Chap 8 - CHAPTER 8 QUADRAT AND POINT QUARTER SAMPLING...

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CHAPTER 8 : QUADRAT AND POINT QUARTER SAMPLING ANALYSIS TO BRING WITH YOU: Please make sure that you bring: your completed datasheets and a calculator. PURPOSE: In this lab, you will learn how to estimate density, dominance and frequency of tree species from the data we collected in the Quadrat and Plotless sampling field exercises. We will also learn how to compute a measure of the relative importance of each species. Density : number of individuals per unit area. As we are using trees, we will use a large area, one hectare, as the unit area. Dominance : a measure of the combined sizes of the individuals per unit area. As we are using trees, we will use a large area, one hectare, as the unit area. Frequency : the number of sample sites in which a species is found. Importance : a combined measure of density, dominance and frequency. DENSITY COMPUTATIONS Density is the number of individuals per unit area. The first step in computing a density is to determine the area sampled. In this case, if we use number of trees per m2, we will have very small numbers; so we will use number of trees per hectare: ( 29 000 , 10 m Area (ha) Area 2 = Compute the area sampled for quadrat and point quarter sampling For the quadrat data , the area of the sample site is the area of the quadrat. So, first, compute the plot area in m 2 and then convert to hectares ( 29 = = (m) width Quadrat * (m) length Quadrat m area Plot 2 ________________________________ ( 29 = = 000 , 10 / ) 2 (m area Plot ha area Plot ____________________________________ Since you used the same size quadrat for each sample, plot area will be the same for each sample, Enter your computation in Table 8-2. For the point quarter data , the computation of plot area is a bit more difficult. The area sampled in each quadrant is the area in which you looked for trees. Remember that, once you located the nearest tree, you stopped looking in that quadrant so the area in which you looked can be described as a quarter circle. The total area sampled is equal to the sum of the areas of the four quadrants and the area of a single quadrant is area of a quarter circle (Figure 8-1): Chapter 1 1 D i s t a n c e t o t r e e ( d ) A r e a o f a r c s a m p l e d ( A ) A 3 A 1 A 2 A 4 To t a l A r e a = A 1 + A 2 + A 3 + A 4 Figure 8-1: Computing plot area for point quarter method.
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( 29 4 2 d m Area 2 π = where d=the distance in meters to the tree. To compute the plot area, you would add up the areas sampled in each quadrant.
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This note was uploaded on 09/08/2010 for the course BIOL 160 at San Jose State.

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Chap 8 - CHAPTER 8 QUADRAT AND POINT QUARTER SAMPLING...

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