a health management plan for sitka spruce
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A Health Management Plan for Sitka Spruce
By: Jeremy Greenwood
April 27, 2007
Management Objective Focus will be on southeast, Alaska Management objective will be timber
production but on a multiple-use forest (Tongass National Forest)
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Introduction to the Species
Sitka spruce (Picea sitchensis)
Photo: J. Greenwood3
Prominent along northwest coasts of N. America Stands have some of the highest growth rates in NA Commercially valuable species for lumber, pulp, &
specialty uses World’s largest spruce Large individuals yield 6-8MBF.
Typical heights are 180’-200’ and DBH of 4’ to 5’ (max. is 315’; 19’)
How to identify
Source: Hardin, J.W., D.J. Leopold & F.M. White. 2001. Harlow & Harrar's Textbook of Dendrology-9th Ed. McGraw-Hill. 534 p.
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Needles 5/8”-1” long, flattened, yellow-green above, blueish white below, sharp
pointed, R. angles from all sides of twig Cones
2” to 3.5”, fall in late autumn/early winter, thin & papery scales Twigs
Orange-brown, with ovoid buds Bark
Thin, silvery gray to purplish gray elliptical scales Form
Long, cylindrical boles with short, open crowns. Branches are pendulous
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Tree Species Adaptations Climate
Coastal Species that is tolerant of ocean spray Wide range of precipitation rates
25” to 221” of precipitation 0.5” to 134” of snow
Moisture is year round & abundant Mild winters & cool summers Frost free days range from 295 days in OR to 111 days in
Cordova, AK
Soils Competes best on alluvial soils, sandy/coarse-textured
soils or soils with lots of organic matter Soils with large amounts of calcium, magnesium &
phosphorus pH ranging from 4 to 5.7 (acidic)
Tree Species Adaptations
Competition Tolerant to intolerant Develops best in gaps Long-lived (up to 800 yrs) Competitors include:
Western hemlock Mountain hemlock Western redcedar Alaska cedar Also several HW species (red alder, Sitka alder, & black
cottonwood)
Tree Species Adaptations
Wind: An Abiotic Stress
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Wind: An Abiotic Stress The most dominant disturbance agent in southeast
Alaska 27% of annual timber loss on the Tongass NF is due to
wind Little is known of the disturbance regime of
Alaska in comparison to other regions where Sitka spruce is found (OR, WA, etc.)
Large storm systems in the fall Development Return interval (8 years) Wind direction
Wind Environment
Found throughout the range of Sitka spruce but ranges from single trees to large-scale blowdown
Highest intensity on hill tops/ridges Lowest intensity on stands on north or northwest
facing slopes
Wind Predisposing Factors
Tree Adaptations Height:Diameter
ratios Vigor Quantity of crown
•Useful measure of tree stability•Measure each dimension in same units (feet)•The higher the ratio the more unstable the tree becomes
H:D Ratios
Phellinus pini
Heart Rot Fungi-Primary factors leading to stem snap-Transport mechanism
Wind: Predisposing Factors
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Wind
Degree of Stress Time of year Quantity of soil Water holding capacity of
soil Sitka spruce rooting
habits
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Wind Inciting Factors
Strong wind events such as gales
Wind speed (up to 100 mph)
Storm characteristics
Counterclockwise spin (cyclone)
Wave development in Gulf of Alaska
24 to 30 hour notice prior to storms reaching landfall
Wind Effects
Tree response Wind snap Wind throw No Effect
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Wind Contributing Factors
Bark beetles Fire
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Preemptive Match silvicultural method to site
Stand replacing wind events=clear cut Individual tree/Small gap windthrow= selection cuts
Increase species diversity
Wind: Control Options
Wind Control Options (cont’d.)
Layout strip cuts in orientation to the prevailing winds
Thin to foster high H:D ratios
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Wind Control Options Reactive
Salvage harvest Potentially controversial (Donato & Biscuit Fire)
No harvest action Risks associated with no harvest
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Wind Control Options: Feasibility
Preemptive measures are more cost effective than reactive measures
Difficulties with salvage harvests in this region Political Terrain
Spruce beetle(Dendroctonus rufipennis)
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Spruce beetle Identification Adults
dark brown w. reddish brown wing covers Cylindrical; ¼” long by 1/8” wide Can be confused w. Ips beetles (wing
covers are evenly rounded on D.r.) Eggs
Oblong, white, 1/16” long Larvae
Cream colored legless grubs; ¼” at maturity
Pupae Opaque white, inactive, similar size/shape
to adults
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Spruce beetle
Life Cycle Varies due to temperature (1 to 3 years) Adults emerge from May thru October Most attacks occur in early summer
Females bore into tree & create egg galleries (2.5”-12”) 4 to 14 eggs/centimeter Eggs hatch in August; Larvae bore out and feed as a group for the 1st
two instars; the 3rd and 4th instars are characterized by individual galleries
Overwinter as Larvae (but eggs and parents can still be present) Larvae pupate one year after attack (pupation lasts 10-15 days) Overwinter as adults either in Larvael chambers or in the bark near
the litter line (decreases predation by woodpeckers)
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Spruce beetles Signs
Red-brown boring dust on the ground
Entrance holes in the bark & crevices
Pitch at entrance holes (dependent on tree health)
Woodpecker activity on stems
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Spruce Beetle Components
What is diseased in trees? Feeds on multiple spruce species (including Sitka, Lutz, &
white spruce) Tissue functions affected are the phloem & cambium;
foliage turns orange-red in the second year of infestation Potential impact on whole tree functioning is dependent
upon the population size of the beetles & tree health Severe infestations create stands that are a complete loss
Spruce beetle Tree Symptoms
None occur until the second summer of infestation Needles turn yellow-green to orange-red Needle drop due to wind/rain (leaving bare
crowns)
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Spruce beetle Predisposing factors
Tree vigor & health (amount of pitch defense) Slower than average growth rate=bad
Mature, large trees (increased food source) Usually attack trees larger than 18” initially Average stand diameter greater than 12”
Proportion of spruce in the stand Stands with 70% or more spruce are highly vulnerable
Spruce beetle
Inciting Factors Any event that increases CWM
Harvesting Wind events Landslides
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Spruce beetle No important secondary/contributing factors
The beetles are quite capable of killing trees by themselves
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Spruce beetle Control Options Preemptive
Maintain stand health & vigor Thinning
Minimize CWM over 12” Minimize number of dominant trees in a stand
Spruce beetle Control Options Reactive
Dependent on scale of outbreak & forest objectives Rapid salvage harvesting focusing on dominant
stems Minimization of logging slash (chip/burn) Antiaggregation Pheromones (as a control?) Insecticides (Carbaryl & pyrethroids)
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Health Management Plan Preemptive
Monitor & Survey Reactive
Feasibility
Preemptive Measures In high value stands that are at risk
Antiaggregation pheromones (MCH) Release must be properly timed to beetle flight
Minimize amount of CWM (over 12”) Thinning from below to keep site vigor high and to
increase component of wind-firm trees with high H:D ratios
Match silvicultural methods to site
Monitor & Survey Aerial monitoring
Steep ground Larger coverage area
Windfall monitoring should be done in spring due to winter storms, but after any major storm system monitoring should be encouraged
Bark beetle monitoring done in regions with lots of blowdown
Reactive Measures A windthrown stand is likely to become
infested therefore: Salvage harvesting
Antiaggregation pheromones & pesticides in high value stands that are too immature to harvest or stands with high aesthetic value (recreation sites)
Trap Trees
Feasibility Economic
Salvage quickly to ensure highest profit Minimize spraying to high value stands
Ecological Decreasing amounts of CWM Decreased wildlife habitat
Political Political opposition is likely with most salvage
harvests Be proactive in attempting to educate the public on the
importance of salvage harvests (to the economy & to the forest)
Review Sitka spruceSitka spruce Management region: SE AlaskaManagement region: SE Alaska Wind is the primary disturbance agentWind is the primary disturbance agent Spruce beetles are the primary insect agent Spruce beetles are the primary insect agent
(linked with wind disturbance)(linked with wind disturbance) HMP PlanHMP Plan
Will I ever grow to be as old as Sitka
spruce…?
Photo by Thomas Magliery
Discussion Question If you were a land manager in a region that
had frequent stand replacing disturbances, what silvicultural method or methods would you use and why?
Discussion Question You are a district ranger for the USDA Forest
Service. Greenpeace is scheduled to make an appearance to your district. You have recently finished all of the necessary paperwork to conduct a salvage harvest on a 150 acre wind event. How do you think your guests will feel about this and how would you rationalize your timber crews actions?
Discussion Question Jerry Franklin, a proponent of old-growth
structures and CWM in forests, is coming to visit your forest. You have recently started a management policy to decrease the amount of CWM in your stands. How would you defend your actions?
Discussion Question You are a landowner who has been tending a
stand of highly valuable Sitka spruce for your lifetime. The USDA Forest Service is predicting massive spruce beetle outbreaks, what actions would you take?
Discussion Question Does Sitka spruce relate to other things we
have seen this semester and can we relate those management practices to this environment?
Discussion Question You are a land manager for a large industrial
company. The new, hotshot forester from New Zealand wants to implement pruning of Sitka spruce. Would you encourage or discourage his suggestion? Why?
Discussion Question Given the few tree species in the region and
the importance of Sitka spruce, what would happen if the climate regime changed and blowdown no longer occurred as frequently?
Photo Credits Unless stated, the photos found in this presentation were taken by the author (J. Greenwood) 1: http://www.alaskatours.com/alaskamap.jpg 2: http://www.snowgoosealaska.com/images/ alaska-map-big.jpg 3: Burns, R.M., & B.H. Honkala, tech. coords. 1990. Silvics of North America: 1. Conifers; 2. Hardwoods.
Agriculture Handbook 654. U.S. Department of Agriculture, Forest Service, Washington, DC. vol.2, 877 p. 4: Washington State Department of Ecology
(http://www.ecy.wa.gov/programs/sea/coast/images/spruce_n2.jpg) 5&7: Farrar, J.L. 1995. Trees of the Northern United States & Canada. Blackwell Publishing, Iowa. 512 p.
6: BCadventure.com (http://www.bcadventure.com/adventure/wilderness/forest/sitka.htm) 8: Cathedral Grove/British Columbia Archives: (http://www.cathedralgrove.se/text/01-Cathedral-Grove-
3.htm) 9:USGS http://vulcan.wr.usgs.gov/Volcanoes/MSH/Publications/MSHPPF/MSH_past_present_future.html 10, 11, 16, 18, 19, 20, 21, 22, 25, 26, 29, 30, 31, 32, 33, 34: Forestry Images
(http://www.forestryimages.org/) 12: Hennon, P.E. 1995. Are heart rot fungi major factors of disturbance in gap-dynamic forests?
Northwest Science. 69: 284-293. 15: Mount Washington Observatory
http://www.mountwashington.org/education/center/arcade/wind/beaufort.html 17: Louis Morin 13, 14, 23, 24 Harris, A.S. 1999. Wind in the forests of southeast Alaska and guides for reducing damage.
U.S. Department of Agriculture, Forest Service, Gen. Tech. Rep. PNW-GTR-244. 63 p. 24, 27, 28: http://na.fs.fed.us/spfo/pubs/fidls/sprucebeetle/sprucebeetle.htm
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