The Study Area

The Joint Fire Sciences project covered
three Western sites in contrasting ecosystems

Three western regions covering temperate steppe, coastal forest, and Mediterranean ecosystems were mapped using GNN imputation for a Joint Fire Sciences Program study (see figure at right). The original study examined the feasibility of mapping wildland fuels and vegetation structure to provide data for fire and fuels management planning (Pierce and others, in review; Wimberly and others 2003). The 2.86-million-ha coastal forest site was located in the coast range of Oregon extending as far inland as the western edge of the Willamette Valley. The forests are primarily coniferous with hardwoods occupying riparian and disturbed areas. The 4.1-million-ha Mediterranean site was located in the central Sierra Nevada occupied by savannah, chaparral, mixed conifer, and alpine woodlands vegetation types. The site stretches from the northern border of Sequoia National Park north through the Plumas National Forest. The 5-million-ha temperate steppe in northeastern Washington was bounded on the west by the Cascade crest and on the south by the Columbia and Spokane rivers. The temperate steppe site is dominated by a combination of mixed coniferous forest and extensive shrub steppe.

Vegetation Data from Field Plots

Vegetation data from regional inventories were derived in each of the three regions from multiple sources including Forest Inventory and Analysis (FIA) plots, Current Vegetation Survey/R6 plots (CVS), R5, BLM, research Ecology Plots in North Cascades National Park (NCNP) (provided by Dave L. Peterson) and Yosemite National Park (provided by Jan Van Wagtendonk). The FIA, R5, and CVS plots were installed on systematic grids. CVS/R6 and R5 plots covered the national forests whereas FIA installed plots on all ownerships. FIA and CVS inventory plots used five subplot arrays within a 1-ha area. Small trees, snags, coarse woody debris line-intercept transects, and ground cover were sampled on each subplot.

Because vegetation data were derived from multiple inventories with different sampling protocols, all individual tree records were converted to per-hectare values. For plots with multiple vegetation or land cover conditions only, the forested portion was used with expansion factors adjusted accordingly. Plot-level summary variables were calculated for each plot.

Stand-summary variables included total basal area, basal area by species, trees per hectare, quadratic-mean diameter, snags per hectare, percent tree canopy cover, and down-wood volume. Different inventories collected down-wood data using different sampling schemes and minimum sizes. As a result, we focused primarily on species basal area.