Biomass Dynamics of Biomass Dynamics of Amazonian Forest Amazonian Forest
FragmentsFragments
William F. Laurance William F. Laurance
& Henrique Nascimento& Henrique Nascimento
Smithsonian Tropical Research Institute, PanamaSmithsonian Tropical Research Institute, Panama
Biological Dynamics of Forest Fragments Project, Biological Dynamics of Forest Fragments Project, Manaus, BrazilManaus, Brazil
Deforestation in Brazilian AmazoniaDeforestation in Brazilian Amazonia
Increased Increased significantly significantly during the last during the last decadedecade-1990-1994: 1.31 -1990-1994: 1.31 million ha/yearmillion ha/year
-1995-2002: 1.92 -1995-2002: 1.92 million ha/yearmillion ha/year
0
0.5
1
1.5
2
2.5
3
1990 1991 1992 1993 1994 1995 1996 1997 1998 1999 2000 2001 2002
Def
ores
tatio
n ra
te (X
10
6 h
a yr
-1)
Year
Rapid Forest FragmentationRapid Forest Fragmentation Every kmEvery km22 of of
each landscape each landscape has 1.3-1.8 km has 1.3-1.8 km of forest edgeof forest edge
Nearly 20,000 Nearly 20,000 km of new edge km of new edge created in created in Brazilian Brazilian Amazon Amazon annually*annually*
* W. Chomentowski, D. Skole, * W. Chomentowski, D. Skole, M. Cochrane, Michigan State M. Cochrane, Michigan State UniversityUniversity
Biological Dynamics of Forest Fragments Biological Dynamics of Forest Fragments ProjectProject
Study AreaStudy Area
Edge-related Changes in Edge-related Changes in Forest Dynamics, Structure, Forest Dynamics, Structure, and Compositionand Composition
Elevated Tree MortalityElevated Tree Mortality
0.5
1
1.5
2
2.5
3
3.5
4
4.5
100 1000
Y = 3.64 - 0.75 log XR=0.51, P=0.0002
Mor
talit
y (%
/yea
r)
Distance to edge (m)
Laurance et al. (1998) Ecology
Loss of Large-tree BiomassLoss of Large-tree Biomass
-100
-80
-60
-40
-20
0
20
100 1000
Y = -52.9 + 18.8 log XR=0.44, P=0.001B
iom
ass
chan
ge (M
g/ha
)
Distance to edge (m)
Laurance et al. (1997) Science
Laurance et al. (2000) Nature
GoalsGoals• To assess impacts of fragmentation on To assess impacts of fragmentation on
all components of aboveground all components of aboveground biomassbiomass• Large (Large (>>10 cm dbh) trees10 cm dbh) trees• Understory biomass Understory biomass • NecromassNecromass
• To estimate effects on forest C storage To estimate effects on forest C storage and atmospheric emissionsand atmospheric emissions
Biomass ParametersBiomass Parameters
•Downed coarse debris (Downed coarse debris (>>10 cm)10 cm)
•Downed fine debris (2.5-9.9 cm)Downed fine debris (2.5-9.9 cm)
•SnagsSnags
•Litter (leaves, twigs, fruits, etc.)Litter (leaves, twigs, fruits, etc.)
•Annual production of wood debrisAnnual production of wood debris
•Turnover of wood debrisTurnover of wood debris
Large-tree biomassLarge-tree biomass NecromassNecromass
•Seedlings (<1 cm)Seedlings (<1 cm)
•Saplings (1-4.9 cm)Saplings (1-4.9 cm)
•Small trees (5-10 cm)Small trees (5-10 cm)
•Stemless palmsStemless palms
•Lianas (Lianas (>>1 cm)1 cm)
Understory biomassUnderstory biomass
•Large-tree biomassLarge-tree biomass
•Biomass incrementBiomass increment
•Annual change in biomassAnnual change in biomass
Ordination of 14 Biomass Ordination of 14 Biomass AttributesAttributes
-1.5
-1
-0.5
0
0.5
1
1.5
2
-1.2 -0.8 -0.4 0 0.4 0.8 1.2 1.6
Edge plotsInterior plots
Axi
s 2:
less
deb
ris-
->
Axis 1: more tree mortality, debris, small trees-->
Edge vs. Interior: Significant DifferencesEdge vs. Interior: Significant Differences
0 10 20 30 40 50 60 70 80
Total necromass
Small-tree biomass
FWD stock
CWD turnover
CWD stock
CWD production
Biomass increment
Tree mortality
Increase (%)
Increased Wood DebrisIncreased Wood Debris
0
2
4
6
8
10
12
100 1000
Y = 10.87 - 2.30 log XR=0.60, P<0.0001
CW
D p
rodu
ctio
n (M
g/ha
/yea
r)
Distance to edge (m)
Nascimento & Laurance, in press. Ecological Applications.
Increased LitterIncreased Litter
5
6
7
8
9
10
11
12
13
100 1000
Y = 9.46 - 0.67 log XR=0.28, P<0.05
Bio
mas
s (M
g/h
a)
Distance to edge (m)
Nascimento & Laurance, in press.
Ecological Applications.
Biomass of Small (5-10 cm dbh) TreesBiomass of Small (5-10 cm dbh) Trees
10
12
14
16
18
20
22
100 1000
Y = 18.12 - 1.35 log XR=0.39, P=0.005
Bio
mas
s (M
g/ha
)
Distance to edge (m)
Total Understory BiomassTotal Understory Biomass
20
25
30
35
40
45
100 1000
Y = 34.1 - 1.2 log XR=0.19, N.S.
Bio
mas
s (M
g/ha
)
Distance to edge (m)
Estimating Edge-related Estimating Edge-related Carbon EmissionsCarbon Emissions
Assume no changes in belowground biomassAssume no changes in belowground biomass Net biomass decline = biomass lost from large trees Net biomass decline = biomass lost from large trees
(22.7 Mg/ha) – increases in understory biomass (1.7 (22.7 Mg/ha) – increases in understory biomass (1.7 Mg/ha) and necromass (10.1 Mg/ha) = 10.9 Mg/haMg/ha) and necromass (10.1 Mg/ha) = 10.9 Mg/ha
Half of biomass is carbon, most is respired quicklyHalf of biomass is carbon, most is respired quickly Thus, committed emissions are 4-6 Mg/haThus, committed emissions are 4-6 Mg/ha Because tree mortality is elevated within 300 m of Because tree mortality is elevated within 300 m of
edges, we expect 12-18 Mg C for every 100 m of edges, we expect 12-18 Mg C for every 100 m of forest edge createdforest edge created
Based simply on current rate of edge creation, annual Based simply on current rate of edge creation, annual emissions would be 2.3-3.5 million Mg/yearemissions would be 2.3-3.5 million Mg/year
Fragmentation and FireFragmentation and Fire Increased wood debris & litterIncreased wood debris & litter Recurring canopy damageRecurring canopy damage Higher insolation, wind & Higher insolation, wind &
temperaturestemperatures Nearby ignition sourcesNearby ignition sources
0
5
10
15
0 1000 2000 3000 4000
Surface fires at Tailândia, Brazil
Fir
e f
req
uen
cy
(n
o./c
en
tury
)
Distance to edge (m)
ConclusionsConclusions Fragmentation causes striking Fragmentation causes striking
changes in the distribution of changes in the distribution of aboveground biomassaboveground biomass– Decline of large-tree biomassDecline of large-tree biomass– More wood debris, litter, small More wood debris, litter, small
treestrees
C cycling accelerates sharplyC cycling accelerates sharply Substantial C emissionsSubstantial C emissions Drastic increase in fire Drastic increase in fire
vulnerabilityvulnerability