The study focuses on growth responses of Larix decidua provenances to climatic transfer based on a regional provenance experiment. This comprises a series of 5 trial plots situated in Germany and Slovakia, where 12 indigenous Sudetic and West-Carpathian larch provenances are planted. Transfer rates were defined as differences in altitudes or climatic variables between the site of plantation and the site of origin. 1st and 2nd-order polynomial regressions were used for the identification of overall trends of growth performance and responses to transfer.
Sudetic provenances clearly outperformed the Carpathian ones on all test sites. When all provenances were considered jointly, height and breast-height diameter mostly showed significant monotonous geographical and climatic trends: the performance generally decreased with increasing altitude and precipitations and decreasing temperatures. The relationships between growth response and transfer rates (ecodistances) were mostly linear. However, when Sudetic and Carpathian provenances were considered separately, most significant response curves were unimodal. There is a very good correspondence between the responses in height and diameter growth within geographic groups, but the responses are not consistent between groups. Joint regression analysis showed that most provenances exhibited average stability. Stability indices are quite consistent between the response traits and did not show any association with the geographical position, climate of origin, or growth performance.
The results indicate that populations in different climates remain adapted to a common optimum, the extent of local adaptation is quite limited. Possible explanations of this observation are briefly discussed.