Key words: 
• botany /
• triploid Populus tomentosa /
• clone /
• leaf nutrient /
• annual change

Abstract: Populus tomentosa is the main tree species for afforestation in north China. To maintain its productivity，annual changes in leaf nutrient concentrations of N，P，K，Ca，and Mg with 11 clones of triploid P. tomentosa （S1 through S9，S11，and S12） were studied with diploid P. tomentosa （S10） as a control. The one-year-old seedlings were afforested in 2005，in Pinggu of Beijing，and leaves were gathered respectively in April，July and October of 2006 by representative sampling method with three replications，for determining N，P，K，Ca，and Mg concentrations in leaves. Results showed that （1） for a given nutrient，triploid P. tomentosa leaves had similar seasonal variations，N，P，and K，levels declined during the whole growth period；Ca gradually increased，while Mg increased and then decreased. Also，（2） greater P concentrations in leaves of different clones were highly significant（P＜0.01，n = 36）with the greatest being 1.85 g·kg－1 in S5. Additionally，（3） compared to diploid P. tomentosa，throughout the growing season，P concentrations in leaves of triploid P. tomentosa increased for clones S1，S3 through S7，and S12. Finally，（4） during the growing season，for the different clones of P. tomentosa，concentrations of these macro elements were similar with the order and average content （in g·kg－1） of the five nutrients as：N（24.31）＞K（17.23）＞Ca（4.36）＞Mg（1.94）＞P（1.56）. ［Ch，5 fig. 2 tab. 8 ref.］