Abstract:

Pinus slyvestris var. mongolica was introduced to Zhang Gutai from Honghuaerji Sandy Lands, Hulunbeier of Inner Mongolia. During its young and middle ages, the growing was stable and fast. However, to those 35～40 years old trees, early decline occurred , growing period shortening resulted. By observation on 17 fixed positions, analysis showed that the early decline was mainly caused by the changes of its growing pattern, such as the peak growth period shifted to an early date and became shorter; peak numerical value was high and the vigorous growing period became shorter. due to moisture and heat differences between its original and present growing places. Moreover, another reason of early decline was the development of Diplodia, which was caused by the local climate, that is less precipitation in May and June and concentrating precipitation in July and August. However, Pinus slyvestris var. mongolica is the main species in afforestation which is superior in ecological and economic benefits to others, therefore, in order to reduce the development of diseases and prolong the growth period, selection of decease resistant species, establishment of mixed plantation with intensive management are adopted as the main measures to solve the problem of early decline.

Key words: Pinus slyvestris var. mongolica, Growing pattern, Moisture shortage, Diplodia, Early deline