DecAID Analysis of Dead Wood Habitat for the Sunflower Fire and Wall Watershed
Analysis Area
Post-fire habitats offer a unique opportunity to manage for areas of high snag density, which are
typically rare spatially and temporally. Because LRMP standards and guidelines likely do not
adequately address species use of these high density habitats, this cumulative effects analysis
was supplemented with analysis using information from DecAID. In order to compare
cumulative impacts to high density dead wood habitat with “natural conditions” in DecAID, an
appropriately-sized analysis area is needed to incorporate a landscape large enough so that high
snag densities in the area are representative of habitat conditions from which the inventory data
were collected. The area must encompass enough acres to account for all of the DecAID habitat
types present in the fire area or affected area. Refer to the DecAID Advisor for more
information on calculating the size of the analysis area.
Two assumptions were made in this analysis:
1) Areas meeting or exceeding the 80% tolerance level represent snag pulses created
by large events like wildfire or insects and disease events.
2) Unharvested inventory plot data (plots with and without measureable snags) from
DecAID represents historic range of variability (HRV) of snag distribution and
density for the analysis area.
Table 1 displays the snag density meeting 80% tolerance level by habitat type for snags ≥10
inches dbh (weighted for all 3 structural condition classes) and the percentage of the landscape
expected to be in that condition from the DecAID histograms. Areas meeting or exceeding the
80% tolerance level represent snag pulses created by large events like wildfire or insects and
disease events. The information provided in DecAID (See Determining Size of Analysis Area for
Distribution Analysis of Current Conditions document) indicates that the analysis area for
determining if the outcome of the disturbance results in excess acres of high snag densities at the
landscape level, as compared to the distributions from unharvested plots in DecAID, the area
would need to encompass at least 3,700 acres of the Eastside Mixed Conifer (EMC_ECB) habitat
type and at least 1,660 acres of the Ponderosa Pine/Douglas-fir (PPDF) habitat type. There are
approximately 51,382 acres of EMC_ECB habitat and 25,686 acres of PPDF habitat in the Wall
Watershed and the affected area from the Sunflower Fire is entirely within the watershed,
making this area an appropriate size with sufficient composition of habitat types for DecAID
analysis.
Table 1. Tolerance Levels (Snag Density) and Percent of Landscape Expected to Meet 80%
Tolerance Levels for the ≥10 inch diameter group under the Reference Condition from DecAID.
Eastside Mixed Conifer
Ponderosa Pine/Douglas-fir
>10”dbh
>10”dbh
Size Class (dbh)
a
20.8 snags/acre
4.8 snags/acre
80% Tolerance Level
% of Landscape >80%
20%
20%
tolerance levelb
a
Data for Eastside Mixed Conifer and Ponderosa Pine/Douglas-fir acquired from DecAID Table inv-3b
(≥10 inch dbh).
b
Data for Eastside Mixed Conifer acquired from DecAID Figures EMC_ECB_O.inv-14,
EMC_ECB_S.inv-14, and ECM_ECB_L.inv-14. Data for Ponderosa Pine/Douglas-fir acquired from
Figures PPDF_O.inv-14, PPDF_S.inv-14 and PPDF_L.inv-14.
The analysis area includes the Wall Creek 5th field watershed. The analysis area totals
approximately 77,000 acres of PPDF and EMC_ECB habitat. Table 2 displays the acres of
habitat with snag densities in excess of the 80% Tolerance Level needed to meet the
historic/reference condition in DecAID by habitat type for snags ≥10 inches dbh.
Table 2. Acres with snag densities in excess of the 80% tolerance level needed to meet the
reference condition.
Habitat Type
Acres of Habitat
Percent of
Total Acres with
Type in Analysis
Landscape Above
Snag Densities
Area
80% TL to Meet
Exceeding the 80%
Reference Condition TL Needed/Expected
51,382
20%
10,276
EMC
25,686
20%
5,137
PPDF
The best available vegetation and dead wood data for the Wall Watershed (GNN modeling
completed in Summer 2014 using data and imagery collected in 2012) indicates that there are
currently approximately 3,664 acres of Eastside Mixed Conifer (Blue Mountains, EMC_ECB)
and 5,805 acres of the Ponderosa Pine/Douglas-fir (PPDF) habitat that have snag densities in
excess of the 80% Tolerance Level for these habitat types (See Table 3).
Table 3. Acres with snag densities in excess of the 80% tolerance level in the Wall Watershed
prior to the Sunflower Fire and other activities and events impacting high snag density patches.
EMC_ECB
PPDF
(acres)
(acres)
Acres of the EMC_ECB and PPDF habitat types that
would be expected to exceed the 80% Tolerance
10,276
5,137
Level under historic conditions in the 77,068 acre
analysis area for the ≥10 inch dbh group (20% of
each habitat type)
Current acreage with snag densities in excess of the 80%
3,664
5,805
Tolerance Level
There are approximately 706 acres of stand replacement or mortality that would result in snag
densities in excess of the 80% Tolerance Level (due to wildfire effects) in the EMC_ECB habitat
type and approximately 248 acres in the PPDF habitat type in the Sunflower Fire Area. This
includes all acres that burned at high and moderate severity that were below the 80% Tolerance
Level pre-fire. There are additional acres of snag densities in excess of the 80% Tolerance Level
in the analysis area resulting from insect and disease mortality. Based on examination of the
most recent insect and disease mapping for 2012 and 2013, there are an additional 169 acres that
would meet or be moving toward the 80% tolerance level in the EMC_ECB habitat and 137
acres in the PPDF habitat type, based on the level of tree mortality in these areas. There have
also been fuels treatments (Wildcat II) in the Wall Watershed since 2012 that have affected
patches of habitat with snag densities in excess of the 80% Tolerance Level; these changes are
reflected in Table 4. Additionally, proposed danger tree felling along roads within the fire area
would impact acres that are currently exceeding, or would exceed in the near future, the 80%
Tolerance Level. Table 4 displays the amount of the analysis area over the expected amount of
high density snag areas (20% of EMC and PPDF is expected).
Table 4. Cumulative Impacts to High Snag Density Patches (Exceeding the 80% Tolerance
Level) in the Wall Watershed.
EMC_ECB
PPDF
(acres)
(acres)
Acres of stand replacement fire or increase in acres with
+706
+248
snag densities in excess of the 80% Tolerance Level
(Sunflower Fire)
Acres of insect and disease locations providing snag
+169
+137
densities in excess of the 80% Tolerance Level
Acres of fuels treatment resulting in a decrease in acres
-52
-7
with snag densities in excess of the 80% Tolerance
Level
Acres of danger tree felling that would result in a
-26
-17
decrease in acres with snag densities in excess of the
80% Tolerance Level
Net change in acreage proving snag densities in excess
+797
+361
of the 80% Tolerance Level
a
All additions are the result of activities occurring since approximately September 1, 2012.
Imagery used for GNN snag modeling was collected at this time; all activities after this date
would not be reflected in the existing snag density data for the Umatilla National Forest.
Table 5 displays the current acreage of high density snag areas, the net change in acreage for
these areas, and how this compares with what would have been expected historically.
Table 5. Cumulative Impacts to High Snag Density Patches (Exceeding the 80% Tolerance
Level) in the Wall Watershed.
EMC_ECB
PPDF
(acres)
(acres)
Current acreage with snag densities in excess of the 80%
3,664
5,805
Tolerance Level
Net change in acreage proving snag densities in excess
+797
+361
of the 80% Tolerance Level
Net acreage with snag densities in excess of the 80%
4,461
6,166
Tolerance Level
Acres expected to exceed the 80% Tolerance Level,
10,276
5,137
based on reference condition/historic information
Acres in excess of expected levels (20% of habitat
-5,815
+1,029
type exceeding the 80% Tolerance Level)
Table 5 indicates that there is currently a deficit (-5,815 acres) in the EMC_ECB habitat type
within the Wall Watershed in areas with snag densities that exceed the 80% Tolerance Level. As
there is a deficit in this habitat type, salvage of high density snag patches created by the
Sunflower Fire would generally not be considered appropriate given the value of ephemeral,
post-fire high-snag density patches to a number of wildlife species, primarily cavity excavating
birds including the black-backed, three-toed, hairy, and Lewis’ woodpeckers. Table 5 also
indicates that there is currently a small surplus in the PPDF habitat type of patches of snag that
exceed the 80% Tolerance Level. Larger patches of fire-killed trees would be appropriate for
salvage in this habitat type. Appropriate design criteria for partial retention (variable retention)
would be provided for affected areas. These recommendations would be based on the best
science available with regard to wildlife habitat requirements in burned stands.