The importance of variance and microsite conditions for growth and hydraulic responses following long-term rewetting in pedunculate oak wood

Key messageEarly rewetting influenced growth variability and hydraulic uniformity in Pedunculate oak wood on disturbed peatland. Long-term study highlighted vessel widening's importance in adapting to water availability changes.AbstractPedunculate oak (Quercus robur L.) is a widely recognized flood-tolerant tree that thrives on fertile and moist soil conditions, such as on or close to peatland ecosystems. In the frame of climate change counteracting policies, rewetting peatland ecosystems is gaining increasing interest, while the ecological consequences are not always clear. Whereas the effect of flooding on wood anatomical traits of pedunculate oak is widely documented, little is known about the effect of permanent rewetting. In this study, we investigated the wood anatomical responses of 12 pedunculate oak trees located on a formerly drained peatland in NE Germany, that experienced flooding and a consequent rewetting. Wood anatomical traits were analyzed via CARROT, a tool that employs the accuracy and efficiency of artificial intelligence to identify tree rings and vessels. Growth anatomical traits (e.g., tree ring width) showed a sudden increase after the rewetting started in 1995, while hydraulic traits (Dh and Ks) displayed a decreasing trend only after the rewetting process was fostered by the opening of an artificial canal in 2004. Variance analysis highlighted subtle changes in the trait's distribution over time: high soil water content triggered variability in the growth anatomical traits and, simultaneously, homogeneity in the hydraulic traits. Results suggest the relevance of the "vessel widening" mechanisms to develop coping strategies in response to the later stage of the rewetting, and pose relevant insights concerning the importance of specific site conditions for the implementation of rewetting policies in peatlands with presence of pedunculate oak.