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PRIMARY RESEARCH PAPER
Terrestrial Sampling Techniques: Calculating Indeces of Dominance and Diversity Nick Khryzzan P. ∙ Abaya ∙ Isabel Acenas ∙ Aubrey P. Alagos ∙ Maire Katrina S. Arnaldo
Abstract In this activity, the group was tasked to determine the diversity of a terrestrial sample using widely used sampling methods: the quadrat and transect methods. The objective of the activity was to calculate the dominance and diversity of non-mobile organisms in terrestrial habitats. After tallying and computation, results showed the transect point method with the h value= 1.7750 possessed the highest diversity, the index value for transect point methd was 0.8084 which had the highest Index of Dominance while the quadrat method had shown the least evenness by 0.3352 and the greatest evenness by 0.7717. Keywords Line transect method , relative density, Shannon-Weiner Index Simpson’s Index, quadrat method,
N.K.P. Abaya Department of Biological Sciences, University of Santo Tomas, Manila, Philippines e-mail:
[email protected] I. Acenas Department of Biological Sciences, University of Santo Tomas, Manila, Philippines A.P. Alagos Department of Biological Sciences, University of Santo Tomas, Manila, Philippines e-mail:
[email protected] M.K.S. Arnaldo Department of Biological Sciences, University of Santo Tomas, Manila, Philippines e-mail:
[email protected]
Introduction One of the most important aspects in ecology is the determination of the number of species in a population, the dispersion or the pattern of distribution in space within the habitat, and the changes in abundance. In most cases, it is impossible to count every individual or plot their location on a map because of the time, effort or money involved. So the most practical way to solve the problem is to get an accurate representation of some spatial characteristics of the population by means of sampling techniques. Dominance and diversity are the main concerns in ecological sampling. Dominance is the degree to which a taxon is more numerous than its competitors in an ecological community, or makes up more of the biomass. Diversity, on the other hand, is the number of different species that are represented in a given community. The Shannon-Wiener Index and the Simpson’s Index are both used to meaure diversity in a population. The three sampling techniques that are widely used in ecology are Quadrat, Belt/Line Transect, and Point-Quarter. The quadrat method is applied to a square or rectangular plot of land, which is used to mark off at random a physical area to isolate a sample and determine the percentage of vegetation occurring within the marked area. Quadrats may vary in size, shape, number, and arrangement, depending upon the nature of vegetation and the
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objectives of the study. A transect is a cut or path through part of the environment showing a range of different habitats. The samples in a transect method are taken at fixed intervals, usually along a line. The line is set up across areas where there are clear environmental gradients. The point-quarter method is a plotless technique to estimate density. It assumes that the key species follow a random spatial pattern, and is sensitive to bias when plants exhibit a more contagious arrangement. It also requires extra field effort and computational input than many of the other distance methods. The objective of the exercise was to learn all the three sampling techniques mentioned, and be able to compare and contrast each. Materials and Methods The materials used for this activity were improvised transect lines, 10”x10” squared quadrat, rice, red beans, white beans, mongo beans, and variety of coins. Quadrat Method The 10”x10” squared quadrat was laid on a random point. The number of quadrat noted was 25. The plants that were found in each quadrat were then recorded. Transect (Point) Method A 98 cm yarn with 2.5 cm intervals was laid along the plant box. The plants that were precisely touching the 2.5 cm intervals were noted and tallied. Quadrat Method Species
Total
Rice
2417
Transect (Range) Method A 98 cm yarn with 2.5 cm intervals was laid along the plant box. The plants that were within the range of the 2.5 cm intervals were noted and tallied. The formulas used for this activity were: (1) Simpson’s Index:
n = the total number of organisms of a particular species N = the total number of organisms of all species (2) Shannon-Weiner Index: H'= − ∑ pi ln pi pi = the proportion of individuals found in species i pi = ni/N, ni = number of individuals in species i N = total number of individuals in the community Index of dominance = 1 – Simpson’s Value Evenness = H / (Hmax * number of species) Results Quadrat Method Conditions: Area sampled: 0.25m2; number of quadrants= 25 Density, Relative Density, Frequency and Relative Frequency: Index 1 Total Species Total Density= 12176 plants/m2 Total Frequency= 5 plants species/ quadr
Transect LineRed (Point) Beans White Beans Mongo 5 Cents 10 Cents
36 66 355 10 1
4 2 5 0 5
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25 cents 138 1 Peso 12 5 pesos 8 10 pesos 1 Table 1. Using Indices of Diversity: Total Per Method
populations counted using the three different methods .
Graph 1 -3. Representation of the different populations counted using the Quadrat, Transect Point and Transect Range Methods
Shannon-Wiener for Degree of Evenness Simpson’s Index Index of Dominance 0.6467 0.3533 0.1952 0.8084
Method Quadrat Transect (Point) Transect (Range)
0.3528
0.6472
Hmax= 2.30 Graph 1 -3. Representation of the different
Density Rice Red Beans White Beans Mongo B. 5 Cents
9668 144 264 1420 40
Quadrat Method Relative Density #Quadrants (%) 35.42 25 8.33 16 4.17 20 10.42 0.00
24 5
Frequency 1 0.64 0.8
Relative Frequency (%) 20 12.8 16
0.96 0.2
19.2 4
4
10 Cents 25 Cents 1 Peso 5 Pesos 10 Pesos Total
4 552 48 32 4
10.42 20.83 6.25 4.17 0.00
1 23 6 4 1 125
Transect (Point) Abunda Rel. nce Abundance Rice 17 35.42 Red Beans 4 8.33 White Beans 2 4.17 Mongo B. 5 10.42 5 Cents 0 0.00 10 Cents 5 10.42 25 Cents 10 20.83 1 Peso 3 6.25 5 Pesos 2 4.17 10 Pesos 0 0.00 TOTA 48 L
0.04 0.92 0.24 0.16 0.04
0.8 18.4 4.8 3.2 0.8
Transect (Range) Abundan Rel. Abundance ce 119 52.42 14 6.17 4 1.76 37 16.30 0 0.00 1 0.44 44 19.38 3 1.32 5 2.20 0 0.00 227
Discussion
Shannon-Wiener index was used in order to solve for the different indices. The Index of Diversity requires the calculation of H value of each point/quadrant involved in the study. The higher the H value, the higher the diversity. In the experiment the transect point with the h value= 1.7750 possessed the highest diversity and 0.7710 having the lowest. Next, the Index of Dominance was computed by solving for the difference between 1 and the Simpson’s value, where 1 is the highest dominance. In the experiment, the transect point with the value 0.8084 had the highest Index of Dominance. For evenness, the values close to one indicate that the species are well distributed while zero for the species that are concentrated or isolated within an area of a whole region. The quadrat method had shown the least evenness by 0.3352 and the greatest evenness by 0.7717. By comparing the different results of the methods used in the study, we can learn which method is more effective to use. First, we know that there is an inverse relationship between the index of dominance and the index of diversity. When there is a dominance of a certain species in a population, there can only be less diversity and vice versa. However, for transect (point) method, both index of dominance and index of diversity is high. We can assume that this method is less advantageous to use in terrestrial sampling. The most advantageous
method to use is quadrat method, because it shows the inverse relationship more clearly than the others.
References: Alejandro, G.J.D., Banag, C. I., Edison, T.E.E., Diesmos, A.C., Diesmos, M.L.L, et al. (2014). Laboratory and field investigations in ecology. University of Santo Tomas. Manila, Philippines. Phillips, E. A. 1959. Methods of vegetation study. Henry Holt and Co., New York, New York, USA. Shaukat, S.S., Khairi, M.A. & Khan, M.J. (1978). The relationship amongst dominance, diversity and community maturity in a desert vegetation. Pakistan Journal of Botany., 10 (2): 183- 196
