Influence of spring phenophasis outbreak on growth processes of Norway spruce provenances (Picea abies /L./ Karst) originated from Volovské vrchy during years 2010-2012

The aim of this paper is to evaluate the spring phenological phases outbreak influence on growth processes and stem circumference changes of Norway spruce (Picea abies /L./ Karst.) during years 2010 - 2012. The stem circumference changes of three spruce provenances originated from Volovske vrchy were measured during vegetation periods from 2010 to 2012 in the Botanical garden of Technical University "Borova hora" Zvolen. Spring phenological phases were observed on chosen tree provenances. Stem radius was monitored continuously with dendrometers DRL 26 (EMS Brno, Cz) with automatic data storage at 1 hour intervals into data-logger. The research provenance plot is located at an altitude 350 m asl. The microclimate elements (air temperature (°C), air humidity (%), precipitation (mm), global radiation (W.m -2 )) and the soil temperature (°C) and soil water potential were measured simultaneously. The changes of a stem diameter started during the phenological stage of needle buds bursting and the diameter increment was measurable since the beginning phenological stage of a needle buds flushing. The length of both phenological stages is significantly influenced by site elevation. The stem growth began the 1 st of May in 2010, the 22 th of April in 2011, the 16 th of April in 2012. Total increment in year 2012 was about 20% lower than in 2011 and about 30% lower than in 2010 that was caused by soil drought during summer 2012.