Response of a Norway spruce forest ecosystem to drought/rewetting experiments at Solling,Germany

As part of the Solling roof project, drought experiments were conducted in a 60 year old Norway spruce (Picea abies L. KARST.) plantation by means of a roof construction, installed below the canopy. It was tested, if the rewetting of a dried out soil leeds to a surplus production of nitrate and to an acidification pulse in the soil solution. Fine root growth and other physiological reactions were observed during the initiated drought phases. Results indicate no marked nitrification pulse during one of the 4 conducted experiments. However, drought reduced fine root growth strongly, but no root dieback could be found. The magnesium content of the needles were lower in trees subjected to water stress and increment parameters were significantly reduced.