Needle water potential of selected pine species during the off-season: A case study

摘要

In this study we investigated the needle water potential of different pine species using a pressure chamber during winter months. Totally, seven pine species Pinus jeffreyi Greville & Balfour, Pinus ponderosa P. & C. Lawson, Pinus uncinata Ramond ex de Candolle, Pinus nigra Arnold, Pinus sylvestris Linnaeus, Pinus heldreichii Christ, Pinus cembra Linnaeus representing ecological variability of this genus were selected for measurements. Although the water potential is well documented in many tree species during the vegetation season, data from the off-season are scarce. During the investigated seasons (November 2014, January and February 2016), days with air temperature (T) above and below 0°C were selected for the measurement. During the days with air T above 0°C and global radiation reaching 3,000 kJ·m^–2·day^–1, the water potential averaged –0.6 ± 0.4 MPa. On the contrary, under T below 0°C and global radiation above 6,000 kJ·m^–2·day^–1, the needle water potential was close to zero (–0.3 ± 0.2 MPa) regardless of the pine species. The reason why the needle water potential reflects air T and is negatively correlated with the global radiation in winter will be an objective of our future investigations