Among the factors that affect the resistance of trees, the intensity and duration of weather disasters are the decisive reasons for the degree of forest damage. For a typical snow disaster, when the weight of snow or ice falling on a tree exceeds the limit of the trees, it can cause bending or breaking of the trees, resulting the permanent internal physiological damage to the trees. The researchers extracted the frozen areas of forest vegetation in the hilly areas of southern China in 2008 according to the freezing standard set by the National Meteorological Bureau (the daily average temperature is below 1 ℃ and the daily precipitation is more than 0 mm), and calculated the total precipitation and average precipitation during the freezing period. What’s more, the precipitation is superimposed with the assessment result of forest vegetation damage, as shown in Figure 1.
Figure 1a shows the relationship between the total amount of precipitation in the freezing period and the degree of damage to the forest vegetation. As the total precipitation increases, the proportion of the serious damage to the forest vegetation continues to rise. And the proportions of the moderate damage and slight damage to forest vegetation have been declined, especially after the total precipitation reaches 140mm, the proportion of severely damaged forest vegetation sharply rises even more than eighty percent. Before the total precipitation reached at 140 mm, the proportion of forest vegetation damage changed little. Figure 1b shows the relationship between the average precipitation during the freezing period and the degree of forest vegetation damage. As the average precipitation increases, the degree of forest vegetation damage is also increasing. Compared with the total precipitation, the average precipitation during freezing period has a relatively small impact on the extent of forest damage. All in all, the total precipitation during freezing period plays an important role in the destruction of forest vegetation.
The information is provided by Disaster Risk Reduction Knowledge Service.
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