Spring and autumn leaf phenology of common beech and sessile oak provenances in relation to different soil phosphorus concentration

This research was conducted on a four-year-old common beech and sessile oak saplings originating from two mature mixed common beech and sessile oak stands (provenance) from the Republic of Croatia (HR). Provenances differ in annual amount of precipitation, which in provenance Slavonski Brod (SB) from the eastern part of the HR is about 770 mm (dry provenance), and in Karlovac (KA) from the north-western part of the HR is about 1112 mm (wet provenance). During year 2021, after the establishment of the experimental trail, the transplanted saplings grew into two soil types, one was characterized by high (0.30 g P2O5/l soil) and the other by low (0.16 g P2O5/l soil) phosphorus (P) concentration. The aim of this study was to examine the effect of higher soil P concentration on the average onset of spring bud burst and autumn leaf senescence in beech and oak saplings. The results showed that the onset of bud burst and leaf senescence in beech compared to oak saplings occurred significantly earlier, in six and ten days, respectively. Differences in the onset of bud burst and leaf senescence between oak provenances were not significant, whereas these differences between beech provenances were significant. Therefore, the onset of bud burst and leaf senescence in beech of dry SB provenance compared to wet KA provenance occurred earlier in five and three days, respectively. The higher soil P concentration significantly affected only the onset of leaf senescence in beech saplings. This means that the onset of leaf senescence in beech saplings under the higher compared to lower soil P concentration occurred three days earlier in the dry SB provenance and four days earlier in the wet KA provenance.