Radiation components of beech stands in Southwest Germany
Holst, Thomas; Mayer, Helmut
Within the framework of an interdisciplinary project on the impact of climate and forest management on beech dominated deciduous forests, forest meteorological measurements are carried out within and above different beech stands (Fagus sylvatica L.) on opposite slopes of a narrow valley located in the Swabian Jura mountain range (south-west Germany). Referring to test plots on both slopes, the following cycles of radiation components are discussed: (1) Monthly mean values of transmission and extinction of global solar irradiance, photosynthetically active radiation as well as UV-A and UV-B radiation through the canopy, (2) diurnal courses of surface albedo α, net short-wave radiation K*, net long-wave radiation L* and net all-wave radiation Q* for a cloudless day in March (leafless period) and a cloudless day in July (fully-leaved period) above and below the canopy of different beech stands, and (3) monthly mean values of α, K*, L* and Q* for the same stand conditions as for (2). The results point out the combined impact on the investigated radiation components emanating from seasonally variable canopy density (quantified by the plant area index), exposure and sun elevation.