The temporal variability of phenological stages of Norway spruce (Picea abies (L.) Karst.) in Slovakia

Abstract

The paper informs about the evaluation of observed selected vegetative (bud burst beginning, the first May sprouts occurrence) and generative (the lasting male flowers and the general flowering) phenological stages of Norway spruce (Picea abies (L.) Karst.). There were analysed data from 38 phenological stations in Slovakia within the period 1996-2008. The stations were situated in the range from 100 m to 940 m a.s.l. and divided into 3 altitudinal groups. The mean onset date of the bud burst stage was from the 21st of April till the 6th of May, the first May sprouts occurred from the 2nd till the 18th of May. Male flowers were lasting from the 12th till the 19th of May, the general flowering lasted from the 17 th till the 24th May on average. The shifts of observed vegetative phenological stages among particular altitudinal groups represented 7-9 days, and they kept their temporal succession. Generative phenological stages began with the differences among p1articular altitudinal groups approaching 2-5 days regardless the altitude itself. At lower situated stations, up to 500 m a.s.l., the vegetative phenological stages were observed shifted positively by 3.3-8.5 days, above 500 m a.s.l. these stages were delayed by 0.8-2.8 days. The generative phenological stages manifested a decreasing trend with a shift by 3.6-11.2 days sooner. The phenological phases shortens are shorter with increasing altitude.