Post-pirogenic Transformation of Soils and Soil Carbon Stocks in Sub-Tundra Woodlands of Kolyma Lowland: a Cascading Effect and Feedbacks

Abstract

It is found that the high diversity of the upland ecosystems in sub-tundra woodlands of the Lower Kolyma River is caused by frequent fi res. The type of successions, the power of the active layer, the degree of gleization of the soil profi le, the intensity of cryogenic processes of mass transfer, the size of carbon stocks, the classificatory status of soils depends on the strength and duration of the fi re. Post-pirogenic transformation of vegetation, soils and tree species evolve according to the cascade principle, when every previous change generates and enhances subsequent change, i.e. feedback mechanisms are working actively. In the first years after the fire the expected reduction in carbon stocks of organic horizons (–3.4 kilogram of carbon per square meter) is observed, however, in the later stages the post-pirogenic effect of surplus (relative to initial) accumulation of organic matter at mineral surfaces (+1.7 kilogram of carbon per square meter) occurs. Such consequences of fi res as the lowering-lifting of roof permafrost and the intensification of cryogenic mass transfer in conditions of active organic matter accumulation of upper horizons can lead to post-pirogenic increase of the carbon pool of mineral depth (+2.5 kilogram of carbon per square meter). The time required to recover after a severe fire the initial stocks of soil carbon is 60–200 years.