4. Ms. Daphna Uni

Among living tree species, Acacia raddiana (Savi) and Acacia tortilis (Forssk), species of the legume family, populate some of the hottest and driest places on earth. Our research investigates the physiological processes underlying the unique survival of trees in extreme environmental conditions. We measured Acacia trees in their natural habitat together with a controlled experiment under scenarios of drought and low N on a lysimeters system to unravel their water use strategies and growth dynamics. In the field, temperature positively influenced the growth rate of the trees, daily and annual gas-exchange curves showed higher gas exchange during noon and in summer, when temperature and radiation are maximal (44°C, 2000 µmol m-2 s-1), and the air is dry (21% RH). Furthermore, in the controlled experiment, Acacia saplings keep transpiring water (180g per day), especially at noontime (0.08 g/gplant/ min), and therefore continue growing in low soil water content of 5%. With climate change predictions, understanding the response of these trees to varying environmental conditions is important both for conservation and to increase carbon sequestration in a warming and drying Earth.