Using tree rings to reconstruct changes in soil P availability – Results from forest fertilization trials

Hitherto, there are only few studies that have analysed the variation of P contents in individual tree rings to reconstruct fluctuations in soil P availability. Therefore, this pilot study aimed to assess the relationship between changes in P content in tree rings and known changes in soil P availability resulting from fertilization of Norway spruce (Picea abies) and Scots pine (Pinus sylvestris) in fertilization trials at two different sites. We compared P contents in single tree rings from fertilized and unfertilized plots formed before and after P fertilization and assessed (1) whether fertilization leads to an immediate increase in P uptake and higher P contents in tree rings formed after fertilization, and (2) whether P is translocated to older tree rings that were formed before fertilization.