The EPA EnviroAtlas Percent Forest and Woody Wetland per 12-digit HUC dataset was clipped to California sub-watersheds (NRCS).
Original Metadata:
This EnviroAtlas national map estimates the percentage of
total land within each subwatershed (12-digit HUC) that is
covered by trees and forest or woody wetlands. The map
layer uses the 2006 National Land Cover Database (NLCD)
to define forested land and woody wetlands and it excludes
agriculture, developed, and barren land.
These data were generated by using the 2006 National Land
Cover Dataset (NLCD) in the landscape assessment tool,
Analytical Tools Interface for Landscape Assessments
(ATtILA). ATtILA is an Esri ArcView extension (soon to be
updated to an ArcMap toolbox), created by EPA, that
calculates many commonly-used landscape metrics. NLCD
classes 41 Deciduous, 42 Evergreen, 43 Mixed Forest, and
90 Woody Wetlands were used for this map. The landcover
data were summarized by 12-digit HUC boundaries taken
from the Watershed Boundary Dataset (WBD). For more
information on the metric calculation, see the ATtILA User’s
Manual.