Martin Dovčiak, Charles B. Halpern, Shelley A. Evans, & Troy D. Heithecker

SUNY ESF, Univ. of Washington, USDA Forest Service

Forest management changes

microclimate & bryophyte diversity

in the Cascade Mts. of western Washington

Photo by Rick Droker

Working Forest Landscapes Original forest cover Current forest cover

Intact Forest Landscapes

Source: World Resources Institute / South Dakota State University, 2009

Global changes in land use

Land use changes threaten biodiversity

Sala et al. (Science 287, 2000): Global Biodiversity Scenarios for the Year 2100

Biodiversity loss may affect ecosystem stability

Tilman et al. (Nature 441, 2006)

E

co

syste

m sta

bili

ty (

μ/σ

)

Realized species number

Dovčiak & Halpern (Ecol. Lett. 13, 2010)

Me

an

po

pu

latio

n s

tab

ility

Mean Richness 5 10 15

0.3

0.6

0.9

A. Syred

Individual species important for ecosystem function

M. Vieira

www.stevesforums.com

Significance of forest trees for bryophytes

Forest canopy reduces solar radiation

and thus affects microclimate

temperature

moisture

Trees provide important microhabitats

Decaying logs Tree trunks Forest Floor

Forest management in Pacific Northwest

Policy: Northwest Forest Plan (NWFP) in 1994

No clear-cuts on federal lands

At least 15% of canopy trees retained in harvested areas

to mediate environmental changes due to harvest

Science: DEMO Study in 1994

(Demonstration of Ecosystem Management Options)

Examine effects of canopy removal on forest species Vascular plants

Bryophytes

Fungi

Birds

Small mammals

Insects

Study hypotheses

Bryophytes can be negatively affected by canopy removal

(Dovčiak et al. Can. J. For. Res. 36, 2006)

H-1. Bryophytes negatively affected on longer time scales

richness, abundance, and liverwort proportion

H-2. Bryophytes negatively affected in all microhabitats

forest floor, decayed logs, and tree bases (NE vs. SW)

H-3. Patterns of bryophyte decline are consistent with

microclimatic changes caused by canopy removal

Study area – Cascade Mts., western Washington

3 sites

mid-elevations (825-1280 m)

mature forests (70-170 years)

Douglas-fir dominated (Pseudotsuga menziesii)

Mt. Adams

Mt. St. Helens

40% 15% 100% ( control)

Treatment (retention level)

Experimental design

Total of 576 quadrats (20 × 50 cm) 16 quadrats per microhabitat and treatment unit

Sampled 8 years after canopy removal

3 treatments

4 microhabitats Forest floor

Decaying logs

Tree bases

(NE & SW)

3 sites (blocks)

40% 15%

Canopy structure after treatments

100% (control)

Treatment (retention level)

Effects of canopy structure on microclimate

Adapted from Heithecker & Halpern (For. Ecol. Manage. 226, 2006)

Canopy retention (%)

Ba

sa

l a

rea

(m

2h

a-1

)

0

40

80

20

60

100 40 15 0

a

b

c

c

25

35

20

30

Air te

mp

. m

ax. (º

C)

100 40 15 0

a

ab

b b

PP

FD

(m

ols

m-2

da

y-1

)

100 40 15 0

a

a

b

c

20

40

10

30

0

Canopy retention (%)

a b c

Forest floor

Canopy retention (%)1 3 5

0

1

2

3

4

5

6n.s.

100 40 15

Tree bases

Canopy retention (%)1 3 5

0

1

2

3

4

5

6

a

b

c

P < 0.0001

100 40 15

Richness of bryophytes

Decaying logs

Canopy retention (%)1 3 5

No

. o

f sp

p.

pe

r q

ua

dra

t

0

1

2

3

4

5

6a

b

c

P < 0.0001

100 40 15

a b c

Forest floor

Canopy retention (%)1 3 5

P < 0.01

a

ab

b

100 40 15

Tree bases

Canopy retention (%)1 3 5

a

bb

P < 0.0001

100 40 15

Decaying logs

Canopy retention (%)1 3 5

Cover

(%)

0

10

20

30

40

50 a

b

c

P < 0.0001

100 40 15

Abundance of bryophytes

Response of liverworts vs. mosses

Mosses

More resilient to

drought & heat stress

Liverworts

Less resilient to

drought & heat stress

Hylocomium splendens Scapania bolanderi

Forest floor

Canopy retention (%)1 3 5

n.s.

100 40 15

Tree bases

Canopy retention (%)1 3 5

n.s.

100 40 15

Decaying logs

Canopy retention (%)1 3 5

Liv

erw

ort

s (

%)

0

10

20

30

a

b b

P < 0.001

100 40 15

Proportion of liverworts in bryophyte community

Richness difference

Canopy retention (%)1 3 5

Diff. in

no

. o

f sp

p.

(N

E m

inu

s S

W)

0

1

2

3

4

a

b b

P < 0.0001

100 40 15

Aspect effects on tree bases on richness

Southwest

Canopy retention (%)1 3 5

No

. o

f sp

p. p

er

qu

ad

rat

0

1

2

3

4

5

6

a

b

c

P < 0.0001

100 40 15

Northeast

Canopy retention (%)1 3 5

No

. o

f sp

p. p

er

qu

ad

rat

0

1

2

3

4

5

6

a a

b

P < 0.02

100 40 15

Hypotheses revisited

H-1. Bryophytes negatively affected over longer time scales

Yes: even after 8 years after logging

H-2. Bryophytes negatively affected in all microhabitats

Yes: decayed logs > tree trunks > forest floor

Yes: SW > NE side of tree trunks

H-3. Patterns of bryophyte decline are consistent with

microclimatic changes caused by canopy removal

Yes: for differences among treatments

Yes: for differences among aspects of tree trunks

Conclusions & implications

Canopy retention under 40% does not preserve overall bryophyte diversity and abundance

Current management prescription to retain ≥ 15% of canopy is not sufficient

Global climate change (warming, droughts) is likely to exacerbate the effects of timber harvest

Photos by Rick Droker

Funding: USDA Forest Service and PNW Research Station

DEMO research partners:

USDA Forest Service Region 6

Pacific Northwest Research Station

University of Washington

Oregon State University

University of Oregon

Gifford Pinchot and Umpqua N.F.

Washington DNR

Web site: http://www.fs.fed.us/pnw/rmp/demo/

Acknowledgements

Rick Droker