This is Version 3, the first public release of this grid. It incorporates the Nature Conservancy Version 5 of VEG1851. The first version (1) of PESVEG was released in June 2000 for internal review, and version 2 followed in early July 2000 after making corrections to several attributes. No further versions are planned at this time.
Following this, a variety of hand edits were performed to smooth the boundary between the two coverages. Individual polygons were relabled for consistency, using the original Andrews data (ORVEG1936) as a guide. There were three main areas of incongruence: Coast Range, Sauvie Island, and Cascades. Most of the changes involved moving the VEG1851_V3 border out into the ORVEG1850 area, to smooth the outer edge of Christy's data, making up for the coarser resolution of the GAP data, and taking into account the different sample times- c.1851-1895 for Christy versus 1926-36 for GAP (coming from the Andrews map). There were some places we changed the ORVEG1850 label, based on the Andrews original call. ONHP labeled Andrew's 21 (Hardwoods- Alder, Ash, Maple) as 'Riparian' which we changed to FFCL or FFA. Andrew's 1 (Non-forest land) was labeled 'Oregon White Oak Savanna' which we changed to OFOZ usually, but HU on top of Mary's Peak. Some of the 'Douglas-fir' polys were changed from FF to FFHC, just to keep with the adjacent VEG1851_V3 polys.
After these edits, the coverage was cleaned with a 5 meter fuzzy tolerance, and splinter polygons were eliminated. At this point the vector coverage was rasterized as an Imagine 8.4 file with 30 meter pixels.
Subsequent editing began with polygons that Andrews had mapped 1 (Non-Forest land) up in the Cascades, which GAP called 'Alpine'. These were examined and most were recoded as OFZ (Woodland), and the mountain tops as UR (Barren). The active and secondary channels from AC1850P were recoded from Water (or other) to a new code WWR (Water Willamette River). The Woodland above 315m elevation (outside of the valley used to define the Natural Shrub/ Forest Open break in EC90) was recoded to Forest Semi-Closed or Forest Open (if burned woodland).
After an initial review, several scientists recommended including or creating more disturbed areas in the forests, since the Andrews map had been collapsed into closed forest classes to form ORVEG1850. To establish early and mid-successional forest cover types in PESVEG, four of Andrews original polygon types from 1936 were selected to represent a 'typical' amount of disturbed area in PESVEG: 9 (Douglas Fir, Seedling-Sapling-Pole); 11 (Spruce-Hemlock-Cedar, Small); 20 (Balsam Fir-Mtn Hem-Upper Slope Types, Small); 25 (Deforested Burns). These polygons were used to recode the PESVEG pixels into disturbed (burned) and early successional classes (FFY, FSCC) based on the Andrews map as well as the existing PESVEG class (which came from ORVEG1850), according to a rule structure. Two new classes were created in this process: FFM (Closed forest; Upland; Mixed conifer mature age), and FFSHBu (Closed forest; Pacific silver fir-mountain hemlock burned).
Finally, a snow class was added to represent the permanent snow fields around Mt. Jefferson and the Sisters. An area was digitized from the 1988 Western Oregon Vegetation Mapping Project data (LARSE; USFS PNW Research Station; Corvallis, OR), and the underlying pixels were recoded to UF- Unvegetated snow and ice.
Version 2 was released following some hand-editing to correct coding errors in Version 1.
Version 3 updated an area around Sauvie Island after the additions to VEG1851_V5 were completed in September 2000. The existing PESVEG_V2 was updated with the new coverage and join lines were smoothed.
At the same time, additions and changes to the hydrological layer were made by Patti Haggerty at the Corvallis EPA Lab. Her procedures follow:
1. A new grid was generated by selecting water classes from the dataset assembled by Doug Oetter and Denis White. Problems with this data are that the large tributaries of the Willamette are coded as permanent water, not as large streams. Also there are very few lakes and other permanent water bodies such as high elevation lakes. Also the tributary rivers do not extend as far as do the rivers in the EC90 and subsequent layers.
2. In order to reclass the main tributaries of the Willamette to large streams, the water classes of the PES vegetation layer were converted to polygons. The tributary polygons were coded to large streams. In addition, stream vectors from the River Reach 2 dataset that were coded as strahler 5 through 7 were selected at the point where they joined the rivers from the PES dataset and converted to a grid via the linegrid command.
3. To add high elevation lakes, polygons from the PNW-ERC LAKES3 coverage that fell within the High Cascades ecoregion were converted to a grid via the polygrid command.
4. Low elevation water bodies were selectively added by selecting water bodies from the LAKES3 coverage that fell within the valley and foothill ecoregions and that were not next to dams (Lake polygons within 100m of a dam were deleted). Dams were identified from the Oregon Water Resources dam coverage. This coverage displays dams that are equal or greater than 10 feet in height and store 9.2 acre foot or more of water. The selected water bodies were translated into grids via the polygrid command.
5. A final composite of the water classes was made by merging grids of the low and high elevation selected lakes, strahler 5-7 arcs, reclassified large tributaries, and original data in such as way as to generate a final grid that could be merged into the existing PES dataset.
The updated water information was overlaid on PESVEG_V3 and the class list was updated to reflect those changes in September 2000 by Doug Oetter.