Studentinformatie

Msc thesis subject: Measuring total leaf area and branch lengths of young trees with TLS in an evapotranspiration experiment in Nieuwegein

Terrestrial laser scanning (TLS) generates high density point clouds. This allows to estimate tree characteristics such as diameter at breast height and crown dimensions remotely and to reconstruct tree architecture in 3D.

Vegetation plays an important role in the water cycle by influencing local climates and soil water balances. A better understanding of actual transpiration rates and rainfall interception needs to be developed to improve computations of regional water balances, especially when groundwater abstractions need to be balanced with the demands of other water users. This is even more important in the face of climate change, when water availabilities change due to changes in rainfall input (intensity, duration, pattern) and in evaporative demands by the atmosphere.
For this purpose, a large experiment has been set up at KWR in Nieuwegein where transpiration and rainfall interception is measured on 80 individual trees of different species. Both coniferous and broadleaved species of different sizes are measured. Transpiration and rainfall interception will be related to leaf area. Therefore, the total leaf area and the number of leaf layers need to be determined for each tree. Although earlier studies have shown that laser scanning techniques can be used to derive tree parameters for full-grown trees, the accuracy for younger trees still needs to be evaluated. This especially concerns the applicability of Quantitative Structure Modelling (QSM) methods.

Objectives

  • Determine TLS acquisition parameters to derive tree parameters in transpiration experiment
  • Develop methodology to derive branch lengths and leaf areas of individual trees in evaporation experiment
  • Explore options to estimate aboveground biomass and crown density of individual trees from TLS point cloud dataset

Literature

  • Wilkes, P., A Lau, M Disney, K Calders, A Burt, JG de Tanago, et al., 2017. Data acquisition considerations for Terrestrial Laser Scanning of forest plots. Remote Sensing of Environment 196, 140-153.
  • Bauwens, S., H Bartholomeus, K Calders, P Lejeune, 2016. Forest inventory with terrestrial LiDAR: A comparison of static and hand-held mobile laser scanning. Forests 7 (6), 127.

Requirements

  • Interest in fieldwork activities with TLS: at least two measurement campaigns will be done: one in leaf off situation (till end March 2018) and one leaf on situation (summer 2018)

Theme(s): Sensing & measuring