Table 1 Initial potential explanatory variables by regression group and data sources. Single asterisks (*) indicate explanatory variables retained after classification tree variable reduction. Double asterisks (**) indicate variables also retained for subsequent BRT and spatial modeling.

Biogeophysical

Percent silt, clay, and sand 1 cm to 100 cm weighted average — NRCS and NPS soil surveys

Available water capacity 1 cm to 100 cm weighted average — NRCS and NPS soil surveys

Soil pH 1 cm to 60 cm weighted average — NRCS SSURGO and NPS soil surveys

Cation-exchange capacity 1 cm to 100 cm weighted average — NRCS and NPS soil surveys

**Elevation (10 m) — National Elevation Dataset

Slope (degrees) (10 m) — Derived from National Elevation Dataset

Topographic Position Index (10 m) — Derived from National Elevation Dataset

Disturbance history — cheatgrass propagule sources

Fire by decade, 1940s to 2000s (10 m) — DINO fire and roads database Distance to roads (10 m) — DINO roads database

Distance to polygon fire boundary (within fire) (10 m) — DINO fire database Distance to all fire disturbances across all years (10 m) — DINO fire database

*Distance to fire disturbance by decade: 1940s, 1950s, 1960s*, 1970s*, 1980s*, 1990s, 2000s (10 m) (Includes both polygon and points) — DINO fire database

Number of fires (polygons and points) — DINO fire database

Climatic

Mean minimum annual temperature 30 yr means (4 km) — PRISM

*Mean maximum annual temperature 30 yr means (4 km) — PRISM

Mean annual precipitation 30 yr means (4 km) — PRISM

Mean maximum and minimum annual temperature 1 yr postfire (4 km) — PRISM

Mean annual precipitation 1 yr postfire fire (4 km) — PRISM group data

Mean minimum winter temperature 1 yr postfire (Dec, Jan, Feb) (4 km) — PRISM

Mean maximum winter temperature 1 yr postfire (Dec, Jan, Feb) (4 km) — PRISM

Mean spring precipitation (Mar, Apr, May) 1 yr postfire (4 km) — PRISM

Mean summer precipitation (Jun, Jul, Aug, Sep) 1 yr postfire (4 km) — PRISM

TasselCap brightness by 1 yr postfire 150 meter mean buffer values (30 m) — Landsat

TasselCap greenness by 1 yr postfire 150 meter mean buffer values (30 m) — Landsat

**TasselCap wetness by 1 yr postfire 150 meter mean buffer values (30 m) — Landsat

Fire properties

**Fire severity — differenced Normalized Burn Ratio per fire (dNBR = NBR postfire — NBR prefire). Increased dNBR = increased fire severity (30 m) — Landsat

Data quality

**Years since last fire at the time of vegetation sampling (polygon)

**Winter precipitation (Dec to Apr) year of vegetation survey (2002, 2003, 2005) (4 km) — PRISM

Winter precipitation (Dec to Apr) year before vegetation survey (2001, 2002, 2004) (4 km) — PRISM

*Summer precipitation (Jun to Oct) year of vegetation survey (2002, 2003, 2005) (4 km) — PRISM

Summer precipitation (Jun to Oct) year before vegetation survey (2001, 2002, 2004) (4 km) — PRISM