Response of phenological events to climate warming in the southern and south-eastern regions of Romania

摘要

The analysis of phenological changes in vegetation is essential for the assessment of the response and adaptation of ecosystems/agro-ecosystems to climate change. This study analyses spatial and temporal changes in phenological events (phenophases) and in the climatic growing season in southern and south-eastern Romania, based on mean monthly temperature values recorded between 1961 and 2010 at 24 weather stations, spread out uniformly in the study area. By using the histophenogram method for extracting the mean phenophases length (eight in total, i.e. growing season onset, budding-leafing, flowering, fruiting, maturing, dissemination, start of leaf loss and end of leaf loss) and that of the overall growing season, this paper aims to analyse current phenological changes (in three periods, 1991-2000, 2001-2010 and 1991-2010) in relation to 1961-1990, which is the reference interval in various global climatic studies. Following the analysis of the theoretical phenology length, based on the temperature thresholds (between 5 and 25 A degrees C) that differentiate biological cycles of vegetation, results showed an overall increase in phenological activity (especially in the past decade, 2001-2010), except for two phenophases (fruiting and dissemination), for which largely dominant length decreases were identified. Quantitatively, increases (and null changes, in a few cases) in phenological length generally range between 0-5 days/0-10% (e.g. in the budding-leafing phenophase) and 11-15 days/10.1-20% (maturing), considering the absolute changes or percentages in the three periods, compared to the reference interval 1961-1990. For the most part, the current decrease in the fruiting and dissemination phenophases falls in the interval -1 to -5 days/-10.1 to -20%, compared to the reference period. At the same time, it was noticed that the entire growing season has been expanding, especially in the past decade, when numerous increase instances of up to 15 days were recorded, corresponding to a dominant interval of 0-10% from the period 1961-1990. The results can be particularly useful for adapting the different types of crops to future climate changes, considering that the study area has a high agro-ecological importance.