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| Heiberg Forest Procedure for Plot Measurement
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| Continuous Forest Inventory Plots: | |||||||||||||
| Continuous forest inventory (CFI) plots are permanent plots that are usually systematically spaced over the entire forest. When first established, they provide an estimate of the total volume of timber of the area. After remeasurement at a later date, the volumes can be compared to the earlier inventory to assess the change in condition of the forest over time. This measurement of change is the principle value of the CFI. It is the best technique available to measure growth and mortality over large areas and because it is based on permanent plots, the precision of the estimate (sampling error) is much better than would ordinarily be obtained from two independant inventories. This page describes the procedures used by ESF personnel to establish CFI plots. Procedures used to locate these plots varied slightly from 2000, 2001, and 2002-2003 field seasons. | |||||||||||||
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| Procedure for Plot Measurement: | |||||||||||||
| Plot Location | |||||||||||||
| Each crew is assigned a plot center locations and given a bearing and distance from a nearby landmark to the plot center. These plot locations are specified by a grid system placed over a map of the forest. Plot centers are marked with a blue plot center stake. | |||||||||||||
| Plot Boundaries | |||||||||||||
| As the actual change over time is of interest, great care is taken to avoid non-sampling type errors, for example, human and instrument errors. A 4.5 ft. pole is used on each tree to establish the DBH point. The tape is placed around the tree so the lower edge of the tape touches the top of the measuring pole. While the tape is still on the tree, the position of the lower edge of the tape is marked with a lumber crayon in a band 3-4 inches long. When the tape is removed, the band is painted so the tape may be applied in the same position at the time of remeasurement. Every living tree 3.6 DBH and over is measured to the nearest 1/10th of an inch. | |||||||||||||
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| The trees are tallied and numbered on the side facing plot center with an aluminum plate, in a clockwise direction from due north, for example, the tree in the northeast quadrant closest to due north and closes to the plot center is tree No.1. Trees are numbered out to the edge of the plot and then back to the plot center in a clockwise direction around the plot. | |||||||||||||
| Plot Information | |||||||||||||
| The plot size is 1/10th acre, radius = 37.24 ft. When the plot center is located, the radii is measured out in each of the four cardinal directions. If there is the least amount of doubt whether any tree is in or out of the plot, the distance is measured from the plot center to determine its proper location. | |||||||||||||
| For each plot, the forest type, slope, aspect, topography, and drainage are recorded. For each tree located in the plot, the dbh, species,crown class, vigor, azimuth and horizontal distance are recorded. | |||||||||||||
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| On the tally sheet, the tree height data is measured and recorded for five trees at each plot. In order to remove subjective bias, the trees chosen are the trees closest to the plot center and nearest to the four cardinal direction. The tape cloth is used to establish the distance from the tree before taking clinometer readings. Because of the uncertainty of the measurement of total height of a hardwood tree, the total height is classified by 10 foot intervals, that is, the 60 foot class would include trees whose estimate height was between 55 and 64 feet. All other heights are measured to the nearest foot. The merchantable height is taken to a 4" top diameter, or to the point where tree form would prevent further utilization. In making the measurement to the base of a live crown, the base is estimated as the point where the branches forming the crown are well established. The intermittent live branch that may be found below this point is not included. Because of the need for accuracy in all the measurements, another member of the crew retakes the height measurements as a check on the first observations. | |||||||||||||
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