compositional shifts in undisturbed neotropical forests: effects of climate change? william f....
Post on 14-Dec-2015
220 Views
Preview:
TRANSCRIPT
Compositional Shifts in Compositional Shifts in Undisturbed Neotropical Undisturbed Neotropical
Forests: Effects of Forests: Effects of Climate Change?Climate Change?
William F. LauranceWilliam F. Laurance1,21,2 & Richard Condit & Richard Condit11
11Smithsonian Tropical Research Institute, PanamaSmithsonian Tropical Research Institute, Panama22Biological Dynamics of Forest Fragments Project, Biological Dynamics of Forest Fragments Project,
Manaus, Brazil Manaus, Brazil
Atmospheric COAtmospheric CO22
• Pre-industrial level was Pre-industrial level was 280 ppm280 ppm
• Current level (378 Current level (378 ppm) is highest in last ppm) is highest in last 20 million years20 million years
• In experiments, In experiments, elevated COelevated CO22 increases increases photosynthesis, growth, photosynthesis, growth, and water-use and water-use efficiency for most efficiency for most plants (for tropical plants (for tropical trees, only seedlings trees, only seedlings assessed)assessed) 310
320
330
340
350
360
370
380
1960 1970 1980 1990 2000
CO
2 c
once
ntra
tion
(ppm
)
Year
Data from Mauna Loa, Hawaii
Evidence for Evidence for pervasive pervasive
changes in changes in Amazonian tree Amazonian tree
communitiescommunities
W. F. Laurance W. F. Laurance et al.et al. (2004) Pervasive (2004) Pervasive alteration of tree communities in undisturbed alteration of tree communities in undisturbed Amazonian forests. Amazonian forests. NatureNature 428428:171-175:171-175
18 1-ha plots in forest interiors18 1-ha plots in forest interiors Monitored 11-19 yearsMonitored 11-19 years 115 most abundant genera115 most abundant genera
Study Design:Study Design:
Changes in Central AmazoniaChanges in Central Amazonia1)1) Concerted shifts in species Concerted shifts in species
composition (14 times more composition (14 times more than expected by chance), than expected by chance), with fast-growing canopy with fast-growing canopy and emergent trees evidently and emergent trees evidently gaining a competitive gaining a competitive advantage over smaller, advantage over smaller, slower-growing treesslower-growing trees
2)2) Accelerating forest dynamicsAccelerating forest dynamics
3)3) Accelerating growth for most Accelerating growth for most generagenera
Barro Barro Colorado Colorado Island Island
-1500 ha in area-1500 ha in area-isolated in 1914-isolated in 1914
50-hectare 50-hectare plot plot
BCI 50-ha PlotBCI 50-ha Plot Established in 1982, recensused in 1985, 1990, 1995, 2000Established in 1982, recensused in 1985, 1990, 1995, 2000 Subdivided into 50 1-ha plotsSubdivided into 50 1-ha plots Included only species present in Included only species present in >>10 1-ha plots and 10 1-ha plots and >>10 cm dbh 10 cm dbh
(142 species)(142 species) Bootstrapping used (at 1% alpha level) to assess changes in density Bootstrapping used (at 1% alpha level) to assess changes in density
and basal area for each species between 1985 - 2000and basal area for each species between 1985 - 2000
BCI: Changes in Tree Density and Basal AreaBCI: Changes in Tree Density and Basal Area
Tree Density:Tree Density:
-19 increased (13%)-19 increased (13%)
-23 decreased (16%)-23 decreased (16%)
Tree Basal-Area:Tree Basal-Area:
-22 increased (15%)-22 increased (15%)
-20 decreased (14%)-20 decreased (14%)
Overall:Overall:
-Nearly 30 times -Nearly 30 times more significant more significant changes than changes than expected by chanceexpected by chance
-10
-8
-6
-4
-2
0
2
4
6
-10 -5 0 5
WinnersLosersOthers
An
nu
al C
ha
ng
e in
Ba
sal A
rea
(%)
Annual Change in Density (%)
Amazonia: Differences in Growth FormAmazonia: Differences in Growth Form
0
20
40
60
80
100
Winners Losers
X2=10.15, d.f.=1, P=0.001
Canopy or emergentsSubcanopy trees
Pe
rcen
t o
f g
en
era
BCI: No Differences in Growth FormBCI: No Differences in Growth Form
0
20
40
60
80
100
120
Winners Losers
X2=0.20, d.f.=1, P=0.65
Canopy or emergentsSubcanopy trees
Pe
rcen
t o
f g
en
era
spec
ies
Amazonia: Larger Trees are WinningAmazonia: Larger Trees are Winning
10 20 30 40 50-40
-30
-20
-10
0
10
20
30
Rs = 0.315, P = 0.0006
Increasing generaDecreasing generaOther genera
Mean trunk diameter (cm)
Ch
an
ge
in d
en
sit
y (%
)
I
I
BCI: No Effect of Tree SizeBCI: No Effect of Tree Size
100 1000-10
-8
-6
-4
-2
0
2
4
Rs= 0.003, P=0.99
WinnersNo changeLosers
Mean tree diameter (mm)
Den
sit
y c
ha
ng
e (%
/ye
ar)
Amazonia: Winners Grow FasterAmazonia: Winners Grow Faster
0
2
4
6
8
10
<1 1-2 2-3 3-4 4-5
t=2.28, d.f.=24, P=0.032
LosersWinners
Nu
mb
er o
f g
ene
ra
Growth rate (mm yr-1)
BCI: No Difference in Growth RateBCI: No Difference in Growth Rate
0
2
4
6
8
10
<1 1-2 2-3 3-4 >4
t= -1.38, d.f.=54P=0.18
LosersWinners
Nu
mb
er o
f g
ene
ra
Growth rate (mm yr-1)
spec
ies
Amazonia: Accelerating Forest DynamicsAmazonia: Accelerating Forest Dynamics
0
0.5
1
1.5
2
1984-1991 1992-1999
MortalityRecruitment
An
nu
al
rate
(%
)
Interval
BCI: Decelerating Forest DynamicsBCI: Decelerating Forest Dynamics
0
0.5
1
1.5
2
2.5
3
1982-1985 1985-1990 1990-1995 1995-2000
MortalityRecruitment
An
nu
al r
ate
(%)
Interval
Mortality:Mortality:
-1982-85 is higher -1982-85 is higher than the other than the other intervalsintervals
-1995-2000 is -1995-2000 is higher than 1990-95higher than 1990-95
Recruitment:Recruitment:
-1982-85 and -1982-85 and 1985-90 are higher 1985-90 are higher than both 1990-95 than both 1990-95 and 1995-2000and 1995-2000
-1990-95 is higher -1990-95 is higher than 1995-2000than 1995-2000
Amazonia: Accelerating Growth RatesAmazonia: Accelerating Growth Rates
Growth accelerated Growth accelerated more for winners more for winners than losersthan losers– Winners: 57% Winners: 57% – Losers: 22% Losers: 22% – Other genera: 40%Other genera: 40%
0.1
1
0.1 1
t=9.74, P<0.00001Paired t-test
WinnersLosersOthersG
row
th r
ate
(m
m y
r-1):
In
terv
al 2
Growth rate (mm yr-1): Interval 1
BCI: Decelerating Growth RatesBCI: Decelerating Growth Rates
0
1
2
3
4
5
82-85 85-90 90-95 95-00
An
nu
al
Rate
(m
m)
1
10
1 10
t=4.71, P<0.0001Paired t-test
Gro
wth
Rat
e 1
985-
90
(m
m/y
r)
Growth Rate 1982-85 (mm/yr)
-Growth was higher -Growth was higher in 1982-85 than in all in 1982-85 than in all other intervals other intervals ((PP<<0.0001)0.0001)
-Growth was also -Growth was also higher in 1985-90 higher in 1985-90 than in the final two than in the final two intervals (Pintervals (P<<0.0003)0.0003)
What is Driving the Tree-What is Driving the Tree-Community Changes on BCI?Community Changes on BCI?
1)1) BCI is a forest fragmentBCI is a forest fragment
2)2) Parts of BCI are Parts of BCI are recovering from recovering from past disturbancespast disturbances
– 70-150 year-old 70-150 year-old regrowth near the regrowth near the plot: previous source plot: previous source of successional-plant of successional-plant propagulespropagules
– Successional species Successional species are now declining on are now declining on the plotthe plot
3)3) BCI has experienced a long-term drying trend and BCI has experienced a long-term drying trend and recent severe droughtsrecent severe droughts
1000
2000
3000
4000
1930 1940 1950 1960 1970 1980 1990 2000
An
nu
al ra
infa
ll (
mm
)
Year
Population Trends vs. Drought TolerancePopulation Trends vs. Drought Tolerance
-10
-5
0
5
0.1 1 10
Rs= -0.164
P=0.051
An
nu
al c
ha
ng
e (%
)
Moisture-demand index
ConclusionsConclusionsTree-community changes in central Amazonia Tree-community changes in central Amazonia
are consistent with elevated productivity, are consistent with elevated productivity, possibly from rising COpossibly from rising CO22 levels levels
Changes are BCI seem to be driven by recent Changes are BCI seem to be driven by recent droughts and possibly nonequilibrium droughts and possibly nonequilibrium conditions on the plotconditions on the plot
The drivers of change may differ among The drivers of change may differ among different forests. Thus, there is a dire need for different forests. Thus, there is a dire need for more long-term studies of tree-community more long-term studies of tree-community dynamics that explicitly test global-change dynamics that explicitly test global-change hypotheseshypotheses
Thank Thank You!You!
top related