Proceedings zur 6. Fachtagung BIOMET - Deutsche ...

Besides the quantitative changes, i.e. changes in the magnitude of radiation fluxes, the Nslope
induce also the qualitative changes - the changes in the spectral composition radiation.
Within the central zone of clear-cut and small gaps in a canopy app. 6% increase of the blue
part of spectrum (400-450 nm) is observed for the northern slope comparatively to horizontal
surface. The N-corner clear shows in contrast a strong decrease of blue part (up to 20%). The
N-borders generally show the increment of green (525-575 nm) part of solar spectrum.
4. Conclusion
The clear-cut of a medium size (150m×150m) within a mixed forest stand produced a complex
effect on the radiation distribution at soil surface and was additionally complicated by its
location on a northern slope. The slope effect was a simultaneous decrease (10% in average)
of radiation input on the most (especially southern) part of studied site and a strong increase
(up to 166%) within the northern parts. The decrease of radiation on northern slope is more
pronounced in spring and autumn. The magnitude of the effect indicates strongly that even the
effects a very gentle slope could not be neglected in ecological studies. Besides that the slopeinduced
“blue shift” of the radiation spectrum at the clear-cut, as well as the green one at the
northern edges should be taken into account.
Abb. 5: Räumliche Verteilung der Unterschiede zwischen horizontaler Approximation und
der tatsächlichen Geländeneigung: 1) absolute Werte (links) und 2) normalisierte
Differenzen (rechts). Schwarze Kreise im rechten Bild markieren die Projektion der
Baumkronen auf der Bodenoberfläche
Fig. 5: Spatial distribution of differences between horizontal approximation and real slope:
1) absolute values (left panel) and 2) normalized difference (right panel). Black circles
at right panel represent projections of tree crowns on soil surface
References
KNYAZIKHIN YU., G. MIESSEN, O. PANFEROV, G. GRAVENHORST, 1998a: Small-scale study of
three-dimensional distribution of photosynthetically active radiation in a forest. - Agr. For.
Meteor. 88, 215--239.
KONDRATYEV K.YA., 1969: Radiation in the atmosphere. – Acad. Press, New York, 912 pp.
KURTH, W., B. SLOBODA, 1999: Tree and stand architecture and growth described by formal
grammars – I. Non-sensitive trees. - J. For. Sci. 45, 16--30.
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