Effect of the forecast climate change on the pear tree water requirements in the Bydgoszcz region

The aim of the present research has been an attempt at evaluating the water requirements of pear trees over 2016-2050 in the Bydgoszcz region drawing on the forecast changes in temperature. The paper draws on the forecasting of mean monthly temperature for the Bydgoszcz region in 2011-2050 according to the climate change scenario for Poland SRES: A1B (Bąk, Łabędzki 2014). The water requirements of the pear tree have been determined based on the indispensable precipitation determined by Kemmer and Schulz. The water requirements were calculated for the period January through December and May through September for each year in the 35-year period (2016-2050). The reference period was made up by a 35-year period immediately preceding it (1981-2015). In the period 2016-2050 in the Bydgoszcz region, in the light of the temperature change scenarios made, one should expect an increase in the water requirements of the pear tree. Determined with the Kemmer and Schulz method, the required optimal annual (January-December) precipitation will increase for the pear tree from 624 mm to 771 mm (by 147 mm, namely by 24 %). The optimal precipitation trend equations show that in the reference period (1981-2015), calculated with the Kemmer and Schulz numbers, the optimal annual precipitation was increasing in the pear tree in each pentad by 5.1-5.5 mm. In the forecast period (2016-2050) the water requirements will increase, on the other hand, in each pentad within a much greater range (7.5-8.4 mm). In, determined by Kemmer and Schulz, summer period (May-September), the total precipitation, expressing water requirements, optimal for the pear tree in 2016-2050 will increase by 73 mm.