Annual cycle refers to the whole process of fruit tree growth and development within 1 year. In deciduous fruit trees in the north, the main characteristics of the annual cycle are obviously manifested in two different stages: growth and dormancy. In the growth stage, it includes germination, flowering, branching, leaf spreading, flowering, fruit setting, and a rooting process if it is from pruning to growing; The process from falling leaves to sprouting again is called dormancy period. Although the life activity of dormant fruit trees is weak, it has not stopped completely. In the annual cycle of fruit trees, with the change of seasons, the growth and development of fruit trees show certain rhythm and regularity. The dynamic growth period of fruit trees with obvious appearance signs and practical significance is called phenology. The main phenological periods in the annual cycle of fruit trees generally include: root activity period, germination period, flowering period (this period can be subdivided into initial flowering period, full flowering period and final flowering period), leaf unfolding period, new shoot growth period, fruit development maturity period, flower bud differentiation period and defoliation period. In different phenological stages of fruit trees, the growth center and growth characteristics of fruit trees are different, and the requirements for environmental conditions and cultivation techniques are also different, and the response to pruning is also different.
Life cycle and annual cycle are the most basic and important development processes of fruit trees, and all cultivation techniques and measures adopted should adapt to the growth and development characteristics of each period. In young fruit trees, the centrifugal growth of crown and root system is faster, the growth potential is stronger, the new shoots grow longer, the amount of branches and leaves and the absorption area of root system continue to expand, and the nutrients accumulated in the tree body also increase with the increase of tree age. Coupled with the effects of endogenous hormones such as auxin, gibberellin, cytokinin and abscisic acid, the fruit tree gradually changed from single vegetative growth to reproductive growth, formed flower buds and began to bear fruit. Therefore, the pruning of young fruit trees should strengthen the comprehensive management of soil, fertilizer and water, promote the healthy growth of young trees, increase the amount of branches and leaves, cultivate fruiting branches and promote flowering and fruiting. Therefore, the pruning amount of young trees must be light, and the fruiting branches and high-yield tree structures should be cultivated at the same time, creating conditions for early high-yield and accelerating the entry into full-fruit period; Fruit trees have the highest yield and the best quality after entering the full fruit stage. The main goal of cultivation management and pruning is to prolong the full fruit period as much as possible. However, in the fruit-bearing period, due to high yield and consumption of many nutrients, trees are prone to aging or fruit-bearing in different years. In the later stage of fruiting, the fruiting branches in the crown died from delicate and began to grow centripetally, that is, the main branches were from more to less, the crown was from big to small, and the yield was from more to less. Therefore, in the fruit-bearing period, the supply of fertilizer and water must be sufficient. On the basis of vigorous growth of trees, careful renewal and pruning should be carried out to adjust the amount of flowers and fruits, maintain the growth and fruiting ability of fruiting branches, prolong the fruiting period and improve economic benefits. After the fruit tree enters the aging period, the crown gradually shrinks, the backbone branches and roots begin to die, the yield decreases year by year, the fruit size also decreases gradually, and the economic benefit decreases year by year. This orchard can be updated and pruned without losing its economic cultivation value, and the whole orchard should be updated in time after losing its economic cultivation value.
In the whole life cycle of fruit trees, aging is absolute, rejuvenation is relative, and pruning is to make fruit trees rejuvenate before natural death.
In the annual cycle of fruit trees, the manufacture, transportation, consumption and accumulation of nutrients have certain changing rules, and organs such as branches, leaves, flowers, fruits and roots also move according to their own rhythms. Whether this rhythm is normal or not will have a significant impact on the balance of various parts of the tree and the yield and quality of the fruit. Therefore, ensuring normal growth rhythm and stable tree balance is an important technical way to achieve high quality and high yield of fruits. Pruning technology, especially in summer, has obvious influence on the annual growth rhythm of fruit trees. The function of summer pruning is to control and regulate the production, transportation and accumulation of nutrients in trees and change the production and interaction of hormones to maintain the balance between growth and fruit. The focus of summer pruning is to adjust the growth intensity, promote flower bud differentiation and fruit growth and development.