Net radiation of mountain cultivated Norway spruce [Picea abies (L.) Karst.] stand: evaluation of short- and long-wave radiation ratio

The radiation exchange drives the plant ecosystems energy balance and provides the energy for photosynthesis, transpiration and plant growth. The investigation on net radiation and its component during vegetation season in relation to the clearness index and sun elevation in a cultivated 31-year-old mountain spruce [Picea abies (L.) Karst.] stand is presented. Downward short-wave radiation – Sd (incident on the spruce stand was the main part of the short-wave radiation balance during the whole growing season (April–October) 2008. The Sd a mount i s seasonally variable factor determined by the duration of solar shine and the atmosphere transmissivity. Obtained value of net radiation (Rn) and downward short-wave radiation (Sd) ratio amounts to 0.61 on average during the growing season 2008 documenting the importance of the downward short-wave radiation in the net radiation of investigated spruce stand.