HomeMy WebLinkAbout20060904.tiff 0310Og
FOREST
SERVICE
Colorado State University
Fort Collins,Colorado 80523-5060
(970)491-6303
FAX:(970)491-7736
February 28, 2006
Dear Reader,
I am pleased to share with you the 2005 Report on the Health of Colorado's Forests. The 2005
report is the fifth in a series of annual publications requested by the Colorado General Assembly,
written in consultation with the Colorado Forestry Advisory Board.
The 2005 report focuses on our state's hallmark aspen forests. Colorado has more aspen than any
other western state. As the state's only major deciduous species, it provides diverse habitat for
wildlife and draws many visitors, providing a boost to local economies.
The report also provides an update on significant forest insect and disease activity that has
occurred over the past year. The mountain pine beetle epidemic in north-central Colorado is the
worst in the state's recorded history. The dead, dry pine trees resulting from the epidemic
increase wildfire hazards and are a particular concern near communities.
Colorado's spruce forests are experiencing a different type of bark beetle, called spruce beetle.
Although we are in the early stages of a spruce beetle epidemic, most of our spruce forests are
old and vulnerable to far-reaching change. Forest management, including tree cutting and
prescribed fire, can play a critical role in both maintaining and restoring good health to
Colorado's forests.
If you would like additional copies of this report or previous issues, please contact Paige Lewis
at plewis(a,colostate.edu. The report can also be found on the web at
htw://www.colostate.edu/Depts/CSFS/.
Thank you for your interest in the future of Colorado's forests.
Sincerely,
Jeff Jahnke
State Forester
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Report on
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The 2005 Report on the Health of Colorado's Forests highlights the ecology
and management of the state's aspen forests and provides an expanded insect
and disease update, with a particular focus on the mountain pine beetle and
spruce hark beetle outbreaks currently spreading throughout Colorado's central
mountains. Both sections of the Report underscore the need to address forest
'r, management in a proactive, rather than reactive, manner.
Many researchers and land managers attribute the size and intensity of
current hark beetle activity, at least partially, to the lack of age diversity in
lodgepole pine and some spruce and ponderosa pine forests. This condition leaves
forests extremely vulnerable to bark beetle attack_
In the absence of natural cycles of wildfire or other disturbance, forest
management treatments can increase age diversity, decrease competition and
improve overall resilience among forest stands. But this action needs to occur
prior to an insect epidemic in order to be most effective.
Once an insect outbreak has reached epidemic proportions, it is very difficult
to slow its expansion. Ultimately, only freezing temperatures will stop the beetles'
reproduction. Forest management actions taken in response to an ongoing
epidemic should focus on public safety and the protection of homes and other
critical infrastructure.
Unlike the mountain pine beetle situation, we still have the opportunity to
be proactive in the management of Colorado's trademark aspen forests. Many
of the state's aspen stands are reaching the end of their life cycle. In some areas,
Colorado Forestry Advisory natural regeneration is not occurring. Strategic forest treatments can stimulate
Board Members regeneration, but must occur before critical root systems decline beyond the point
of recovery.
Don Ament Colorado's aspen forests provide both residents and visitors with a
Commissioner of Agriculture
tremendous range of values, including rich and diverse wildlife habitat, economic
Joyce Berry opportunities from recreation, tourism and timber harvest and unique cultural
Dean, Warner College of
Natural Resources and scenic opportunities. If we wish to maintain these and other values, we must
Colorado State university support forest management treatments that sustain aspen forests in their full
Tom Borden range of natural diversity.
Private Landowner As members of Colorado's Forestry Advisory Board, we encourage all
Fort Collins, Colorado Coloradoans to better understand the natural processes and human decisions that
Nancy Fishering influence the condition of our forests — and to support proactive treatments that
Colorado Timber Industry improve that condition before negative impacts occur.
Association
Russell George Sincerely,
Director, Colorado Department
of Natural Resources
Doug Robotham
Trust for Public Land Nancy M. Fishering
Tom Stone Chairperson, Colorado Forestry Advisory Board
Commissioner, Eagle County
2005 Report on the Health of Colorado's Forests
.a AtrA a
Fay ;2005 ' { rt on the Health of Colorado's Forests
Executive Summary
People enjoy and appreciate Fr 5 x-
Colorado's forests. mountains. wildlife i.1 '
and weather Although they often seem v• t N/ 1 ',
1 ! i
unchanging, each component of the } s" r 4o, 4 {Mr
state's beloved scenery is part of a ',, it
"" r 3E s, _
constantly shifting natural system Many !
it.
forests, for example, arc dependent on
cycles of wildfire and native insects fora ���sfi
renewal. The current mountain pine ° �• Ilk ' '
p11 t
beetle epidemic in Colorado's north-central mountains is giving residentseb �� ; ►
and visitors alike a vivid glimpse of this 4
...
,
renewal process in action. W,
The combination of aging lodgepole '1', 1 �' � " ' ort, 1
pine forests and several years of severe �� `r', _!R! �. '
drought has allowed the current mountain ' .IC
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pine beetle epidemic to grow to a scale flt �, '7 ilea '" '
not previously recorded in Colorado. In i tT X .v .'`. -� , i . t
4, -
2005, over 425,000 acres of Colorado 'v,-' . '
� j
forests were infested with mountain pine WI A, yt t $ kiit
beetle. Reducing wildfire hazard has ;k 11,. it k s 1 `" x
become even more critical in mountain Mountain pine beetle
many levels. dramatically changing the p
communities with beetle-killed forests. trapped in pitch.Despite
recreational and scenic experience of their small size,bark beetles
Since the majority of Colorado's
these special places.
spruce forests have the mature, large- are effecting across
major ssrhe we r.
sized trees that are sought by another Like lodgepole and spruce,
tree-killing insect, the spruce beetle, the Colorado's aspen also have far more old
state's spruce forests are also vulnerable forests than young. The 2005 Report
to far-reaching change. Not only are
on the Health of Colorado's Forests
spruce beetle outbreaks becoming more continues a series begun in last year's
numerous, a recently observed shortening
report by providing a detailed look at
of the beetle's life cycle is enabling it to the ecology, condition and management
expand faster than previously seen. of aspen forests across the state.
Spruce forests are among Colorado's In addition to its glorious fall colors,
longest-lived, having life cycles of 300 aspen is a tremendous asset to the
or more years. The onset of widespread state's economy, recreation, wildlife,
spruce beetle infestations could transform and watersheds. There are more aspen
this high country scenery in the matter forests in Colorado than any other state
of a few decades. A major turnover of in the West.
older spruce forests will affect people on
ill
2005 Report on the Health of Colorado's Forests
•
s
;1 4, ` r ' Although fire suppression is not growing into trees. More research is being
he main cause of vulnerability in conducted on this serious management
IColorado's spruce forests, it has had dilemma.
i , deleterious effects on the state's aspen Coloradoans enjoy tremendous
and other lower-elevation forests. benehts from the state's forests and, in
Continuing to severely restrict fire's return, have a responsibility to be good
•
i
role, without the addition of forest stewards of the land. This may include
management. has serious long-term bringing back disturbance to forests where
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implications for the sustainability of vital natural processes, like wildfire, have
aspen on the landscape. been interrupted. Forest management,
Elk, cattle, and other animals pose including tree cutting and prescribed fire,
another threat to aspen throughout can play a critical role in keeping, and
Although aspen will the West. Where aspen sprouts are returning, Colorado's forests to
dominate the foreground of
thisphoto for many decades, eradicated by browsing animals, young good health.
the distant hillside will soon
be obscured by conifers in aspen suckers are prevented from
the absence of fires or other
disturbances.
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Introduction
Insect and disease activity in 2005
provided a study in contrasts. Expanses of Mountain Pine Beetle
red beetle-killed trees drew tremendous Infestation in Lodgepole Pine 2005
P g =+ ---------- -- e,
public attention to the insect epidemic
s readin throu h the state's north-central
mountains. While in other areas, wetter I T
weather actually reduced the dramatic
insect activity seen in recent years. ����
Mountain pine beetle, an aggressive I` . Denver — I
native insect, is the primary culprit in thejra
— f _
death of millions of pines in Colorado and ; _ ___
across the West. Like other bark beetles, i
mountain pine beetle plays a natural role
in the life cycle of forest ecosystems, II 1
helping to precipitate the change from old
stands to young. 1 r"` - - Mountain Pine Beetle
'l -Lodgepole Forests
The extent, severity and rate-of-spread - Survey Areas
that characterize the current outbreak II ,
L J State Boundary
may be outside the norms of this natural c cony Bounden/
cycle due to a combination of drought •
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impacts and the generally old, even-aged u
condition of many Colorado forests.
Colorado's aging spruce forests are ibeerleoutbpF w*dhrs ra
bpoised to host the next big bark beetle ig10r.1O i°d
tiers than anypevon eOtdemktn
epidemic, as spruce beetle populations the stares rii:adedhistory.
continue to build in the state's high
country. Spruce beetle is a primary
agent of change in spruce forests, but < _
researchers are concerned about a recent 's�'t'
trend in the beetle's life cycle that has - :iIt'll,, sr w+, i?Mf t
reduced its usual life span from two years ��
to one. This adaptation allows the beetles - -gg 4
to proliferate much more quickly, a reality r }" -
that will likely bring vast changes to =" ; �` t
Colorado's spruce forests. r' w• {� :. . VFT, -� ,
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Mountain pine beetle
infestation in Grand
County,Colorado.
2005 Report on the Health of Colorado's Forests fill
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( In southwest Colorado, homeowners
U - - and land managers are beginning to Impacts to People from
see the recovery of pinon -juniper Widespread Beetle-Killed Trees
ai • > ; forests devastated by a drought-
K
id, er induced pinon ips outbreak in 2002 which may result in:
- ^= and 2003. Increased moisture has • Loss of life and property
S. q' caused a corresponding decline in insect
i ila •vmersh. • Reduced real estate values
e miliionsof activity, while also promoting growth of
1 k • Changes to tourism-based
z p taw;
emairise in precipitation
Bearow� A rise in precipitation throughout the economies
;'• mtheir • Long-term costs of water
state also lead to lush growth of grasses
at 1. en Plops supply and reservoir clean-up
•ve , .Iles of tree and (orbs. Small rodent populations • Safety hazards from falling
�y,!a' tops can be i exploded in response to this abundant dead trees
eta hip or haul food source. During winter, voles and
a 'dnl.ycreateair Potential impacts to recreation
q " imp tswhen I other rodents caused widespread
such as hiking, camping
b ' damage by chewing the stems of
If junipers, aspens, small ornamentals and and skiing include:
.L I various shrubs. • Scenery changes
• Reduced wind protection
• Safety hazards from falling
dead trees
Potential landowner impacts
include:
;., • Property value reductions
• Erosion issues from increased
water yields
�� . - • Wood and tree branch disposal
challenges
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Damage to aspen from voles.
2005 Report on the Health of Colorado's Forests
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Aerial Survey: Art or Science?
Traveling at 100 miles per hour, the air. Validation, or ground
1 ,500 feet above the forest canopy, truthing, of causal agent and
aerial surveyors have a challenging location is critical.
assignment. They are tasked with Despite limitations of the s
capturing the essence of insect activity, data, aerial surveying is an
intensity and location by sketching invaluable tool for examining
their observations on maps. Turbulence, insect trends over time. Maps ct
cloud shadows and physical discomfort and numbers referenced in
can increase the job's complexity. this report were derived from yz
"Patterns form that you can't see aerial surveys conducted in .t.� ,
the summer of 2005. s �ri
from the ground,"said Crystal Eventually, satellite x.
Tischler, a Colorado State Forest imagery may replace aerial '
surveying, but currently
Service aerial surveyor. "Some insects y
move progressively through an area the data is too expensive to
while others go from spot to spot." purchase and interpret. Aerial
surveying costs about a half a
A few insect signatures, like spruce cent per acre.
beetle, are hard to distinguish from
Mountain Pine Beetle
(Dendroctonus ponderosae)
In Colorado, mountain pine beetles Winter Park, Granby and Fraser in
primarily attack ponderosa and lodgepole Grand County;
pines. The beetles carry a bluestain Vail Valley in
fungus that infects their chosen trees. Eagle County; and zoo '^'v w°^
The fungus spreads through and clogs the parts of Summit, ♦`
tree's water-transporting vessels while Jackson and Routt oo w ECo
beetle larvae eat the tree's inner bark. The counties saw
no
fungus and the larvae's activities interrupt remarkable rates
the tree's nutritional system, causing the of mountain pine i4 Li.
tree's death. beetle expansion MOUNTAIN PINE BEETLE LIFE CYCLE
in 2005. Forest
Today, many of Colorado's high country Mountain
entomologists predict large-scale pine uone-year
a pine
ti a beetle
h s
elein
forests are dense, mature, eight inches mortality from Vail to the Continental Colorado.In the summer,
in diameter or larger lodgepole pine; Divide. adults leave the dead trees
where they developed.
this is precisely the habitat in which Ponderosa pine forests in Colorado
mountain pine beetle thrives. also experienced mountain pine beetle
outbreaks in 2005. Population build-ups
The current mountain pine beetle were detected near Salida and Buena
outbreak, which started in a few small Vista in eastern and central Chaffee
areas in the 1990s, has affected over County; outside Woodland Park in
425,000 acres in 2005, primarily in Northern Teller County; and southwest
lodgepole pine forests of north-central of Bailey in Park County.
fil
Colorado.
2005 Report on the Health of Colorado's Forests
4'1:,2; i,,s.
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t' Unseasonably low temperatures Fires in some areas of these beetle-
{- during early Pall (below 0" F), winter killed stands are likely during the next few
! 2. i (below -34° I-0, or mid-spring (below years. Weather will be a primary influence
0" F) can retard outbreaks, but beetle on the timing, as well as the size, of fires
_ survivors can re-start epidemics where in these areas.
, 1 overcrowded mature pine forests Fire danger increases during the first
, ' remain. to years after k a
forest,three whenfive needles arebeetles dr but ill remain
I' Extreme weather or lack of Y
i tt` remaining mature pines is the only
3
t means of stopping an epidemic of this
T
: intensity.
Wildfires in the second half of the
"
19th century, including several in the
dry year of 1851 , were widespread in a
Colorado. Many lodgepole pine forests
on the west side of Rocky Mountain
National Park and east of Grand Lake :, y4_:„
regenerated after the 1851 fires. In the
late 1800s and early 1900s, settlers Young,small-diameter trees,as seen in the foreground,
are not susceptible ro mountain pine beetle.
harvested trees for mining, railroads and
housing. The combination of wildfires
and human settlement activity led to on the trees. Once needles fall off, wildfire
large sections of forest starting over at hazard decreases for a period. Fire danger
about the same time. These forests have increases again in approximately 15 to 20
since matured to a size susceptible to years when the trees rot and fall down,
mountain pine beetle attack. adding woody material to the young trees
Lodgepole pines at about 80 years and other fine fuels growing on the forest
of age and older are susceptible to floor. A fire in this arrangement is difficult
mountain pine beetle. Future landscapes to suppress and would pose safety hazards
will be vulnerable to another outbreak to firefighters. Severe wildfires have higher
as widespread as this one if a more intensities and longer durations which can
balanced distribution of ages is not be very detrimental to plant communities,
reached. soils, and watersheds.
Less than a quarter of Colorado's Acres
lodgepole pine trees are small enough 100000 ,
140.000
to be resistant to mountain pine 100000 — -
100.000
beetle. Without forest management, . .
future landscapesI"ei"°'al
will be vulnerable ,,
to ,,.. '
another widespread outbreak. ■
LL
Recent drought conditions ° °-ID 01.40 41.10 11-00 11.100 100♦ Ul
weakened trees and enabled mountain
ilik pine beetle populations to swell to This graph from the ArapahoeRooseveltNational
record levels. Forest(located age b in north-centraln lodo)gepole
pole shows a
typical age breakdown in Colorado's Roosevelt
National
forests.
2005 Report on the Health of Colorado's Forests
d 'jjyy ' Y' �_� +��; ke �' s t a•It
n` I T '.i • } h l T. t
a' x �
To lessen wildfire Mountain Pine Beetle-Northern Colorado pine trees with
hazard, especially Infestation in Lodgepole Pine 2005 diameters above
where homes are eight inches. In
located in forests, it ,� r ` <4 LAR,MER lodgepole pine,
is critical to reduce .c.....*
( ""°^ clearcutting mimics
sacrcso,v .
�
the number of dead, ,, 1 natural processes and R
L . ,''
dry trees. Removing �_�•. ,•, remains one of the
z ,
this material can ROUTT best methods to create
lower a fire's intensity , q. conditions conducive
and thus speed R'N 9.-'� ' , 'c agULDER to regeneration.
- GRAN 2 1 )
regeneration and '� k;. Lodgepole pine'sE �x
recovery. Currently, ARFlELG r z wood is typically too ' t,� ,) , ,d
timber removal is t ' R solid, whether infested ..14,...J::1,^s ,'' m -
only occurring on a °�E ` - with mountain ,'� .�, d 1 ,
small percentage of GEAR pEK' pine beetle or not, ‘04-1,,v. fi a'
lands affected by bark ;410 '1 to provide habitat l °, -.x° A£"
beetles, primarily " N (L to cavity-nesting .1s' t :4_;/4,::-. t `
/ten vaRN" xykY� ���:
in wildland urban __ °'*^'N 'LANE S.. birds found in large
interface areas. m Lodgepore F-..ti C State Boundary trees with heart ' r+
=mount-p,.a...[ I�M+eo,m r—w•Rn.Rm•°•e. ,n
�' w
rot. However, other
There is no practical
way to stop a large- animal populations,
g Red areas depict the presence of mountain such as tree squirrels,
scale mountain pine pine beetle killed trees,and represent varying pine martens, and
degrees of mortality.Foresters expect that
beetle epidemic once most lodgepole pine forests in north-central woodpeckers, may
it has begun. Colorado will be impacted by this epidemic. experience population
shifts that correspond The distinctive rusty-red
Management strategies may focus on with changing habitats. needles on recently killed
removing standing dead trees (salvage), g g pine trees increase wildfire
Because lodgepole pine is a direct potential in the short term.
infested green trees (sanitation) and competitor to aspen, in sunlit areas of Long-term risk is associated
susceptible host material (thinning or with accumulation of large
clearcutting) or protecting high-value trees pine mortality aspen should flourish if it amounts of deadfall.
with preventive insecticide sprays. The is a component
in those forests.
latter strategy is not recommended for
Where lodgepole
treating entire forests due to its expense pine has been
and the difficulty of reaching vulnerable r °
removed,
tree trunks. Aerial spraying of insecticides ecologically
is not effective in preventing mountain beneficial stands
pine beetles. of aspen will
As with most insect and disease provide rich
problems, the best way to reduce habitat to many
unwanted damage is to alleviate stress N
wildlife species.
and extreme competition or otherwise u
improve forest conditions prior to attack.
In bark beetle prone areas, the most
effective approach may be a combination
of greensalvage/sanitationnnremoving
nsthinning
of green stands and removing selected
..14
2005 Report on the Health of Colorado's Forests
i' r b den` ( I, t
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7
- Oral ,',in p '-..., ° iih:ifl.,,.'
i
f; 1 d
I t{
it such as avalanches, temporary flooding
il. I Community Impacts by spring runoff, or root disease. The
,i4, I occurrence of spruce beetle epidemics
, dI'%'. I ' Infested Trees Removed across the West indicates the presence
1, 9 16,000 of large acieages of old, closely-spaced
"ti?, ! i 4,000 spruce trees as well as several triggering
t l � I 12000- events.
d i
t 10,000 --
i e.000 Unlike mountain pine beetle, which
.. 6.000 El spends few hours outside of its host
'a : I 4,000 0 MilIn tree, this tree-killing insect usually
= ,I o z,oao
Or
• takes a week to find a new host. With
7 2003 2004 2005 4
U winds, spruce beetle can fly up to 30-40
Despite actively removing mountain miles.
pine beetle infested trees, residents in a Many of Colorado's spruce forests are
subdivision near Granby Reservoir have in remote locations that can be difficult
seen increasing number of trees dying to access. Several designated wilderness
I in their neighborhood. areas have growing spruce beetle
j '.. populations.
• Spruce Beetle Forest management efforts can reduce
(Dendroctonus rufipennis) the impacts of spruce beetle by making
Spruce beetle is a primary ecological spruce forests more diverse age-wise.
change agent that regenerates old Reintroducing fire in lower-elevation areas
spruce forests. A period of 250 years or abutting spruce forests, and mimicking
more may pass between widespread the effects of fire by cutting different areas
epidemics. Intense wildfire is another over time are two available methods for
disturbance in spruce forests; the moist, increasing age diversity.
high-elevation sites where spruce/fir Spruce Beetle Infestation 2005
occur burn on a time scale of about 300- --
500 years. f°�
Entomologists are concerned about —
an unusual recent change in the spruce
beetle's typical life cycle, reducing I
the span from two years to one. This I
change enables the insects to proliferate - ] " _ [ —
at much faster rates than previously v,
observed. Many attribute the life cycle . ;
rg ::"÷ om.ero,mi.ry
change to milder temperatures and ? I I e.,bw
possible climate change influences. , s n .., v
Many spruce beetle outbreaks are
triggered by blowdown; others have Red areas depict the presence of spruce beetle killed
trees,and represent varying degrees of mortality.If
causal events that are less obvious, current spruce beetle outbreaks continue to grow,
Colorado's high country spruce forests may look very
different in a few decades.dt. 2005 Report on the Health of Colorado's Forests
lir 9
Pinon Ips Subalpine Fir Decline _. .
(Ips confusus) (Dryocoetes confusus and Armillaria spp, y,.
Pinon ips beetle activity, which killed Heterobasidion annosum, etc.) ,1„r„,,
t
record numbers of pinon pine trees in Mortality of subalpine fir, which ).,, , i
2002 and 2003, decreased for a second is attributed to the western balsam
year in 2005. This corresponds with the bark beetle and/or root diseases, P -
improved winter and monsoon moisture continued to be the most widespread ,
over much of the state since mid-2004. forest health issue in Colorado in 2005. .
The additional stress of twig beetle activity Because tree mortality is sporadic and f
seen in 2003 and 2004 also decreased because subalpine fir does not have ; i,
with the increased precipitation. a high commercial value, it does not t r� ,.,
In Colorado, pinon ips beetles draw much attention. This insect and r . t
impacted over 800,000 acres in 2003 disease combination killed over 600,000 > a.A w �iiv t
and over 500,000 acres in 2004. Rough subalpine fir trees in 2005. ' t `� azy
estimates suggest that over 9,000,000 t"t`, ., � ' :
pinon trees were killed in this epidemic, t i ...
i'�' 5.4�' ]i
mostly in the state's southwestern and
southern forests.
The result has been a major shift in
pinon-juniper forests in favor of juniper. t
Some pinons survived the outbreak and .
will provide the seed for a slow recovery -
of the species over the next hundred or
more years. ;
Douglas-fir Beetle
(Dendroctonus pseudotsugae) • Rti�•-^ 'i' �;
Douglas-fir beetle increased on .� r . ?��
Colorado's Western Slope and decreased ,' '''''?-4..'.:-.1-..".--
tom �,. --
on the Front Range. Douglas-fir pole
"�- ' �` '
beetle and various engraver beetles ', ,,,^•-• -As:-t1 .-,-C` —.
' 'Ill ."'� -.. a.;y
44
associated with Douglas-fir beetle `' .r i y�t „y` }
activity escalated somewhat as well.
Some pockets of Douglas-fir beetle are - i Yz'' � " `: lyi �,, glir fi'j a ,d u_associated with previous years' wildfires r ��`Sr}Gt ,!
like the 2002 Million Fire outside of South Spruce beetle populations
Fork and the 2002 Missionary Ridge Fire that exploded after the
near Durango. Douglas-fir beetle tends 13,000-acre Routt Divide
to populate areas that burned at high Slowdown in 1997 have
killed most of the spruce type
temperatures, but not hot enough to ruin within many miles of the
the trees' inner bark layers. blowdown area.
III
2005 Report on the Health of Colorado's Forests
r
M.
T
1Ij • t. r ,
I
Fy ,
zF ;,
,J Economics of Dead Trees
, After a few months of
} infestation, a blue-stain fungus - ' =A,
i It associated with mountain pine
• i #;
beetle turns the tree's wood light ��
i J�
1 ` i blue. This blue stain limits the ��' iik.k
products that can be made from •t
it il
ir I ' , the wood and reduces the wood's a''N>
,.I , t value.
;it Standing dead trees also lose
value over time because the wood
dries and cracks, making part of = �• `
the wood unusable. To retain the -
most value, infested wood should e : Lrw� ;1...-- --'--- - `
be removed from the forest as soon
as possible.
Western Spruce Budworm the past few decades. Without fire or
(Choristoneura occidentalis) active management, the fire sensitive
Western spruce budworm is chronic Douglas-fir has proliferated beyond its
throughout mountainous portions of historical territory, expanding even onto
Colorado, and it increased along the south-facing slopes. Recent Douglas-fir
Front Range in 2005, particularly in tussock moth outbreaks on these drier,
Jefferson County. Thinning forests can atypical locations may be a result of hre
promote tree vigor and may help trees suppression and may prove ecologically
better withstand repeated western beneficial by removing Douglas-fir from
spruce budworm attacks. Chemical inappropriate sites.
spraying can be used to protect high- Fir Engraver Beetle
value trees from defoliation and (Scolytus ventralis)
associated damage. Fir engraver beetle typically attacks
Douglas-fir Tussock Moth drought-stressed, pole-size and larger
(Orgyia pseudotsugata) fir trees. A 2004 fir engraver beetle
The Douglas-fir tussock moth infestation in white fir along the eastern
outbreak detected on the east slope of slopes of the Wet Mountains had no
Doubleheader Mountain in 2004 spread apparent new mortality in 2005. Improved
slightly northward in 2005. Additional moisture conditions likely caused the
defoliation occurred near this area on collapse of this insect population. Another
the south side of U.S. Highway 285. notable fir engraver beetle population,
Although Douglas-fir tussock also declining, continues in the area
moth was rarely observed for most between Durango and Molas Divide.
of the 1900s in Colorado, there
have been increased outbreaks over
10
2005 Report on the Health of Colorado's Forests
a,
Dwarf Mistletoes
9 x lc
(Arceuthobiurn spp.) . II:,
i4 tv ae t. as
Dwarf mistletoes, a group of aSit -r am
parasitic plants, can reduce their host ` '
trees' growth and seed production, as
well as increase susceptibility to insect
attack, root disease and storm damage.
Heavily infected trees show decline and ;:5,1,ret P
mortality. Fire suppression in lower-
elevation forests has reduced the number 4;1� r
of openings that should serve as barriers r ,4.i )m. t
to dwarf mistletoes' spread, favoring the t ,;
development of denser understory stands
beneath dwarf mistletoe infested trees.
a
E
O
O
O
p
An important strategy in bark beetle management,
as with many forest insects and diseases,is the
recognition and prevention of susceptible stand
conditions that may lead to epidemics.
Ski Area Battles Beetle
Intensive efforts to protect
'; small pockets of infestation can be
successful. The Steamboat Ski area has
been gaining ground in areas affected
t _ by spruce bettle through persistent
M removal of infested trees. Although
•
• • there is a high cost to aggressive
sanitation, spruce beetle populations
have abated for the third straight year
in the ski area, while increasing on
nearby lands.
— � V
Forest o S delimb beetle-killed trees on a run at
Steamboat Ski Area.
2005 Report on the Health of Colorado's Forests
4 '� �a. „
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I s I t to 1�,t 1
!, ¢ r,
s
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l Other Forest Health Issues
Yi1 • Dutch elm disease losses were 100 aspen trees. City managers are
7 much lower in 2005 than in previous effectively controlling the insect
a"
f years. Despite this positive trend, the incidence with dormant oil treatments.
value of large-leaved varieties of elms • Spruce ips beetle attacks in
If n Colorado's urban and community urban areas declined in northern
I., forests demands continued monitoring Colorado, including Boulder.
of this fungal disease and its two • Gambel oak borer on oaks in the
insect vectors, which are from Europe Denver metro area declined.
and Asia. • Surveys for emerald ash borer,
• Colorado State Forest Service set an Asian pest of ash species, will likely
1 ,578 gypsy moth traps statewide begin in a limited number of Colorado
in 2005. No moths were detected. If locations in 2006.
imported, gypsy moth could threaten • White pine blister rust,
Colorado's urban, riparian, and a serious disease of limber and
orchard trees. bristlecone pines, continues to
• Deciduous trees in southeast spread into Colorado. Its impact and
Colorado sustained leaf and stem management options remain unknown.
damage from scales, plant bugs, • De-icing and dust control salts
leafhoppers, aphids, mites, and other continued to cause discoloration of trees
sucking pests in 2005. along Colorado's roadways.
• The city of Aspen had a new
outbreak of willow scale on about
' is Ha{ 74
7s g a
' tL z
i� pmt' ,x �' a ilk 2005 Report on the Health of Colorado's Forests
As' en Forests in Colorado
Overview
Aspen (Populus tremuloides) is a 04
/ r-
hallmark of Colorado_ Its stunning autumn
/
colors. the rustling sound of its leaves
iiii ' ,"quaking.' in the wind, and the unique i� 4
quality of light filtering down through its
.: IP ,
open canopy have inspired generations
of artists, musicians and outdoor /`
adventurers. Its spectacular foliage draws �' '
thousands of visitors to forests throughout it
the state, resulting in a crucial economic . 1
boost to adjoining communities. And as
Colorado's primary deciduous tree, aspen
provides valuable diversity to the state's
scenic and recreational experiences.
Aspen's lush understory and nutritious
shoots and buds also make it good forage c' ear
for wildlife and cattle. The biodiversity
found in aspen forests, as well as its )-
characteristic soft wood, provide excellent %tt
habitat for many species, especially birds.
Prior to European settlement, periodic I /
wildfires rejuvenated declining aspen
stands by removing competing conifers 144
t
and stimulating new growth. In the
absence of these cyclic fires, Coloradans s
may see once golden slopes transformed dit t.
into carpets of piney green.
Aspen's majestic foliage
The two primary threats to aspen today brings millions of dollars to
are fire suppression and chronic animal Colorado's economy every fall.
browsing of young aspen shoots. Y . • r
aging or otherwise declining :-r
Many of Colorado's current aspen aspen forests. „re, -rr� i .
forests are reaching the end of their t t) e►+srr
natural life cycle and being replaced by In Colorado, the question P 1,,,,"”4•,; ,
faster growing conifers. Because they may not be one of aspen's :".
have not been renewed by fire or other historic range, but rather
disturbance, aspen stands are also more where aspen stands are .
vulnerable to extensive insect and disease beneficial and what action
is needed to ensure they are -
problems and animal browsing. ;
Although it is unclear to what sustained. t. .., o
extent aspen existed on pre-settlement €
landscapes, researchers and land C^ I' 4,
managers are exploring a variety of
management techniques that may mimic
natural disturbance cycles and revitalize
2005 Report on the Health of Colorado's Forests
I ,4i:',1, s
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I ,d �r ,6+i p i "" F R Iw•
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Ecological Characteristics of Aspen as opposed to lodgepole pine, Colorado's
'
: j 1 fastest growing conifer species, which
Aspen is the most widely distributed
j • might only grow two feet in that time.
tree species in North America and the
IL only major deciduous forest type in the Aspen has been a component of
" Colorado's landscape since the last
`fir Rocky Mountain region. Pure and mixed
, ice age, moving through cycles of
i i stands of aspen cover approximately 4
establishment,
, million acres
n Colorado, replacement by
.t F Ay,cr ) ;I , th, l ," conifers, and
making aspen
i re-establishment
state'
s
's
i IOW after the conifers
second most
]6iR are removed
. , prevalent forest _
type after "°°° through fire or
spruce-fir. i �s°° other large-scale
disturbance.
Researchers r ,°o.
. Aspen occurs
are unsure ,°°
in pure stands
why Colorado
., ur ar iu Mi vv of one or more
has a relative
N COMMERCIAL NONCOMMERCIAL clones or in
abundance of mixed stands with
aspen. Some
cite past Although the majority of aspen forests are in Canada and the various species of
Lake States,Colorado has more aspen than any of its western conifers. Although
climate and neighbors.
aspen clones may
disturbance
history. Aspen is known to be an early persist on a site for hundreds or even
invader of glaciated lands by seeding-in thousands of years, individual aspen trees
Ahealthy,mature root on the moist, bare soil left by receding are more ephemeral, living from 60 to
system can put out 4000ooto glaciers. Aspen can grow on a variety of 150 years of age.
a million shoots per acre.They Commonly known as "quaking
thin themselves as they soils, but thrives on the deep clay soils
mature. found on the Colorado Plateau. aspen," the tree's individual leaves have
Aspen trees grow in a characteristic flutter which results from
'46d ' .� ',1,17,;-1,_s: yea: clones that are made up leaf stems that are flat in cross-section,
'4 i 9E r rather than round. This adaptation gives
��Y , e of genetically identical
ma lig ay., F `"� 4. stems. Each stem
the leaves strength while allowing them to
"i twist flexibly in the wind.
� �`. sprouts from a common
11--t z a.3 i,�y ancestral root system Aspen's bark, which can be can be
42 green or yellow in addition to the more
4Ix through a process known
se 6 6-i ; as suckering. This unique common white, is a living layer, capable of
!It'll'.' k it - photosynthesis. As a result, aspen displays
ability gives aspen a
distinct advantage over wounds very clearly. Bark injuries, such
species that reproduce as bear scratches, heal into black scars,
r only from seed. The recording the event. Historical aspen
established root system carvings by Basque sheepherders from
provides young shoots, or suckers, with the late 1800s remain in many parts of
the water and nutrients needed to grow Colorado and the West.
quickly. In ideal, moist conditions, aspen Aspen occurs at elevations from about
can grow about 10 feet tall in five years 6,900 feet to timberline, approximately
ilk_ 2005 Rep ort on the Health of Colorado's Forests
it toil.
10,500 feet. Aspen in the West can grow Biodiversity .. s
to about 30 to 70 feet tall, reaching In the West,
diameters of one to two feet. The least aspen's plant and .til
I shade tolerant of Colorado's native trees animal communities e rj �
aspen requires full sunlight to thrive. �
are second only to �E; ,
Colorado's Western Slope has a much riparian areas in � 4�i1,
higher proportion of aspen than the Front p ' r
g p p p biodiversity richness. � ; �� ^^ � ' , � ,
Range. Extensive stands of pure aspen This tremendous .re
are located on the state's western mesas, �' ,c-I
biodiversity provides t
which are outside the natural range of
critical habitat for a -
lodgepole pine, a frequent competitor wide variety of wildlife, ' ';' �'�
with aspen. �� � . I
especially birds. I _ a= j�
The moisture regime on the Western Aspen's tender bark
Slope is also better suited for aspen.
and nutritious foliage i ; ,
A large portion of the Front Range's �� S v
also provide important wildlife forage. , ti,c.„**4;
moisture comes as rain in the summer,
much of which is intercepted by the forest Aspen is a valuable part of many
x
floor and subsequently lost to evaporation. western landscapes. In Colorado and
The Western Slope receives the majority Utah, aspen stands can be extensive °
of its precipitation in the winter as snow.
and form a major
When the snowpack melts, a pulse of
moisture saturates the soil, making it habitat component
available to aspen's roots. The timing of for many species.
the spring snowmelt precedes aspen's Aspen forests
vital leaf-out period. can have several
layers of vegetation. }e
' Plant communities v
`c/ associated with v` ,
aspen include a
X small trees such as c
' 0 rAi • . chokecherry; shrubs t 3
i I x �' such as snowberry, aspen occurs in a wide
'T'' serviceberry, and common juniper; variety of ecosystems and
� , 4.1.4!;,,, wildflowers; and grasses. Aspen is also
found mixed with spruce/fir, Douglas-
climatic regimes in mixed
- and pure forests.
+ i I fir, lodgepole pine, ponderosa pine,
t< '` Gambel oak, and sagebrush. Meadows
xg.
q and shrublands, which have decreased
ev over much of Colorado in the last
z' '. , �. . 3. l century, are sometimes neighboring
c- communities associated with aspen.
The bark of quaking aspen was used by pioneers
and Native Americans as a fever remedy,as well as
fo sc ing.Iaiicontains saaspirin.
which is similar to the
active ingredient in aspirin.
2005 Report on the Health of Colorado's Forests fill
f'', +%A' x. P; ,
.' 1:'149.14$ .Nd tk a AiA
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Animals That Use Aspen Habitat
Animals that use aspen as habitat chickadee, red-breastednuthatch and
t4-
:,L, include deer, elk, moose, black bear, pine siskin. Bird species in old aspen
mountain lion, snowshoe hare, stands are distinct from and more
; cottontail rabbit, beaver, porcupine, diverse than those of younger aspen
i �1 pocket gophers, bats, ,� f stands.
, snails, insects and y , , Beaver, which is a
$ '" ',� keystone species in the
butterflies.
West, depends on aspen
: Many birds, including $�t X4)4
1 songbirds, cavity nesters, 41 ,' it ", E for food and building
birds of prey, and ',n 4"y,� " ,.Y' ' materials. A keystone
gamebirds, benefit from .�' .:��.
.y_ v species significantly
aspen forests as well. a -
Jew' ti i o enriches ecosystem
Some avian species feed $ ' " ° function relative to its
on aspen buds and seeds. Northern saw whet owl abundance. Its removal
Year-round residents in initiates changes in
include ruffed ecosystem aspen communities structure and often loss
grouse, hairy woodpecker, mountain of diversity.
,a ,,,,z,,,.,
lcuk''.° i ri•p
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�1 er .
,,, . Y"H"1, A
Elk Calf Black Bear Cub Porcupine Beaver
Dan Binkley Terry Spivey Joseph O'Brien Terry Spivey
The Aspen Life Cycle
Aspen is considered a pioneer However, even when aspen trees have
species, being the first to proliferate disappeared from the canopy, its root
following fire or other disturbances. systems may persist for a long time, ready
Conifers, which start growing more to re-sprout if a disturbance removes the
slowly, will out-compete aspen over conifer overstory. Successional aspen are
time. Although conifers often succeed dependant on change agents like wildfire
aspen, aspen can persist as a pure forest or tree cutting to maintain a presence on
on sites where either a coniferous seed the landscape. These aspen forests would
source is lacking or environmental eventually disappear in the absence of
conditions prevent the establishment of such disturbance.
other trees. Because of its rapid early growth and
Some aspen, called successional establishment, successional aspen may
aspen, succeed to conifers within dominate a site for about 50 years. Aspen
410„. one generation without disturbance. mortality typically begins at 60 to 80
2005 Report on the Health of Colorado'sForests
1
414.
S x yt�y -y,
years of age, when larger conifers begin " v 1� « 17s R P w ti ; , ty -e
to significantly shade aspen stems. Most , i ., a r_--'J �" Yr`
aspen trees die between 80 and 100 years -. • 'i � �i �i , t z,,1 - ek a i �( , s:. F
old. Conifers, such as lodgepole pine, may ::' - ' ' , ,. .,if_ '�+�,, , �i f�
then dominate until the next fire or other -'_ t )
9 j
k , b
large-scale disturbance. However, aspen ! - ' '�tilt, � '' � �' 4 �� � � �
are more likely to live to 150 years old
or more in forests where conifers do not
ff + ! i•��� I I
succeed aspen. ... " i, ail ,:�'
Data from a state-wide study indicate `" A i x t i ;�
that the current average age of aspen ?. ';''.-c�
trees in Colorado is 120 years, suggesting � ..
that many are approaching the end of u � .
their life cycle. The oldest recorded aspen - ..--i=4;4.:,, :, _ ,.,
in Colorado is 276 years old and is located
outside of Paonia. Th. 5- b ' A
Although aspen is capable of Rf
reproducing from seed, it does not often >•.4.-4 !
r
occur. In order to germinate from seed, 4.
aspen needs full sunlight, a constant
supply of moisture during the first growing
season, and bare mineral soil. The climate • .'''''1*-
in the central Rocky Mountains is typically �' � �
too dry for aspen to grow from seed; y,
therefore, most aspen propagation is W -
from suckering. Genetic studies indicate
that aspen has germinated from seed at I
least occasionally during the last several . s
centuries; a few instances occurred after
Colorado's 2002 wildfires.
Unlike other western tree species, aspen �rTh �
on :)
will not readily regenerate from seed �. + F
once lost from the intermountain west .6 I.
landscape. -/ t . I
I ,
In select areas where aspen stems and
root systems have fully disappeared from ' fl; r
the landscape, re-introducing aspen will / ,
require planting. Insufficient moisture is
4:: ;
a critical challenge to this approach and Aspen and lodgepole pine often compete for the
increases the importance of preventing same sites.Aspen will flourish in many open areas
declining aspen stands from dying created by the mountain pine beetle epidemic in
north-central Colorado.
altogether.
2005 Report on the Health of Colorado's Forests -fil
IFdl
L i L1 P1 i� n, t r
s t j:
i
The Aspen Regeneration Triangle Fire and Other Agents of
II', I ' Successful
regeneration of Disturbance
aspen through root Like many of Colorado's forests,
sprouting involves three aspen is a disturbance-driven species
components: hormonal that developed in response to natural
stimulation, proper periodic fires and other landscape scale
growth environment, and disturbance events. Prior to extensive
sucker protection. human settlement, fire served as the
primary agent of change in aspen forests.
y 1. Hormonal
stimulation could be Fire maintains aspen stands on the
Thee xi2MillionFirethat, landscape either by burning competing
".oursideof5outhF k from any disturbance that
• : k interrupts the auxin/cytokinin hormone conifer stands, thereby allowing aspen
can!rdo inta!n spenontf how fire to re-establish, or by burning the aspen
canintainaspenonthe balance between the roots and stems.
lanpe.Aspen will likelq- The hormone balance is responsible stands themselves and stimulating
donwAbte parts of the bum regeneration.
for suppressing or triggering new
areafseso next se00 rs - r growth
g gg g Aspen's adaptations to fire include
because some conifer seed sucker g from root buds. Auxin is
sources were consumed. produced by leaves and transferred to its preference for sunny sites, rapid early
the roots where it suppresses cytokinin growth, prolific seed production and the
from stimulating the sucker buds. ability to regenerate through suckers.
When the flow of auxin is interrupted, Although individual trees easily succumb
cytokinin causes buds to sprout to fire, aspen forests usually contain
2. The proper growth environment more succulent, moist plants than conifer
involves sun and water. The initiation forests, making them harder to burn. Also
of bud growth must be accompanied in contrast to conifers, aspens lack resins
by sufficient sunlight and and volatile compounds that burn easily.
ir
; warmer temperatures at In addition to fire, several secondary
7' �f' �,� i the forest floor for the new factors act as change agents that help
i suckers to thrive. regenerate aspen. These include:
I - '` ''A' 'l If the clone and root
windthrow (blowdown), fungal diseases,
1. system are healthy, new
tent caterpillars and other defoliating
insects, burrowing animals, avalanches,
Sz 4 -, cIA L suckers will grow, but a
: ' weak root system may not snow damage, hail, and lightning. Cutting
8 :\::.* `<` aspen trees or severing lateral roots from
t : --:---s- :,. - regenerate. Inadequate
pparent trees can also act as a regenerating
a T. �x. :' '- _ x carbohydrate reserves,
Wind blew these trees down. damage from insects and disturbance.
Within a year,aspen suckers will
abound in the opening. diseases, as well as drought and climate
conditions, could all limit the suckering
response.
3. Protecting suckers from browsing
may be necessary until the tender
branch tips grow out of browsing
animals' reach. Heavy browsing by
herbivores can prevent suckers from
CC. maturing into overstory trees.
2005 Report on the Health of Colorado's Forests
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.� "Y 7 a! } u " ,� 4• � phi€ ` 1.v, V
` � ��'sAA itrlad�l tsar #CT ", ' # •� k yxW ip
Damaging Agents in Colorado's Aspen Forests in 2005 r ag t�a„.r k : , -z3
Aspen is renowned for being • Defoliators/Other ,5 y �:-T .3
P �
. x ei tTrt ft,
tt
susceptible to damaging agents like In 2005, aerial surveyors detected �' t , , '14
,3O
diseases and defoliating insects. Its about 20,000 acres of aspen defoliation , , », 4y*K ,1,� + , i?
thin, living bark is a host to rot and in the Dolores Canyon area which was sl , �s 3, '€ t .
canker disease organisms that can enter not observed in 2004. Whether a short- Q 2,,,,,,,,,...,,,,,J,,.., k ₹, a ,,,,,t!q
through even the smallest bark wounds term defoliation from an insect �z t=
and may rot or kill the tree. occurred, or if the trees were killed, will .f�� tr = f $ ,..”,44-4,:,
• Western Tent Caterpillar be determined in s r 4 a 'a- 0", ,
p the spring of 2006. _. - - t,..,.„,?,-,,,,-,.--
Western
tent caterpillar was
observed on the San Juan National • Aspen Decline - , -
Forest, between Durango and Durango A dieback of ,-. x•
Mountain Resort (formerly Purgatory aspen, including h
Ski Area). On the west side of La Veta mortality of
Pass, an infestation has the potential overstory trees, ,r,�'
for significant expansion. Western tent is widespread
caterpillar was also detected north of in the northern 5i
tilg t'
the Molas Divide, outside Silverton. Front Range. In ' O e ,
2005, most of _r
• Foliage Disease of Aspen
P '
these affected
An orange discoloration of the
foliage of aspen from leaf scorch was stands appeared to
observed in South Park, outside Idaho
have a dense and
v
healthy understory o
Springs, and in the Waugh Mountain
of aspen Li
area.
regeneration,
• Canker Fungi and Rots indicating that new
Canker fungi are present in almost aspen will replace
all aspen stands over 100 years old. the trees that died.
Many heart rots, root rots, and butt rots
are also present. +'
49 ., -;[
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c 4, 1,,k I°,
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Ir igt
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Heart-rot
2005 Report on the Health of Colorado's Forests
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Hi'-.'
° . '^ Consequences of Change Many researchers also attribute
� ! � � The extent to which aspen's current high proportion of older
� �fc � t., ` aspen covered past age classes to fire suppression. These
1,'.2-','"", ,� k mature forests (as with all sta es of
''IAA : landscapes is a current topic g
t forests) play an important ecological
' ' ' 'R{r i,, , v F of debate and research. P g
" l ' �.�ois w, ii,441,9n4'`� Fire suppression, herbivore role, but with a majority of Colorado's
P,S I" � t gs ' -sus damage and climate change
aspen stands in older age classes, many
r l i f c °� i g g
are three influences that landscapes are not providing the full range
b ' l ,''� i •r * r of benefits - from recreation opportunities
Al, i''' r � may have altered aspen from pp
- ' �� f b � to wildlife forage - that would be available
4 1 till < its cyclical coverage on the g
��� from a forest with a more diverse mix of
y4s landscape. Although forests
` '' a t i - ii V can be returned to an aspen- ages.
. t. , v-1 � :. j dominated condition, action Herbivore Damage
o R•. " i E - + will likely be needed to bring Since older aspen forests produce
V ' w ,I
�t \ about this change. less forage than young ones do, many of
Y Fire Suppression Colorado's aging stands are at heightened
Prior to human settlement Unlike ponderosa pine,
vulnerability to animal browsing. A few
e standsfr-burnedona p aspen stands may even face potential
scale ranging from decades to which can live through several fires and p
centuries. record each disturbance in its growth eradication in heavily impacted areas.
rings, aspen trees either do not burn
or are consumed in the fire, leaving 11 M1L /
.R
no discernable record. This makes
fire history in aspen very difficult to f
determine. The fire history evidence i (\ ' ! i r +l I
that does exist suggests �;'��^ � ;', i �i
x �,� that frequent, patchy i
K.+
s fires occurred on aspen o• landscapes in western
w Vet; Colorado in the latter Elk Damage to Aspen
- *I half of the 19"' century.
t• While research when aspen suckers are repeatedly
continues into the extent browsed, they are not able to grow into
"�+ }„ 't trees. An aspen forest with greater age
., nta
�x� k i ' r, , ^ of fire's role in other
o t+ i parts of the state, it is diversity would have an increased number
3„: '• clear that Colorado's of sprouts and would be less at risk
o . .�� ' __ '_ ; <+k-r n: current aspen stands from the impacts of elk, cattle and other
si
co are declining due to browsing animals.
While aspen's presence is still lack of disturbance. Although there is a lush understory
widespread in Colorado's Fire suppression over the last century in many aspen stands, elk prefer aspen's
forests,some researchers has undoubtedly prevented some nutritious twigs, leaves, and bark. Elk have
estimate that aspen- historically browsed aspen, but chronic,
dominated stands in other Colorado landscapes from returning to
parts of the west have aspen-dominated forests. Continuing intense browsing is a relatively recent
decreased between 50-96%. o severely restrict fire's role has threat. Over the past several decades,
serious long-term implications to aspen some aspen areas in Colorado have been
sustainability. severely impacted by animal browsing.
20 These impacts coincide with an increase
_ 2005 Report on the Health of Colorado's Forests
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to decline at its lower elevation limits, ' i.r t , , ,
*Ft t
;, particularly in areas of shrubland sct i4.
,, y such North Park and South Park in ', r , ti°
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Management Options '
3' Various management options „ < ;x41t-';',,',01�
3^k can be employed to maintain or re- S t1
•, — *At::
I e "s
- "'"7 I>' r : . * establish aspen on the landscape for aq ,, +"
v ecological, commercial, and aesthetic ! `
x
�^,- •.-� �...r- ,,..r+-' ••«�+* .__ reasons. Fencing can eliminate animal `
lin ° obrowsing
= and allow suckers to grow a � '-
into trees. Cutting trees or conducting tt . ,i
There are still many elk in Yellowstone,but the threat prescribed fire in areas that are _ � ,ak rr^,
of re-introduced wolves has changed their browsing � '!'t
large enough to disperse herbivores `
habits and aspen suckers now have a chance to
grow into trees.Despite the unhealthy appearance
can also help some aspen suckers ` �'
of the parent stems,this Lamar Valley photo shows a survive. Experience in Colorado has 'k
functioning system with aspen sprouting.The aspen shown that harvesting several 15- to
sprouts have not been browsed,indicating a significant 20-acre clearcut units at one time in
improvement in the area's aspen's prospects.
a landscape can result in successful
in elk populations and a decrease in aspen regeneration, even if large
natural predators. numbers of browsing animals are
While natural predators can reduce present.
elk populations through mortality, it Forest management can alter the
is the return to natural travel patterns succession of aspen forests to
that improves young aspen survival. Elk
behavior has changed significantly in the coniferous forests just as wildfire did
absence of its major predators. Rather naturally.
than moving from one location to another, Due to numerous pathologic,
elk have become increasingly stationary biotic, and environmental factors,
This concentrates browsing, allows less active monitoring is key to aspen
time for aspen stands to recover, and management, especially for the first
reduces survival of aspen suckers. In the five years after stand establishment.
ten years since wolves were re-introduced
in Yellowstone National Park, aspen Wildfire Use
sucker survival has visibly improved in the Wildfires have had ecological benefits,
area. such as re-establishing aspen, for millennia. '!-' ¢,,
Climate Change
Wildfire Use is a type of management
that allows wildfire to fulfill its vital role in
Many current aspen clones are rejuvenating ecosystems. This important
believed to have established from seed c
tool can be employed on some lightning-
during cooler and wetter times. Aspen started fires. The benefits of Wildfire Use
will be at a disadvantage in a warming are increasingly apparent. Its use can be
Ci
climate because it cannot change its range very complex near populated areas.
with seed production, except during rareCU
establishment periods. If temperatures
01
become warmer, researchers expect aspen
2005 Report on the Health of Colorado's Forests
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, Common Aspen Management 15 feet tall to survive under extreme elk
1 Techniques browsing pressure. In most cases, eight to
' ,
,, ' I. No Action 10 years of normal growth are necessary
1 Not taking action is a form of for suckers to attain these sizes.
i management. In aspen stands that are 4. Prescribed Fire
s able to regenerate themselves without Prescribed fire can provide ideal
r I disturbance, no action may still result in growing conditions for aspen suckers.
I the retention of aspen on the landscape. Fire removes competing vegetation and
1 ,i I '_i. Such stands are prevalent on the blackens the soil surface, which absorbs
a Western Slope, but are less common in the sunlight's warmth, encouraging sucker
' . the Front Range. Even if aspen clones production. Prescribed fire can also
j;
are in decline, they may still be able to improve forage quality and small mammal
4 regenerate successfully. habitat.
2. Release from Competition Prescribed fires that burn the
Removing conifers can slow or set periphery of aspen stands will stimulate
back the shift from aspen-dominated new aspen suckering along clone
to conifer-dominated forests. Removing boundaries, even if the overstory aspen
small conifers is less expensive and are not killed. This can create a diverse
can result in less injury to aspen stems landscape in which some areas wilt be
than cutting full-sized conifers. Although covered by new suckers while others will
removing competing conifers does not have some surviving overstory trees.
directly stimulate sucker production, it When fire regenerates aspen, the
does allow sunlight to clone not only grows back, it expands
C. • Ft . F
�L� ( j reach the forest floor. from one to one and a half times a tree
�, -,, i Resulting warmth height out from the area previously
g.o- ?_ s k. may encourage occupied, because aspen roots extend that
Pot. s \ . I the natural sucker far away from trees.
t
1 % ;* production that is In remote mixed conifer/aspen stands,
' a I already occurring in prescribed crown fire can promote aspen
P,
'��` j * �:'I -. declining clones. regeneration or development. Crown
" �I, • 3. Protection from fire not only rejuvenates aspen and
it resets vegetation succession, it can also
�4 ;`. v _ ,, -ta Herbivory g
tr e -E, t+ ."''•i ' Where browsing increase understory plant diversity, forage
"° production, and water yields, as well as
animals are present,
Fencing must be kept protecting new suckers improve habitat for many wildlife species.
functional long enough to may be the key technique needed to In these cases, conifers carry the
allow aspen to outgrow their q
most susceptible stage to elk achieve successful aspen regeneration. crown fire through the forest, killing all the
damage. Fencing is the only proven means of aspen as well as the conifers. If conducted
directly protecting aspen sprouts from when soil moisture is high, such burns can
herbivory. It also reduces the risk of avoid excessive damage to aspen roots.
herbivores injuring aspen. However, Combining fire with other aspen
game-proof fencing is costly, labor management techniques can greatly
intensive, and time consuming to benefit aspen regeneration and maximize
construct and maintain. suckering. Blending this technique with
ck, Stems need to be larger than one others mimics natural fire disturbance
and a half inches in diameter and about cycles in mixed aspen/conifer ecosystems.
2005 Report on the Health of Colorado's Forests
'd- W "c i " e+N."f°a4 e nl . t Sf Th ,t q .A4'tr- '�` - .
pr ."+ it "+ A•i".ka{I afd 1�1Yf t ty . `4' ..
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5. Mechanical Treatments Areas of Aspen Management
Harvesting can establish groups of
Because it is a very desirable
aspen at different ages in otherwise large, species, there are many efforts to
single-aged landscapes. Removing all of return aspen to the landscape. The
the aspen in patches, including understory following projects highlight some aspen
stems if present, will stimulate dense management efforts in Colorado.
suckering.
An advantage of harvesting aspen U.S. Forest Service Fraser
is the treatment of black canker. If an Experimental Forest
infected stand is clearcut, the new suckers At the Fraser Experimental Forest,
managers are working to enhance aspen
,� n conjunction with mountain pine " ,� ,
jiti _
beetle salvage efforts. While removing '""�1 ' ' '`
I dead and infested lodgepole pine 0 " L `
trees, they also cut areas of competing
conifers surrounding aspen trees, which
hi Ili, —
stimulates aspen suckering.
"fii. d West Side Project, Salida
In a cooperative
effort called the litl� �' -`' E .-
•
4
West Side Project, n I
The Dixie forest in southern Utah used prescribed the U.S. Forest +N 4` % f'1mt � 1h 1 i r ,
crown fire in mixed conifer/aspen forests. s`e. 4 i 4 4 -1 1
Service, Bureau of `s d. ,
Land Management, cot 'o ;
will be free of the canker. However, Colorado State t""' +
removing all stems in small stands near Forest Service, and thf.
elk populations may result in loss of local landowners - aQ;t r k
overstory trees as well as the root system are working across m , �'�Y` ' -,...a
if protection from elk is not provided. property boundaries +w+;r ^,'' ly
Severing lateral roots is another form to reduce mountain r . i 4 ,: - k'F : ° 1 g,
of mechanical treatment that regenerates i - w ., a
g pine beetle impacts _ _ � -t, y� +ti �, • - _ o
,. -
aspen. It relies on the wide-spreading and mitigate I —7,-,— �' �' ''""�� o
root habit of aspen to establish suckers at wildfire hazard. aearcutting small patches of
the edge of aspen stands where they will Because of its fire-resistant properties, aspen increases valuable edge
receive direct sunlight. encouraging aspen is a primary goal. habitat,which gives wildlife
A singlepass with a ripper along the cover and access to food that
g PP Thousands of acres have been is available in meadows and
edge of a clone can effectively stimulate treated in the few short years since the young forests.
suckering by cutting roots to a depth of West Side project started. Thinning and
about eight inches. To be effective, the patch-cutting in this landscape-scale
roots only need to be separated from effort is changing an unnaturally dense
parent trees. Multiple passes, or use of forest to one that favors aspen and
discs or rototillers, is not recommended increases age class diversity. Specific
because they cause too much injury to aspen improvement measures include
lateral roots. removing old aspen and cutting conifers
in mixed aspen/conifer forests.
2005 Report on the Health of Colorado's Forests fill
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opportunities and revenue. However,
a San Juan National Forest pp
M In Montezuma and Dolores when wood supply decreases, mills
i i Counties, foresters have been actively struggle. These mills receive about 20 to
yl l' managing aspen for several decades. 50% of their aspen wood from federal
l By harvesting, they mimic how wildfire timber sales, about 40 to 50% from
I rivate land, and up to 40% from state
e historically re-set succession. This p
a '` , ; regenerates older, declining stands and lands.
t ' t increases the number of younger aspen The 387-acre Upper Lost Timber
ti forests in an area where most are old. Sale, planned for 2006, contains about
„ ,r
1 " Land managers target areas of five million board feet of aspen. U.S.
j; • i , I mature aspen trees with extensive Forest Service plans to continue these
•' I tlC• insect and disease problems. They then ecologically and economically beneficial
li
j design harvest units to break up the aspen management activities in future
• ° ' forest canopy. Cutting all of the aspen years.
Fwithin the five- to 40-acre units allows Uncompahgre National Forest and
warm sunlight to reach the ground and Grand Mesa National Forest
C maximizes aspen suckering. Management efforts in the
Although the smaller material Uncompahgre and Grand Mesa
remaining from National Forests help retain the area's
harvest activities aspen stands. When aspen stands are
Illellpirll decomposes excessively diseased in these National
relatively quickly, Forests, south and east of Grand Junction,
large woody respectively, foresters consider them for
debris breaks harvesting.
,, down slowly Wildlife habitat factors help determine
and provides the size and shape of the cutting units.
habitat for small Land managers use patterns that will
o animals. For this enhance wildlife habitat over the long
reason, some term, ensuring that future aspen areas
o � logs are left on have some mature stands. Currently most
Long term site productivity site, distributed aspen stands in the area are nearing the
is enhanced by leaving some through the cutting areas. This can also end of their life cycle. If all of these areas
logs and tree branches on the help protect aspen regeneration, making
ground. P g were to regenerate at about the same
some sprouts less visible and accessible time, there would be vast expanses of
to elk and cattle. young stands with little or no mature
The harvested wood is put to many cover to provide security for wildlife.
uses. One local mill makes tongue Local markets also benefit from aspen
and groove aspen paneling, used for management. Products made locally
interior walls and ceilings. Another local from aspen timber include paneling,
mill shreds the wood to make erosion palettes, mine props and commodities
control mats, which help stabilize soil from shredded wood. Between the
and allow plants to establish. Uncompahgre and Grand Mesa National
Because mill work is one of Forests, about 200 acres of aspen are
the better paying local jobs, the harvested annually.
communities of Mancos and Dolores ilk. benefit from the mills' employment
2005 Report on the Health of Colorado's Forests
At • • -
•
•
• • •
• 1 - II ' ► a • IIi
Baker, F. S. 1925. Aspen in the central Rocky Mountain Region. USDA Department
Bulletin Number 1291.
Barnes, B. V. 1966. The clonal growth habit of American aspens.
Ecology 47:439-447.
Bartos, Dale L. 2001. Landscape Dynamics of Aspen and Conifer Forests.
In: Sustaining aspen in western landscapes: Symposium Proceedings;
13 - 15 June 2000; Grand Junction, CO. Proceedings RMRS-P-18. Fort Collins, CO:
U.S. Department of Agriculture, Forest Service, Rocky Mountain Research Station.
460 p.
Bartos, D. L. and R.B. Campbell, Jr. 1998b. Water depletion and other ecosystem
values forfeited when conifer forests displace aspen communities. In: D. F. Potts (ed),
1998 Proceedings of AWRA Specialty Conference, Rangeland Management and
Water Resources. American Water Resource Association. Herndon,Virginia.
TPS-98-1. 474 p.
Chong, G.W., S.E. Simonson, T.J. Stohlgren and M.A. Kalkhan. 2001.
Biodiversity: aspen stands have the lead, but will nonnative species take over?
In: Sustaining aspen in western landscapes: Symposium Proceedings;
13 - 15 June 2000; Grand Junction, CO. Proceedings RMRS-P-18. Fort Collins, CO:
U.S. Department of Agriculture, Forest Service, Rocky Mountain Research Station.
460 p.
Cottam,W.P. 1954. Prevernal leafing of aspen in Utah mountains. Journal of the
Arnold Arboretum 35:239-250.
DeByle, N.V. 1985. Wildlife. In: N.V. DeByle and R.P. Winokur, editors.
Aspen: ecology and management in the Western United States. General
Technical Report RM-119. U.S. Department of Agriculture, Forest Service, Rocky
Mountain Forest and Range Experiment Station.
DeByle, N.V. and R.P. Winokur, editors. 1985. Aspen: ecology and management in
the Western United States, General Technical Report RM-119. U.S. Department of
Agriculture, Forest Service, Rocky Mountain Forest and Range Experiment Station.
2005 Report on the Health of Colorado's Forests
.
Ii
s a N. ', j" 'A tp,, t 4.
1 w EYI C.• � �. I �f
¢ it, r`1, i ` .'40 4a Y 6, - ,
ti.
.
1 .
I, 1,; Jones. J.R. and N.V. DeByle. 1985. Morphology. In: N.V. DeByle and R.P. Winokur,
f editors. Aspen: ecology and management in the Western United States. General Tech
nical Report RM-119. U.S. Department of Agriculture, Forest Service, Rocky Moun-
; ` tam Forest and Range Experiment Station.
Yiii if., ill
`.
Kaye, C.E. 1997. Is aspen doomed? Journal of Forestry. 95:4-11.
; , Mueggler, W.F. 1985. Vegetation associations. In: N.V. DeByle and R.P. Winokur,
4, editors. Aspen: ecology and management in the Western United States. General Tech-
• nical Report RM-1 19. U.S. Department of Agriculture, Forest Service, Rocky Moun-
t tam Forest and Range Experiment Station: 45-55.
Floyd-Hanna, D.D. Hanna, and E. Bartlett. 2001. Aspen's
W. H. L.
Romme,
ecological role in the West. In: Sustaining aspen in western landscapes:
Symposium Proceedings; 13 - 15 June 2000; Grand Junction, CO. Proceed
ings RMRS-P-18. Fort Collins, CO: U.S. Department of Agriculture, Forest Service,
I Rocky Mountain Research Station. 460 p.
Shepperd, Wayne D.; Binkley, Dan; Bartos, Dale L.; Stohlgren, Thomas J.; and
Eskew, Lane G., compilers. 2001. In: Sustaining aspen in western landscapes:
Symposium Proceedings; 13 - 15 June 2000; Grand Junction, CO. Proceedings
RMRS-P-18. Fort Collins, CO: U.S. Department of Agriculture, Forest Service,
Rocky Mountain Research Station. 460 p.
Shepperd, W. D. and J. R. Jones. 1985. Nurse crop. In: N.V. DeByle and R.P.
Winokur, editors.Aspen: ecology and management in the Western United States.
General Technical Report RM-119. U.S. Department of Agriculture, Forest
Service, Rocky Mountain Forest and Range Experiment Station.10,, 2005 Report on the Health of Colorado's Forests
r
a .aoik
Acknowled a ements
The 2005 Report on the I lealth of Colorado's Forests was developed by the
Colorado Division of Forestry in conjunction with Colorado State University
Publications and Printing. The primary author was Jen Chase.
Significant contributions to the section on Aspen Forests were provided by Dr.
Wayne Shepperd of the USDA Forest Service Rocky Mountain Research Station and
Drs. William Romme and Dan Binkley of the Department of Forest, Range and
Watershed Stewardship at Colorado State University.
The 2005 Insect and Disease Update was compiled with substantial assistance
from entomologists Robert Cain with the USDA Forest Service and Dave Leatherman
with the Colorado State Forest Service. USDA Forest Service entomologists Tom Eager
and Roy Mask also contributed to this report.
Maps were created by Skip Edel, Colorado State Forest Service, using data from
the 2005 Aerial Survey of insects and diseases in the Rocky Mountain Region, a
cooperative effort between the USDA Forest Service and Colorado State Forest Service.
Special thanks to Paige Lewis, Colorado State Forest Service, and to the Colorado
Forestry Advisory Board for their oversight, and to Barbara Dennis for her always
tremendous help in facilitating design and production.
2005 Report on the Health of Colorado's Forests
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Colorado Department of Natural Resources
Division of Forestry
1313 Sherman Street, Room 718
Denver, Colorado 80203
(303) 866-3311
www.dnr.state.co.us
CO4Z4g10
FOREST
SERVICE
COLORADO
001iPIPIPPW
DEPARTMENT OF
NATURAL
RESOURCES
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