Land use changes in Finland:
impacts of forest management
changes to carbon balance
Eero Nikinmaa & Timo Vesala,
University of Helsinki
Impact of land use change on
global carbon cycle
Source: IPCC/ WGI 1995
Contribution of land use change vs.
emissions
IPCC 2007
Historical development
Why?
• Sink = Change in the carbon pool
• Carbon pool = A x D
– A = surface area of the vegetation
– D = carbon density of the vegetation
• Land use changes influence the carbon
sequestration by:
– changing the surface areas of vegetation types
– changing the carbon density of the given vegetation
typ
Land use in tropical region
• Trends
– Degradation of forests (decrease in Dc)
• timber production, shifting cultivation
– Deforestation (decrease in A)
• forest to grass lands, permanent fields
– Relative importance for the carbon loss (case of Mexico):
• deforestation 1/3, degradation 2/3
• Particular case of tropical peatlands (Jauhiainen 2008)
– Tropical peatlands: 13% of the global mire area, one third of the
carbon of all mires
– Indonesia’s peatlands drained for agriculture and plantations
release about 2 Pg of CO2 every year (8% of global fossil fuel
emissions)
– Indonesian peat fires in 1997-1998 freed 3 - 9.4 Pg CO2 into the
atmosphere. Equals 15 - 40% of the global fossil fuel emissions
in that year (25 Pg).
Different story in the boreal
region
• The carbon balance of
boreal forests
– 90´s
• 0.77-1.1 Gt C a-1
– 80´s
• 0.36 (Sedjo 1992)
• 0.26-0.72 (Dixon et al.
1994)
– North-America ~ 30%
– Europe ~12%
– Former Soviet Union ~
51%
Liski, J., Korotkov, A.V., Prins, C.F.L., Karjalainen, T., Victor, D.G. & Kauppi,
P.E. 2003. Increased carbon sink in temperate and boreal forests. Climatic
Change 61 (1-2): 89-99.
Land use changes in Finland
Current land use in Finland
METLA: Forests in brief
Afforestation
Agricultural land use change
Spatial distribution of afforested
fields 1990-1998
Annually afforested agricultural fields
Tilli & Toivonen 2000
Impact of afforestation
• Total turnover of agricultural land into
forest only about 200 000 ha´s during the
last 40 years
• Comparable number to annually clearfelled area
• The estimated carbon sequestration of this
land use change has been on the average
about 150 GgC/a
Changed forest management
Land use change in forest land
•
Change in silvicultural
practises
– after WWII aim to increase
forest stand stocking and
growth
– 1950's move from selective
cuttings toward regeneration
cuttings started
– 1960's introduction of artificial
regeneration
• soil scarification, sowing,
planting
• fertilising
– regeneration of "low
production" sites
• old and sparse stands
•
Coincided with increasing CO2
levels, increased N-deposition
(in southern part of the
country)
Land use change in forest land
Large scale
draining
of mires
Metla: Forests in Brief
Result
AxD
In terms of carbon balance
CO2
NEE -250-270 gC/m2
P=GPP=1010-1050 gC/m2
Ra=350 gC/m2
NPP = 660 gC/m2
Rh=400 gC/m2
L = 400 gC/m2
Measured carbon accumulation into Hyytiälä
pine stand
g m-2 = 10 kg ha-1
Development over age
GPP
Ra
Growth
Increment
Standing
stock
Litterfall
Organic matter content after cuttings
Rh and Soil
decomposition rate
• Soil decomposition
lags behind the litter
production
• The time lag depend
on the litter quality
• Soil carbon increase
depend on the litter
production rate and
decomposition rate
Rate of change of organic
matter after cutting
Litter weight loss of 5-20 cm (black
dots) and 20-60 cm (open dots) thick
wood in forest soil
Liski et al. 2003
•
After disturbance stand is a
Impact of age
carbon source (GPP
decreases, Rh increases,
500
•
Clear cut, 2000
40 v, 2000
40 v, 2001
75 v, 2001
Young stands accumulate
carbon (GPP>TER tai
•
400
300
200
100
NPP>Rh)
0
Steady state when Rh = NPP,
-100
-200
current evidence suggests that
-300
accumulations continues until
-400
major disturbance
0
50
100 150 200 250 300 350
date
-2
)
Cumulative NEE (g C m
GPP<< TER)
Impact of changed forest
management
• High stocking
– high GPP
• Young stands
– high NPP, low Rh
– high NEP, C-seq
– increasing litter prod
• Large negative NEE
• Increasing vegetation
carbon store
• Increasing soil carbon
store
Development of carbon sink of Finnish
forests and national carbon emission
• Growing stock has varied
between source and sink but
on average has been a sink
of 3000 GgC a-1 (0.003
GtCa-1), but larger during the
last 30 years
• Soil has been a sink of ~ 700
GgC a-1
• Carbon store in trees ~ 700
Tg C and forest soil ~ 1000
Tg C
Lähde: Liski ja Lehtonen 2003
(päästöt: Monni ym. 2003)
Flux vs Store?
• Forests can be grown to
maximise the carbon
store
– maximising forest area in
near steady state
Natural mortality
remains as litter at
the stand
• Or to maximise the intake
– biomass harvested and
used as stores or replacing
e.g. fossil fuels
• Including the timber value
for product processing
optimal management
scenarios can be derived
Thinning wood,
can be used for
wished purpose
Drainage of peatlands
Pristine
CO2
CH4
CH4
Peatland carbon cycle
CO2
moss layer
oxic peat layer
CH4
DOC
CH4
water table
anoxic peat layer
Kari Minkkinen
Recent
drainage
CO2
CH4
Peatland carbon cycle
CO2
moss layer
oxic peat layer
water table
CH4
DOC
CH4
anoxic peat layer
Kari Minkkinen
Long-term
drainage
CO2
Peatland carbon cycle
CH4
CO2
moss layer
oxic peat layer
water table
CH4
DOC
CH4
anoxic peat layer
Kari Minkkinen
Overall outcome
Carbon balance of different
ecosystems in Finland
Ecosystem
Trees
C store
C balance of
C02
C balance of
methane
Tg C
Tg C
Tg C
700
-5
Soil
1000
-2
Natural
2300
-0.8
0.4
Drained
3300
-2.6
0.07
700
?
Forest
Mires
Lakes
Sum
-0.01 Gt C a-1