Discriminating between biotic and abiotic contributions to CO2 efflux from permаfrost soil

Abstract

The rate of carbon dioxide efflux ( CDE) from permafrost cryoarid floodplain sandy loam soil were determined without roots and crop residues contribution. The research site was located at the Experimental Station “Marhinsky” near the city of Yakutsk (62°08´51´´N 129°45´45´E). Fallow systems: conventional (CnF, found in 2003) where weeds were removed by cultivation and conservation (CnsF, found in 2008 ) – where soil has not been treated after ploughing perennial grasses and weeds were removed manually. CDE was measured in one week intervals during growing season using static chamber methodology. Each chamber (n=3) was placed in the middle of a square with 1m side length. CO 2 was absorbed by 1n NaOH and the amount of C-CO 2 was determined by titration. The duration of each exposition amounted to 48 hours. Cumulative production of C-CO 2 was calculated on the basis of daily average speed of CO 2 emissions by the method of linear interpolation. In the CnF from 6 th to 11 th year of the experiment (2008-2013) CDE was about 800-900 kg/ha annually during the vegetation period. In CnsF after the first year of ploughing up CDE amounted 2,500 + 190 (mean + 095 confidence interval), in the next 2-5 years has stabilized at a level of 1,500 + 150 kg C-CO 2 ha -1. In the 6th year (2013), which was characterized by an unusually early warm spring (2 weeks earlier than average) and humid summer (annual norm was exceeded in 1.5 times), CDE on the CnsF reached 2,100 + 150 kg C-CO 2 ha -1. In CnF changes were not detected. Thus, in the present climatic conditions of Central Yakutia lower steady state of CDE from the investigated soil makes up about 800 – 900, the upper level makes up 1300 – 1500 kg C-CO 2 ha -1 . The increase in CO 2 production by soil with increasing warmth and moisture vegetation period (approximately 500 kg C-CO 2 ha -1 ) was negated by the same increase carbon sequestration in plant biomass.