buffer strips and tree windthrow: problem or habitat

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


From Martin and Grotefendt 2007

Logged Unlogged

0.0

0.2

0.4

0.6

0.8 Cumulative Stand Mortality(N = 124)



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


Logged Unlogged

0.0

0.2

0.4

0.6

0.8 Cumulative Stand Mortality(N = 124)




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 after logging is probably increasing the quantity and distribution of fish habitat in streams in timber harvest areas.








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.








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

buffer strips and tree windthrow: problem or habitat

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