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I am learning how to use lidar to study forest structures, but I cannot find any methodology on how to map understory trees. It is for a school project where I am mapping forest developmental phases in a specific area of interest which is a beech forest. The lidar data I have is airborne full waveform taken during leaf-off conditions. I am working on QGIS 2.18.25 and LAStools. Does anyone have any suggestions on how understory trees could be identified?

gigi
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    Are you looking to map individual trees or to estimate understory cover? – Aaron Jan 11 '19 at 13:45
  • Here is a related Q&A. – Hornbydd Jan 11 '19 at 15:21
  • First we need to know what is 'identify forest structure'. Is it obtaining the vertical profile (e.g., https://gis.stackexchange.com/questions/54691/retrieving-average-building-height-in-urban-areas/54721#54721), or counting how many trees? Or going further and segmenting crowns? What is considered to be a understory in a beech forest? Second, the question is broad. This is not something trivial to do, it is still at the academic frontier. Can you provide more details about data, what you have tried, what you want to achieve, and where you got stuck. – Andre Silva Jan 11 '19 at 21:31
  • You can get help starting from the following posts: https://gis.stackexchange.com/questions/124224/extracting-tree-crown-areas-from-remote-sensing-data-visual-images-and-lidar; https://gis.stackexchange.com/questions/246859/identifying-joshua-trees-with-lidar-data and https://gis.stackexchange.com/questions/184981/identifying-individual-trees-and-segmenting-crowns-from-lidar-chm-data. – Andre Silva Jan 11 '19 at 21:34

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The following literature highlights several approaches that should help get you started:

Hamraz, H.; Contreras, M.A.; Zhang, J. Vertical stratification of forest canopy for segmentation of understory trees within small-footprint airborne LiDAR point clouds. ISPRS J. Photogramm. Remote Sens. 2017, 130, 385–392.

Wing, B.M.; Ritchie, M.W.; Boston, K.; Cohen, W.B.; Gitelman, A.; Olsen, M.J. Prediction of understory vegetation cover with airborne lidar in an interior ponderosa pine forest. Remote Sens. Environ. 2012, 124, 730–741.

Latifi, H.; Heurich, M.; Hartig, F.; Müller, J.; Krzystek, P.; Jehl, H.; Dech, S. Estimating over- and understorey canopy density of temperate mixed stands by airborne LiDAR data. Forestry 2015, 89, 69–81.

Amiri, N.; Yao, W.; Heurich, M.; Krzystek, P.; Skidmore, A.K. Estimation of regeneration coverage in a temperate forest by 3D segmentation using airborne laser scanning data. Int. J. Appl. Earth Observ. Geoinf.

Fleming, S.; Cottin, A.; Woodhouse, I. The first spectral map of a forest understory from multispectral lidar. Lidar News 2015, 5, 26–30.

Hill, R.; Broughton, R. Mapping the understorey of deciduous woodland from leaf-on and leaf-off airborne LiDAR data: A case study in lowland Britain. ISPRS J. Photogramm. Remote Sens. 2009, 64, 223–233.

Korpela, I.; Hovi, A.; Morsdorf, F. Understory trees in airborne LiDAR data—Selective mapping due to transmission losses and echo-triggering mechanisms. Remote Sens. Environ. 2012, 119, 92–104.

Heinzel, J., & Ginzler, C. (2019). A Single-Tree Processing Framework Using Terrestrial Laser Scanning Data for Detecting Forest Regeneration. Remote Sensing, 11(1), 60. [1]: https://arxiv.org/pdf/1701.00169

Aaron
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