Intra-cultural Differences in the Importance of Plant Resources and Their Impact on Management Intensification in the Tehuacán Valley, Mexico

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  Management of plant resources is a complex process that involves the interaction of numerous cultural, environmental, economic, and ecological factors Therefore, understanding factors influencing management decisions requires multidisciplinary
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  Intra-cultural Differences in the Importance of PlantResources and Their Impact on ManagementIntensification in the Tehuacán Valley, Mexico Martha Sofía González-Insuasti  &  Alejandro Casas  & Ignacio Méndez-Ramírez  &  Carlos Martorell  & Javier Caballero Published online: 18 January 2011 # Springer Science+Business Media, LLC 2011 Abstract  Management of plant resources is a complex process that involves the interaction of numerous cultural,environmental, economic, and ecological factors Therefore,understanding factors influencing management decisionsrequires multidisciplinary approaches, including both quan-titative and qualitative perspectives. This study exploresquantitative approaches as methodological tools with whichto identify patterns underlying more intensive management of plant resources. The research was conducted in the villageof Santa María Tecomavaca, Oaxaca, in south-centralMéxico, within the semiarid Tehuacán-Cuicatlán BiosphereReserve. Three models explaining the management intensitytendencies were identified, consistent with the pattern of multiple variables influencing plant management. Keywords  Domestication.Edible plants.Intraculturalvariation.Resources management .Tehuacán-Cuicatlan Valley Introduction Rural peoples throughout the world practice different manage-mentstrategies,varyingincomplexity,tomodifytheabundanceand quality of useful plant species, either in areas where theynaturally occur, or in anthropogenic environments outside their srcinal habitat (Alcorn 1981; Rindos 1984; Colunga  et al. 1986; Caballero 1987; Anderson and Posey 1989; Balée 1989; Casas  et al.  1996, 1999b, 2001, 2007; Harris 1996; Bye 1998; Caballero  et al.  2000). Previous studies in Santa MaríaTecomavaca, a village in the Tehuacán Valley, Mexico(González-Insuasti and Caballero 2007) classified the villagers ’ management practices according to their degree of complexityas: (1) simple gathering of plant resources with no particular selection; (2) non-selective incipient management entailingtolerance, protection, or promotion of a useful species without artificial selection of specific plants); (3) selective incipient management tolerating, protecting or promoting of individual plants with phenotypes considered desirable; (4) occasionalcultivation of seeds or propagules of wild plants in cultivatedland; and (5) agriculture  —  the cultivation of domesticated plants in specifically selected areas. According to González-Insuasti and Caballero (2007), management intensity can beoperatively defined as a function of the number of personsengaging in some kind of management and the number andcomplexity of their practices.In Santa María Tecomavaca farmers ’  decisions regardingdegreesofmanagementintensityofdesirablespeciesdependonthenatureoflandtenurerightsoftheareaswherethespeciesaredistributed(themostimportantconsideration),thelengthoftimeneeded for the first harvest, and the species ’  importance in their diet (González-Insuasti 2006; González-Insuasti and Caballero2007; González-Insuasti  et al.  2008). The cultural importanceof edible plant resources was identified to have a significant influence on management intensity of slow growing species M. S. González-Insuasti ( * )Universidad de Nariño, Colombia,Pasto, Nariño, Colombiae-mail: masogo@gmail.comA. CasasUniversidad Nacional Autónoma de México,Morelia, Michoacán, Méxicoe-mail: acasas@oikos.unam.mxI. Méndez-Ramírez :  C. Martorell : J. CaballeroUniversidad Nacional Autónoma de México,México D.F., MéxicoI. Méndez-Ramíreze-mail: imendez@servidor.unam.mxC. Martorelle-mail: martorell@ciencias.unam.mxJ. Caballeroe-mail: jcaballero@ibunam2.ibiologia.unam.mxHum Ecol (2011) 39:191  –  202DOI 10.1007/s10745-010-9369-4  occurring in communal areas, and on those with short  production periods found in private areas. Nevertheless, our  previous studies did not analyze whether the cultural impor-tance given by different persons to an edible plant resourcecould lead them to make specific decisions regarding itsmanagement intensity and the reasons of those decisions.In general, the cultural importance of a plant resource is afunction of its role in a human group, and is reflected in suchaspectsasitsnomenclature,theeasewithwhichitisrecognized,andtheperiodoftimeitisused(Berlin et al.  1974; Hunn 1982; Turner  1988; Stoffle  et al.  1990; Philips and Gentry 1993a, b). The cultural importance of a plant resource influences howknowledge regarding its use is shared among the different inhabitants of a region through exchange of information and asa result of direct experience (Berlin  et al.  1974; Hunn 1982; Turner  1988; Stoffle  et al.  1990). The shared knowledge of important plant resources encourages people of different communities to develop similar productive strategies in similar habitats,andeventoadoptmeasuresfortheirconservationwhereit is evident that these resources are disappearing (Gadgil andBerkes 1991; Berkes 1998; Berkes  et al.  2000; Kottak  2004).  Nevertheless, in all local knowledge systems there can bevariability in personal perceptions concerning a plant resource(Goodenough 2003). For instance, differences in persons´occupation may influence that a species he or she uses duringtheir main activity will be more important than others (Philipsand Gentry 1993a, b; Lawrence  et al.  2005; Camou-Guerrero et al.  2008). Wild plant resources may be culturally moreimportant among the elderly than among younger individualswho have received a formal education as opposed toimmersion in a largely oral tradition (Philips and Gentry1993a, b; Turner   et al.  2000; Lawrence  et al.  2005).In the analysis of cultural importance of plant species it isnecessary to consider the degree of dependence and the costsof potential change in availability. What Platten and Henfrey(2009) call  “ keystone species ”  play a crucial role in the lifeof a human community. In the particular case of edible plant species, Pieroni (2001) and González-Insuasti (2006), term as culturally more important those plant resources consumed by the most people, those prepared in the highest variety of forms, and those with the highest number of other non-edibleuses. González-Insuasti  et al  . (2008) suggest that cultural importance of edible plants may influence how frequentlythe resources are obtained or whether they are bought whenthey are not locally available.González-Insuasti  et al.  (2008) modified the indexdeveloped by Pieroni (2001) to evaluate the culturalimportance of edible plant species, considering the followingfactors: (1) their identification by people, (2) their consump-tion frequecy, (3) the plant parts used, (4) their preparationforms, (5) their flavor appreciation, (6) their additionalmedicinal use, (7) their gathering exclusivity (the explicit affirmation that a person goes to a place exclusively for gathering a particular plant resource with no other purpose,versus the affirmation that its gathering occurs whileconducting other activities such as agricultural practices,extraction of fuelwood, among others); (8) their potentialcommercialization, and (9) their form of procurement (e.g.,obtained through direct collecting, market purchase or both).Management of plant resources is a complex process that involves the interaction of numerous cultural, environmental,economic, and ecological factors. Therefore, understandingfactors influencing management decisions requires multidis-ciplinary approaches, including both quantitative and qualita-tive perspectives. This study explores quantitative approachesas methodological tools with which to identify patternsunderlying more intensive management of plant resources.In Santa María Tecomavaca, as in other rural communi-ties (Philips and Gentry 1993a, b; Turner   et al.  2000;Lawrence  et al.  2005), person ’ s age, schooling andoccupation influence their appreciation of the importanceof a certain edible plant resource, its management intensity,and the type of land tenure regime of the area where it isobtained. In this study we measured the relative importanceof the following in the management of edible plants.(Fig. 1): (a) age, influencing the educational level andoccupation of people, (b) both education level andoccupation, influencing the perception of importance of edible plants, and in turn (c) the perception of importanceof edible plants and land use rights, influencing theselection of areas for obtaining plant resources and thelevel of management intensity in those areas. Methods Our research was conducted in the village of Santa MaríaTecomavaca, Oaxaca, in south-central México, within thesemiarid Tehuacán-Cuicatlán Biosphere Reserve (Fig. 2). Fig. 1  Hypothetical causal relations among different socio-culturalfactors, cultural importance, land tenure regime of the area whereresources are obtained, and management intensity. The hypothesis wasexamined by means of a path analysis.  Arrows  represent the directionof cause-effect relationships among variables, respectively192 Hum Ecol (2011) 39:191  –  202  Santa María Tecomavaca has a area of 221.99 km 2 , theelevation ranging between 500 and 1,800 m. Rainfallfluctuates between 500 and 600 mm/year, and annual meantemperature is 24°C (Grupo Mesófilo 2001). The munici- pality of Santa María Tecomavaca is inhabited by 1,831 people (892 men and 939 women) in three settlements:Santa María (1509 mestizo and 153 Mazatec people),Buenavista (113 Mazatec people), and Santiago El Viejo(44 Mazatec people) (INEGI 2001).There are two main types of land tenure in Santa MaríaTecomavaca, what is termed communal property and a form of  “  private ”  stewardship. The legal recognition of the communal property occurred in 1945, and currently there are 500 owners(Grupo Mesófilo 2001). What is here termed  “  private ”  property is land assigned by a Community Council for  particular use by some families, although no property titlesare provided and people using this land do not have the right to inherit or sell it. In this study we will refer to the assignedland as  “  private ”  areas, and that not assigned as  “ communalareas ” . Simmilarly, we will use the term  “ owners ”  to refer to people with assigned  “  private ”  areas, and  “  jornaleros ”  to refer to those people without   “  private ”  land who work for andreceive a salary from land  “ owners ” .The main economicactivity in the area is irrigated and rainfed agriculture. Maize, beans, sugar cane, tomato, melon, watermelon, papaya, andlemon are the main crops. In addition,  “  jornaleros ”  sell fruit gathered from the native columnar cacti  Escontria chiotilla,Stenocereus stellatus , and  S. pruinosus. According to the land planning project developed by the NGO Grupo Mesófilo (2001), 75% of land of the territoryis forest, 18% is agricultural area, and 7% is transformedtropical dry forest. According to the Secretaría de Gober-nación (1998), 700 ha of the municipality are under irrigated agriculture, 400 ha are rainfed agriculture,500 ha are used for free raising of livestock, and the rest are forest areas of comunal property.We selected 20 native species of edible plants which arecurrently under different non-agricultural management forms: gathering, non-selective incipient management,selective incipient management, and occasional ex situcultivation. The species selected include herbs, shrubs andtrees under different use forms (Table 1).A total of 84 households of mestizo people wererandomly selected within groups classified according totheir type of land property and agricultural regime practiced (rainfed and/or irrigated). Selection of house-holds based on an official list of households heads provided by the local authority (Comisariado de BienesComunales). A total of 40 households (20  “ owners ”  and20  “  jornaleros ” ) practicing rainfed agriculture, and 44households (24  “ owners ”  and 20  “  jornaleros ” ) practicingirrigated agriculture were chosen. Nearly 44% people interviewed had only the basic primary school, 23% studied the secondary school, 20%had no formal education, and the remaining had prepara-tory, technical education level or university studies. Nearly44% people interviewed were 31 to 40 years old, 39% were51 to 60 years old, and the rest 20 to 31 years old.Semi-structured interviews were conducted with theselected households. General socio-economic data consid-ered were those provided by family heads (either the father or mother), whereas information on use and management was a consensus of information provided by the wholehousehold. Households with family heads younger than20 years old were excluded in the sample since previousstudies (González Insuasti 2006) identified these people inthe village to have poor knowledge of and scarcely useedible wild plants. The following socio-economic informa-tion and data on forms of use and management of plant resources were recorded for each household:1. General information of the household head, includingage, occupation based on his/her rights on land use (0 = “  jornalero ” ; 1 =  “ owner  ” ) and degree of formaleducation (1 = no formal education; 2 = basic primaryschool; 3 = secondary school; 4 = high school; 5 =university studies).2. Land tenure of the areas where plant resources wereobtainedfrom: (0= communalareas;1 =  “  private ”  areas).3. Management intensity, including the different manage-ment practices carried out on each plant resourcecategorized according to the index of management intensity developed by González-Insuasti and Caballero(2007): 1 = simple gathering; 2 = non-selectiveincipient management; 3 = selective incipient manage-ment, including selective gathering; 4 = occasional ex Fig. 2  Study area. Geographic location of Santa María Tecomavaca inthe Tehuacán-Cuicatlán Biosphere Reserve, Central MexicoHum Ecol (2011) 39:191  –  202 193  situ cultivation; 5 = agriculture. When an interviewed person carried out more than one management practice,we established the intensity value as the average of management practices.4. Edible cultural importance: Variables related to theeconomicdependence,theusetradition,andconsumptionforms of edible plants were analyzed. With informationfrom these variables an index was constructed to evaluatewhich plant resources are relatively more or lessimportant for people. The edible cultural importancewas estimated according to the index developed byPieroni (2001) and modified by González-Insuasti  et al. (2008). In this index, one factor considered is thenumber of persons consuming a plant resource, but thisfactor was not considered in our study since the indexwas calculated per household and not per person. Whena household reported it did not consume a plant, itsedible cultural importance was considered to be 0. Thevalue of edible cultural importance (  EI  C  ) was calculatedas (see Table 2 for variable definitions):  EI  C   ¼ U    S   W     F    M     A e  C    A m 10000Low  EI  C   values correspond to the culturally lessimportant species. The index values range from 0 whenthe plant is not consumed at all, to 12,150 when thehighest scores in each of the eight individual edibleimportance metrics. Data Analysis Statistical models were used to explore how socio-culturalvariables interact among themselves and with management intensity, analyzing direct and indirect causality relations, based on an a priori causality hypothesis (Bentler and Bonnet 1980; Shipley 2000; Bentler  2002). Our hypothetical model (Fig. 1) considered the simplest possible relationships between socio-cultural variables (age, education and occu- pation), the edible importance of plant resources and aspectsrelated to their management (land tenure type of thecollecting site and management intensity). This causalhypothesis was tested through path analysis, based onStructural Equation Models (SEM), which establish a seriesof equations determining all correlations among the variablesanalyzed in order to obtain the following main results: (1) anevaluation of how close are the empirical observations withrespect the causal chains proposed, (2) an estimation of theweight of each relation through the path coefficients, and (3)a calculation of the direct and indirect effects of one variableon the others (Bentler and Bonnet  1980; Shipley 2000; Bentler  2002).All variables were standardized with mean values 0 andvariance 1. Besides the variables that we measured, thereare most certainly other external factors that determine theactual values of our response variables. This was acknowl-edged by allowing unmeasured factors (known as  “ errors ” in the SEM jargon; Shipley 2000) to affect the dependent  Table 1  Species studied, life forms and edible structuresFamily Especies Life form Edible structureAgavaceae  Agave seemanniana  Jac. Giant herb BudAmaranthaceae  Amaranthus hybridus  L. Herb Steam and leaf Anacardiaceae  Cyrtocarpa procera  K. Tree Fruit Annonaceae  Annona palmeri  Saff. Tree Fruit Asteraceae  Porophyllum ruderale  (Jacq.) Cass. Herb Leaf Bombacaceae  Ceiba parvifolia  Rose Tree Root and seedCaesalpinaceae  Enterolobium cyclocarpum  (Jacq.) Grises. Tree SeedCactaceae  Escontria chiotilla  (F.A.C.Weber) Rose Shrub Fruit Cactaceae  Ferocactus latispinus  (Haw.) Britton & Rose Herb Stem and fruit Cactaceae  Myrtillocactus geometrizans  (Mart. Ex Pfeiff.) Console Shrub Fruit Cactaceae  Neobuxbaumia tetetzo  (J.M. Coult.) Backeb. Tree BudCactaceae  Opuntia pilifera  F.A.C. Weber Shrub Steam and fruit Cactaceae  Pachycereus weberi  (J.M. Coult.) Backeb. Tree Fruit and seedCactaceae  Stenocereus pruinosus  (Otto ex Pfeiff.) Buxb. Tree Fruit Cactaceae  Stenocereus stellatus  (Pfeiff.) Riccob. Tree Fruit Mimosaceae  Leucaena leucocephala  (Lam) De Wit. Tree SeedMimosaceae  Pithecellobium dulce  (Roxb.) Benth. Tree SeedMyrtaceae  Psidium guajava  L. Tree Fruit Sapotaceae  Sideroxylon palmeri  (Rose) T. D. Penn. Tree Fruit Solanaceae  Solanum nigrescens  M. Martens & Galeotti Herb Leaf 194 Hum Ecol (2011) 39:191  –  202  variables. It is possible to estimate the effect of theunmodelled error variables through path coefficients in thesame way as for measured variables. The path coefficientswere calculated through the least squares method and havea similar meaning as in multiple regression analyses. Pathcoefficients estimate the changes expected in a dependent variable when the explanatory variable is increased or decreased. Due to standardization, the changes in bothexplanatory and dependent variables are measured instandard deviation units (Shipley 2000; Bentler  2002; Méndez-Ramírez 2003).Construction of the models was carried out through the program EQS version 6.0 (Bentler  2002), which analyzeswhether the data correspond with the hypothetical modelthrough  χ 2 tests. Significant tests indicate that discordanceis not attributable to random processes and the modelshould be rejected. This software also generates theBentler-Bonet index, a goodness-of-fit measure with values between 0 and 1, values closer to 1 indicating that dataadjust better to the model (Bentler  2002).We initially tested our causality hypothesis using thecomplete set of species, but the resulting model did not fit reasonably well to our data. We then analyzed separatelygroups of species classified according to different criteriasuch as biological attributes, economic value, or manage-ment strategy. The different models were assessed through χ 2 tests and the Bentler-Bonet goodness-of-fit statisticusing the same hypothetical model shown in Fig. 1. At the end, three plant groups were formed according to usetype, and place and management form: (1) Plants under simple gathering, which are those obtained in wild environ-ments without any type of selection or restriction; (2)culturally important plants with commercial value, whichare those generally consumed and commercialized (mainly by  “  jornaleros ” ) for obtaining monetary incomes; thesespecies are managed with different intensities in both wildand artificial environments; (3) culturally important edible plants forming part of the regional diet but commerciallyunimportant, which are those generally consumed byhouseholds, and that are collected in wild areas but alsomanaged in artificial environments.The resulting models where then simplified by eliminat-ing some of the non-significant hypothetical causalityrelations indicated in Fig. 1. Simplification was carried onuntil we obtained a residual sum of squares smaller than0.15, a value of   P  >0.05 for the  χ 2 test, and a Bentler Bonet coefficient >0.90. Models with these characteristics areconsidered to be well adjusted, informative, and with nostatistical reasons to be rejected (Bentler and Bonet  1980;Bentler  2002). Results All of the studied species were found to be consumed bylocal people, but not all of them were consumed by allhouseholds interviewed. In total, six species were con-sumed by all the households interviewed, 13 species were Table 2  Variables used to estimate the edible cultural importance index. With the exception of   A e ,  A m , and  C  , all the values assigned correspondto those proposed by Pierroni (2001). All of the assigned values are of the ordinal typeVariable Symbol ScaleExclusive or casual acquisition  A e  occasional = 1; occasional and exclusive = 2; exclusive = 3Manner of acquisition  A m  through harvesting = 1; through buying = 2; through buyingand harvesting = 3Commercialization possibilities  C   non existing = 1; existing = 2Flavor appreciation  F   poor = 5.5; regular = 6.5; good = 7.5; very good = 9Perception of medicinal use  M   not medicinal = 1; no specified therapeutic action but foodconsidered healthy = 2; the food is very healthy = 3; clear specification of the treated affections = 4; the foodis a medicine = 5Structure that is used  S  b shoot = 0.75; bud flowers = 0.75; root = 1; stem = 1; youngwhorls of leaves = 1; mature leaves = 1.5; fruits = 1.5; leavesand stems = 2; seeds = 1Frequency of consumption  U   never = 0; less than once per year = 0.5; once a year = 1; morethan once a year but less than once a month = 2; once a month =3;once a week = 4; more than once a week = 5Complexity of the preparation process  W  b raw = 0.5; soup = 0.75; scrambled with eggs = 1; stew = 1;stuffing = 1; roasted = 1; sweet = 1; boiled then stewedor fried = 1.5; juice = 1.5; ice cream = 1.5 tinned 1.5 a  The categories  “ terrible ”  and  “ very terrible ”  proposed by Pieroni (2001) were excluded since none of the plants was classified in those categories  b When more than one answer was recorded, the values were added as proposed by Pieroni (2001) Hum Ecol (2011) 39:191  –  202 195
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