Lecture 7. Quantitative methods: one-hectare plots

Summary

An important methodological development in ethnobotany in the 1990s has been the increased use of quantitative methods. Oliver Philipps and many other colleagues have demonstrated the use of computer-assisted statistical analysis to understand the cultural importance, domestication, use, and variation in traditional knowledge of plant resources. Ghillean Prance and his collaborators innovated the use of one-hectare plots for ethnobotanical studies, a technique borrowed from plant ecological studies and now widely applied by ethnobotanists. Charles Peters has stressed the importance of going beyond recording of names and uses of plants to focus on questions of management and sustainability. Stanford Zent complements this view, by encouraging an emphasis on the behavorial aspects of the relationship between people and their natural resources. Studies of ethnobiological classification and cognitive anthropology inspired other approaches that yield quantitative data, including sorting exercises, tree trails, specimen identification tasks. Some of these techniques – and the software used to analyze the results – will be demonstrated during practical exercises.

Definitions

Emic world view, "the cognitive world of the observed", includes perceptions, nomenclature, classifications, knowledge, beliefs, rules and ethics as defined by a native of the local cultural community. Emic knowledge allows people to behave in a culturally appropriate and meaningful ways in different social contexts. An emic approach to culture seeks to describe and explain cultural patterns in terms of local categories and semantic structures.

Etic world view, "the cognitive world of the observer", refers to the perspective of an outsider – for example, a researcher – whose ideas and understandings are derived from a distinct cultural experience. Etic-oriented researchers describe and explain culture based on their own observations of the behavior (including verbal behavior) of the study population and according to the semantic framework provided by science.

Defintions taken from S. Zent 1996. Behavorial Orientations towards ethnobotanical quantification.

Example:

The use of one hectare plots in ethnobotany draws upon a well-established ecological approach. The basic methods and measurements have been developed various projects, including the United States Man and the Biosphere and Smithsonian Institution (MAB/SI) program on long-term monitoring of biological diversity in tropical areas. The MAB/SI teams select a 25-hectare zone and divide it into 25 1-hectare plots. Each 1-hectare plot is then divided into 25 quadrats, each measuring 20 x 20 m, which are further subdivided into 16 subquadrats of 5 x 5 m. Individual trees are tagged with a unique number that includes the reference of the plot, quadrat and subquadrat in which they are found. The diameter at breast height (DBH) is measured, a voucher specimen is taken for species identification, and then the tree is mapped as shown below.

1.Pithecellobium latifolium (Legumenosae-Mim) 2. Brosimum lactescens (Moraceae)

3. Scheelea princeps (Palmae) 4. Brosimum lactescens (Moraceae)

5. Brosimum lactescens (Moraceae) 6. Scheelea princeps (Palmae)

7. Brosimum lactescens (Moraceae) 8. Scheelea princeps (Palmae)

9. Brosimum lactescens (Moraceae) 10. Scheelea princeps (Palmae)

11. Brosimum lactescens (Moraceae) 12. Heisteria nitida (Olacaceae)

13. Brosimum lactescens (Moraceae) 14. Brosimum lactescens (Moraceae)

16. Scheelea princeps (Palmae) 17. Brosimum lactescens (Moraceae)

18. Brosimum lactescens (Moraceae) 19. Cupania inerea (Sapindaceae)

20. Salacia –I (Hippocrateaceae) 21. Salacia –I (Hippocrateaceae)

It is common practice to make the following measurements for trees and woody vines in plots, as described in Dallmeier 1992; different methods are used for herbs, shrubs, grasses and other small plant. Density is the measurement most widely mentioned in ethnobotanical studies:

Basal area = area occupied at breast height, calculated from a measurement of the diameter at breast height (1.4 meters from the ground); this is only one way of measuring the size of trees, and can be complemented by measurements of height, crown size and other parameters.

Density = number of individuals of a species in the plot, expressed as "x" per hectare

Relative density = number of individuals of a species, divided by the total number of individuals of all species, and multiplied by100

Dominance = the basal area of a single species

Relative dominance = combined basal area of a single species, divided by the total basal area of all species, and multiplied by100

Frequency = numbers of quadrats in which a species is found

Relative frequency = frequency of one species, divided by the sum of all frequencies, and multiplied by100

Diversity = number of species (and/or genera) in one botanical family

Relative diversity = number of species in one family, divided by the total number of species, and multiplied by100

The importance value (IVI), calculated by adding the relative density, relative dominance and relative frequency, is not widely considered to be a good measure of the ecological importance of a botanical resource.

Using the above example of a 20 x 20 m quadrat, calculate:

• the density of Brosimum lactescens in the quadrat, and extrapolate the density in a one hectare plot.

• the frequency of Brosimum lactescens, based on an estimate of its occurrence in the 20 subquadrats that subdivide the quadrat.

References:

Casas, A. & J. Caballero. 1996. Traditional management and morphological variation in Leucaena esculenta ssp. esculenta. Economic Botany 50(2):167-181.

Dallmeier, F. (editor). 1992. Long-term monitoring of biological diversity in tropical forest areas: methods for establishment and inventory of permanent plots. MAB Digest 11. Paris, UNESCO.

LaFrankie, J.V. 1994. Population dynamics of some tropical trees that yield non-timber forest products. Economic Botany 48:301-309.

Peters, C.M. 1996. Beyond nomenclature and use: a review of ecological methods for ethnobotanists. Pages 241 – 276 in Alexiades, M.N., editor, Selected Guidelines for Ethnobotanical Research: A Field Manual. New York, The New York Botanical Garden.

Phillips, O.L. 1996. Some quantitative methods for analyzing ethnobotanical knowledge. Pages 171-197 in Alexiades, M.N., editor, Selected Guidelines for Ethnobotanical Research: A Field Manual. New York, The New York Botanical Garden.

Phillips, O.L. and Alwyn H. Gentry. 1993. The useful plants of Tambopata, Perú. I: Statistical hypotheses in quantitative ethnobotany. Economic Botany 47: 33- 43.

Phillips, O.L. and Alwyn H. Gentry. 1993. The useful plants of Tambopata II: Further statistical tests of hypotheses in quantitative ethnobotany. Economic Botany 47:15-32

Prance, G.T., W. Balée, B.M. Boom and R.L. Carneiro. 1987. Quantitative Ethnobotany and the Case for Conservation in Amazonia. Conservation Biology 1:296 - 310.

Voeks, R.A . 1996. Tropical forest healers and habitat preference. Economic Botany 50:381-400.

Zent, S. 1996. Behavorial orientations towards ethnobotanical quantification. Pages 199 – 239 in Alexiades, M.N., editor, Selected Guidelines for Ethnobotanical Research: A Field Manual. New York, The New York Botanical Garden.

Questions for discussion:

What are the advantages and options of using qualitative versus quantitative approaches to address the following issues in ethnobotany:

• the contrasting knowledge, management and use of resources by women and men
• the importance of various ecological zones (or habitats) to a particular community

Perspective for discussion:

"Ethnobotany and plant ecology are natural partners, and their collaboration can contribute greatly to the study of people and plants. Coupling plant use information with quantitative data on the distribution, abundance and yield of different resources provides a useful new framework for addressing the question, How important is this species? Perhaps of even greater relevance given current realities, however, is that this integrated focus also allows the investigator to probe deeper into the questions, How quickly is this resource being used up? What can be done to prevent overexploitation? The conservation and rational use of the innumerable plant resources "discovered" by ethnobotanists over the last 100 years will inevitably require the collection of density and yield data. Although the fact is seldom mentioned, ethnobotanical research is really the first step toward effective resource management. The more ambitious the first step, the faster effective resource management can be achieved."

From Peters, C.M. 1996. Beyond nomenclature and use: a review of ecological methods for ethnobotanists. Page 271.

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