Sociocultural and ecological factors influencing management of edible and non-edible plants: the case of Ixcatlán, Mexico

Abstract

Background

Identifying factors influencing plant management allows understanding how processes of domestication operate. Uncertain availability of resources is a main motivation for managing edible plants, but little is known about management motives of non-edible resources like medicinal and ceremonial plants. We hypothesized that uncertain availability of resources would be a general factor motivating their management, but other motives could operate simultaneously. Uncertainty and risk might be less important motives in medicinal than in edible plants, while for ceremonial plants, symbolic and spiritual values would be more relevant.

Methods

We inventoried edible, medicinal, and ceremonial plants in Ixcatlán, Oaxaca, Mexico, and conducted in-depth studies with 20 native and naturalized species per use type; we documented their cultural importance and abundance by interviewing 25 households and sampling vegetation in 33 sites. Consumption amounts and preferences were studied through surveys and free listings with 38 interviewees. Management intensity and risk indexes were calculated through PCA and their relation analyzed through regression analyses. Canonical methods allowed identifying the main sociocultural and ecological factors influencing management of plants per use type.

Results

Nearly 64, 63, and 55% of all ceremonial, edible, and medicinal wild plants recorded, respectively, are managed in order to maintain or increase their availability, embellishing environments, and because of ethical reasons and curiosity. Management intensity was higher in edible plants under human selection and associated with risk. Management of ceremonial and medicinal plants was not associated with indexes of risk or uncertainty in their availability. Other sociocultural and ecological factors influence management intensity, the most important being reciprocal relations and abundance perception.

Conclusions

Plant management through practices and collectively regulated strategies is strongly related to control of risk and uncertainty in edible plants, compared with medicinal and ceremonial plants, in which reciprocal interchanges, curiosity, and spiritual values are more important factors. Understanding how needs, worries, social relations, and ethical values influence management decisions is important to understand processes of constructing management strategies and how domestication could be started in the past and are operated at the present.

Background

Management of plant resources and traditional ecological knowledge (TEK) are intimately related biocultural aspects that crucially influence the modeling of strategies of multiple use of natural resources in rural communities [1,2,3]. Understanding how management systems do operate, and identifying the factors influencing and motivating them, is greatly important for analyzing how and why plant management is currently decided, how the ongoing processes of domestication are operating, and how these could have operated in the past [4]. Therefore, studies of these processes may be relevant for designing current strategies of sustainable use of plant resources and ecosystems, as well as for understanding factors that led humans to start domestication and agriculture in the past.

Management can be defined as all practices, interventions, transformations, strategies, or decisions deliberately made by humans on ecosystems, their components, functions, and even their emergent properties, in order to use, conserve, or recover them [5, 6]. In traditional contexts, management practices are based on ancient knowledge transmitted from generation to generation, but innovations are continually constructed influenced by new observations, experimentation, and information from recent sources (information from neighboring villages, schools, communication media, interventions by NGOs, governmental promoters, researchers, among others). Both old and new management practices are organized in dynamic systems of knowledge, beliefs, cultural and spiritual values, and local institutions [7, 8].

For studying domestication, it is particularly interesting to document the morphological and genetic divergences between wild and managed populations directed to maintain or increase the availability of particular phenotypes of managed species. Such aspects provide valuable elements for explaining how processes of domestication currently operate and how these could have operated in the past. The ongoing processes of domestication can be documented in numerous rural communities of the world and are responsible for a continuous mechanism of divergence and generation of a new variation of genetic resources. As a research group, we have focused our attention on domestication processes occurring in Mesoamerica, one of the most active areas of plant management and one of the earliest centers of plant domestication in the World [5, 9, 10]. Numerous studies have documented the consequences of domestication, but relatively few have analyzed what factors motivate people to manage and domesticate plants, animals, and other organisms. In this study, we focus our attention to analyzing the main causes of the process.

Management involves several types of practices, tools, and relations between energy invested and amounts of resources obtained; such aspects reflect different degrees of management intensity [11, 12]. Authors analyzing this topic coincide that management intensity of plants goes from gathering, let standing, special care, protection, and transplanting, to practices procuring increase of desirable plant abundance by enhancing and deliberately propagating them [5, 6]. Some variables have been proposed as relevant for analyzing the degree of management intensity: (1) the number and complexity of practices carried out, (2) the number of people or social units (i.e., persons, households, or communities) participating in such practices, (3) the involvement and level of complexity of planning strategies, (4) social agreements regulating the actions, (5) the occurrence of human selection favoring particular phenotypes and the intensity in which it operates, (6) the deliberate practices favoring human-mediated gene flow and manipulation of plant reproduction, (7) the amounts of fossil or human energy invested in practices, (8) the complexity of tools used, and (9) the amount of products obtained per area unit [11,12,13].

In several case studies with cacti, agaves, herbs, and trees, mainly with edible use, we have documented that managed plants under higher management intensity are those more consumed or commercialized and whose future availability becomes compromised due to their relatively low availability in relation to the demand on them [11,12,13,14,15,16,17]. In other words, plant management is influenced by the amounts of products required by social units (which is in turn influenced by their cultural and economic value) but also by people’s perception of the product quality and their substitutability or not by other resources. In addition, management is influenced by the natural availability of plant products, determined by parameters like distribution and abundance, their resilience capacity after human impact on populations, their vulnerability, and management feasibility [11, 12, 18], as well as the ease of access to resources regulated by land tenure and communitarian agreements. All these relations have allowed proposing that management is a response to the need of facing risks or uncertainty in the current and future availability of resources [12]. In other words, it is a response of people’s worries for ensuring availability of resources [12, 19] or preventing their loss [15].

However, some studies have documented that cultural motives such as relations of reciprocity among persons and communities, some spiritual aspects, and efforts to maintain customs and traditions [20, 21] commonly motivate management practices. In addition, practices such as tolerance or let standing of plants in disturbed areas may be associated with ethical principles like the right of plants to live, whereas enhancing abundance of some species may be associated to favor variants of higher quality to embellish the sites where they occur [22,23,24,25,26]. Transplanting and other forms of propagation may simply be motivated by the need to have particular plants closer because of their beauty, odor, and role in rituals or simply because of curiosity to know how plants grow and reproduce [19, 23]. These scenarios allow supposing that management type and intensity are not only responses to risk, but also practices related to ethic or esthetic values, symbolism, or curiosity, and all factors may be operating simultaneously. Analyzing how people make management decisions on plants with different purposes may allow visualizing more clearly different motives for managing plants and management intensity [12, 27]. Therefore, this study explores management motives for plants with different use types.

We hypothesized that uncertainty in availability of plant resources is a main factor motivating management of plants, especially those directed to satisfy basic needs. We therefore expected that edible plants would have higher management intensity as the higher the risk or uncertainty in their availability, as similarly documented in previous studies [12, 13]. Uncertainty would be influenced by the scarcity of plant resources and human pressures on them; therefore, scarce species with high cultural value would be more intensely managed. Ecological aspects of plants like survival, vigor, or resprouting capacities, which may be affected by use, and others that influence the ease of management like life cycle length, reproductive systems, ease of propagation, and adaptability to human-made environments would influence management types and intensities. Medicinal plants are generally used in smaller amounts than edible plants (except those that are extracted for commercialization); therefore, we expected that the pattern of management as a response to risk would be less pronounced than in edible plants [12]. Finally, we expected that the management of plants used for rituals and ceremonies, is not necessarily influenced by risk since purposes and amounts of plants used for these purposes follow different rationalities in which reciprocity relations, esthetic and symbolic values could be important.

Summarizing, our study aimed to analyze how management type and intensity are influenced by sociocultural and ecological factors in edible, medicinal, and ceremonial plants among the Ixcatec from Santa María Ixcatlán, Mexico. We analyzed whether or not people’s worries about availability of plants operate similarly in plants with different use type and look for evaluating the weight of different motives for decisions on managing plant resources.

Methods

Study area

Santa María Ixcatlán belongs to the Tehuacán-Cuicatlán Biosphere Reserve, Central México (Fig. 1). It is located at elevations from 800 to 2600 m, with annual rainfall of 721 mm and average temperature of 17.2 °C. Climate is temperate sub-humid in high zones and semiarid in lowlands [28, 29]. The traditional General Assembly regulates decisions on land, natural resources, and social life [30]. Ixcatlán is inhabited by 171 households [31], almost all of them catholic [26]; 80% of the people consider themselves to be indigenous, but only 15 persons speak Ixcatec, and this is the only village of the world where the Ixcatec language is spoken [31, 32]. Subsistence of the people is based on the multiple use of natural resources and ecosystems, seasonal agriculture, livestock raising, and forest resource extraction [26]. We previously reported 630 plant species used by local people for satisfying different needs [26], nearly 400 species receiving some type of management in order to increase their abundance [26]. Gathering and management of plants is carried out in 18 types of forests, agroforestry systems, and homegardens over a 41,530-ha territory [26, 31,32,33,34,35].

Fig. 1

Location of the community of Santa María Ixcatlán, Oaxaca, Central México

Inventory of edible, medicinal, and ceremonial plants

Ethnobotanical studies by Rangel-Landa et al. [26] documented names, uses, and management of all plant species through semi-structured interviews with 44 persons (see Table 1) in 73 sessions. The information was systematized into the ethnobotanical database of Mexican plants (BADEPLAM), at the Botanical Garden, UNAM, and voucher specimens were deposited in the herbaria MEXU, EBUM, IEB-Bajío, and IBUG. The nomenclature of plant species followed APG III consulted through the site www.theplantlist.org [36].

Table 1 Consultants’ details and the activities in which they collaborated

In-depth interviews and surveys

In order to analyze how management is influenced by sociocultural and ecological factors, we selected samples of edible, medicinal, and ceremonial plants. The samples included 20 species of native and naturalized plants per use type, representing the management intensity gradient [26].

In-depth interviews were conducted to obtain deeper and detailed information on uses, values, perception about availability, vulnerability, and management practices (Table 2) for the selected species. These interviews were conducted with 25 persons selected at random (17 women and 8 men, see Table 1). In order to estimate the proportion of families that consume the studied plants in the village, we conducted a survey documenting the role of plant resources in people subsistence [26]. The survey included 20 households selected at random.

Table 2 Criteria of variables considered for analyzing sociocultural and ecologic factors that influence management intensity

Free listing

For exploring the use preferences of the plants studied, we included different valuing criteria (utilitarian, symbolic, esthetic, and emotional) through the free listing technique [37, 38]. We interviewed 38 persons (22 men, 16 women, Table 1) [26], asking them to list plants used: (1) in ceremonies and offerings to Saints and dead people, (2) as food, (3) for health care [26], and (4) for satisfying basic needs, those considered indispensable to live. We estimated their cognitive prominence for each use type through the formula S = F/(N mP), where F is the frequency of each plant species, N the number of people interviewed, and mP the average position in which a plant was named [39]. The index was calculated with Flame v1.0 [40].

Vegetation sampling

In order to identify the places where the plant species studied are managed, and how abundant they are in forests and agroforestry systems (AFS), we sampled vegetation in 7 agricultural plots, 21 homegardens, and 5 AFS associated to sites of mescal production [26].

Selection of variables for the analyses

Socio-ecological and technological variables were selected based on our previous studies [11, 12], which were organized in three main data matrixes. One matrix was with information on indicators of social, cultural, and economic importance of the species studied. A second matrix had information on biological aspects (life cycle length, types of reproduction, growth patterns, among others) and on people’s perception about the availability and vulnerability of each species. The third matrix had information about management practices and management intensity. Information on qualitative variables were categorized assigning numeric values from lower to higher management intensity according to the complexity of strategies and practices, occurrence or not of human selection, and low to high number of persons involved in the management type, among others. We also categorized from lower to higher social, cultural, and economic importance, considering that the higher their importance, the higher the potential risk associated to human pressure. Finally, we categorized from lower to higher vulnerability associated with biological characters considering the impact of human extraction of resources on individual plants and populations (Table 2). We averaged values of different categories, and in variables involving counting or binary records, we calculated the proportions of the states (Table 2). We excluded highly correlated variables, selecting those better representing the importance and management intensity of the plant species analyzed (Table 2).

Data analyses

In order to characterize the use and management of plants with edible, medicinal, and ceremonial uses, we used our previous data about all the species recorded [26] and the in-depth interviews for the selected species. We analyzed these data by cross-checking information and using descriptive statistics. We conducted principal component analysis (PCA) with data about management of all the native and naturalized species in order to classify management intensity among use types. The scores of the first principal component were used as management intensity index [12, 15]. We performed Kruskal-Wallis tests in order to identify differences among scores of management intensity of plants with ceremonial, edible, and medicinal uses. With the data of selected species, we performed two PCA per use type, one with the variables of the management type matrix and the other with the sociocultural and ecological variables (Table 2); the scores were used as an index of management intensity and a risk index, respectively. The relationships between risk and management intensity were analyzed through regression analyses.

Partial canonical analyses were performed using canonical correspondence analysis (CCA) per use type, in order to identify which fraction of the variation in plant management is explained by sociocultural and ecological factors and the effect of the interaction between the two types of variables [12, 15, 16, 41]. For each analysis, we used three matrices, a Y matrix containing the response management variables, an X matrix with sociocultural explanatory variables, and a W matrix of the ecological explanatory variables. Through this method, we conducted partial analyses with different combinations of the matrixes of the explanatory variables: (1) CCA for matrix Y, (2) CCA with matrix Y explained by matrix X, (3) CCA with matrix Y explained by matrix W, and (4) CCA with matrix Y explained by the combined effect of the W + X matrices. The total constrained eigenvalue of each analysis was tallied to evaluate how much the management intensity matrix is explained by the sociocultural and ecological variables.

For each analysis, the sum of all canonical eigenvalues divided by the sum of all canonical eigenvalues of the CA with management data allowed calculating the corresponding fraction of variation explained by the analysis. The significance of the models was estimated by permutation tests. All analyses were conducted through the R software [42]. In the PCA and CCA analyses of medicinal plants, Agave potatorum and Quercus acutifolia were excluded since these species were outliers.

Results

Ceremonial plants

We recorded 128 ceremonial plant species, 78 of them native or naturalized (Table 3); 22 species are considered by people to be basic for their life (Table 4). We recorded 48 species used for altars at homes for venerating Saints (Fig. 2). The most valuable species are those appreciated for their beauty and odor of their flowers (Table 5). As part of the communitarian celebrations, local people use 33 species as incense-like resin called copal (Bursera spp.), in the religious processions (Litsea glaucescens), and as ornaments offered to Saints (orchids, Dasylirion serratifolium, Tillandsia grandis, Beaucarnea stricta) (Fig. 2). Brahea spp. leaves blessed are used for weaving shoes for dead people. The copal resin is used in praying, altars, processions, masses, and funerary rites and for protecting against “aires” (negative feelings, dangerous situations that may cause illnesses or accidents).

Table 3 Management of native and naturalized species of Santa María Ixcatlán by use type

Table 4 Native and naturalized plants of Santa María Ixcatlán with ceremonial, edible, and medicinal use

Fig. 2

Ceremonial, edible, and medicinal plants of Santa María Ixcatlán community. a Offering “adornment” of Brahea dulcis leaves, Euchile karwinskii flowers, Litsea glaucescens branches, and wasp honeycombs to San Ramón in Palm Sunday celebration. b Beaucarnea stricta arch to welcome the Saints in “posadas” celebrations. c Tillandsia grandis and Dasylirion serratifolium arch to welcome the Saints in “posadas” celebrations. d Bursera biflora resin. e Porophyllum ruderale subsp. macrocephalum cultivated in a homegarden. f Dysphania ambrosioides transplanted in a bucket to protect it from animals and to facilitate its care. g Tender branches of Amaranthus hybridus collected during agricultural labor.; h Boiled floral buds of Dasylirion serratifolium. i Grindelia inuloides plant cultivated in a homegarden. j Red Ricinus communis variety managed in a homegarden. k White Ricinus communis variety. l Bunch of Tagetes lucida dry plants

Table 5 Sociocultural parameters estimated for species considered in in-depth studies

Commercialization of ceremonial wild plants is uncommon, except the resin of Bursera spp., which is used for celebrating the day of the dead. People used to share part of flowers collected in forests or managed in homegardens (mainly Chiococca alba, Lindleya mespiloides, orchids, and copal resin (Bursera spp.)) and give them as presents to people who organize the communitarian feasts. Dasylirion serratifolium, Beaucarnea stricta, and Tillandsia grandis are involved in practices of reciprocity among most of the local households in communitarian feasts (Table 5).

Ornamenting of altars is mostly attended with plants cultivated in homegardens. Due to the scarcity of copal and other plants used in ceremonies, people practice gathering them in different sites throughout their territory (Tables 5 and 6). In addition, we recorded storing of copal resin for use throughout the year (Table 5).

Table 6 Meaningful consultant’s commentaries about the use, abundance, and their motives to manage plants

Several species considered scarce in the wild are, however, enough for satisfying the needs of the community; this is particularly the case of Tillandsia grandis (Table 5). The availability of useful plants depends on seasonality, annual rainfall, and incidence of pests (Tables 5 and 6).

Gathering was the only practice for 28 ornamental species (Table 3); species used for ornamenting the altars are gathered by women in areas close to the village, but plants used in communitarian celebrations, as well as the resin of Bursera spp., are carried out by men (Table 5). Journeys for gathering these products may take several hours or days and are considered dangerous activities, particularly those to obtain Beaucarnea stricta, T. grandis, and Burmannia biflora (Table 6). For the extraction of these plants, several techniques are common to prevent damage, such as leaving stems and main branches of the most valuable species (orchids, B. biflora, B. stricta, C. alba, and L. glaucescens). These techniques favor survival and resprouting of plants (Table 6). In total, 22 species that germinate and become spontaneously established in AFS are tolerated and their abundance enhanced, by leaving plants producing seeds or deliberately dispersing seeds in sites propitious for their growth (Tables 3 and 7). About 38 species receive special care such as irrigation, addition of organic matter, control of pests, and removal of competitors (Tables 3 and 7). Transplanting of juvenile plants of 26 species and propagation of 19 species is conducted with the purpose of having them closer to homes (mainly homegardens) in order to enjoy their beauty, having available their flowers, satisfying their curiosity to know how plants grow, and experimenting horticultural practices (Tables 3 and 6). We recorded experiments of in situ vegetative propagation of B. biflora and transplanting of several species of orchids and Bromeliaceae species (Tables 6 and 7). We in addition documented reasons why local people do not practice management. They consider unviable planting plants that are abundant or have special requirements and low probability of survival or those for whom they do not have information about plants’ requirements to survive and grow (Table 6) or when people have limitations of space for maintaining plants.

Table 7 Ecological and management parameters estimated for species considered in in-depth studies

Selective harvesting of plants based on use quality of their parts and absence of signs of herbivory are criteria for gathering most species documented. Although local people recognize at least five species with intraspecific varieties (identified according to flower color and forms), their use and management are indistinct (Tables 5 and 7). Except for Tagetes erecta, in which people select seeds for cultivation, and Cosmos bipinnatus, a species commonly producing violaceus ligula, people select the scarcer variety with white ligula.

Local regulations forbid extraction of plants for commercialization out of the village and establish restrictions in using some plants in communitarian celebrations (Table 7).

Edible plants

We recorded 138 plant species used as food, 80 of them being wild and naturalized species and 20 considered as “basic” (Tables 3 and 4). The most valuable species are Amaranthus hybridus, Porophyllum spp., Opuntia lasiacantha, Dysphania ambrosioides, Dasylirion serratifolium, Peperomia quadrifolia, and Physalis philadelphica, which are consumed by more than 90% of households from 1 to 10 times per season (Fig. 2, Table 5). About 40 species are occasionally consumed where they are gathered and rarely carried to homes. These are the cases of Chrysactinia mexicana and Cyrtocarpa procera. Other 30 species are consumed occasionally, but it is considered that most of them were highly consumed in the past; these are the cases of Chenopodium spp., Anoda cristata, Nasturtium officinale, Agave kerchovei, and A. potatorum. Consumption of these plants has decreased due to higher presence of cultivated and processed food (Table 6). Other species are consumed occasionally by few households, as is the case of L. glaucescens which is used as a condiment or Tagetes lucida, Lippia sp., and Turnera diffusa, which in the past were commonly used as infusions and now were substituted by coffee.

Commercialization of managed weedy plants is allowed, and the most common is the green tomato P. philadelphica. Others occasionally commercialized are O. lasiacantha and cooked A. potatorum (Table 5). P. philadelphica, C. mexicana, Porophyllum spp., and D. ambrosioides are interchanged in local stores (Table 5). Local people share with relatives and friends part of the plants gathered or harvested (Tables 5 and 6). These are the cases of D. serratifolium, P. quadrifolia, C. mexicana, P. philadelphica, D. ambrosioides, Opuntia spp., Porophyllum spp., A. potatorum, and A. hybridus.

Most edible plant species are considered abundant (Table 7), but such abundance is associated with care during extraction or the management in crop fields and homegardens as it was documented for P. philadelphica (Table 6). Most species are considered vulnerable to environmental factors and pests (Table 7), and some of the most appreciated resources are perceived to be scarce. This is the case of D. serratifolium, which due to the scarcity of its inflorescences people stopped consuming them (Table 6).

Gathering of edible plants is generally carried out while practicing other activities—by men when plants are gathered from the forest and by women and children when plants are harvested from agricultural fields and homegardens. Gathering is the only practice for 30 species, which are immediately consumed (Table 3). Practices of care during gathering of useful parts aim to procuring plant survival, and these are carried out only in gathered plants and those under management (Tables 6 and 7). In order to ensure further availability, the abundance of seven species is enhanced by letting individual plants produce seeds and deliberately dispersing their seeds in appropriate places (Tables 3 and 7). At least 40 species are let standing in AFS, with the purpose of ensuring their availability (Tables 3, 6, and 7). For ensuring productivity and quality of products for consumption, 28 species receive irrigation, addition of organic matter, and exclusion from domestic animals (Tables 3 and 7). Nearly 20 species of weedy plants (among them P. philadelphica and D. ambrosioides) are transplanted into homegardens where people consider the plants to have better conditions for growing (Table 3). Other species occurring in the wild are transplanted to homegardens with the purpose of having them closer and to consume them for longer time (Porophyllum spp.) or for ornamental purposes (Mammillaria spp. and Lantana spp.) (Fig. 2, Tables 3 and 7). We recorded the deliberate propagation of 11 species through seeds and vegetative parts (Tables 3 and 6), as food (Porophyllum spp., D. ambrosioides, P. philadelphica, Opuntia spp.), for ornamental purposes, and for satisfying curiosity (Oxalis aff. nelsoni). Other species have started to be propagated, as is the case of A. potatorum, and others have had failed attempts (L. glaucescens, C. mexicana).

From seven species whose varieties are distinguished by morphology, flavor, and odor, we identified human selection in five of them; the preferred variants are tolerated, protected, or enhanced. For D. ambrosioides, O. lasiacantha, and P. philadelphica, we documented human selection favoring plants providing seeds or cladodes for cultivation (Tables 6 and 7).

Local customs and regulations forbid gathering wild edible plants for commercializing them out of the village, with the only exception of Brahea dulcis and A. potatorum, which are edible, but parts commercialized are destined for other uses. In the Communitarian Assemblies, we recorded discussions among local people and the Biosphere Reserve authorities for regulating and planning the use of A. potatorum, B. dulcis, and D. serratifolium. In the case of L. glaucescens, the Assembly decided to allow external people to extract it, but the permit stopped.

Medicinal plants

We recorded 219 medicinal plant species, 178 of them being native and naturalized, and 22 considered “basic plants” (Tables 3 and 4). Currently, 85% of households use medicinal plants, generally complementing their healing treatment with massages, cupping therapy, and treatments by the national system of health through the local health center and private physicians. Women heads of families mainly make the decision on the appropriate treatment, while for traditional treatments, it is common to consult the relatives with more experience or one of the four traditional physicians in the village. The native plant species are mainly used for attending accidents (hurts, cuttings, twists, fractures, bites of poisonous animals), respiratory and stomach infections, pains, child tantrums, angers, “susto” (frightens), illnesses caused by “aires,” monitoring of pregnancy, and recovering of childbirth. Medicinal plants may be ingested and placed in affected body zones, steam baths, and “limpias” (ceremonies for cleaning the body and spirit).

Almost all medicinal plants are collected when they are needed, but for some of them (Lippia oaxacana, T. lucida, T. diffusa, Chrysactinia mexicana, Ambrosia psilostachya), people used to store dry materials or ask somebody else to get the needed plant (Fig. 2, Table 5).

No commercialization of medicinal plants was recorded; most medicinal plants are shared. Some plants are interchanged for plants with other uses, for instance, Quercus acutifolia, used and commercialized as fuelwood, and A. potatorum used in mescal production (Table 5). Except C. mexicana and Pittocaulon praecox, all medicinal plants are considered abundant, but dryness and frosts are factors affecting their availability (Table 7).

Gathering of wild medicinal plants is conducted by men and women; men gather plants occurring far away and women those occurring in homegardens. Gathering is the most common practice for all medicinal plants, and the only practice for 81 species (Tables 3 and 4). Practices for preventing damage of gathered plants are common on the most valuable plants (Ambrosia psilostachya, Clinopodium mexicanum, C. mexicana, L. oaxacana, T. diffusa, T. lucida, Ageratina mairetiana, Grindelia inuloides) (Table 7, Fig. 2). In AFS, 79 medicinal plants are let standing during vegetation clearing, as well as the 65 species distributed in homegardens (Table 3). Among them, Ricinus communis, Marrubium vulgare, and Malva parviflora are submitted to practices for controlling their abundance through weeding, similarly to 37 other species (Table 1). We recorded 31 species receiving care such as removal of competitors, addition of organic matter, and irrigation (Table 3). Abundance of nine species is enhanced by leaving plants to produce seeds or by spreading the seeds in appropriate sites for their germination and growth (Tables 6 and 7). We also documented the transplanting of 25 species, 8 of them from forests to homegardens (G. inuloides, P. praecox, and A. mairetiana) for their medicinal and ornamental uses (Tables 3 and 7). In addition, we recorded the propagation by seeds of 12 species, 2 of them mainly motivated to have them available when needed (G. inuloides and Matelea purpusii) (Fig. 2, Tables 3, 6, and 7). We documented failed attempts of transplanting and propagating six species, among them A. mairetiana, A. psilostachya, G. inuloides, and L. oaxacana (Table 6). Reasons for not transplanting individual plants from forests to homegardens were the following: lack of information about plant requirements and the supposition or experience that in changing habitat, plants do not survive and that using appropriate techniques of extraction or storing strategies are enough for ensuring their availability (Table 6). We recorded the recognition of varieties of three species, but people make differential use and management only of R. communis (Fig. 2, Table 7).

Management intensity and risk

Management intensity of edible, ceremonial, and medicinal plants studied is explained mainly by practices and communitarian regulations in the first component and by their presence in AFS in the second component (Fig. 3). Management intensity among use types was significantly different (KW X ² = 9.9, df = 2, p = 0.007). Edible plants had the highest management intensity, most of them managed in AFS involving human selection, while most species used for ceremonial and medicinal purposes are gathered from forests and protected through communitarian regulations (Fig. 3).

Fig. 3

Management of ceremonial, edible, and medicinal plants according to principal component analysis (PCA). Edible plants tended to be managed most intensely, since ceremonial and medicinal plants are less intensely managed. Variation in spatial arrangement is mainly explained in the first principal component by management practices and collective regulations = (eigenvalues 0.631, −0.133 respectively) and by collective regulations and management in AFS in the second principal component (eigenvalues 0.986, −0.007 respectively)

In plants with ceremonial use, the regression analysis indicates no relation among management intensity and risk indexes (R ² = 0.003, p = 0.819) (Fig. 4, Table 8). Partial CCA explains 95% of the variation of management, significantly explained by the intersection of sociocultural and ecological factors (14%) (Fig. 5a, Table 9). In plants with intermediate management intensity (Table 8), management regulated by collective rules occurs in plants basic for life and exclusively with sexual reproduction. These are the cases of L. glaucescens, D. serratifolium, B. stricta, and T. grandis (Fig. 5b, Table 9). Plants intensively managed (Table 8) in AFS are those providing several parts or the whole plant as resources, having asexual reproduction, and being abundant, like Tillandsia usneoides, or that are scarce, like Laelia albida, Euchile karwinskii, Epidendrum radioferens, and Rhynchostele maculata (Fig. 5b, Table 9).

Fig. 4

Relation between management intensity and risk. Regression analysis of the management intensity index as a function of the risk index due to sociocultural and ecological factors. Indexes were calculated as the scores of the first principal components performed by use type

Table 8 Management intensity and risk indexes of ceremonial, edible, and medicinal plants

Fig. 5

a–f Relative influence of risk due to sociocultural and ecological factors in plant management. Schemes show the relative influence of sociocultural and ecological factors and their interactions on management of ceremonial, edible, and medicinal plants based on partitioned canonical correspondence analyses (CCA) performed by type use. Ordination planes of CCA performed by type use show how species (numbers) and management variables (red words) are influenced by sociocultural and ecological variables (blue arrows)

Table 9 Significance of explanatory variables on management associated with the canonical correspondence analyses (CCA) for ceremonial, edible, and medicinal plants

In edible plants, the regression analysis indicates that there is a highly significant relation among management intensity and risk indexes (R ² = 0.48, p = 0.0007) (Fig. 4, Table 8). Partial CCA explained 92% of the variation of management, significantly explained by sociocultural factors (60%) and the intersection of sociocultural and ecological factors (14%) (Fig. 5c, Table 9). Plants with the lowest management intensity (Table 8) are those protected through collective regulations, like D. serratifolium and L. glaucescens, which are shared among relatives and used in communitarian ceremonies, as well as in those gathered and perceived to be scarce, like N. officinale, P. quadrifolia, and C. mexicana (Fig. 5d, Table 9). Plants with the highest management intensity like P. philadelphica, O. lasiacantha, A. hybridus, and D. ambrosioides (Table 8) are those with different varieties, under human selection through several types of practices, considered to be abundant, shared among members of the community, and obtained through different strategies, among them interchange and commercialization (Fig. 5d, Table 9).

In medicinal plants, the regression analysis indicates no significant relation among management intensity and risk (R ² = 0.19, p = 0.074) (Fig. 4, Table 8). Partial CCA explains 79% of the variation of management, mainly by sociocultural factors (46%) (Fig. 5e, Table 9). Plants with low risk like Pinaropappus roseus and Gymnosperma glutinosum are directly consumed by people who gather them and, along with Marrubium vulgare, occur in most of the homegardens and crop fields sampled. These plants are only gathered and let standing (Fig. 5e, Table 9). Management through collective regulations determining care during gathering was documented on C. mexicana, L. oaxacana, and A. psilostachya, with relatively high management intensity and risk (Table 8) associated to their value in reciprocity, use frequency, strategies for obtaining them, and the perception of vulnerability to environmental factors (Fig. 5e, Table 9).

Discussion

Management intensity

As we hypothesized, the gradient of management intensity is higher in edible plants, which are managed through different types of practices in AFS, more frequently, and involving human selection. Contrarily, plants used for ceremonies and as medicine are mostly tolerated or simply gathered. These general trends are similar to other reports for edible plants studied in the region which are managed with more complex practices than other useful plant species [6, 22, 43,44,45].

Collective regulations importantly influence the management intensity, but differently to that proposed for a general model of management intensity [46], the highest complexity of such regulations was observed in plants that are only gathered in areas of common access, such as the most valuable medicinal and ceremonial plants. For the contrary, edible species are mainly managed in AFS, where managers have higher control of access to plant resources. These differences reflect the trade-offs in managing natural resources of common use, as it has been discussed previously for edible plants of the region and for several resources of common use [13, 47]. In the case studied, this pattern is illustrated by the fact that collective regulations appear to be effective for plants culturally valuable but not for plant resources with high economic value. The inefficacy of collective regulations for plants like A. potatorum appears to be due to the lack of rules coherent with the weakening of local institutions for ordering the use of a resource of increasing demand [28]. The failure of regulations for achieving a balance between cost and benefit of its management has enhanced private management in sites for exclusive use. But also, external actors have promoted the reforestation in areas of common use [16, 26], actions that should be accompanied by strengthening the effectiveness of local institutions.

The selective management characterizes the high management intensity in plants under the three types of use, according to flavors, colors, and sizes of plants or plant parts, which indicates ongoing processes of domestication, which may have advanced expressions like in P. philadelphica or, rather incipient, like in O. lasiacantha and R. communis [5, 15, 48]. The indistinct use of species with varieties recognized such as Chenopodium berlandieri suggests that there exists a process of decreasing of consumption and interest in human selection, differently to what is happening with A. potatorum, whose propagation starts with gathering seeds from several sites where agaves are recognized to have differential productivity. Such contrasting situations indicate the dynamic aspect of the processes of domestication, in which changes in values, the introduction of new food or products, and changes in markets, among other factors, have direct effects on management of plant resources.

Sociocultural and ecological factors and management intensity

As expected, management intensity in edible plants is associated with their high risk to disappear, compared to the pattern found in medicinal and ceremonial plants. However, in the analysis about how sociocultural and ecological factors influence on variation of management, we found a high variety of interactions. The economic value, which has been considered one of the most important factors motivating plant management [12, 13], was not significant in any of the systems studied. This result can be due to the low proportion of plant species that are interchanged through barter and commercialization, as well as the isolation of the community, a factor recognized to be significant for introducing non-timber forest products in markets [49]. Nevertheless, among the more intensely managed species, we recorded some whose management represents expenses (P. philadelphica) or their commercialization represents main incomes for households (B. dulcis and A. potatorum), which indicates a relation between management intensity and the economic role of plants in subsistence [46].

Consumption was only significant in ceremonial plants, explaining the gradient of management intensity according to the feasibility of propagation, which may be difficult in plants highly used (Tillandsia grandis and Chiococca alba), compared with species lowly used but having vegetative propagation that makes easy their management (Plumeria rubra, Dahlia sp.).

The perception of abundance and its interaction with cultural value and management feasibility was a meaningful factor for explaining gradients of management intensity of ceremonial and edible plants. For instance, Peperomia quadrifolia, a highly valued species as food, is only gathered following the principle of leaving part of the plant in order that it continues propagating, since it is scarce, but it has very specific habitat requirements. Tillandsia usneoides is intensely managed in homegardens, although it is abundant in forests, since it is easily propagated; P. philadelphica, a basic species, is considered abundant because of the effect of intense management. The examples suggest that the balance between the invested effort in management and benefits obtained according to needs is an important factor for making decisions [50].

The interchange of plant species related to reciprocity was significant for explaining variation of management of edible and medicinal plants. In both use types, the interchanged plants are the most valuable species. In the case of edible plants, our analysis explained the variation in the extremes of the gradient of management intensity; plants of difficult access are managed by collective regulations, and those intensely managed are in AFS. Among the medicinal plants, our analysis identified those species managed following collective regulations and stored, but in the case of emergency, people practice interchange. Importance of this factor coincides with other reports analyzing management of AFS, where it has been found that the social relations of local people are a main factor influencing biodiversity in these systems since plant species are introduced to the systems and because numerous species are maintained to be shared [44, 51, 52]. The study of these relations is covering importance for understanding management of AFS. We suggest that these may be considered for understanding management of species, since these are expressions of affect, respect, and solidarity, through which people construct social nets of mutual support that are part of the cultural identity and strategies for facing risks in their subsistence [28, 53,54,55].

In edible and medicinal plants, the interest for obtaining resources through sociocultural strategies influences the management intensity. Strategies like mobility for increasing the harvesting area and gathering for storing, among other practices, may determine some degree of risk on plants, which are placed through collective regulations and management practices.

The cognitive prominence by use type may be an indicator of resource quality, but this was no significant factor in our analysis. The perception about the quality of resources arose as a factor related to the place where plants grow. This aspect enhances plant management in AFS [51, 53, 56], which was documented with P. philadelphica and O. lasiacantha. In wild plants, this perception influences the communitarian regulations, as was recorded for Bursera biflora, whose resin is naturally produced and is preferred over that produced after cutting the stem [57].

Management motives

Interactions between cultural importance, perception of scarcity, and feasibility of management suggest that several factors contribute to motivate management techniques, which was confirmed through the in-depth interviews qualitatively analyzed (Table 6). The worries expressed by people about the future availability of plants with ceremonial, edible, and medicinal uses suggest that uncertainty is a main motive determining management. Such worries can be explained because of the fact that in the analysis of cognitive prominence of plants considered as basic, people mentioned plants with the three uses, which means that they are considered indispensable elements of subsistence. This fact coincides with the general hypothesis of control of uncertainty as a main motive of management for ensuring resource availability [12]. However, the differences documented in types of management strategies and their intensity among use types may be due to the differential operation of other motives, as we hypothesized in this study.

Making easier the access to plants was an important motivation for transplanting or cultivating wild and weedy plants for the three use types analyzed. For edible and medicinal plants managed in homegardens, the main management motive is to have them close to home [22, 45, 58, 59]. And this is why people transplant and propagate plants that are naturally abundant into other ecosystems (e.g., Porophyllum spp.), protect with different labors the maintenance of D. ambrosioides, or tolerate weedy and ruderal plants like Malva parviflora and Barkleyanthus salicifolius. In ceremonial plants, the need to have flowers easily accessible is also an important motive for transplanting and propagating plants (for instance orchids and Dahlia spp.), but this motive is associated with the purpose of embellishing an area (60% of the ceremonial plant species are considered ornamental), a quality highly valued by the Ixcatec [6, 23, 24, 26, 52, 53, 60].

The symbolic value associated with plants and animals has been proposed relevant for making management decisions [8, 61, 62]. It is particularly important in plants used for ceremonies, like B. biflora [21], L. glaucescens, Euchile karwinskii, and other orchids, and may influence the perception of importance of being careful during their gathering and as a motive for propagation.

Our study suggests that ethical principles are important for regulating use and management in order to prevent damage to plants (Table 6), recognizing them as living beings with “the right to exist.” This is expressed in numerous tolerated plants with low cultural and economic value or even those without use [26]. Such criteria interact with others particularly in weedy and ruderal plants, with edible and/or medicinal uses such as A. hybridus, M. parvifolia, R. communis, and M. vulgare in which the perception of their potential as invasive plants determines a balance of efforts for maintaining and removing them [23, 26]. Other motives identified in the maintenance of homegardens [59, 63, 64], such as experimental curiosity, were mentioned by people in order to develop continual innovation in management techniques.

This study aspires to contribute to understand the multifactorial influence of social and ecological aspects on decisions for managing plant resources [26, 65] with different purposes. It is clear from this and other studies that management of edible resources are mainly influenced by factors associated with availability of food or means for obtaining it, whereas medicinal plants, which are consumed less frequently, involve quality rather than quantity, and ritual plants involve symbolic aspects. The three groups of plants involve management, but the intensity required in each case varies. However, some plant resources are particularly valuable because of their multi-functionality [65]; these are species that in this study are called “basic” by local people and are outstandingly important resources receiving the greatest management intensity.

Ixcatlán is the only site in the world where the Ixcatec language is spoken, and only 15 persons speak this language. Our ethnobiological studies look for contributing to efforts of a linguistic group working in favor of conserving and recovering this language. Information recovered in this study includes audio and image systems that have helped to produce educative materials useful for teachers in schools for teaching the Ixcatec language. In addition, the information about resource use, and particularly about management techniques, are helpful for planning actions for ordination, conservation, and recovering forest areas and resources, as well as agroforestry systems, which are part of the biocultural heritage of the Ixcatec for the Ixcatec people, people of the Biosphere Reserve Tehuacán-Cuicatlán, and the Mexican people.

Conclusions

For managing edible, medicinal, and ceremonial plants, the Ixcatec have developed a broad variety of practices and regulations. Management strategies are motivated as responses to uncertainty in their availability and other motivations like embellishing an area, satisfying customs, emotions, and curiosity operating simultaneously in the decisions. Such a variety of factors is associated to a well-being premise combining both material and spiritual needs, as well as maintaining social relations and traditions that are part of the Ixcatec cultural identity [27, 50].

The highest management intensity in economic valuable species, mainly edible plants, indicates that uncertainty is significant in indispensable plants for satisfying subsistence needs. However, species of medicinal and ceremonial uses and some edible plants are managed through diverse management practices without response to abundance perception. These facts make necessary to analyze more deeply how needs, worries, external pressures, and management responses are articulated with subsistence strategies of households and communities in these processes, as well as the role of systems of ethical values and traditional regulation institutions.

Our study confirms the importance of sociocultural factors associated with use and interchange of resources, and ecological processes influencing the vulnerability and feasibility of managing them [12, 16, 17]. The multiple criteria may be useful to analyze conditions guiding early management motives that modeled the biocultural heritage of peoples of the Tehuacán Valley.