LD3-2: Human activities reduce the resilience of boreal fire regime by increasing ignition frequency, reducing average fire size and total area burned, and introducing fire-prone species that amplify these effects. The long-term consequence of these effects depends on the edge-to-area ratio of landscape regions dominated by anthropogenic vs. natural fire regime.

To test the effects of human activities in determining fire regime, we will use fire data for interior Alaska from the national database system of the Alaska Fire Service (Bureau of Land Management [BLM]). This database contains data on all fires that occurred in this area since 1950, including the cause of the fire, the discovery date, and the management option of the land that burned, initial attack size of fire (i.e. size when suppression activities began), and final fire size. This database includes information about fires smaller than 0.4 ha (1 acre), in contrast to the GIS database at the BLM web site (http://agdc.usgs.gov/data/blm), which contains only fires larger than 400 ha from 1950 to 1986, and fires larger than 40 ha from 1987 to 2001. Data for fire suppression management options are available from the BLM website (http://agdc.usgs.gov/data/blm).

We will test human impacts on fire regime in three ways. (1) We will compare fire regime in 1-km pixels classified for suppression vs. those classified to receive no suppression, because our previous work shows that suppression has a larger effect on fire regime than does number of ignitions. (2) To test the effect of ignitions, we will compare the size distribution of human-caused vs. lightning caused fires within a given fire suppression category. (3) We will examine the effect of location within a fire suppression category on fire regime (for example, whether areas within an area designated for high-suppression are more likely to burn if they are next to an area with a let-burn policy than if they are surrounded by areas with a high-suppression category).

We will test the interaction of human impacts and vegetation flammability by comparing fire regime in the following sets of conditions: high suppression in black spruce, low suppression in black spruce; high suppression in open (less flammable) fuel types, low suppression in open fuel types.

We will document fire regime in terms of fire number per unit time and area, average fire size, fire size distribution, and area burned (as a percentage of total area). Other funded research explores the socioeconomic, cultural, and policy dimensions of human-fire interactions (Chapin, Rupp, McGuire, et al.).