Snag Habitats in the Sierra
Nevada and Management
Indicator Species
Ralph Warbington
Ecosystem Planning Staff
Pacific Southwest Region
Management Indicator Species
Hairy woodpecker
• The most widespread
resident woodpecker in
North America
• Habitat is Snags within
green mature forests with
large trees
• Feeds on insects and
other arthropods, fruits,
and seeds
Management Indicator Species
Black-backed woodpecker
• An uncommon woodpecker of
the northern coniferous
forests
• Habitat is Snags within burned
forests
• Moves from place to place,
following outbreaks of woodboring beetles in recently
burned habitats
• Feeds on larvae of bark
beetles and wood-boring
beetles
The FIA Data Connection
• Can we use FIA data for snag habitat existing
condition within green forests?
• Can we use FIA data for snag habitat trends
over time in green forests?
• Can we use FIA data for snag habitat existing
condition within recently burned forests?
• Can we use FIA data for snag habitat trends
over time in recently burned forests?
Analysis Area and Information
• Sierra Nevada Mountain
Range
– 10 National Forests –
Modoc, Lassen, Plumas,
Tahoe, Eldorado, LTBMU,
Stanislaus, Sierra,
Sequoia, and Inyo
– Periodic Inventories
available from 1994-1999
– Re-measurement
Inventories available from
2001-2004
– Around 3000 FIA Plots
HEX_NONHEX
Forest Name
HEX
Eldorado
HEX
NONFOREST
INACCESSIBLE
106
2
0
Inyo
184
131
17
HEX
Lassen
179
16
0
HEX
Modoc
215
65
1
HEX
Plumas
204
3
3
HEX
Sequoia
159
20
4
HEX
Sierra
193
21
6
HEX
Stanislaus
136
15
1
HEX
Tahoe
145
3
3
HEX
LTMU-Basin
25
2
1
1546
278
36
129
0
0
89
0
0
Total HEX Plots
FOREST
NONHEX
Eldorado
NONHEX
Inyo
NONHEX
Lassen
165
0
0
NONHEX
Modoc
120
0
0
NONHEX
Plumas
173
0
0
NONHEX
Sequoia
198
0
0
NONHEX
Sierra
149
0
0
NONHEX
Stanislaus
154
0
0
NONHEX
Tahoe
154
0
0
NONHEX
LTMU-Basin
71
0
0
278
36
Total NONHEX Plots
Grand Total FIA
Plots
1402
2948
Previous Estimates - Source Information
National Forest
Vegetation Map Date
Sample FIA Plot Dates
Inventory Type
Eldorado
1996
2000
Periodic
Inyo
1997
1994
Periodic
Lassen
1997
1999
Periodic
Modoc
1997
1999
Periodic
Plumas
1997
2000
Periodic
Sequoia
1997
1999
Periodic
Sierra
1997
1998
Periodic
Stanislaus
1997
1999
Periodic
Tahoe
1997
2000
Periodic
Tahoe Basin
1997
1999
Periodic
Current Estimates - Source Information
Vegetation Map Date
Sampled FIA Plots
Dates
Inventory Type
Eldorado
2000
2003
Updated Periodic
Inyo
2001
2001-2004
Annual Inventory
Lassen
1999
2002
Update Periodic
Modoc
1999
2002
Updated Periodic
Plumas
2000
2003
Updated Periodic
Sequoia
2003
2001-2004
Annual Inventory
Sierra
2001
2001-2004
Annual Inventory
Stanislaus
2000
2003
Updated Periodic
Tahoe
2000
2003
Updated Periodic
Tahoe Basin
2000
2003
National Forest
Updated Periodic
SNAG Habitat Analysis
Current and Trends
• Uses the compiled vegetation inventories and strata
population maps for two time periods:
• Modoc, Lassen, Plumas, Tahoe, LTBMU, Eldorado,
Stanislaus, Sierra, Sequoia, Inyo
• Snags, all tree species, by Medium (15-29.9 dbh) and Large
(30+dbh), by decay class, number per acre inventory strata
averages, by National Forest
• Expanded by mapped strata acres and then calculated the
weighted average by major forest type for each National
Forest
• Weighted average by major forest type across the 10 National
Forests in the Sierra Nevada
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Acres by Major Forest Type
3,000,000
2,500,000
2,000,000
1,500,000
1,000,000
500,000
0
Previous - Snags >15"DBH per Acre by Type
10.00
9.00
8.00
7.00
6.00
5.00
4.00
3.00
2.00
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Current - Snags > 15"DBH per Acre by Type
10.00
9.00
8.00
7.00
6.00
5.00
4.00
3.00
2.00
1.00
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Number per Acre
4.00
Snags Per Acre Differences Current vs Past Inventories
3.50
3.00
2.50
2.00
1.50
1.00
0.50
0.00
Major Forest Type
What about Snags in Burned Forests ?
• Analysis Requirements
– Fire killed trees are only
habitat for Black-backed
Woodpeckers up to 5 years
post fire
– Usable FIA plot samples
must be post fire and less
than 5 years old
– Fire perimeters required for
stratification
– Fire severity and Stand
Density are likely correlated
with post fire snag densities
Wildfires Last 8 Years Total Acres
619,000 : Average = 77,000 per year
ADMIN_FORE (All)
FIRE_NAME (All)
Total
Sum of Acres
180,000
160,000
140,000
120,000
100,000
Drop Series Fields Here
Total
80,000
60,000
40,000
20,000
0
2000
2001
2002
2003
YEAR_
2004
2005
2006
2007
Last 8 years - Acres by Fire
Severity
Acres by Fire Severity
250,000
200,000
Acres
150,000
100,000
50,000
0
Unburned
Low
Moderate
Severity
High
Very High
Annual Fires – Annual Inventories
•
•
•
•
•
Sierra Nevada Forests - 11 million acres
About 9 million acres of forestland (83%)
About 80,000 acres burn each year x 5 years
National Design is 1 hex plot per 6000 acres
1/10th of plots is measured each year therefore 1 in
60,000 acres is sampled each year
• (400,000 fire acres * .83 forested) / 60,000 acres =
5.5 forested hex plots per year
• Might be able to use previous years measurements
for some fires still less than 5 years old (2 or 3 plots)
What If All Burned Over FIA
Plots were Measured the Year
After the Fires?
• There are 30 Forested Hex Plots in areas
burned in the last 5 years
• There are 26 Forested Non-Hex Plots in
areas burned in the last 5 years
• For a total of 56 plots for Analysis
What Analysis is Possible with
56 FIA plots?
• Total dead trees per acre over 15 inches
DBH from fire related mortality
• Maybe able to see trends in mortality and
fire severity
• Maybe a test of significant for number of
snags inside and outside of burned area
• No forest type analysis possible
Conclusions
• Number of FIA plots are adequate for estimates
of current snags per acre for all forestlands
(green forests) and by forest type
• Trends in overall snag densities are possible
using previous and current inventory estimates
• Number of FIA plots in burned over forests less
than 5 years is inadequate
• At a minimum, burned over FIA plots both Hex
and Non-hex should be sampled year after the
fire occurred to accumulate enough samples for
a basic analysis of snags per acre.
• Additional temporary plots should be installed
within fires for determining fire severity related
mortality rates within common major forest types