Resilience of Norway spruce (Picea abies (L.) Karst) growth to changing climatic conditions in Southwest Germany

Abstract

Knowledge gaps still exist concerning the resilience of Norway spruce growth to changing climate conditions especially outside their natural range. We used a dendroecological approach to assess growth resilience of Norway spruce to changing moisture availability on different sites in southwest Germany near the xerothermic range limits of this species. We described the temporal and spatial variation of Norway spruce tree-ring width, comparatively assessed the response of tree-ring width to changes in moisture availability between different study sites and assessed the capacity of Norway spruce growth to absorb disturbance by drought. To assess the capacity, we applied the concept of resilience and the concept of early-warning signals to tree-ring width data. The results indicated no adequate short-term adaptive capacity to changing climate conditions for the respective Norway spruce trees within the study period. Furthermore the results showed an enhancement of growth synchronicity among the trees at each study site which is highly correlated with changes in moisture availability. Critical slow down, loss of buffering ability and simultaneous increase in spatial correlation are indicative of a loss in growth resilience of Norway spruce. We assume that the capacity of Norway spruce trees to absorb disturbance in terms of their growth response to moisture deficits decreased presumably as a consequence of a series of drought events in the more recent past.