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| Titel |
The effect of wood ash fertilization on soil respiration and tree stand
growth in boreal peatland forests |
| VerfasserIn |
Maarit Liimatainen, Marja Maljanen, Jyrki Hytönen |
| Konferenz |
EGU General Assembly 2017
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| Medientyp |
Artikel
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| Sprache |
en
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 19 (2017) |
| Datensatznummer |
250147768
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| Publikation (Nr.) |
 EGU/EGU2017-11974.pdf |
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| Zusammenfassung |
| Out of Finland’s original 10 million hectares of peatlands over half has been drained for
forestry. Natural peatlands act as a sink for carbon but when peatland is drained,
increased oxygen concentration in the peat accelerates the aerobic decomposition of
the old organic matter of the peat leading to carbon dioxide (CO2) emissions to
atmosphere.
Increasing use of bioenergy increases also the amount of ash produced as a byproduct in
power plants. Wood ash contains all essential nutrients for trees to grow except nitrogen.
Therefore, wood ash is ideal fertilizer for nitrogen rich peatland forests where lack of
phosphorus or potassium may restrict tree growth. At the moment, wood ash is the only
available PK-fertilizer for peatland forests in Finland and areas of peatland forests fertilized
with ash are increasing annually.
The effects of wood ash on vegetation, soil properties and tree growth are rather well
known although most of the studies have been made using fine ash whereas nowadays mostly
stabilized ash (e.g. granulated) is used. Transporting and spreading of stabilized ash is easier
than that of dusty fine ash. Also, slower leaching rate of nutrients is environmentally
beneficial and prolongs the fertilizer effect. The knowledge on the impact of granulated wood
ash on greenhouse gas emissions is still very limited. The aim of this study was to
examine the effects of granulated wood ash on CO2 emissions from peat and tree stand
growth.
Field measurements were done in two boreal peatland forests in 2011 and 2012. One of
the sites is more nutrient rich with soil carbon to nitrogen ratio (C/N) of 18 whereas the other
site is nutrient poor with C/N ratio of 82. Both sites were fertilized with granulated wood ash
in 2003 (5000 kg ha−1). The effect of fertilization was followed with tree stand
measurements conducted 0, 5 and 10 years after the fertilization. The CO2 emissions of the
decomposing peat (heterotrophic respiration) were measured from study plots where
vegetation and litter were removed to eliminate respiration by vegetation (autotrophic
respiration). Roots were cut by installing aluminum tubes into the depth of 30 cm.
Emissions were measured with chamber method using portable CO2 analyzer. Soil
temperature was measured simultaneously with gas measurements manually from the
depth of 5 cm as well as continuously with data loggers embedded into the peat.
Annual soil respiration was modelled assuming that emissions change as a function of
temperature.
According to preliminary results, fertilization with granulated wood ash increased CO2
emissions of the peat significantly, especially in nutrient poor site. Ash fertilization increased
also strongly the accumulation of carbon into the trees. Nonetheless, in both sites
CO2emissions from decomposing peat where higher than carbon that was stored in biomass.
This was the case especially in the nutrient poor site where trees are growing poorly and due
to low peat nitrogen content the area is not considered suitable for ash fertilization. However,
at the more fertile site both stand C sequestration and soil C efflux increased similarly. |
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