Water potential of coniferous trees growing at METU Ataturk forest

In this study, the drought resistance of the black pine (Pinus nigra Arnold. subsp. pallasiana (Lamb.) Holmboe), scotch pine (Pinus silvestris L.) and cedar (Cedrus libani A. Richard.) which are widely distributed at the METU Atatürk Forest by measuring their water potential during growth period are determined. To do this, the healthy and approximately even age trees were selected and marked as sample trees from each species at three different optimum growth sites for the water potential measurement. The first water potential measurements were made at the dates between 02.08.2003 and 15.08.2003 just before sunrise between 05:00 a.m. and 07:00 a.m. oclock from the smooth and uniform cut side branches having diameter of 0,3-0,7 cm from the selected sample trees by a sharp knife; and they were placed in a pressure chamber immediately. Similarly, the second water potential measurements were repeated at the dates between 20.08.2003 and 04.09.2003. Statistical analysis showed that there is no significant difference between localities (p>0,005) but, there is a significant differences between species (>0,001). The mean values of water potentials for time 1 and time 2 are -9,767 Bar and -10,27 Bar respectively. The water potential values ranged from the highest to the lowest as cedar, black pine and scotch pine respectively. There were no significant water potential differences among the interaction for the measuring time, species and growth localities. As a conclusion, cedar because of having higher water potential as compare to the black pine and scotch pine is the least affected species from water stress.