## 2 Materials and Methods  
### Study Area  
The study area, located in the U.S. Pacific Southwest, occupies the major part of Southern California, (Figure 1, Lat. 121-116\({}^{\circ}\)W, Lon. 33-35\({}^{\circ}\)N), covering a land area of approximately 57,600 km\({}^{2}\). It is mainly comprised of four physiographic provinces: the Transverse Ranges extending from northwest to central east, the Peninsula Ranges at the southeast end, the low-lying Los Angeles Basin between the two coastal ranges, and the Mojave Desert at the northeast corner [40]. The topography of this region is rugged and complex. The lowest coastal plains (<400 m a.s.l.) and the relatively higher inland desert (600-1200 m a.s.l.) are interrupted by a stretch of mountains (>1200 m a.s.l.). The coastal and mountainous regions are predominately controlled by a Mediterranean climate with mild, wet winters and warm, dry summers. In the narrow south coast and the southeast lowland, the Mediterranean climate gives way to a semi-arid climate, which is drier and where evaporation exceeds precipitation throughout the year. Both temperature and precipitation demonstrate variation with latitude and elevations. Further north and from the coast to the mountains, precipitation increases from 300 mm/yr to more than 800 mm/yr and annual mean temperature decreases from 20 \({}^{\circ}\)C to less than 8 \({}^{\circ}\)C. The Mojave Desert, which lies in the rain shadow of the Sierra Nevada Mountains and the Transverse Ranges, has a dry desert climate, receives limited precipitation (less than 300 mm/yr). The annual temperature ranges between 16-20 \({}^{\circ}\)C [55].  
The land cover distribution reflects the rugged topography and the diversity in climate, with the more forested area at the tops of the Transverse Ranges; principally developed, cultivated lands or oak woodlands, shrulands and grasslands over the lower plains; and vast desert scrubs over the Mojave Desert (Figure 2). The coastal mountains are dominated by CSS and chaparral communities, both of which are mainly composed of drought-tolerant species. However, CSS plants are generally shallow-rooted and drought-deciduous, compared to the mostly evergreen chaparral [39]. Due to the extremely dry summers, Southern California is a fire-prone region. Fire is a significant vegetation disturbance, which can degrade chaparral communities to grasslands abruptly. Shrub canopies recover in the following years; nevertheless, the post-fire regeneration largely depends on the fire intensity [57; 58].  
Figure 1: (**a**) Distribution of the global Mediterranean climate zone, according to the Köppen–Geiger climate classification [56]. (**b**) Topography of the study area in Southern California, USA (derived from SRTM data: [[http://dwtkns.com/srtm30m/](http://dwtkns.com/srtm30m/)]([http://dwtkns.com/srtm30m/](http://dwtkns.com/srtm30m/))). Brown polygons: burned regions (2000–2017). The coastal ranges (>1200 m a.s.l.) divide this domain into the lower coastal plains (<400 m a.s.l.) in southwest and the relatively higher inland desert (600–1200 m a.s.l.) in northeast. The lowest elevations (<200 m a.s.l.) are dominated by developed or cultivated lands. The native Southern California forest, shrubland, and grassland are mainly distributed over the mountain ranges.