Fig 1.
Study area maps of land tenures and communities.
(A) Land tenures (defined by ownership and management practice), towns, and major highways. See Table 1 for land tenure descriptions. (B) Communities as defined by US Census data on core community area and surrounding SILVIS wildland urban interface (WUI) polygons. Community boundaries (light gray polygons) represent the combination of the core community area and associated WUI.
Table 1.
Major land tenures and transmitted wildfire estimated with wildfire simulation.
Fig 2.
Simulated fire perimeters and ignition locations and associated land tenure map.
Perimeters and ignition locations of (A) six of the largest fires based on area burned, and (B) two of the most destructive fires based on exposure to the most number of structures. Perimeters were extracted from over 63,736 simulated fires sampled from distributions modeled from historical ignition location and fire size. See Table 1 for land tenure descriptions.
Table 2.
Organization of risk governance and wildfire transmission into networks.
Fig 3.
Spatial distribution of historical ignitions by fire cause.
(A) Human and (B) natural caused ignitions in the study area based on historical ignition data between 1992 and 2009 [64], totaling 11,618 ignitions.
Fig 4.
Temporal and seasonal distribution of historical ignitions in the study area.
(A) Monthly distribution of total number of human and natural caused ignitions based on historical ignition data between 1992 and 2009 [64], and (B) associated monthly maximum energy release component (ERC) for the same time period based on 25 remote automated weather stations [49]. (C) Total number of ignitions by day-of-year and fire cause during the same time period.
Fig 5.
Wildfire area burned by land tenure classified by transmission type and fire cause.
Total annual fire transmission from human (A, C) or natural (B, D) caused ignitions. Data shown both as the average annual area burned (A,B), and the percentage of total fire transmitted (C, D). See Table 1 for land tenure descriptions.
Fig 6.
Variation in fire hazard for the seven largest land tenures.
Cumulative proportion of pixels in the study area by (A) conditional flame length, and (B) burn probability for the seven largest land tenures in the study area. See Table 1 for land tenure descriptions.
Fig 7.
Wildfire transmission networks for the seven largest land tenures.
Networks show wildfire transmission between the seven largest land tenures in the study area, separated by human (A) and natural (B) ignitions. Network edges represent wildfire transmitted from one land tenure to another, as shown by the arrow and colored by its source. The size of each node corresponds to the amount of fire transmitted from that node. Only edges greater than 20 ha yr-1 are shown, representing 75% of the all transmitted fires. See Table 1 for land tenure descriptions.
Fig 8.
Community exposure to external wildfire by fire cause.
Total annual area of fire transmitted to the 16 communities within the study area that received the most fire, separated by (A) human and (B) natural ignitions as estimated from simulation modeling. Wildfire received from adjacent lands is colored by large land tenure. Numbers following community names indicate node in-degree (number of neighbors transmitting fire). See Table 1 for land tenure descriptions.
Fig 9.
Wildfire transmission networks from major land tenures to communities.
Wildfire exposure to the 16 communities that received the most fire from adjacent land tenures in the study area, divided between (A) human, and (B) natural ignitions. Network edges represent wildfire transmitted from one land tenure to a community, as shown by the arrow and colored by its source. Edge thickness corresponds to the magnitude of transmission. Solid lines show wildfire transmission >10 ha yr-1 calculated by combining the ignition sources. Dashed lines represent edges with values <10 ha yr-1 and >1 ha yr-1 when separated by ignition source. Nodes of major land tenures are sized by amount of fire transmitted; community node size is fixed. Note that transmission between major land tenures is not shown. The network diagram corresponds to information shown in Fig 8. See Table 1 for land tenure descriptions.
Fig 10.
Relationship between community wildfire exposure and land tenure diversity.
Number of land tenures transmitting fire (i.e. node in-degree) and total fire received (incoming fire) per year for the 56 communities in the study area for (A) human and (B) natural ignitions. Note that the outlier Warm Springs is not shown.
Fig 11.
Fireshed map showing the area predicted to transmit fire into communities based on structure exposure. Orange = developed areas; dark gray = individual firesheds for the 16 communities that received the most fire; light gray = firesheds for the remaining 40 communities.
Fig 12.
Community fireshed composition.
Community firesheds represent the land tenure composition around each community most likely to contribute to fire exposure. See Table 1 for land tenure descriptions.
Fig 13.
Comparison of community wildfire exposure and fireshed composition by land tenure.
Each panel represents one of the 16 communities with the highest level of exposure. Diagonal line indicates an exposure of 2 structures per 1000 ha of fireshed area. Land tenures above the line have higher than this value, indicating high efficiency at transmitting fires to structures. Land tenures below the line indicate lower transmission per area in the fireshed. See Table 1 for land tenure descriptions.