mixed conifer forests what and where are they?
TRANSCRIPT
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Mixed Conifer Forests Definitions and Background
Thomas Spies PNW Research Station
July 1, 2014
Pendleton, OR
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A Definition of Moist Mixed Conifer Forests Diverse Forest Type where:
1. Grand fir, white fir, Douglas-fir are the late-successional species
2. Old shade-intolerant/fire-tolerant species:
– Ponderosa pine, Douglas-fir, or western larch
3. Low to mixed-severity fire regime
4. Not too hot and dry, not too cold and wet
5. More productive than Ponderosa Pine and dry MC
6. Ecosystems altered by human activity
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Really About • Ecosystem change • Desirability of change • What we want from these forests in the future
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Altered landscapes and fire regimes
Ochoco Mtns
Heyerdahl, unpublished
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Potential (PVT) Current Vegetation
• Theoretical climax vegetation on a site
• Understory plant community, tree regen
• Environment of a plant community
• Rough surrogate for disturbance regime
• Classification system for National Forests
• Types Vary among National Forests
• Actual structure, age and composition of vegetation
• Product of – Local Environment – Disturbance history – Local seed sources – Biotic interactions
• Lack locally valid maps • Field check it
How to find it:
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Major Potential Vegetation Groups
PVT Group Includes Area in Ha (federal lands)
Pine Ponderosa, Lodgepole dry
1,167,600
Dry Mixed Conifer
Grand fir warm, Douglas-fir dry, Mixed conifer dry
1,692,613
Moist Mixed Conifer
Grand fir/White fir cool, moist
1,099,100
Cool, Wet Conifer
Subalpine fir, mt. Hemlock, W. Hemlock
1,247,346
2,791,713 ha (6,895,531 ac)
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Precipitation varies across the mixed conifer Region from dry to wet But precipitation is only part of the story of moisture availability
• Local climate • Soil • Topography
Dry to Moist MC
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Old growth mixed-conifer Central Oregon
Xeric Dry-mixed conifer Mesic Wet-mixed conifer
Andrew Merschel
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Moist-Dry Mixed Conifer Grand Fir, Deschutes NF
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Moist Mixed Conifer Grand Fir, Malheur NF
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Moist Mixed Conifer Douglas-fir, East Cascades WA
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Wet/Cool Mixed Conifer Grand fir, Umatilla NF
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Wet/Cool Mixed Conifer Subalpine fir Umatilla NF
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Mixed conifer plant associations grouped by moisture and disturbance regimes
Moisture/Disturbance Fire Regime E.g. Vegetation Series/associations
Dry, Low-severity I, III A, IIIB, IVA
Grand fir/elk sedge, Blue Mts; Grand fir/snowberry, OR E Cas.
Moist-Dry, Low to mixed severity
IIIA, IIIB, I, IIIC, IVA
Douglas-fir/mallow ninebark, Blues and Ochoco; Grandfir/prince’s pine, OR E Cas.
Moist, mixed severity IIIB, IIIC, IIIA, IVB, IVA
Grandfir/Big Huckleberry, Blues and Ochoco; Grand fir/Twinflower, OR E Cas.
Moist to Wet, high severity IIIC, IVB Grandfir/Swordfern-Ginger, Blues.
Regime Frequency (yrs) Severity
I 0-35 Low
IIIA <50 Mixed
IIIB 50-100 Mixed
IIIC 100-200 Mixed
IVA 35-100 High
Based on Evers 2002
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Fire Severity Classification
• Low—0-20% canopy tree mortality
• Mixed 20-70% canopy mortality
• High > 70% mortality
10% 20%
40%
70%
Agee 1990
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Human impacts vary across moisture and disturbance regime gradient of
mixed-conifer types
Type Fire Exclusion
Partial harvest /Loss of large fire resilient trees
Clearcutting/ Loss of large live and dead
Altered stand and landscape pattern and dynamics
Dry MC XXXX XXXX X XXXX
Dry-Moist MC XXXX XXXX X XXXX
Moist MC XXX XXX XXX XXXX
Moist to Wet XX X XXXX XXXX
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10 ~40 ~60 145
Subalpine/ Mt. Hemlock
Wet Mixed Conifer
Moist Mixed Conifer
Dry Mixed Conifer
Ponderosa Pine
Juniper Woodland
High Mixed Low
Fire Severity
Fire Interval yrs <20 20-40 >40
Elev
atio
n
Annual Precipitation
IDEALIZED PVT DISTRIBUTION EAST SLOPE OREGON CASCADES
Alpine
PIPO ABGR PSME
Species Distribution
Before 1900
After 1900
Regeneration
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Some people in collaboratives equate grand fir with “moist” mixed conifer
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Grand Fir is a recent component in many pine and dry mixed conifer sites in central Oregon
Moist
Dry Ponderosa Pine Grand fir Douglas Fir
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Grand fir takes over Seed sources matter
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How to think about Mixed Conifer Forests:
More than structure and PVT at a site
Structure
Composition
Succession Competition Growth Dispersal
Disturbance
States Processes
Fire
Pathogens
Seeds
Water
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Current Landscapes Fire Exclusion, High Severity Fire, Plantations
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Consequences of Change in Dry and Moist Mixed-Conifer Forest
• Increases: – Stand Density – Risk of high severity fire – Mortality from insects and disease – Shade tolerant tree species and seed sources – Habitat for dense-forest wildlife species
• Decreases: – Large old pines and other fire tolerants – Regeneration of pine and other fire tolerants – Growth rates of fire tolerant species – Resilience in face of fire, pathogens, drought – Habitat for species of open old pine forests
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Key Points
• Diverse forest in a variable and dynamic landscape
• Definitions Dry, Moist, and Wet MCF vary
• MCF types typically intermixed in landscape scales
• MC types types can have similar disturbance regimes in some ecoregions
• Grand fir and other shade tolerants encroaching into both dry and moist mixed conifer sites
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Key Points
• Finding DMC, MMC and WMC requires triangulation between maps of PVT and current vegetation
• Not really about a PVT--Really about altered ecosystems current vegetation, and future forests
• Numerous ecological consequences—not just density
• Many of the changes are undesirable, but some may be desirable
• Restoration needs will differ across moisture and disturbance regime gradients
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Thank You