Forest damage induced by bark beetle
attacks can cause major economic losses in forest-
ry. Hyperspectral remote sensing data and state of
the art very high spatial resolution satellite data of-
fer a great potential for assessing tree vitality. How-
ever, a better understanding of the effects of vitality
decrease and its impact on the spectral behaviour of
needles is needed. Filling this knowledge gap can
make a significant contribution to improve the in-
terpretation of remote sensing data. However, it is
still unclear which method for needle spectra col-
lection is most suitable. In this work, two methods
for spectral reflectance measurements of Norway
spruce needles using portable spectroradiometers
were tested and analysed: using a classical fore op-
tic and a so-called contact probe. The spectral re-
flectance data were evaluated with different statis-
tical similarity measure techniques. Besides ana-
lysing the measurements themselves, the methods
were compared in terms of their practicality. Fur-
thermore, the impact of storage on the reflection
behaviour was investigated. The spectral measure-
ments were performed in the field as well as in a
laboratory and repeated three times during the
2013 growing season. Based on the obtained results
we recommend measuring needle samples with the
contact probe of portable spectroradiometers.