Influence of site climate on the radial growth of Sequoiadendron giganteum and Picea abies.

Title of the paper: Influence of site climate on the radial growth of Sequoiadendron giganteum and Picea abies. Current climate changes raise the question which tree species can be grown in Central Europe in the future. Cultivation of non-native species like Giant Sequoia (Sequoiadendron giganteum) could be of interest due to its high radial stem growth. From June 2008 until September 2009 the radial stem growth of five individuals of Sequoiadendron giganteum (Giant Sequoia) and six individuals of Picea abies (Norway Spruce) were measured in the Ecological-Botanical Gardens of Bayreuth. High resolution point dendrometers were used to record continuously the radial stem size variation of both species as well as the influence of site climate on growth. Radial variation of the 30 years old trees was induced by shrinking and swelling due to stem water variations and by cambial cell growth (Figure 2). During the growing season both species showed different levels of radial growth while relative growth was similar (Figure 3). During the study period the total radial increment of S. giganteum was 15.7 mm while abies grew by 4.5 mm (Figure 4). Daily radial increment was significantly different between both species and most of the days growth of S. giganteum was exceeding that of P abies. During the growing season Sequoiadendron and Picea showed a mean daily radial increment of 52 mu m d(-1) respectively 14 mu m d(-1). Both species achieved high radial increment during the same days. Especially during drought periods P. abies displayed considerably more days without radial increment (Figure 5). Correlation analysis showed that precipitation of the previous day is of great importance for daily radial increment of P abies whereas S. giganteum shows a greater dependency on volumetric soil water content (Table 1). The study demonstrates that S. giganteum has a much higher radial stem growth than R abies and is less sensitive to drought. Considering future climate changes in Central Europe, S. giganteum has potential for silvicultural cultivation and may on the long run serve as a replacement for P. abies.