Abstract:

Historical forest fires datum from Alaska State (1950—2000), California State (1895—2001), USA and Heilongjiang Province (1980—1999), P.R. China were used to calculate the longitude and latitude of annual burned area's centroids of these regions. Fluctuation phenomena by year were analyzed using spectrum analysis. The results showsed that burned area's centroids in these three regions are in fluctuation condition encircling the distribution center. The distribution centers in Alaska State, California State and Heilongjiang Province are 151.11°W Longitude, 64.96°N Latitude, 120.02°W Longitude, 37.11°N Latitude and 127.07°E Longitude, 49.59°N Latitude respectively. Fluctuation of burned area's centroids in Alaska State and California State in longitude has clear periodicity, and the periodicities are 4.2 a, 6.25 a in Alaska State and 6.24 a,106 a in California State. Fluctuation of burned area's centroids in Heilongjiang Province has periodicity both in longitude and latitude, and the periodicities are both 3.3 a, 6.67 a. Fluctuation of burned area's centroids in Alaska State and California State in latitude does not have periodicity, and low frequency large forest fires domain most of them.

Key words: forest fires, fuel, global change, fluctuation