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Table 1 Topographic variables used in site selection for 2016 sampling on the Tripod Complex fires in the Okanogan-Wenatchee National Forest, Washington, USA, and as candidate predictor variables. All variables were computed at 100 m resolution from a digital elevation model (DEM)

From: Topography and post-fire climatic conditions shape spatio-temporal patterns of conifer establishment and growth

    Tripod Fire data range
Variable Description and units Source Range Mean
Elevation Elevation above sea level in meters National Elevation Dataset ( 697 to 24261 1722
Slope Slope angle in degrees Computed from DEM with ArcGIS v10.4 Spatial Analyst (ESRI, Redlands, California, USA.) 0 to 48 17
Heat Load Index (HLI) Unitless index that accounts for slope, aspect, latitude, and potential direct incident radiation. Smaller values correspond to less heat loading and larger values correspond to more heat loading. Computed from DEM using the Geomorphometry and Gradient Metric ArcGIS Toolbox v2.0 (Evans et al. 2014) 0.22 to 1.03 0.69
Topographic Position Index (TPI) Unitless index that expresses relative ridge or valley position by comparing the elevation of each cell in a DEM to the mean elevation of a specified neighborhood (here, 1000 m) around that cell. More negative values correspond to valleys and more positive values correspond to ridges. Computed from DEM using the Land Facet Corridor Designer ArcGIS Toolbox (Jenness et al. 2013) −231.84 to 277.11 2.81
Topographic Wetness Index (TWI) Steady-state wetness index that expresses flow-accumulation as a function of both slope and upstream contributing area, thus reflecting potential site moisture balance. Smaller TWI values correspond to less potential moisture, larger TWI values correspond to more potential moisture. Computed from DEM using the Geomorphometry and Gradient Metric ArcGIS Toolbox v2.0 (Evans et al. 2014) 3.42 to 16.98 5.89
  1. 1Areas above 1800 m were categorically excluded to ensure that sites would be within the elevational range where forest management activities in this region are most likely to occur. Furthermore, large swaths of the highest elevations burned at high severity, limiting accessible interfaces with unburned or low-severity burn patches, which was an important criterion in site selection.