Variable | Description |
---|---|
Topography | |
 Terrain | Terrain ruggedness index derived using a digital elevation model (1 km resolution). Defined as the mean of the absolute differences between the value of a cell and the value of its eight surrounding cells. |
Climate | |
 Spatial climate | ClimateWNA bioclim layers based on climate normals 1981 to 2010 at 1 km resolution (Wang et al. 2016; https://adaptwest.databasin.org/pages/adaptwest-climatena). Bioclimatic variables: MAT: mean annual temperature (°C) MWMT: mean temperature of the warmest month (°C) MCMT: mean temperature of the coldest month (°C) TD: difference between MCMT and MWMT, as a measure of continentality (°C) MAP: mean annual precipitation (mm) MSP: mean summer (May to Sep) precipitation (mm) AHM: annual heat moisture index, calculated as (MAT+10)/(MAP/1000) SHM: summer heat moisture index, calculated as MWMT/(MSP/1000) DD_0: degree-days below 0 °C (chilling degree days) DD5: degree-days above 5 °C (growing degree days) DD_18: degree-days below 18 °C DD18: degree-days above 18 °C NFFD: the number of frost-free days bFFP: the Julian date on which the frost-free period begins eFFP: the Julian date on which the frost-free period ends FFP: frost-free period PAS: precipitation as snow (mm) EMT: extreme minimum temperature over 30 years EXT: extreme maximum temperature over 30 years Eref: Hargreave’s reference evaporation CMD: Hargreave’s climatic moisture index RH: mean annual relative humidity (%) Tave_wt: winter (Dec to Feb) mean temperature (°C) Tave_sm: summer (Jun to Aug) mean temperature (°C) PPT_wt: winter (Dec to Feb) precipitation (mm) PPT_sm: summer (Jun to Aug) precipitation (mm) |
Ignition sources | |
 Lightning | Average annual density of lightning strikes per unit area (~10.5 km resolution), for 1995 to 2005 (strikes per km2 per year) from NASA Global Hydrology and Climate Center: annual high-resolution data on lightning (Albrecht et al. 2016; https://doi.org/10.5067/LIS/LIS/DATA301). |
 Roads | Major roads mapped at 1:10 000 000 (CEC 2009, http://www.cec.org/tools-and-resources/map-files/major-roads-2009) and resampled to 1 km resolution. |
 Human population | United Nations-adjusted population density Gridded Population of the World-v4 output at 30 arc seconds. (Socioeconomic Data and Applications Center: http://sedac.ciesin.columbia.edu/data/collection/gpw-v4), resampled to 1 km resolution. |
 Human influence | Anthropogenic biomes mapped at 4 km resolution: (CEC 2008, http://www.cec.org/tools-and-resources/map-files/anthropogenic-biomes; Ellis and Ramankutty 2008). Villages Dense agricultural settlements  • Cropped and pastoral: villages with a mix of crops and pasture villages  • Pastoral villages: villages dominated by rangeland Croplands Annual crops mixed with other land uses and land covers  • Residential irrigated: irrigated cropland with substantial human populations cropland  • Residential rainfed mosaic: mix of trees and rainfed cropland with substantial human populations  • Populated irrigated cropland: irrigated cropland with minor human populations  • Populated rainfed cropland: rainfed cropland with minor human populations Rangeland Livestock grazing; minimal crops and forests  • Residential rangelands: rangelands with substantial human populations  • Populated rangelands: rangelands with minor human populations  • Remote rangelands: rangelands with inconsequential human populations Forested Forests with human populations and agriculture  • Populated forests: forests with minor human populations  • Remote forests: forests with inconsequential human populations |
Vegetation | |
 Biotic communities | Brown and Lowe’s Biotic Communities of the Southwest (Brown et al. 1979; https://databasin.org/maps/new#datasets=e8e241e869054d7e810894e5e993625e). Source scale 1:1 000 000. Map developed by The Nature Conservancy, Arizona, USA, in 2004. Conifer Forest/Woodland  • Petran Subalpine Conifer Forest  • Great Basin Conifer Woodland  • Petran Montane Conifer Forest Evergreen Woodland  • Madrean Evergreen Woodland  • Interior Chaparral Thornscrub  • Arizona Upland Subdivision - Sonoran Desertscrub  • Sinaloan Thornscrub  • Chihuahuan Desertscrub  • Plains of Sonora Subdivision - Sonoran Desertscrub Grassland  • Semidesert Grassland  • Plains and Great Basin Grassland |