, Volume 36, Issue 3, pp 261-274

Carbon storage in forest soil of Finland. 2. Size and regional pattern

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Abstract

For confidently estimating the amount of carbon stored in boreal forestsoil, better knowledge of smaller regions is needed. In order to estimatethe amount of soil C in forests on mineral soil in Finland, i.e. excludingpeatland forests, and illustrate the regional patterns of the storage,statistical models were first made for the C densities of the organic and0–1 m mineral soil layers. A forest type, which indicated siteproductivity, and the effective temperature sum were used asexplanatory variables of the models. In addition, a constant C densitywas applied for the soil layer below the depth of 1 m on sortedsediments. Using these models the C densities were calculated for atotal of 46673 sites of the National Forest Inventory (NFI). The amountof the soil C was then calculated in two ways: 1) weighting the Cdensities of the NFI sites by the land area represented by these sites and2) interpolating the C densities of the NFI sites for 4 ha blocks to coverthe whole land area of Finland and summing up the blocks on forestedmineral soil. The soil C storage totalled 1109 Tg and 1315 Tg, whencalculated by the areal weighting and the interpolated blocks,respectively. Of that storage, 28% was in the organic layer, 68% inthe 0–1 m mineral soil layer and 4% in the layer below 1 m. The totalsoil C equals more than two times the amount of C in tree biomass and20% of the amount of C in peat in Finland. Soil C maps made usingthe interpolated blocks indicated that the largest soil C reserves arelocated in central parts of southern Finland. The C storage of theorganic layer was assessed to be overestimated at largest by 13% andthat of the 0–1 m mineral soil layer by 29%. The largest error in theorganic layer estimate is associated with the effects of forest harvestingand in the mineral soil estimate with the stone content of the soil.