Abstract: Taking the Populus euphratica in Corps 150 ‘foison forest’ at south edge of Junngar Basin as test object, and by comparing it with Haloxylon ammodendron and Tamarix ramosissima, this paper studied the change characteristics of water potential of P. euphratica in arid environment, and analyzed the relationships of these change characteristics with soil moisture and air temperature and humidity. The diurnal variations of P. euphratica  leaf  and stem water potential presented “V” type, while those of H. ammodendron and T. ramosissima’s were in “W” type. For elder P. euphratica , its leaf- and stem water potential was significantly negatively correlated with air temperature (r=-0.839 and -0.818, respectively); for young P. euphratica , its leaf water potential was positively correlated with air humidity (r=0.786), and its stem water potential was significantly negatively correlated with air temperature (r=-0.650). In the morning, the water potential of elder P. euphratica  leaves and stems at height 2 m was significantly different from that of the leaves and stems at heights 5 m and 10 m (P<0.05), but no significant difference was observed for the leaves and stems at heights 5 m and 10 m (P>0.05). At noon, the water potential of elder P. euphratica  leaves and stems at heights 2 m, 5 m, and 10 m all had significant differences (P<0.05); at 20:00, the water potential of the leaves at all heights had significant differences (P<0.05).

Key words: Grassland, Free grazing, Uptake and emission