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, 萌芽内氮素营养水平最高，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 Chinese 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 optiaml cutting seasons by which the sprouting amount from a stump, the N nutrition Ievel in the sprouting buds and the growth rate of sprouts were the highest. Sprouting 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 optimal cutting season and predicting the growth rate of sprouting.