Acid rain has harmed a large area of forest. In the fire, many burned trees lost their lives and were frozen and cracked. In winter when the temperature is low and changes greatly, trees are easy to freeze and crack. When the temperature fluctuates greatly, frost cracking is most likely to occur. When the temperature drops below 0℃ and freezes, the outer xylem dries and shrinks. At the same time, due to the poor thermal conductivity of wood, the internal cells still maintain a high temperature and humidity. Therefore, the internal and external shrinkage of wood is uneven, resulting in great tension, which eventually leads to longitudinal cracking of the trunk. Frost cracking generally does not directly lead to the death of trees, but because of bark cracking, xylem loses protection and is easy to cause diseases and pests.
Freezing drought Freezing drought is a physiological drought caused by soil freezing. In cold areas, because the soil freezes in winter, it is difficult for the roots of trees to absorb water from the soil, while the branches, buds, leaf scars and leaves of evergreen trees on the ground are constantly losing water. Eventually, the destruction of water balance will lead to cell death, or even the death of the whole plant. winter injury
Insect pests and water shortage