杉木伐桩萌芽的氮素营养

在北亚热带黄棕壤上的２８年生杉木林分内，设置不同季节伐木的５个处理（秋伐、冬伐、初春伐、初夏伐和夏伐），研究它们的伐桩萌芽内氮素营养、内源激素、休眠芽萌发数及萌条生长量的差异。结果表明：前１年冬伐（１２月８日）和当年早春伐（３月８日）是最佳伐木时间，此时杉木伐桩上的萌发势最强，萌芽内氦素营养水平最高，生长量也最大。休眠芽的萌发数主要与细胞分裂素关联；而不同伐桩萌芽内氮素营养状况的差异，主要是与氮素养分在植株内的运转（特别是还原态氮向树干基部和根系的回流作用）有关。不同季节采伐，意味着在不同时期截断植株的向上运输和回流，因而得到氮素营养水平的不同结果。环割试验进一步证实了这项推论。由此可见，伐桩萌芽内的全氮量和氨基氮浓度，可以作为论证合适伐木季节和预测萌条生长量的生理指标。

Nitrogen Nutrition in Sprouting Buds from Chinese Fir Stumps.

In the northern subtropics of China,in a 28-year-old Chinese fir stand grown on yellow-brown soil,5 treatments of various cutting seasons were established to study the differences in nitrogen nutrition, endohormones,sprouting amount and growth rate of the sprouting dormant buds from Chi-nese fir stumps.It turned out that winter cut (Dec. 8 of last year) and early spring cut(Mar. 8 of the current year)were the optimal cutting seasons by which the sprouting amount from a stump,the N nutrition level in the sprouting buds and the growth rate of sprouts were the highest.Sprout-ing amount per stump was closely related to CTK level in sprouting buds,while the difference of N nutrition in the sprouting buds from various stumps was mainly attributed to the translocation of N nutrients within the tree,especially the downward reflux of reductive N to the basal part of stem and root system.The ring-barking experiment further proved this inference.Therefore,the concentrations of total N and amino N in the sprouting buds can be adopted as the physiological indice for demonstrating the opt imal cutting season and predicting the growth rate of sprouting.