Abstract: To understand the effects of water stress on non-structural carbohydrate (NSC) distribution in leaves, stems and roots of poplar seedlings, one-year-old poplar seedlings were grown under suitable water level, mild, moderate and serious drought treatments for 15, 30, 45 and 60 days in pots. The results showed that compared with the suitable water treatment, soluble sugar and NSC contents firstly increased and then decreased in leaves and stems with increasing treatment time under water stress treatments. Soluble sugar and NSC contents declined in roots under mild and moderate stress treatments, whereas they firstly elevated and then reduced under serious stress treatment. Starch content in leaves firstly increased and then declined under mild stress treatment, whereas it firstly decreased and then increased under moderate and serious stress treatments. Water stress significantly decreased starch and NSC contents in stems and roots after 45 days of water treatment. On the 60th day of water treatment, the decline rate of NSC content in different organs followed the order: roots>stems>leaves. Meanwhile, the decline rate of starch content was greater than that of NSC content. Soluble sugar content declined in leaves, but being stable in stems and roots. These results indicated that water stress decreased NSC reserves of poplar seedlings, which may lead to death due to environmental stresses.

Key words: evapotranspiration, eddy covariance, oasis-desert, soil moisture.