International workshop on

  
Koli (c) Metla/Erkki Oksanen

Development of Models and Forest Soil Surveys for Monitoring of Soil Carbon

April 5-8, 2006 at Koli, Finland
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Detecting C stock changes in soils of afforested areas in Hungary

Balázs Horváth1 and Zoltán Somogyi2

1 Forest Research Institute of Lower Saxony, Grätzel str. 2, G-37075, Göttingen, Germany;
e-mail: bhorvath@gwdg.de; Tel.: +49 551 69 401 136
2 Joint Research Centre, Ispra, Italy

Large scale afforestations are thought to have considerable potentials that can contribute to international efforts to sequester carbon, and thus mitigate climate change. Hungary is among the countries with large areas to afforest, and declared to increase her forest cover from 19 to 25 % in the next decades. The amount of C that can be fixed in the biomass can easily be predicted, however, little is known about what may happen in soils.

In this study the C-stock changes in the forest floor and mineral soil (0-60 cm) after afforestation of croplands and grasslands were measured at 6 different sites using chronosequences, and an asymptotic function was fitted on data over age. It was found that increases of C in the soil of afforested croplands amounted to 43 Mg ha -1 over 150 years. In average 7 Mg C ha -1 was fixed in the forest floor, the rest in the mineral soil. This is confirmed by a more detailed sampling of ten sites of stands of ages up to 20 years, which showed no carbon loss even in the first years, and an increase of C in litter and in the soil. In contrast, afforestation of grassland does not increase the C stocks in a long term, rather, a net C emission of 10 Mg ha -1 could be measured in the first three decades, which is than offset over the following 100 years.

The C-budget of a large-scale (750,000 ha) afforestation scenario, which was put forward as a policy option, was calculated assuming a proportion of 1/3 grassland and 2/3 arable land. Our results suggest that C-stock change in the soil of the afforested areas is too insignificant to exert a major influence on the C-budget of Hungary, as it would take approx. 300 years to fix the annual gross emission of the greenhouse gases of the country. Furthermore, the soil itself becomes a net C emitter in the first decades, even if only to a small magnitude. These results suggest that, with soils, protecting current C stocks seems much more important than to use soils as potential means of mitigation.

 
   Päivitetty:   02.03.2006 / EKel Metla : Events   Palaute Metlan etusivulle
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