Forest management changes
microclimate & bryophyte diversity
in the Cascade Mts. of western Washington
Martin Dovčiak, Charles B. Halpern, Shelley A. Evans, & Troy D. Heithecker
SUNY ESF, Univ. of Washington, USDA Forest Service
Photo by Rick Droker
Global changes in land use
Source: World Resources Institute / South Dakota State University, 2009
Intact Forest Landscapes
Working Forest Landscapes
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)
Dovčiak & Halpern (Ecol. Lett. 13, 2010)
Ecosystem stability (μ/σ)
Mean population stability
0.9
0.6
0.3
Realized species number
5
10
Mean Richness
15
Individual species important for ecosystem function
M. Vieira
A. Syred
www.stevesforums.com
Significance of forest trees for bryophytes
¾ Forest canopy reduces solar radiation
and thus affects microclimate
‰ temperature
‰ moisture
¾ Trees provide important microhabitats
Decaying logs
Tree trunks
Forest Floor
Forest management in Pacific Northwest
¾ 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
¾ Science: DEMO Study in 1994
(Demonstration of Ecosystem Management Options)
‰ Examine effects of canopy removal on forest species
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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
¾ 3 sites
‰ mid-elevations
(825-1280 m)
‰
mature forests
(70-170 years)
‰ Douglas-fir dominated
(Pseudotsuga menziesii)
Mt. St. Helens
Mt. Adams
Experimental design
¾ 3 sites (blocks)
Treatment (retention level)
100% ( control)
40%
15%
¾ 3 treatments
Decaying logs
¾ 4 microhabitats
Forest floor
¾ Total of 576 quadrats (20 × 50 cm)
‰ 16 quadrats per microhabitat and treatment unit
¾ Sampled 8 years after canopy removal
Tree bases
(NE & SW)
Canopy structure after treatments
Treatment (retention level)
100% (control)
40%
15%
a
40
60
c
30
40
b
20
20
c
c
0
100
40
b
15 0
Canopy retention (%)
10
0
a
a
100
40
15 0
Canopy retention (%)
Air temp. max. (ºC)
80
PPFD (mols m-2 day-1)
Basal area (m2ha-1)
Effects of canopy structure on microclimate
35
30
b b
ab
a
25
20
100
40
15 0
Adapted from Heithecker & Halpern (For. Ecol. Manage. 226, 2006)
No. of spp. per quadrat
Richness of bryophytes
6
Decaying logs
a
P < 0.0001
5
b
4
3
P < 0.0001
5
4
c
Tree bases
6
5
c
1
1
1
0
0
0
5
15
Canopy retention (%)
1
100
b
1
100
3
40
cn.s.
2
2
3
40
a
3
b
2
1
100
Forest floor
4
a
3
6
3
40
5
15
Canopy retention (%)
5
15
Canopy retention (%)
Abundance of bryophytes
Decaying logs
Cover (%)
50
a
Tree bases
P < 0.0001
Forest floor
P < 0.0001
a
b
P < c0.01
40
30
20
a
ab
b
10
0
a
b
c
100
1
40
3
15
5
Canopy retention (%)
b
b
100
1
40
3
15
5
Canopy retention (%)
100
1
40
3
15
5
Canopy retention (%)
Response of liverworts vs. mosses
¾ Liverworts
‰ Less resilient to
drought & heat stress
Scapania bolanderi
¾ Mosses
‰ More resilient to
drought & heat stress
Hylocomium splendens
Liverworts (%)
Proportion of liverworts in bryophyte community
30
20
Decaying logs
n.s.
n.s.
P < 0.001
a
10
0
Forest floor
Tree bases
1
100
b
b
3
40
5
15
Canopy retention (%)
1
100
3
40
5
15
Canopy retention (%)
1
100
3
40
5
15
Canopy retention (%)
P < 0.02
5
4
No. of spp. per quadrat
Northeast
6
a
a
3
b
2
1
0
1
100
3
40
5
15
Southwest
6
P < 0.0001
5
4
a
3
b
2
c
1
0
1
100
3
40
5
15
Canopy retention (%)
Canopy retention (%)
Diff. in no. of spp.
(NE minus SW)
No. of spp. per quadrat
Aspect effects on tree bases on richness
4
Richness difference
P < 0.0001
3
b
2
b
1
0
a
1
100
3
40
5
15
Canopy retention (%)
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
¾ Canopy retention under 40% does not preserve overall
bryophyte diversity and abundance
¾ Current management prescription to retain ≥ 15% of
canopy is not sufficient
¾ Global climate change (warming, droughts) is likely to
exacerbate the effects of timber harvest
Photos by Rick Droker
Acknowledgements
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/
Rick Droker