Trend analysis of long-lasting air temperature and precipitation time series in a mountainous fir forest in central Greece. Implications for nitrogen uptake by plants

In the present work meteorological data, concerning temperature and precipitation in a mountainous Bulgarian fir (Abies borisii-regis Mattf.) forest, was analyzed in order to find trends for the period 1973-2019. The results showed that temperature values on annual and seasonal base, especially in summers, showed a significant increasing trend. In addition, the number of days with particularly high temperatures increased together with the daily temperature range. With regard to the rain height an increasing trend was found significant at the 0.1 probability level. The nitrogen concentration in current year needles of the Bulgarian fir measured in the period 1997-2019 showed an increasing trend. This fact could be a sign of increased mineralization rates of organic matter as a response to the temperature increase.