Effect of biometeorological variables on the onset of phenophases derived from MODIS data and visual observations

In this study we analyzed the effect of selected biometeorological variables on the onset of phenophases in three beech stands in different climatic areas (warm, moderately warm and cold). We have focused on two phenophases - leaf unfolding and leaf colouring. Timing of both phenophases was identified visually and using series of MODIS satellite images. The data were collected during a 13-year period (2000-2012). For the spring period, we found a significant dependence between temperature and precipitation-based biometeorological variables and leaf unfolding in both datasets - those based on visual and remote sensing-based observations. The average air temperature in the period from February-April was the most significant factor which initiated the onset of beginning of leaf unfolding in all three investigated stands. The evapotranspiration-based biometeorological variables (climatic water balance, actual evapotranspiration, dryness index) had no effect on the onset of the beginning of leaf unfolding observed using both methods. The high precipitation totals in April caused the later onset of leaf unfolding in all stands. The relationship between the first autumn phenophase - leaf colouring and biometeorological variables was found significant in beech stand in the warm climatic area only.