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Result of this task shows distribution of the volume of lying dead trees among different types of forest. Output table is classified also by different stages of wood decomposition.
Requirements:
For that task is necessary to run the stratification by forest development types (see Stratification) and to calculate volume of each lying deadwood (see Calculate tree biomass (volume) action).
Procedure:
- Add new task and rename it
- Select “Deadlogs” layer
- Select “Deadlogs.Volume o.b., m3 (V_deadwood_ob_m3)” attribute
- Set “m3” in the Units combo box and number of decimal places of your choice (e.g.0)
- Select “Forest development type (Forest development type)” in Stratifier section and tag Use stratifier in output checkbox
- Select “Deadlogs.Decay status (DecayStatus)” as classifier (Note: Click Add classifier button, tag “Deadlogs.Decay status (DecayStatus)” check box and click OK)
- Select Total and desired Alpha (e.g. 0,05) in Statistics section
- Set “Volume o.b., m3 (V_deadwood_ob_m3)” as Plot weight attribute. Option If > 0 than 1 is set automatically
- Limit the survey to the inner circle of radius equal to 7 m
- Run the task using Perform button
Comments:
Whole plot is assigned to particular forest development type while performing stratification. At the same time the total area of each forest development type is calculated based on existing vector map (shapefile).
Setting attribute ForestDevelopmentType as stratifier increases precision of the output since there is available information about size of the stratums derived from the map of forest development types.
Calculation of the total is used and weight is set to be RepreArea_ha attribute. If any weight for total is included, the box “if > 0 than = 1” will be checked automatically. This is called virtual stratification and it excludes plots with missing weight attribute (plots without deadwood) from the calculation of confidence interval. In other words excluding plots without presence of any dead log from calculation of total volume decreases variability within particular stratum and thus calculated confidence interval is smaller. This procedure does not affect calculation of the total itself.
As the calculation is based on the data from deadwood layer, not tree level, the including/excluding trees of regeneration have no effect on the results.
Calculation has to be performed on smaller 7 m of radius subcircle. This follows the methodology and the way of deadwood data collection right in the field.
Screenshots:
Results:
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