I. Estimating Biomass in Plantations
I-1 Plot/Setting a plot for measuring
A four-sided plot is to be set in a given targeted forest stand. The length of the shortest side of this plot must be longer than that of the mean height of the trees within the plot, i.e., for the mean tree height of 15m, the length of the shortest side of the plot must be more than 15m, in other words, the size of the plot is larger than 15m x 15m.
To avoid overestimating the biomass of the plot by what is known as edge effect, two or three rows of planted trees at the edge of a forest stand or open-canopy site must be excluded from measuring. Because the tree growth at such a location is usually better than the mean growth of the plot due to the better sun light conditions.
I-2 Fundamental information of the plot
1) Basic data of the plot such as its size, location, gradient, direction, and soil type must be collected.
Tools: A field note, map, tapes for enclosing the plot, 50m tape measure, and a compass.
- 2) Basic data of the trees in the plot such as the diameter at breast height (DBH) of every standing tree, must be collected and noted in the field note (appendix 1). The locations of dead or missing trees, if any, must also be noted in it, so that the field note would reflect the reality. The data, thus, collected would provide more accurate information for estimating the tree density and survival rate of the plot. If a tree is branching off under the breast height, the diameter of each branch must be measured at the breast height and noted in the field note.
Tools: diameter tape for DBH measurement.
I-3 Felling sample trees
Five to six trees shall be selected for sampling that would represent the whole plot. The DBH of the selected trees must, therefore, range from small to large DBH according to the DBH distribution data collected in the field note in the above.
(Pic Selecting sample trees for felling,
according to the DBH distribution data.)
Fig 1 Felling a sample tree and cutting into logs. Boughs must be separated.
1) Chain saw can be applied for felling the sample trees. The tree must be felled at 0.3m from the ground (Fig1). The undercut from the felled tree must be set aside for weighing as the weight of which must be included in the total weight of the felled trunk.
2) The remaining stump must be cut off at the ground level that would make the log of 0.3m in length for weighing (Fig1). The weight must be included in the total weight of the felled trunk.
3) All the boughs must be cleared off the felled trunk and the stump and collected for weighing .
4) The height of the felled tree must be measured before the trunk is being cut into logs.
(Pic Clearing all boughs from the trunk with chain saw.)
5) The tree trunk must be cut into logs for the convenience of weighing (Fig1).
It is advisable to mark the felled trunk with cutting positions beforehand at the positions indicating, for example, 1.3m, 3.3m, 5.3m and so on from the ground ("1.3m" shall be marked at 1m from the cut bottom as the tree is felled at 0.3m from the ground).
It is also advisable to mark the position of each log on its surface to avoid errors in recording data. For example, to the log corresponding to the part of the trunk 0.3m to 1.3m from the ground mark "0.3-1.3", and the next log corresponding to 1.3m to 3.3m mark "1.3-3.3" and so on (Fig1).
Note: Each sample tree must be numbered and the logs cut out of it must bear the same number. The length of a log can be varied from one tree to another depending on the size of the tree.
6) When cutting, the trunk must be cross-cut at the marked positions so that the diameter of the bottom end of each log can be measured accurately. Two sets of two diameters of the longest and the shortest must be measured; one set with the bark and the other without it, and be noted in the field note (appendix 2).
(Pic Cutting the trunk into logs at the marked position by chain saw.)
7) Each log must be weighed and noted in the field note (appendix 3). Use of various spring scales according to the weight is advisable (Fig2).
Tools: A saw or a chain saw, chalks, tape measures, and various spring balances.
(Pic Weighing a log with spring balance.)