The smooth transition in the process of transplanting can reduce the temperature difference of tree species and improve their external cold tolerance. Through a step-by-step way, the intrinsic potential of tree species is constantly stimulated, and finally it is completely adapted to the brand-new low-temperature environment, so that the intrinsic potential is consistent with the external performance.
The external expression of cold tolerance of tree species is intuitive, and how many degrees of cold a tree can endure in a certain environment can be measured and recorded by data. The meteorological data of decades and hundreds of years and the corresponding cold resistance performance of tree species have great guiding significance for garden-related work. However, these guiding significance is limited to conventional tree species. For new and rare varieties, it is very important to tap their inherent cold tolerance potential and threshold and find the critical value.
Some unusual tree species also have strong cold tolerance potential, such as Tilia microphylla' Green Mountain', Tilia hybrid' Jiahe', Tilia amurensis' Green Umbrella', Freeman Acer' Autumn Flame', Freeman Acer' Mamu' and Freeman Acer' Fairy'. For less common tree species with certain cold tolerance potential, we should gradually transition from south to north and from east to west to enrich the diversity of tree species in northeast and northwest cities.
The cold tolerance of some tree species in the critical area is not fixed, and they can survive in this small environment, but not necessarily in another small environment not far away. Trees that have survived for more than ten years may be destroyed by a severe cold. Therefore, for some tree species with uncertain cold tolerance in the critical area, priority should be given to experimental planting and careful application, especially not to be widely used as main street trees.
In the process of combining the external cold resistance of tree species with the internal cold resistance potential, some tree species need special care during wintering. The formation of this process is closely related to the external living environment and the internal individual growth. The worse the living environment and the greater the change, the worse the cold resistance of tree species; The more vigorous the individual growth, the stronger the plant and the stronger the cold tolerance, and vice versa. Therefore, the cold and antifreeze work in seedling production is basically to improve the robust value of tree species and the comfort of living environment. This truth is described in an anthropomorphic way, that is, a person with good physical quality, living in a warm house, will have little chance of catching a cold.
When the external cold resistance of tree species does not reach the internal cold resistance potential, or when the tree species is in special circumstances, corresponding cold and antifreeze measures should be taken, and according to the local microenvironment, combined with various measures, the protection should be in place as far as possible to ensure the safe overwintering of seedlings. There are many common cold and antifreeze measures, but they can be roughly divided into two categories: improving the comfort of living environment and enhancing the robust value of trees.
Anti-freezing measures to improve the comfort of living environment: ① pour anti-freezing water and turn green water; (2) establish a windbreak barrier; 3 wrap the trunk; (4) root neck culture; (5) snow accumulation at the base of trees; ⑥ Surface coverage; ⑦ Build crescent mound in early spring; (8) Knock off the snow on the branches, etc.
The measures to improve the robustness of tree species are: painting the trunk white before freezing; (2) spraying antifreeze; ③ Fertilization in spring; ④ Appropriate application of phosphorus and potassium fertilizer in autumn; ⑤ plastic trimming, etc.