Transpiracja drzewostanu i ewapotranspiracja ekosystemu sosnowego w powiązaniu z ewapotranspiracją potencjalną wyznaczoną różnymi metodami

The aim of the study was to estimate the transpiration (TR) and actual evapotranspiration (EVT) of Scots pine stand, i.e. a typical Polish forest ecosystem. The study was performed in the 74−year−old stand growing on poor sandy soil. Transpiration of pine trees was determined by sap flow measurements of some individual trees by Thermal Dissipation Probe method. Actual evapotranspiration was determined based on measurements of soil moisture using Time Domain Reflectometry method and on changes in soil water storage. Based on these results, the reduction ratios were determined to estimate TR and EVT from potential evapotranspiration (ETP) calculated according to Priestley−Taylor (PT), Hargreaves (H), Makkink (M), Penman (Pen org), Penman−Shuttleworth (Pen Shut), the FAO Penman Monteith (FAO PM) and Penman Monteith (PM) methods. Measured transpiration of Scots pine stand reached 56% of the actual evapotranspiration. The methods used for the calculation of the ETP can be ranked in terms of the results from the lowest to the highest: METP were calculated for transpiration in a Scots pine stand in Poland and equal: PT – 0.256, H – 0.490, M – 0.562, Pen org – 0.301, Pen Shut – 0.279, FAO PM – 0.318 and PM – 0.308. Reduction factors for actual evapotranspiration amount to: PT – 0.462, H – 0.872, M – 0.999, Pen org – 0.535, Pen Shut – 0.498, FAO PM – 0.565 and PM – 0.548.