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Volume 71—1991

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Review of Sampling Techniques used in Studies of Grassland Plant Communities

Lisa Sorrells and Susan Glenn
Oklahoma Natural Heritage Inventory, Oklahoma Biological Survey
2001 Priestly Avenue, Norman, OK 73019-0543
Received: 1991 January 3

An annotated bibliography (1) was compiled on references pertaining to sampling methods for grassland and herbaceous communities. References from Science Citation Index, Biological Abstracts, selected textbooks, and current journals were included. All papers were in English.

This bibliography has 66 references arranged alphabetically by first author. With each citation are brief comments on sampling techniques used. Fourteen keywords, which pertain only to sampling techniques, were included to indicate the method(s) used. References were classified into the following five general sampling techniques: quadrat methods, transect methods, point methods, distance methods, and gradsect.

Sampling techniques which study the vegetation or environment of a limited and definitely circumscribed area, a quadrat or plot, were placed in the quadrat method category. These included several variations of size and shape of the quadrat. Those techniques which measured the vegetation occurring along a line or narrow belt were classed as transect methods. Distance methods include point-to-plant, angle order, point-centered-quarter, and nearest neighbor techniques, all of which involved the measurement of distance between plants. Inclined and vertical point techniques were included in the category of point methods. Transects that incorporated significant environmental gradients, selected to represent the environmental variability present in an area, were placed in the gradsects category.

Quadrat methods were the most widely used among the 66 references (Table 1). The quadrat method is for grassland analysis (2, 3). In general, the chief value of the quadrat method lay in the results obtained when quadrats of sufficient number to adequately sample the study area and of a size suitable to the character of the vegetation are used (2, 4, 5, 6). The size of the quadrat must be based on the approximate cover of vegetation (2). For example, Mosley, Buning, and Hironaka (7) found that dense vegetation required larger quadrats (50 x 50 cm). Hanson and Love (8) found that a 1-m2 area did not justify the additional time required. Van Dyne, Vogel, and Fisser (9) noted that quadrats 6 ft2 or larger included few species more than did 2-4 ft2 quadrats. Optimum plot size and shape may depend upon the distribution of the species measured (9). If several species with greatly varying plant sizes, distributions, and densities are to be measured, more than one quadrat size may be required (10). Data obtained from the use of quadrat methods were used to measure spatial pattern (11-14), to measure cover of vegetation (4, 5, 16), and to make quantitative analysis (5, 17). Quadrats were reliable samples of the true plant populations (18).

Transect methods were used to measure density and composition accurately (19) and were recommended by some authors as less time consuming than mapping in quadrats (3, 18, 20). Bauer (21) found that transect samples and quadrat samples indicate the actual percentage of cover with about equal accuracy when vegetation was of uniform size; with various vegetation sizes, transects indicated coverage with considerably more accuracy than quadrats.

The point method gave results agreeing with those of dry weight measures (22). When compared to quadrat and transect methods, points were more time consuming to obtain and gave less accurate results (8, 23). However, the point method was preferred over distance measures (24).

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Distance methods were generally less accurate than others. The point-centered-quarter method gave data that underestimated density and frequency (25, 26). Angle-order methods gave values that were approximately equal to transect values and were more accurate than the point-centered-quarter or nearest-neighbor methods (25).

Gradsects gave a representative floristic sample (22), and when compared to the transect methods, gradsects were preferred (28).

Most of the 66 references in this bibliography are post-1940 (see Fig. 1) Methodology papers dominate the early papers, with a trend later toward applications. The selection of an appropriate sampling procedure should follow directly from considerations of the objectives of the study (25). Sampling decisions in population and community ecology are dependent on context and should be consistent with the objectives of an investigation, and the methodology must be capable of providing data that can best answer the proposed question (29).

The complete annotated grassland bibliography is available from the authors.

ACKNOWLEDGMENTS

We thank Scott Collins, Daniel Sorrells, and Ian Butler for their support and contributions, and the Oklahoma Natural Heritage Inventory and the Biological Survey for financial support.

REFERENCES

1.   Sorrells, L.R. and Glenn, S.M., Annotated Bibliography of Techniques for Sampling Grassland Plant Communities. Unpublished Report, Oklahoma Biological Survey, Norman, Ok (1990).

2.   Gleason, H.A., Some Applications of the Quadrat Method. Bull Torrey Bot. Club 47, 21-33 (1920).

3.   Arrhenius, 0., A New Method for the Analysis of Plant Communities. J. Ecol. 10,185-199 (1922).

4.   Costello, F. and Klipple, G.E., Sampling Intensity in Vegetation Surveys Made by the Square-Foot Density Method. J. Am. Soc. Agron. 31, 801- 810 (1939).

5.   Horton, J.S., The Sample Plot as a Method of Quantitative Analysis of Chaparral Vegetation in Southern California. Ecology 22, 457- 468 (1941).

6.   Pielou, E.C., The Effect of Quadrat Size on the Estimation of the Parameters of Neyman's and Thomas's Distributions. J. Ecol. 45, 31-47 (1957).

7.   Mosley, J.C., Bunting, S.C., and Hironaka, M., Quadrat and Sample Sizes for Frequency Sampling Mountain Meadow Vegetation. Great Basin Naturalist 49, 241-248 (1989).

8.   Hanson, H.C. and Love, L.D., Size of List Quadrat for Use in Determining Effects of Different Systems of Grazing Upon Agropyron smithii Mixed Prairie. J. Agric. Res. 41, 549 - 560 (1930).

9.   Van Dyne, G.M., Vogel, W.G., and Fisser, H.G., Influence of Small Plot Size and Shape on Range Herbage Production Estimates. Ecology 44, 746-759 (1963).

10.   Smith, S.D., Bunting, S.C., and Hironaka M., Evaluation of the Improvement in Sensitivity of Nested Frequency Plots to Vegetational Change by Summation. Great Basin Naturalist 47, 299-307 (1987).

11.   Cottam, G., Curtis, J.T., and Hale, B.W., Some Sampling Characteristics of a Population of Randomly Dispersed Individuals. Ecology 34, 741-757 (1953).

12.   Dale, M.R.T., and Blundon, D.J., Quadrat Variance Analysis and Pattern Development During Primary Succession. J. Veget. Sci. 1, 153-164 (1990).

13.   Dale, M.R.T., and Macisaac, D.A., New Methods for the Analysis of Spatial Pattern in Vegetation. J. Ecol. 77, 78-91 (1989).

14.   Nosek, J.N., Spatial Processes in a Grassland Community, III. Acta Bot. Hung. 32, 61 - 78 (1986).

15.   Daubenmire, R., A Canopy-Coverage

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Method of Vegetational Analysis. Northwest Sci. 33, 43-64 (1959).

16.   Molnar, E.N., and Nosek, J.N., Spatial Processes in Grassland Community, II. Acta Bot. Acad. Sci. Hung. 26, 375-388 (1980).

17.   Aberdeen, J.E.C., The Effect of Quadrat Size, Plant Size, and Plant Distribution on Frequency Estimates in Plant Ecology. Aust. J. Bot. 6, 47-58 (1957).

18.   Anderson, K.L., A Comparison of Line Transects and Permanent Quadrats in Evaluating Composition and Density of Pasture Vegetation of the Tall Prairie Grass Type.   J. Am. Soc. Agron. 34, 805-822 (1942).

19.   Parker, K.W., and Savage, D.A., Reliability of the Line Interception Method in Measuring Vegetation on the Southern Great Plains. J. Am. Soc. Agron. 36, 97-110 (1944).

20.   Hasel, A.A., Estimation of Vegetation Type Areas by Linear Measurement. J. For. 39, 34-40 (1941).

21.   Bauer, H.L., The Statistical Analysis of Chaparral and Other Plant Communities by Means of Transect Samples. Ecology 24, 45-60 (1943).

22.   Arny, A.C., and Schmid, A.R., A Study of the Inclined Point Quadrat Method of Botanical Analysis of Pasture Mixtures. J. Am. Soc. Agron. 34, 238 - 247 (1942).

23.   Whitman, W.C., and Siggeirsson, E.J., Comparison of Line Interception and Point Contact Methods in an Analysis of Mixed Grass Range Vegetation. Ecology 35, 431-436 (1954).

24.   Crockett, J.J., Preliminary Studies in the Evaluation of Grassland Sampling Techniques in Tall-Grass Prairie Sites. Proc. Okla. Acad. Sci. 43, 43 - 46 (1963).

25.   Becker, D.A., and Crockett, J.J., Evaluation of Sampling Techniques on Tall-Grass Prairie. J. Range Manage. 26, 61-65 (1973).

26.   Good, R.E., and Good, N.F., Vegetation of a Minnesota Prairie and Comparison of Methods. Am. Midl. Nat. 85, 228-231 (1971).

27. Austin, M.P., and Heyligers, P.C., Vegetation Study Design for Conservation: Gradsect Sampling of Forests in North-Eastern New South Wales. Biol. Conserv. 50, 13-32 (1989).

28.   Gillison, A.N., and Brewer, K.R.W., The Use of Gradient Directed Transects or Gradsects, in Natural Resource Surveys. J. Environ. Manage. 20, 103 - 127 (1985).

29.   Kenkel, N.C., Juhasz-Nagy, P., and Podani, J., On Sampling Procedures in Population and Community Ecology. Vegetation 83, 195 - 207 (1989).