The impermanence of life.
The laws of life development in nature. Anyone will have a time to fall leaves. The leaf falls or returns to the place where it was raised. This is: from where it comes, to where it goes.
People often use the phrase "the autumn wind sweeps away the falling leaves" to describe the autumn scenery in temperate regions. Autumn is here, poplar trees, acacia trees and other broad-leaved trees leaves gradually aging, with the rustling autumn wind, yellow leaves will quietly fall. You may be sorry for the fall of the leaves, but have you ever thought that the fall of the leaves is precisely the self-protection of the trees.
There are two kinds of leaf fall: one: whenever the drought or cold season comes, all the tree leaves die and fall off, only the branches and trunks, for deciduous trees, such as peach. The other: in the spring and summer after the occurrence of new leaves, the old leaves gradually fall off, on the whole tree to see, all year round evergreen, for evergreen trees, such as camphor.
Causes of defoliation:
1, internal causes: leaf after a certain period of physiological activity in the cell a large number of metabolic products, such as mineral accumulation, causing physiological decline and death (chlorophyll destruction).
2, external causes: the weather becomes cold, the soil temperature is reduced, the rain is reduced, the root system water absorption capacity is greatly weakened.