Abstract: In recent years, extreme weather disaster happens frequently, and much attention has been paid to the disasters caused by frozen rain and snow. Behaving as intense disturbances, extreme frozen rain and snow disasters could exert strong effects on forest ecosystems, especially in the subtropical area of China where frozen rain and snow weather rarely happens. In South China, a long-lasting extreme meteorological disaster occurred from January to February 2008. This meteorological disaster was characterized by frozen rain and snow with extreme low temperature, which caused huge damage to the forests across a large region. Many studies have been made in this country on the general situation of this disaster, damaged conditions of forests, and related affecting factors, but the measurement criteria of damaged trees were rather subjective, rough, or incomplete, and the relevant concepts were confusing, which made it difficult to compare the results among different studies. In order to standardize the classification criteria of damaged trees and to clarify relevant concepts, we proposed the physiological and mechanical classification criteria of damaged trees based on previous studies and the climatic and biological characteristics of extreme meteorological disasters, which could be a reference to relevant studies. Meanwhile, the factors that could affect the damage status of forest trees during this disaster were analyzed, and they were summarized into two categories, i.e., one, affecting the weights of frozen snow and ice, and the other, affecting the resistance of trees. In the last, some comments for the forest restoration and reconstruction after the disaster were proposed, based on the affecting factors of the disaster and the secondary damages easily to be happened after the disaster.

Key words: Northeastern region, Forest resources, Ecological risk assessment