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
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
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