LABORATORY 5 POINT-CENTERED QUARTER METHOD

Transcription

1 BIOL 475 VEGETATION DESCRIPTION AND ANALYSIS LABORATORY 5 POINT-CENTERED QUARTER METHOD OBJECTIVE The purpose of this lab is familiarize you with the Point-Centered Quarter Method (PCQ) of sampling forest vegetation and methods for determining tree height, and overstory cover. During this lab we will determine the following for each of the forest stands we sampled with the relevé method: 1. Absolute density, relative density, absolute frequency, relative frequency, absolute dominance, relative dominance, importance value, and relative importance value for each tree speices. 2. Percentage cover of the overstory. 3. Average tree height for the top layer in the canopy. Each team should collect forest structure s data for three stands of their forest type. After collecting all the data for your aspect, visit the sampling area of the other teams, and brief each other on the species composition and points that you have noted about the general ecology, forest stand structure, and factors controlling the distribution of trees. READING ASSIGNMENT Mueller-Dombois and Ellenberg Aims and Methods of Vegetation Ecology. New York: John Wiley and Sons, page "The Point-Centered Quarter Method". Lemmon, P. E. (1957). A new instrument for measuring forest overstory density. Journal of Forestry 55: MATERIALS 100-m tape Biltmore stick Spherical densiometer Meter stick Data sheets (Tables 1 and 2, this handout) Table of dbh to basal area conversions (Table 3, this handout) Pencil Hand calculator Graph paper METHODS Species density, frequency, dominance (basal area) and importance value: the point-centered quarter method. Randomly locate a point in the stand of trees. Make sure that it is well within the stand and a 100-m transect will not extend beyond the stand. Limit your sampling only to relatively homogeous areas; for example, eliminate points that occur in ravines or sites where the aspect, slope, or soil is different. This is the east end of a transect. Stretch the meter tape to its full length. If on a slope, follow the elevation contour of the slope. Sample points will be at 10-m 1

2 intervals along the tape, or at intervals far enough apart to not sample individual trees more than once at successive points. At each sample point, define an imaginary X formed by the meter tape and a line perpendicular to the tape at the sample point. The X should define four quadrants (NE, SE, SW, and NW). Record the following for the nearest tree in each quadrant: (1) the tree species, (2) the distance from the sample point to the tree, and (3) the diameter at breast height of the tree. Sample a total of 10 points (40 trees) in three representative stands of your forest type. You may have to locate several random transects in each stand to do this. After the data are collected, calculate the density, relative density, frequency, relative frequency, dominance, relative dominance, importance value and relative importance value for each species in each stand and the means of the three stands. You may want to revisit the field site to examine the ecology of the forests in light of your results. Table 1. Data sheet for point-center-quarter samples. Forest type TEAM MEMBERS (1) Point No. (2) Quadrant No. (3) Species code (4) Distance (m) (5) dbh (cm) (6) Basal area (cm 2 ) Stand

3 m=10 n=40 d t = Stand

4

5 m=10 n=40 d t = Stand

6 m=10 n=40 d t = Calculate the absolute density of all trees: Step 1. Calculate the total distance, d t : d t = n d i i=1 = meters where d t is the total distance, d i is the distance to tree number i, and n is the total number of trees. _ Step 2. Calculate the average distance between trees, d: _ d = d t n = meters Step 3. Calculate the average area occupied per tree, A: _ A = d 2 = meters 2 Step 4. Calculate the absolute density for all trees, Da, in trees per hectare (ha): Da = (10 4 m 2 ) A = trees/ha Note: One hectare is 100 x 100 meters, or 10,000 meters 2. How would you calculate absolute density in other units, such as trees/acre or trees/square mile? 6

7 Step 5. Fill in Table 2 (note that capital letters match column headings and in certain cases are not in order!): A. Species code. Record the names of all species encountered. Use a six letter code for each species (first three letters of the genus name and first three letters of the species name). Then calculate each of the following values for each species. B. Absolute frequency of species j, Faj: Fa j = M j m where M j is the number of points where species j occurs, and m is the total number of points (probably 100). C. Relative frequency of species j, Frj, is the absolute frequency of species j divided by the sum of the absolute frequencies for all species: p Fr j = Fa j Fa k 100% k=1 where the denominator is the sum of the absolute frequencies (i.e., the sum of column B in Table 2) for all species, k is the species number, and p is the total number of species. E. Relative density of species j, Drj, is the number of occurrences of species j divided by the total number of trees: Dr j = N j n 100% where N j is the number of occurrences of species j and n is the total number of trees. D. Absolute density of species j, Daj, is the relative density of species j times the absolute density of all trees: Da j = Dr j Da where Da is the absolute density for all trees (calculated in Step 4). F. Absolute dominance for species j, Baj, is the mean basal area for species j times the absolute density of species j: - Ba j = Ba j Da j where k is an individual of species j, and t is the number of occurrences of species j. G. Relative dominance of species j, Brj, is the absolute dominance of species j divided by the sum of dominance for all species: 7

8 Ba j Br j = p 100% Bai i=1 where the denominator is the sum of the absolute dominance (i.e., the sum of column F in Table 2) for all species, and p is the total number of species. H. Importance value for species j, IVj, is the sum of the relative frequency, relative density, and relative dominance for the species: IV j = Fr j + Dr j + Br j Table 2. Stand structure information for sampled forest stand. A. Species code B. Absolute frequency (Fa j ) C. Relative Frequency (Frj) D. Absolute Density (Daj) E. Relative density (Drj) F. Absolute Dominance (Baj) G. Relative Dominance (Brj) H. Importance Value (IVj) Stand 1 Stand 2 Stand 3 Mean 8

9 Standard deviation Standard error Table 3. Conversion of dbh to basal area. dbh (cm) BA dbh (cm) BA dbh (cm) BA dbh (cm) BA (cm2) (cm2) (cm2) (cm2)

10 Forest over-story cover: Follow the instructions on the lid of the spherical densiometer to sample the over-story cover of trees taller than eye high (about 1.5 m). Select 5 random trees in each of three stands of your forest type. At each tree, use the densiometer to calculate the forest cover on the N, E, S, and W side of the tree. Determine the average cover for each stand of trees, and take the mean to determine the average cover, standard deviation, and standard error for your forest type. Stand number Tree # aspect Percent cover Stand number Tree # aspect Percent cover Stand number Tree # aspect Percent cover 1 1N 2 1N 3 1N 1E 1E 1E 1S 1S 1S 1W 1W 1W 2N 2N 2N 2E 2E 2E 2S 2S 2S 2W 2W 2W 3N 3N 3N 3E 3E 3E 3S 3S 3S 3W 3W 3W 4N 4N 4N 4E 4E 4E 4S 4S 4S 4W 4W 4W 5N 5N 5N 5E 5E 5E 10

11 5S 5S 5S 5W 5W 5W Mean Mean Mean s.d. s.d. s.d. s.e. s.e. s.e. Overall mean s.d. s.e. Tree height: Hold a meter stick or Biltmore meter vertically such that the angle between your eye and the top of the stick is 45. (The distance between your eye and the center of your fist should equal the distance of the stick above your fist.) Position yourself with respect to the tree being measured such that your line of sight to the top of the stick also intersects the top of the tree. From this point measure the horizontal distance to the tree. This distance equals the height. Record the height of five of the tallest trees in each stand. Stand number Tree # Height Stand number Tree # Height Stand number Tree # Height Mean Mean Mean s.d. s.d. s.d. 11

12 s.e. s.e. s.e. Overall mean s.d. s.e. 12