湖南冰雪灾害致森林毁损的气象原因

Meteorological Reasons for Forest Damage by Ice and Snow in Hunan Province

比较分析2008年初冰灾期间湖南部分地区气象资料,并与各地森林冰灾损失情况进行比较。湖南森林损害主要表现为腰折或翻蔸、断梢、折枝等机械损伤,有的树种伴随有生理损害。各地马尾松、湿地松、杉木、针阔混交林受害程度为中、重度的蓄积量比例达40%～100%不等,主要随地区冰灾严重程度而异。郴州、永州、衡阳等南部地区是特重灾区,益阳、常德、岳阳等地系一般灾害区,其余地区为重灾区。造成冰灾的主要气象原因是接近0℃的日平均气温(-1～0℃)和高于85%的日平均相对湿度的配合及上述2种组合条件的长时间维持。这样的冰棱形成条件,造成空中和地面树枝、树干、电线等附着物结冰和冰晶过度发育,并使得此次冰灾不同于本区域有记载的其他历次冰灾。这一现象,与全球气候变暖和中低空纳米级悬浮物密度增加有一定关系。

Based on the meteorological data and forest investigation data in several regions of Hunan Province during the huge ice disaster from January 13 to February 5,2008,damage degree of the forests was compared and analyzed.It was found that the forests were mechanically damaged by the stems broken,whole tree fell down,or tops and twigs broken.Some tree species also suffered from physiological harm besides mechanical damage.The proportions with intermediately to seriously damaged timber volumes were in a range of 40% to 100% for Pinus massoniana,Pinus elliottii,Cunninghamia laceolata,and the mixed wood of conifer and broadleaf trees in different regions,depended on intensity of the ice disaster.The most serious disaster occurred in the southern regions,such as Chengzhou,Yongzhou,Hengyang and etc.The disaster degree in the north part of Hunan,such as Yiyang,Changde and Yueyang,was relatively light.The other regions of Hunan were recognized as the serious disaster area.The meteorological reasons causing the ice disaster included high average dairy air temperature（-1℃-0℃）that was higher than that occurred during the terms when similar ice disaster happened in the previous years,combined with high average dairy relative humidity（greater than 85%）.The weather lasted for many days so that ice crystals formed easily and over developed on the surface of trunks,twigs or electric wires.Those characteristics made this ice disaster different from others recorded ones in the same area.This rare phenomenon may relate to the global warming climate and the density increase of floating dust particles in sizes of nanometers.