buffer strips and tree windthrow: problem or habitat
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Buffer Strips and Tree Windthrow:Problem or Habitat Enhancement?
Douglas Martin, Martin EnvironmentalRich Grotefendt, Grotefendt Photogrammetric Services
Alice Shelly, TerraStat Consulting
Windthrow in buffer strips is significantly increased following logging
Windthrow in buffer strips is significantly increased following logging
From Martin and Grotefendt 2007
Logged Unlogged
0.0
0.2
0.4
0.6
0.8 Cumulative Stand Mortality(N = 124)
Windthrow in buffer strips is significantly increased following logging
Windthrow in buffer strips is significantly increased following logging
0
10
20
30
40
50
0 0-0.05
0.05-0.10
0.10-0.15
0.15-0.20
0.20-0.25
0.25-0.30
0.30-0.35
0.35-0.40
0.40-0.45
Windthrow mortality
Perc
enta
ge o
f uni
ts
Buffer Reference
Magnitude of Windthrow Disturbance
From Martin and Grotefendt 2007
Logged Unlogged
0.0
0.2
0.4
0.6
0.8 Cumulative Stand Mortality(N = 124)
Windthrow in buffer strips is significantly increased following logging
Windthrow in buffer strips is significantly increased following logging
From Martin and Grotefendt 2007
0-10 m 10-20 m 0-20 mZone
0.0
0.2
0.4
0.6
0.8
1.0
Cum
ulat
ive
stan
d m
orta
lity
Buffer typeLoggedUnlogged
Cumulative Stand MortalityVaries by Distance
What are effects of tree windthrow in buffer strips on fish habitat?
Habitat is strongly associated with LWD
0
1
2
3
4
5
6
7
0 20 40 60 80
In-Stream LWD (no/100 m)
Pool
Fre
quen
cy (n
o/10
0 m
)
CW = 5 m CW = 15 m
0
20
40
60
80
100
120
0 20 40 60 80
In-Stream LWD (no/100m)
Perc
ent o
f uni
ts w
ith g
rave
l dom
inan
t
• Beechie & Sibley 1997• Montgomery et al. 1997• Martin 2001
Habitat is strongly associated with LWD
0
1
2
3
4
5
6
7
0 20 40 60 80
In-Stream LWD (no/100 m)
Pool
Fre
quen
cy (n
o/10
0 m
)
CW = 5 m CW = 15 m
0
20
40
60
80
100
120
0 20 40 60 80
In-Stream LWD (no/100m)
Perc
ent o
f uni
ts w
ith g
rave
l dom
inan
t
• Beechie & Sibley 1997• Montgomery et al. 1997• Martin 2001
Question:What is the magnitude and duration of habitat change following logging?
Trend in LWD Load In-StreamPre- and Post-Harvest Group
0
10
20
30
40
50
60
70
-10 -5 0 5 10
Years Before or After Harvest
LWD
(no/
100
m)
Caldera 1 Coco 1a Coco 2a Game 3 Game 4a Raven 1
Avg. Post - Pre Density = 6.46Difference significant(paired t-test p-value = 0.010)
Trend in LWD Load In-Stream Post-Harvest Group
0
10
20
30
40
50
60
70
80
90
0 2 4 6 8 10 12 14
Years Since Harvest
LWD
(no/
100
m)
Cabin 4b Cabin 5 Eagle 1 Eagle 3 EEagle 1 EEagle 2a Game 6a
Mean slope = 1.51Trend significant(t-test p-value = 0.0003)
Trend in Pool FrequencyPre- and Post-Harvest Group
0
1
2
3
4
5
6
7
-10 -5 0 5 10
Years Before or After Harvest
Pool
Fre
quen
cy (n
o/10
0m)
Caldera 1 Coco 1a Coco 2a Game 3 Game 4a Raven 1
Average post - pre frequency = 0.56Difference significant(paired t-test, p-value = 0.061
Trend in Pool FrequencyPost-Harvest Group
0
1
2
3
4
5
6
7
0 2 4 6 8 10 12 14
Years Since Harvest
Pool
Fre
quen
cy (n
o/10
0 m
)
Cabin 4b Cabin 5 Eagle 1 Eagle 3 E Eagle 1 E Eagle 2a Game 6a
Mean slope = 0.09Trend significant(t-test, p-value = 0.005)
Decay Class Aging Indicates Timing of Recruitment
DecayClass N
Avg.Age*
95% CL(lower)
95% CL(upper)
Green --
41
74
Nub-Rotten 285 30.0 27.5 31.6
<1 -- --
Twig-Branch 7.6 6.4 8.9
Primary 17.3 15.2 19.3
The Proportion of Recuited Trees that Function to Form Habitatis Related to Decay Class
0
20
40
60
80
100
120
Green Twig-Branch Primary Nub-Rotten All
Recr
uits
(%)
In-Ch Function In-Ch NonFunction Over Ch
955
143
274
24
514
(Decay class distribution based on 2005 data)
0
10
20
30
40
50
60
Green Twig-Branch Primary Nub-Rotten
Rec
ruits
(%)
In-Ch Function In-Ch NonFunction Over Ch
Pre-logging recruits
Avg Age17.3
Avg Age30.0
Avg Age7.6
Avg Age<1
Post-logging recruits
Decay Class Age and Function Indicates:
• Only younger decay class recruits (11%) may be affecting habitat since logging
• Full effect of post-harvest recruitment may not occur, on average, for about 30 years
Habitat Formation Needs Morethan Riparian Stand!
From Fox & Bolton 2007
152012N =
LWD by Channel Type
FPMMLC & MC
LWD
(pie
ces/
km)
800
600
400
200
0
From Martin 2001
Natural Wood Loading is Highly Variable
Southeast Alaska
Washington
Wood Recruitment and Forest Management?
Wood Recruitment Processes• chronic mortality• wildfires• bank erosion• landslides• ice storms• windstorms
Wood Recruitment and Forest Management?
Wood Recruitment Processes• chronic mortality• wildfires• bank erosion• landslides• ice storms• windstorms
Benda et al, 2003. Wood recruitment processes and wood budgeting. The Ecology and Magement of Wood in World Rivers.
Patterns of Windthrow Vary Naturally Across
Landscape
Kuiu Island
(From Kramer et al. 2001)
Harvest Management Patterns and Windthrow in Buffer Strips may be Influencing the Quantity
and Distribution of Fish Habitat?
Habitat Augmented by Windthrow Over Past 2-3
Decades with Birth of Buffer Strip Rules on Federal and Private
Timberlands
Federal Timberlands (green)
Private Timberlands (grey)
Timber Harvest may be More Concentrated in
Geographic Areas That are Naturally Less Prone
to Windthrow
Kuiu Island
Conclusion and HypothesesWindthrow in buffer strips is increased following logging
Windthrow is naturally greater in storm exposed landscapes
Conclusion and Hypotheses
Fish habitat is strongly associated with the amount and distribution of LWD in streams
Windthrow in buffer strips is increased following logging
Windthrow is naturally greater in storm exposed landscapes
Conclusion and Hypotheses
Fish habitat is strongly associated with the amount and distribution of LWD in streams
Windthrow after logging is probably increasing the quantity and distribution of fish habitat in streams in timber harvest areas.
Windthrow in buffer strips is increased following logging
Windthrow is naturally greater in storm exposed landscapes
Conclusion and Hypotheses
Fish habitat is strongly associated with the amount and distribution of LWD in streams
Windthrow after logging is probably increasing the quantity and distribution of fish habitat in streams in timber harvest areas.
Windthrow in buffer strips is increased following logging
Windthrow is naturally greater in storm exposed landscapes
In the absence of logging, fish habitat may be more concentrated in streams that are in areas prone to windthrow
Conclusion and Hypotheses
Fish habitat is strongly associated with the amount and distribution of LWD in streams
Windthrow after logging is probably increasing the quantity and distribution of fish habitat in streams in timber harvest areas.
Windthrow in buffer strips is increased following logging
Windthrow is naturally greater in storm exposed landscapes
In the absence of logging, fish habitat may be more concentrated in streams that are in areas prone to windthrow
Fish habitat may vary spatially and temporally across the landscape as a result of natural patterns of windthrow.
Conclusion and Hypotheses
Fish habitat is strongly associated with the amount and distribution of LWD in streams
Windthrow after logging is probably increasing the quantity and distribution of fish habitat in streams in timber harvest areas.
Windthrow in buffer strips is increased following logging
Windthrow is naturally greater in storm exposed landscapes
In the absence of logging, fish habitat may be more concentrated in streams that are in areas prone to windthrow
Fish habitat may vary spatially and temporally across the landscape as a result of natural patterns of windthrow.
Timber harvest may be more concentrated in geographic areas that are naturally less prone to windthrow.
Conclusion and Hypotheses
Fish habitat is strongly associated with the amount and distribution of LWD in streams
Windthrow after logging is probably increasing the quantity and distribution of fish habitat in streams in timber harvest areas.
Windthrow in buffer strips is increased following logging
Windthrow is naturally greater in storm exposed landscapes
In the absence of logging, fish habitat may be more concentrated in streams that are in areas prone to windthrow
Fish habitat may vary spatially and temporally across the landscape as a result of natural patterns of windthrow.
Timber harvest may be more concentrated in geographic areas that are naturally less prone to windthrow.
Windthrow disturbance following logging may be increasing fish habitat in streams where windthrowwas historically infrequent.
Acknowledgements
Sealaska CorporationAlaska Department of Natural ResourcesAlaska Department of ConservationAlaska Clean Water Action Program
Clearwater Logging Research Team - 1974
Clearwater Logging Research Team - 1974
http://www.dnr.wa.gov/hcp/research/pubs/index.html
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