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ŠUMARSKI LIST 5-6/2012 str. 35     <-- 35 -->        PDF

1. Dormant vegetation, all the leaves have fallen (F0),
2. Leaves begin to develop (F1),
3. Leaves are fully developed (F2),
4. Leaves begin to change colour (F3),
5. Leaves have completely changed colour (F4),
6. The leaves begin to fall (F5).
The relevant indicators of the dynamics of phenophases were obtained by collecting and organizing data through phenological observations: average time of appearance in the annual cycle, the average duration of the annual cycle and the frequency of certain phenophases (table 1). Based on systematic observations of phenological data, the frequency of crossing between phenophases was determined as the neighbouring phenophases state differences (table 2). Data on the dynamics of air temperature were obtained from the State Meteorological and Hydrological Institute. The process of determining the characteristic distribution was carried out for the weekly mean air temperature for all phenophases when they are present, or when the state of phenophase is greater than 0 (table 5).
Gathered and processed data have allowed the building of the simulation model of the system of phenophases. Simulation model was based on system-dynamic approach (figure 1). In order to determine whether the model represents the real system satisfactorily, the process of model validation was carried out (table 6 and table 7).

The research of the influence of air temperature on leaf phenophases was conducted with the developed model, through different scenarios from 1 to 6. The results of the simulated scenarios (table 8, 9 and 10) confirmed the crucial influence of temperature on the leaves phenophases. The results of these studies have shown that on average, phenophases F1, F4 and F0, are the most sensitive on the fluctuations in air temperature, but above all F1 as first that reacts to change. However, they also showed that all phenophases are not equally responsive to temperature changes. It is interesting that phenophases F3 and F5 showed the least sensitivity to temperature changes, in terms of average time of occurrence. Such result of the simulation experiments indicates that those phenophases are significantly influenced by other factors.

Key words: phenology, phenophases, climate changes, modelling, simulation, system-dynamic approach, pubescent oak