Zuwachstrend und Stressresilienz von Tanne und Fichte im Vergleich

The study compares long term growth trend and resilience performances due to drought stress of Silver fir (Abies alba Mill.) and Norway spruce (Picea abies (L.) Karst.). In total, 118 trees of each tree species were den-droecologically analysed. The sample trees were selected from 22 mixed stands of Silver fir and Norway spruce in Bavaria and Lower Saxony (Fig. 1) representing a wide range of ecological growth conditions (Tab. 1). During the last hundred years both tree species show a general increasing level of growth which is interrupted by a growth decline mainly during the 1960ies and 1970ies (Fig. 4). Due to the species specific differences in growth different growth relations occur in the period of observation (Fig. 3). In the time of high rates of sulphur dioxide emissions spruce outranges fir whereas in particular during the last 20 years the growth relation inverts (Fig. 4). Beside the obvious higher vitality in that time Silver fir shows a more stable resilience to the drought stress in 2003 compared to 1976 with higher loads of sulphur deposition (Fig. 6). No differences in resilience behaviour between the two dry years could be observed at Norway spruce. Significant effects by site conditions could only be detected in terms of growth level of Norway spruce (Fig. 7) but not in terms of resilience of both species. Drought reduces growth of both species whereas the effect is lightly stronger pronounced with Norway spruce. The results are discussed with regard to their relevance in understanding the gap between fundamental and real niche of both species and how those are modified by additional stress factors (Fig. 9). Silvicultur-al implications concerning the involvement of Silver fir in particular in the framework of climate change are drawn.