<正>据养分平衡原理对落叶前后刺槐不同器官养分的迁移动态进行了分析，计算了各养分元素参与内循环和外循环的养分通量及循环率，结果表明：刺槐叶子在凋落前，氮、磷、钾、镁、硫均发生不同程度的回流，回流率分别为６３．９４％、６１．８３％、７６．３９％、１８．３３％和６９．６０％。钙却发生顺流，使落叶、果的钙含量增加１倍之多。在各养分元素中，钾的总循环率最高达５９８１％，其它较低，约为２６１７％～３７．１９％，而且氮、磷、钾以内循环为主，内循环率分别为２２８６％、１６８１％和５１５％，而外循环率大致为８３５％～９９９％。钙、镁、硫的内外循环率基本接近，大致为１５１０％～２１８３％。且有迹象表明，在落叶前后刺槐仍然从土壤中摄取少量的钾、镁，而随雨水淋溶或分泌向外排出少量的硫。

According to the principle of nutrient balance, the nutrient movement in different organs of blacklocust about the leaching of leaves has been analysed. The flux and cycling rates of every nutrient participating in internal and external nutrient cyclings have aslo been calculated and the results show that the nutrients of N、P、K、Mg and S backflow (from leaves and fruits to other organs) in different extents before the leaching of leaves and the backflowing rates are 63．94％，61．83％，76．39％，18．33％ and 69．60％. respectively except that Ca flows from other organs to leaves and fruits and makes their Ca content 2 times as before. Amonge these nutrients, the gross cycle rate of K is 59.81%, as the greatest of all, and the others are 26.17%～3719%. N、P、K participate in internal cycles mainly and the intercycle rates are 22.86%, 16.18% and 51.51% respectively, but their extercycle rates are 8.35%～9．99％. Ca、Mg and S praticipate in both intercycle and extercycle with the similar cycle rates nearly as 15.10%～2183%. The results aslo show that blacklocust absorbs K、 Mg from soil and gets rid of S with raindrop or secretion in little amout about the leaching of leaves.