| Based on the investigation in 1985 and 1994, and analysing the data of forest resource in 1998, 2000, the result of tendency of shrinking of forest resource in last 30 years,especially in 90s last century was found. The character of main meteorological data in 1971-2000 has been considered. The factor which affects the forest resource are annual accumulated temperature (≥0℃) and precipitation. It is more important to match the rain with heat. The suitable index of precipitation of year is 525 mm, ranging 495555 mm;of annual accumulated temperature (≥0℃) 3 930 (℃·d), ranging 3 555~4 340(℃·d),The line of 3 930(≥0℃) annual accumulated temperature has been moved to north clearly and the line of 500 mm precipitation has been more to south obviously. The tendency of climate changing to dry and warm is the main reason for forest line moving to the south and the forest resource decreasing rapidly. |