How uncertain are the forest carbon sinks in Finland and what
factors influence the precision of the estimates?
Mikko Peltoniemi1, Suvi Monni2, Taru Palosuo3, Aleksi Lehtonen1, Raisa Mäkipää1 & Ilkka Savolainen2
Introduction
United Nations’ Framework Convention on
Climate Change (UNFCCC) aims at reducing
anthropogenic greenhouse gas emissions and in
the Kyoto Protocol legally binding commitments
were set to reduce emissions. The estimates of
emissions and removals have to be appended
with estimates of uncertainties. Comprehensive
uncertainty analysis and key category analysis
can provide guidance for prioritizing efforts in
further development of the inventory.
The aims of this study were a) to compare the
uncertainties of annual forest carbon sinks with
uncertainties of emissions in other sectors, and
b) to assess what factors affect the uncertainties
of forests sinks.
Fig. 1.The litter
input (L) for the soil
model is derived
from growing stock
(V), area (A), drain
(D), and growth
variation (GI), using
model parameters
like biomass
expansion factors
(BEF) or (BA),
turnover rates (TR),
and carbon density
(C%).
Forest carbon model
CO2
TREES
VEG Ct
· BEFi
· BEFi
· C%
Dt
· BEFi
Lgv
· BA
· C%
(t, A1, A2)
At
· BA
· TRGV
SOIL Ct-1/
At-1
Results and discussion
The forest carbon model combines aggregated
forest inventory data, models of biomass and
its turnover, and a dynamic soil carbon model,
Yasso (Fig. 1). The precision of the sink estimates
and the key factors affecting uncertainties were
analysed with Monte Carlo simulations. In sectoral
comparison, the estimates of soil uncertainties
are prepared for upland mineral soils, only (Fig.
2). Key factors affecting uncertainties of sinks,
average sinks and stock of carbon are analysed
for upland mineral soils, for both vegetation and
soil (Figs. 3 and 4).
The uncertainties of vegetation and soil carbon
sinks were largest among inventory categories
(Fig. 2). The estimates of sinks fluctuated notably
between the years, mostly due to variability in
growth, harvests, and decomposition.
Waste
Agriculture
Industrial processes
Fugitive emissions
Fuel combustion
-20
0
20
Tg CO2-eq
40
60
80
Fig. 2. Comparison of uncertainties between inventory
categories (from Monni et. al, in press)
Area
Stock
Avg. sink
Sink
Natural mortality
Biomass, mean change, gr. veg.
0.0
(T, Drought,
soil model
parameters)
· C%
ACt,
· ∆At,t-1
Due to the large uncertainties in annual sink
estimates of forests in comparison to other
inventory categories, it seems reasonable to
report them as long-term averages.
More information:
TR change, foliage
BEF, foliage
Carbon density
TR, foliage
Growth indexes
Biomass, mean, gr. veg.
TR, fine roots
TR, gr. veg.
Temp. sensit. of decomp.
Drain
Biomass, fine roots
Upland drain−%
Temperature sum
Others total
Soil model params
Area
Soil initial state
Vegetation
Biomass, mean, gr. veg.
SOIL Ct
The quality of annually varying input data was
more important for the precision of vegetation
and soil sink estimates than the quality of
constant model parameters (eg. biomass models
and soil model parameters). Role of soil model
initialization decreased with time elapsed from
initialization.
Soil
Forest biomass
-40
Average sinks of vegetation and soil during the
period were considerably more precise than
annual sinks (data not shown). Uncertainties
of average sinks, annual sinks, and stocks of
carbon were affected by different factors (Figs.
3 and 4).
1990
2003
Forest soil
· C%
GROUND VEG.
Materials and Methods
Other LULUCF categories
Li
Vt
(t, V1, V2,
GI, Dt)
· BEFTOT
· C%
Stock
Avg. sink
Sink
Peltoniemi, M., Palosuo, T., Monni, S.,
Mäkipää, R., 2006. Factors affecting the
uncertainty of sinks and stocks of carbon
in Finnish forests soils and vegetation.
Forest Ecology and Management 232,
75-85.
Monni, S., Peltoniemi, M., Palosuo, T.,
Lehtonen, A., Mäkipää, R., Savolainen,
I. Uncertainty of forest carbon stock
changes - implications to the total
uncertainty of GHG inventory of
Finland. Climatic Change, in press
0.2
0.4
0.6
Approx. share of variance
0.8
Fig 4. Key variables and parameters affecting the variance
of sinks, average sinks and stocks of soil carbon (from
Peltoniemi et al. 2006).
BEF, stand total
BEF change, stand total
· • · · · · · · · · · · · • ·
Contact information: [email protected],
+358 10 255 2506,
Carbon density
Growing stock
Drain
Upland drain−%
Growth indexes
0.0
0.2
0.4
0.6
Approx. share of variance
Fig. 3. Key variables and
parameters affecting
the variance of sinks,
average sinks and
stocks of vegetation
carbon (from Peltoniemi
et al. 2006).
1
Finnish Forest Research Institute, P.O. Box 18,
FI-01301 Vantaa, Finland
VTT Technical Research Center of Finland,
P.O. Box 1000, FI-02044 VTT, Finland
2
European Forest Institute, Torikatu 34,
FI-80100 Joensuu, Finland
3
www.efi.int/projects/uncertainty
Metla/3399/SElo/08.2006