Transcript Sapling performance across a montane deciduous/coniferous

Climate change effects on New England
montane forests: evidence from the past,
implications for the future
Matthew Landis
Dept. Biology, Middlebury College
[email protected]
New England forests – 2100?
Iverson and Prasad, 1998
http://www.fs.fed.us/ne/delaware/atlas
The deciduous – coniferous ecotone
Cogbill and White, 1991
Past and future changes
► Has
the location of the DCE changed in the past?
 witness tree surveys – comparison with present-day
► What
sets the DCE? How will it respond to future
climate change?
 a demographic approach – which life stages are most
affected?
 What is the role of sapling competition vs. direct climate
factors?
Changes in New England climate
since 1895
Keim and Rock, 2001
Elevation shift in the ecotone – an
upper limit
► 1.1°
C change in annual temperature since
1895 (Keim and Rock, 2001)
► Lapse rate:
 0.61° C / 100 m (Siccama 1974)
 0.57° C / 100 m (Richardson et al. 2004)
►~
150 – 200 m shift in the
deciduous/coniferous ecotone
► e.g. 800 m -> 600-650 m in 1780’s
Witness tree survey records
► Surveyor’s
records from original lotting
surveys (1780’s – 1790’s)
► Vermont is unique – surveyors covered even
the high elevations
► Maps obtained from C. Cogbill, Vermont
State Archives, Town Offices
► 10 towns digitized
Sampled towns
Witness tree locations
► 950
trees from 88 m to
1119 m (most between
200 and 700 m)
► Elevation
error
estimated at 15 m
(based on 75 m buffer)
► beech,
birch, maple,
spruce comprised 88%
of all trees
Forest composition– 1780’s
100
► Ecotone
 beech: 875-900 m
 maple: 820-860 m
90
Percent composition
(?)
► Upper limit of
80
70
Birch
60
Maple
50
Beech
40
Fir
30
Spruce
20
10
0
630
720
810
900
990
Present day sampling locations
►9
transects across the
DCE
► Point-centered quarter
every 25 m elevation
(625 m – 975 m)
► Up to 15 points per
transect
Forest composition– 2006
► Ecotone
80
70
Birch
60
Maple
50
Beech
40
Fir
30
Spruce
20
10
0
625
700
775
850
925
775
850
925
40
Number
 beech: 850 m
 maple: 825 m
90
Percent composition
800-850 m
► Upper limit of
100
30
20
10
0
625
700
Elevation (m)
2006
100
100
90
90
80
80
70
Birch
60
Maple
50
Beech
40
Fir
30
Spruce
20
10
70
Birch
60
Maple
50
Beech
40
Fir
30
Spruce
20
10
720
810
900
0
625
990
700
775
850
925
775
850
925
40
Number
0
630
Percent composition
Percent composition
1780’s
30
20
10
0
625
700
Elevation (m)
Summary
► Ecotone
much less pronounced in 1780’s
than now
► Much
greater abundance of red spruce in
1780’s
► Upper
limit of beech and maples has not
increased over the past 200 years
Sapling competition across the DCE
Cogbill and White, 1991
Performance
Colder
Temperature
Warmer
Loehle 2000
Mt. Abraham, VT (1221 m)
Methods
►
Locate gaps across DCE
(680, 740, 770, 800, 830,
890)
►
Measure extension growth
(internode length) of
dominant saplings
►
Multiple regression to
control ‘nuisance’ variables
(height and light)
►
Measured size distribution
along gradient
growth = height + canopy openness + elevation
Species
n
total R2
ABBA
73
0.54
PIRU
99
0.41
0.04
0.034
BEAL
124
0.30
0.05
0.021
ACPE
62
0.52
0.16
0.0002
FAGR
65
0.35
0.15
0.0013
ACSA
44
0.28
0.07
0.14
elevation elevation
R2
P
0.15
< 0.0001
0.15
0.04
0.05
NS
0.16
0.15
Sapling growth partially consistent with adult
abundance
n = 5 plots at each elevation
Conclusions
► No
support for parabolic model of sapling
growth
► Suggestion
of trade-off model – competition
between species likely to delay invasion of
northern hardwoods
► Weak
trends in growth along gradient
suggest other performance parameters and
life-history stages likely to play a strong role
Acknowledgements
► Charlie
Cogbill
► Undergraduate
research assistants: Alyse Forrest,
Sarah Fortin, Kerry Cebul, and Jill Morrison
► Bill
Hegman, Middlebury College
► Vermont
EPSCoR
► Middlebury
► U.S.
College
Forest Service
► Vermont
Dept. Forests, Parks, and Recreation
Proportion browsed
Browsing varies by species and elevation
1
abba
piru
0.8
beal
0.6
acpe
0.4
fagr
acsa
0.2
0
650
700
750
800
Elevation (m)
850
900
www.esd.ornl.gov
ABBA