Publication Date:
2008-11-01
Description:
Canada annually reports on all of its annual greenhouse gas emissions to the United Nations Framework Convention on Climate Change (UNFCCC), including estimates of CO2 emissions and removals from cropland management. Soil carbon (C) change in cropland resulting from management is estimated by using C change factors multiplied by the area of cropland subjected to a management change. In this paper we compare soil C change factors in Canadian cropland obtained using a C modelling approach (Century model) to both empirical estimates obtained from the scientific literature, and to default Intergovernmental Panel on Climate Change (IPCC) estimates. Factors were estimated for land management changes from annual to perennial cropping, tillage to no-tillage and from summer fallow to continuous cropping. Empirical data comparing C change between conventional tillage (CT) and no-tillage (NT) were highly variable, but the modelled factors were still within the range derived from the empirical data. Factors for changes from CT to NT varied from 0.06 to 0.16 Mg C ha-1 yr-1 across the country. When considering the change from annual to perennial cropping, the modelled factors ranged from 0.46 to 0.56 Mg C ha-1 yr-1, which is in the range of empirical values, and were slightly greater in the eastern than the western soil regions. For conversion of crop-fallow to continuous cropping, the modelled rate of C storage (0.33 Mg C ha-1 yr-1) was more than double the average rate of 0.15 ± 0.06 Mg C ha-1 yr-1 derived from two independent assessments of the literature. For each of the management changes considered, the modelled factors were generally lower than IPCC estimates, and this is partly attributable to differences in calculation methods and to the fact that C changes likely occur more slowly in the cold climate of Canada. Generally, the results show that the modelling approach used at present to derive C change factors for use in Canada's inventory is adequate. However, soil C change factors for cropland soils in Canada would be greatly improved by a reduction in the high variability usually associated with empirical data, and by improved simulation of the Century model under varying management conditions. Key words: Soil organic carbon, Canada, tillage, perennial cropping, cropping intensity, carbon change factors
Print ISSN:
0008-4271
Electronic ISSN:
1918-1841
Topics:
Geosciences
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Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
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