Research project S0/01/013 (Research action S0)
Project summary:
Vitality assessment of trees is used in pomology and forestry to estimate harvests or to focus treatments, but if often means a time-consuming and tedious procedure of questionable reliability. This project aims to improve conventional methods of vitality assessment of trees through the use of air- and satellite borne spectroscopic images, in order to facilitate the detection of unhealthy trees, their degree of vitality and specific stress factors. The spectral reflectance of 5 different kinds of naturally occurring stress factors (aphids, viruses, bacterial infections, fungi and nitrogen deficiency) is investigated from test-plots in the orchard of Velm (OSTC-project "Hypercrunch") and the pine stands of Pijnven (OSTC-project "“Texture and change detection in forest ecosystems") in the same region.
The increasing degree of complexity in the reflection signal on different spatial levels is a major challenge for the identification of specific stress signals on coarser resolutions and is therefore followed up with measurements on different scales:
Direct measurements of spectral reflectance on stressed and unstressed leaves are performed with a handheld field-spectrometer in both test-plots. Vitality of these leaves is assessed with biochemical analyses, fluorescence measurements, and leaf structure oriented measures. The whole orchard and forest stands are investigated with airborne imaging spectroscopy and the position of stressed and unstressed trees; their LAI and structural properties are measured.
Ecophysiological significance is given tot the project due unexpectedly high growth rates of unhealthy Pinus nigra tree at Pijnven. The assessment of photosynthesis with fluorescence measurements on needles shall give more insight in this relationship between growth and vitality.
The comprehensive structural measurements at the Pijnven site are completed by fine structural measurements in the framework of the project "Describing biophysical and optical properties of forests through computer modeling and visualization" (Onderzoeksfonds K.U. Leuven) which aims at the development of a fractal forest model as a basis to model the spectral reflectance of forests. The flight data are foreseen as validation data for this modeling approach.
