Salick, Jan 1989 Ecological Basis of Amuesha …Palcazu valleySalomão, Rafael de Paiva, Nelson A. Rosa, Daniel C. Nepstad, Andrea Bakk 1995 Estrutura Diamétrica e Breve Caracterização Ecológica… Shoemaker, Robin 1981 Peasants of El Dorado. SatipoSmith, Nigel J. H., J. T. Williams, Donald L. Plucknett, and Jennifer P. Talbot 1992 Tropical Forests and Their Crops. Unruh, Jon and Salvador Flores Paitán 1987 Relative Abundance of the Useful Component …Brillo NuevoUnruh, Jon and Alcorn, Janis B. 1987 Relative Dominance of the Useful Component in Young Brillo NuevoVickers, W. T., and T. Plowman. 1984. Useful plants of the Siona and Secoya …Siona and Secoya

Table 1 Sources of useful species in database

Secondary succession has become a dominant vegetation type as many lands revert to this type with trends including economic recessions, reduction of incentives that had encouraged land conversion, previous overestimation of soil or other land conditions and the decline in enthusiasm of directed or spontaneous settlements or projects (Brown and Lugo 1990). This trend was particularly prominent following the 1980s when abandoned pastures had reached over 100,000 square kilometers in Amazonia (Anderson 1990). However, the process of appearance of areas of sucessional vegetation generally accompanies colonization, settlements, and swidden agriculture-based economies.

Here we compare an extensive list of economically useful plant species with inventory data derived from field assessment in five Amazonian regions. The species indicators used for this analysis largely fulfill human needs of acquiring cash income, construction, cultivation, and food. Obviously, not all of the uses are necessarily practiced in the areas sampled.

Narrow use categoryWide use category Aggregate

vine for wicker furniture (commercial) market NTFPessential oilsfiberlatexoilpulpcash cropexportindustrialmarketrubbercaulkconstructiongumsrope made from fiberthatchtimber, construction, and thatching

posts wood constructioncultivateddomesticateintensively managedritual belief systemveterinary medicinaldyeornamentalclothinghammocksperfumepersonalchewing gummusical instrumentshadestimulantbeveragefoodspicestem contains potable watermanaged remnant forest plantwindbreakfish baitfish poisonfood processinghuntinginsecticidewaterceluloseessential oilsfiberlatexoilpulpresincharcoalfirewoodresin/latex used for incandescencesecondary firewood

Table 2. Categorization of plant uses

food

forest subsistence

timber

cash

construction

cultivation

extra-economic

fuel

substance extraction

foodgetting and economic activity

personal

recreation

food

ecological management

ornamental

extraction of substance for market

construction material

cultivation

The vegetation inventories carried out by the Anthropological Center for Training and Research on Global Environmental Change (ACT) were conducted for the purpose of studying relationships between demographic and market variables, land cover, ecosystemic change, productive practices, and ecological responses to these such as land use history, soil fertility, and floristic and structural composition of secondary succession.  The data collected by the ACT survey encompasses several vegetation types, soil fertility and geoclimatic variations. This has been achieved by data collection from five regions that provide a wide range of comparison in terms of ecology and predominant land-use. This paper builds upon an existing database of seventy-nine sites inventoried in Amazonia. There are 1047 species in this database derived from these inventories. The categories of previous land uses inventoried may be generalized as mature forest, logging, swidden agriculture cleared by manual means, swidden agriculture with mechanized clearing, and pasture. This enumeration also represents a continuum of magnitude of impact on the respective ecosystems and vegetation, which is an important factor in the rate and composition of regrowth.

Fig. 1. Five regions were sampled: 1. Altamira, 2. Ponta de Pedras, 3. Tomé-Açu, 4. Bragantina, and 5. Yapú. Our seventy-nine study sites were selected within these regions to represent a gradient of soil fertility and settlement history, therefore, encompassing native (indigenous and caboclo populations) and colonist populations settled during the past 100 years.

The resulting data was entered into an Access database (Fig. 2). To allow comparison between and the individuals present and their potential uses, forty-nine published sources were used to make a table of species and uses for the comparison. In this way the use-categories of any species located in any site with a specific age or land use could be determined. The results yielded cross tabulations of the categories of plant use reported by the corresponding researchers for each land use type and fallow age. We compare the presence of plant resources among fallows of different ages, land use history, and regional location by examining presence across sites and similarity across these categories.

The 1047 species in the vegetation inventory are compared with a categorized list of 1033 useful species derived from the literature. 312, or 30%, of the inventoried species are found to be useful when compared to this list. The average number of species present per site is used to eliminate the effect of the “Swidden agriculture” land use category accounting for 47 of the 79 sites. In examining the occurrence of economic species according to plant use categories, both categorizations in terms of age and previous land uses suggest that more economic resources are present where the impact or extent of human use, or the time since the last human disturbance, results in more vegetation being present. This is true for all plant use categories except the “cultivated” category, in which planted species expectedly decrease with the progress of natural regrowth.

In comparing sites by overall species composition (fig. 3), the Yapú region appears as the most divergent. Also, the degree of dissimilarity among sites shown in the table and figure below appears to reproduce the spatial distance among them.

When comparing sites by overall species composition across previous land use (fig. 4), the pasture category appears as the most divergent, with previously logged land as slightly more similar to mature forest that previous swidden land.

In the above figures 3 and 4 Jaccard’s similarity index is calculated among the regions and then among the land use types surveyed (Greig-Smith 1953). The two dot plots below are multi-dimensional scaling outputs using SPSS calculated on the resulting matrices of similarity indices between regional species composition and species composition across land use respectively for each plotted output. Distance between points represents scaled dissimilarity in species composition. The two graphs following these show an overall increase in the average number of plant resources per site with increasing land cover and duration of regrowth.

When a cleared area of land is allowed to regenerate, the relative occurrence of species of that area is influenced by several factors such as soil, previous land use, crop composition, weeding practices. Fast-growing species with a shorter lifespan tend to dominate first. Then saplings follow and later trees, which will eventually create a canopy that eliminates light-demanding species on the ground and it can be distinguished from an understory.

At a glance, even the species that rank near the top in terms of frequency of occurrence in our database have important uses. Cecropia palmata is the most frequently occurring tree in all areas sampled. According to Balée (1995) this is used as a secondary food source for indigenous groups. Furthermore, Cecropia are an early colonizer of fallows, being prominent in intermediate SS2 stage  (Moran and Brondízio 1998). Cecropia species including Cecropia palmata are also found to contribute to the restoration of nutrients through the high Phosphorus content of the litter produced by their leaffall. (INPA 1998). Banara guianensis has a high frequency of occurrence in our data primarily in successional sites. Balée has classified this as an animal food distinguished by the Ka'apor. Likely, in some area, this species has an important role in maintaining the supply of food sources for game resources. Futhermore, animal attractants also assure regeneration by attracting animals as seed propagators. Banara guianensis is also a prominent colonizer in the early stages of succession (Brondízio 1996:192).

Two similar studies which inventory vegetation in fallows have been carried out by Denevan et al. (1987) and Irvine (1989). Irvine refers to cultivation in the neotropics as essentially a process of management of secondary succession. While cultivation plots do not usually mimic the forest in terms of reproduced vegetation as Geertz 1953 suggested, sustainability may be evaluated in terms of the integrity with which it reproduces natural succession cycles (Beckerman 1983). The succession of crops planted in native systems mimic order of natural succesional colonizing types. Thus by making swiddens as holes in the forest canopy and prompt abandonment, cultivators in Yapu acheive succession intervals comparable to those of all other regions except Altamira, despite inferior, acidic soils.

Succession management, or fallowing, can be considered to be universally characterize agriculture within the basin (Cotton 1996). The Tomé-açu case may minimize fallowing through exceptionally high labor and chemical inputs which are out of the range of most producers, but does not qualify as an exception since multi-level cropping and the mixture of perennial and herbaceous crops is actually recreating the successional process.

Forest regeneration accordingly varies depending on the conditions under which it is cleared - be it manual, mechanized , by the possible use of burning or management by fire and the type of production for which clearing is carried out whether this is cattle ranching or swidden agriculture. Agriculture is necessarily a succession management behavior because agricultural plots are subject to the same constraints and influences as natural secondary succession and because in a subset of the cases agriculture reproduces the natural process of disturbance and stages of regrowth. While the universality of this observation is compelling basin wide, a divergence is identifiable between whether the behavior of fallowing is compelled by positive or negative feedback. Anthropogenic secondary succession is addressed, its description can be grouped into two qualitatively distinct patterns that meet to form a continuum. These patterns correspond to two feedback loops that compell abandonment of intensely cultivated plots to fallows. Positive feedback occurs as yields decrease due to nutrient decline eventually beyond productive viability. This type of feedback that stimulates fallowing is the decline in yield returns with labor and chemical inputs remaining constant. It corresponds to cultivators who either do not adequately perceive or anticipate the first type of feedback or have the needed knowledge, or do not anticipate occupancy for a sufficient period of time to benefit, who work from a non-cyclic agricultural model, or there is a shortage of land which makes optimal fallow cycling impossible. This results in compounding feedback as, shorter fallow periods decrease the nutrients released by burning and overall fertility decline slows secondary succession rates or chemical input regimes allow greater depletion of overall fertility In the cases sampled this is observable in Bragantina and the non-alfisol areas of Altamira. In comparing these two cases with agroforestry in Ponta de Pedras, that produced palm products for the large Belém urban market, it can be inferred however, that the association of high population pressure with shortened fallow cycles as postulated by Boserup (1965) is not a universal.

Negative feedback is comprised in the returns to producers in terms of nutrients, microenvironment complexity, and resources that management of the succession cycle can produce, the availability of which is contingent on appropriate management. This loop that includes conversion of nutrients in natural biomass followed by intensive cultivation followed by planting of perennials is not usually included agroecolocal models imparted by commercial or technocratic sources. It is also contingent on a tenure relations system which prescribes a limit to population density to allow sufficient fallow lengths and tenure security which gives producers an interest in the future of the land occupied. Tenure stability also permits familiarity with the succession process and viable management techniques specific to localized environments.

an important distinction is whether fallows are managed to increase resource diversity or whether the productive limits of the area under cultivation is pushed beyond immediate profitability and abandonment of the land as a perceived non-resource takes place. The former scenario, as put forth here can even be acheived in reasonably dense populations where the knowledge and economic, environmental, and tenure stability exists to manage fallows as resources.

The increasing extensiveness of secondary succession in Amazonia necessitates the assessment of the value of these lands in supporting human populations. Understanding the processes of regrowth can enhance knowledge of agronomic practices and other land-use forms and the landscapes that these evetually create. The comparison of vegetation inventories collected to a list of economically important species reveals that in most cases relatively less disturbed sites are richer in human plant resources even in comparison to fallows that have preceded human cultivation of such resources. This finding suggests the economic importance to populations of maintaining extensive forest and continuous land cover. These findings, which correspond to relatively higher population densities and higher impact land use are thus different from findings that human disturbances increase biodiversity of naturally occurring resources at lower population densities (Devenan and Padoch 1987; Balée 1995). This difference is likely attributable to differences in population density. This role of secondary succession managed within optimal cultivation cycles is demonstrated however, in the indigenous Yapú site along the Vaupés, which has the longest fallow cycle and lowest population density, where we find more resource species in swidden fallows than in forests. Likewise, the availability of biological resources in fallows is relatively greater in the regions inventoried with lower population densities and where longer fallow cycles are practiced. The results also accentuate the availability of a diverse array of resources in both forests and fallow samples that remain unexploited likely due to the absence of knowledge and habits corresponding to their use. Since many of the plant uses used in these calculations are not known or practiced by the populations present at these sites, this suggests the importance of transfer of ethnobiological knowledge and ascertaining the current processes of such transfer in the areas studied.

Ongoing research activities …

•Expansion of database

•Focus on specific taxa

•Improve data interpretation using other vegetation metrics and techniques

•Investigation of the local small producer economy and land use history of the regions sampled

Figure 2Figure 5. Figure 6.