Carbon and nitrogen sequestration during primary succession in granodiorite quarries

Studies assessing the potential of mining areas for carbon sequestration focused mainly on areas after the extraction of energy raw materials, especially coal or oil shale, but little attention was paid to stone quarries and quarries of other non-energy raw materials. We investigated carbon and nitrogen pools (stocks) along a chronosequence in the organic horizon and to a depth of 20 cm of the mineral soil in granodiorite quarries. We compared these pools and sequestration rates with other mining sites. The advantage of this study is that several differently aged quarries in a small area have the same rock chemistry and climate. Thus, the rate of pedogenesis is purely a function of time and vegetation. It is not affected by fossil organic matter or organic matter and nutrients in the topsoil used for reclamation. The vegetation succession tends towards tree cover dominated by Pine (Pinus sylvestris), Birch (Betula pendula), Willow (Salix caprea), Aspen (Populus tremula) and Alder (Alnus glutinosa). Analysis of soils from granodiorite quarries showed a natural accumulation of carbon and nitrogen in the soil to a depth of 20 cm during about 60 years of natural succession. The total soil organic carbon and nitrogen pools to a 20 cm depth average of 2482.4 g C m(-2) and 179.1 g N m(-2), respectively, in the oldest plots >50 years old. These values are for carbon 2.6 and nitrogen 2.4 times lower compared to pools in the same depth on control plots. Carbon and nitrogen stocks and sequestration rates are lower than in compared coal mining sites and spoils. The sequestration rates of the total sampled soil profile decreased with time from 57 g C m(-2) year(-1) and 4 g N m(-2) year(-1) for sites younger than 25 years to 46 g C m(-2) year(-1) and 3 g N m(-2) year(-1) for sites older than 50 years.