Covariates
The TerrAdapt:Cascadia forest structure models use a variety of covariates as environmental predictors. The data sources for these covariates are described in the DATA INPUTS section. All covariates were stored in Google Earth Engine (either in the public data catalog or TerrAdapt's private asset storage) and available for use in our dynamic workflow. The forest structure model covariates are listed below under the following sections that correspond to the different data input sources.
All Landsat covariates are derived from Landsat imagery processed to remove clouds and other artifacts and harmonized using the CCDC algorithm, as described in the Remote Sensing Data inputs section.
Raw band values (BLUE, GREEN, RED, NIR, SWIR1, SWIR2), July 1st
Landsat indices, July 1st
Normalized difference vegetation index (NDVI, Kreiger et al. 1969)
Normalized difference water index (NDWI, Gao 1996))
Leaf area index (LAI, Fang et al. 2019)
Normalized difference bare soil index (NDBSI, Liu at al. 2022)
Normalized difference snow index (NDSI)
Normalized burn ratio 2 (NBR2)
CCDC harmonic coefficients (1st, 2nd, and 3rd order sine and cosine), RMSE, phase, amplitude, and slope for the following bands and indices:
NIR band
Normalized burn ratio (NBR)
Tassled cap wetness index (TCW)
Enhanced vegetation index (EVI)
Slope
Topographic position index
Heat load index
Multi-resolution valley bottom flatness
Topographic wetness index
Climatic moisture deficit
Summer heat moisture index
Freezing degree days
Growing degree days
Number of frost-free days
Mean annual precipitation
Mean summer precipitation
Precipitation as snow
Mean annual temperature
Mean coldest month temperature
Mean warmest month temperature
Relative humidity
Temperature differential
Water occurrence
Distance to water
Height above nearest drainage
Soil density
Soil pH
Soil organic carbon
Sand fraction
Clay fraction
Silt fraction
Water capacity
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