Studentinformatie

Msc thesis subject: Monitoring the growth of Dutch forests using AHN and relate this to local soil characteristics

The height growth of trees follows a typical curve, where the height increment and the maximum height are highly influenced by the local soil characteristics. Soil maps can be used to predict the potential growth of a forest site. However, soil maps generally lack in spatial resolution for this purpose, representing not the full spatial variability of the soil quality that actually has effect on the growth potential of trees.

The ‘Algemeen Hoogtebestand Nederland’ (AHN ) is a publicly open available Digital Elevation Model with national coverage in the Netherlands. The AHN can be used for estimating the height of objects as is already done by Alterra (OHN). The method they developed is an example of how the heights of objects, like houses or stand-alone trees, can be derived.

Since the recent availability of the AHN in two time periods (AHN 2 & recently AHN 3) the question arises whether AHN datasets can be used to refine the spatial variability of a soil map, by looking at the local height increment of forests sites. By comparing the measurements of the AHN in time (AHN 2 and AHN 3 dataset) there is now the potential to extract direct height increment information and relate this to the local soil characteristics.

Questions that need be to tackled are:

  1. Is the AHN suitable for deriving individual tree heights in forests sites?

    • with AHN point cloud or raster 0.5 meter?
    • How accurate can this be done?
    • taking into account different tree types?
  2. Does the estimated height increment of trees relate to the soil characteristics?

Objectives

Exact Research Objectives will be formulated with supervisor, but possible directions are:

  • Process and analyse AHN 2 and AHN 3 to extract tree heights for forest trees: using point cloud data and raster (0.5m) data
  • Compare different models and methods and validate using field measurements.
  • Relate growth of forests sites extracted from AHN with soil maps and examine differences

Literature

  • Carmean, W.H., Lenthall, D.J., 1989. Height growth and site index curve for jack pine in north central Ontario. Canadian Journal Forest Research 19: 215-224.
  • Monserud, R.A. 1984. Height Growth and Site Index Curves for Inland Douglas-fir Based on Stem Analysis Data and Forest Habitat Type. Forest Science 30: 943–965.
  • Wang, G.G. 1998. Is height of dominant trees at a reference diameter an adequate measure of site quality? Forest Ecology and Management 112: 49-54.

Theme(s): Sensing & measuring, Integrated Land Monitoring