Changes of flowering phenology of six herbal species in a beech forest [Central Slovakia]: a decade analysis

The variability in flowering phenology of six forest herbaceous species: Pulmonaria officinalis L. (early spring species), Dentaria bulbifera L. (mid spring), Galium odoratum Scop. (late spring), Veronica officinalis L. (early summer), Mycelis muralis (L.) Dumort. (mid summer) and Campanula trachelium L. (mid/late summer) was analysed over the period of the past ten years (1995–2004). Observations were done in a beech forest at the Ecological Experimental Stationary in Kremnické vrchy Mts (Central Slovakia, 48°38´N, 19°04´E, 450–520 m a.s.l.). Two phenological events – the first flowering and full flowering as well as the duration of interphase interval were analysed. The timing of observed phenological events was related to selected climatic factors (temperature and precipitation). The highest variation in the first flowering date was observed in early spring species- standard deviation (SD) was equal to 7.2 days. As for full flowering date, the highest value of standard deviation was detected in late summer species (SD = 8.5 days). In respect to the duration of interphase interval (in days), the highest relative variability (cv > 53%) was ascertained in early spring species. The significant correlations (P <0.001) were detected between dating of full flowering and cumulative temperatures in all phenological types (excepting early spring); the coefficients of correlation (r) moved from – 0.85 (early summer and mid summer species) to – 0.91 (mid spring species). Significant correlations were revealed between precipitation and timing of flowering only for mid summer (r= +0.70) and late summer species (r= +0.75), respectively. Despite of the fact, that no significant trends were detected in timing of flowering in the species, the effect of the global warming is evident. The values of the possitive deviations of the mean air temperatures averaged for the period of the last decade were increased in comparison to the long-term mean. Onset of flowering has been shifted earlier a few days in majority of the species during the past decade. Decade tendency showed a slight increasing of values of cumulative temperatures during the periods crucial for the development of the phenophases.