**4.2 Applications for biomass estimation**

Terrestrial laser scanning has been applied within the commercial forestry sector. An example of which is TreeMetrics Ltd., Cork, Ireland, who have adapted this technology and developed purpose built software called AutoStem Forest™ to process laser scans into forest inventory-specific data. The principle behind this methodology is to extract greater value from the resource.

The application is intended principally to complement existing inventory methods by creating and measuring individual tree volumes, their straightness and calculating their potential end products. The technology may be considered as a virtual timber harvesting machine that gathers precise data as it scans trees. By positioning laser scan plots throughout a forest, it is possible to measure the variability within the forest and to describe the forest as a Timber Warehouse™ for commercial purposes or to map biomass distribution for inventory applications.

the combination of several scans is often required to accumulate adequate information for analysis of the scene within a plot. Low vegetation and heavy branching can affect the quality of the data and in some studies were removed before the site was scanned. This difficulty is especially important with the trees closest to the scanner as they cause the most occlusion. Research into the detection and reconstruction of stems (e.g. Huang *et al.*, 2011) and branches (e.g. Bucksch & Fleck, 2011) is a current area of development which is of great interest. For forestry purposes this would permit the quality of timber to be determined more easily, such as stem straightness, branch number and branch angle. The ability to reconstruct the tree geometry from terrestrial laser scanning is unprecedented. Whilst for the purposes of forest inventory, the ability to detect the ground surface, height above the ground along the tree stem and to determine the size of the stem allows diameter at breast height to be directly measured, which is one of the most fundamental operational

Fig. 7. Below-canopy plot sampling using terrestrial laser scanning. Images courtesy of

Terrestrial laser scanning has been applied within the commercial forestry sector. An example of which is TreeMetrics Ltd., Cork, Ireland, who have adapted this technology and developed purpose built software called AutoStem Forest™ to process laser scans into forest inventory-specific data. The principle behind this methodology is to extract greater value

The application is intended principally to complement existing inventory methods by creating and measuring individual tree volumes, their straightness and calculating their potential end products. The technology may be considered as a virtual timber harvesting machine that gathers precise data as it scans trees. By positioning laser scan plots throughout a forest, it is possible to measure the variability within the forest and to describe the forest as a Timber Warehouse™ for commercial purposes or to map biomass distribution

parameters collected by foresters in the field.

Forest Research, UK.

from the resource.

for inventory applications.

**4.2 Applications for biomass estimation** 

Aside from forestry management objectives, the use of terrestrial lidar can potentially complement traditional field data collection by improving the efficiency and accuracy of survey approaches. Whereas the time required to measure the trees within an inventory plot by a team of surveyors may be quite considerable, the combination of lidar scans of a few minutes each could substantially reduce this whilst providing additional contextual information which could not be achieved with field measurements.

Terrestrial laser scanning measurements are restricted to small area sampling, similar to typical field data collection. However, this permits the plot to be 'revisited' visually and analytically for multiple purposes without returning to the field, allowing the scene to be reconstructed to enable trees to be placed in the context of their immediate surroundings. For management purposes, this could be invaluable to determine optimum thinning or harvesting times or to assess growth trends against model predictions through the measurement of diameter increments.

Once diameter distributions within measured plots are calculated, in the same way as with field approaches, allometric relationships allow wider stand-level forest attributes to be inferred. If applicable species groupings are known, general DBH-based regression equations can be applied to estimate forest stand-level biomass. For sites within the USA, Jenkins *et al.*, 2003, 2004 present diameter-driven allometric equations for biomass of North American species whilst for Europe, a similar resource is provided by Zianis *et al.*, 2005.
