Keywords: 
• Populus simonii ×(P. pyramidalis +Salix matsudana)cv .Poplaris /
• soluble salt ions /
• soil /
• groundwater

Abstract: The contents of soluble salt ions in different parts of Populus simonii (Populus pyramidalis +Salix matsudana)cv .Poplaris in the soils with different salt contents in natural habitats and the effect of soluble salt ions in the soil and groundwater on the salt content of Populus simonii (P .pyramidalis + Salix matsudana)cv . Poplaris were studied .The experiment on the contents of soluble ions in different parts of the tree was conducted with the water solution method .CO32 -and HCO3-were measured with dual-indicator titration method ;Cl -with AgNO3 titration method ;SO42 - , Ca2+ and Mg2+ with EDTA capacity method ;Na+and K+with flame photometer . The salt content in soil was determined according to Soil and Agricultural Chemistry Analysis .The results showed that there was significant difference in the total salt contents in soils under two forest belts , but there was no difference in soluble salt ions contents (=0.01)of corresponding parts (leaves , roots , heartwoods and sapwoods)under two forest belts .And there were some common characters :the sequence of total salinity of positive ions in each part was K+ Ca2+ Mg2+ Na+ , negative ionswas HCO3- SO42- Cl- .In the whole growth period , ions contents in leaves were higher than in other parts and changed within the largest range ;ions contents in heartwoods and sapwoods were lower and changed within a rather small range .Ions contents in roots were between leaves , heartwoods and sapwoods .The study showed that without salt stress ,Populus simonii (P. pyramidalis +Salix matsudana)cv .Poplaris absorption of the soluble salt ions and the distribution and accumulation of salt ions in it depended on its physiological characteristic and biological characteristic .The effect of salt content in soil was small.But the salt content in the water absorbed byPopulus simonii (P. pyramidalis +Salix matsudana)cv .Poplaris had remarkable effect on the salt ions contents in every part .In the non-irrigation reasons , the correlation between salt ions contents in different parts ofPopulus simonii (P. pyramidalis +Salix matsudana)cv .Poplaris and that in groundwaterwas significant .In the irrigation seasons or rainy , seasons , there was no correlation between salt ions contents in different parts of Populus simonii (P. pyramidalis +Salix matsudana)cv .Poplaris and that in groundwater .[ Ch , 3 fig .5 tab .10 ref .]