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EXPERIMENTAL ASSESSMENT OF GREENHOUSE GASSES EMISSION (CO2, CH4) FROM DECOMPOSED COARSE WOODY DEBRIS IN NORTHERN TAIGA FORESTS OF CENTRAL SIBERIA

Dr. Liudmila Mukhortova, Svetlana Evgrafova, Dr. Maria Meteleva, Dr. Leonid Krivobokov

Abstract

The aim of this study was experimental assessing the emission of greenhouse gasses (CO2, CH4) from decomposed coarse woody debris in northern boreal forests of Siberia, where the main forest-forming species is larch (Larix gmelinii (Rupr.) Rupr.). Logs samples were collected in northern boreal larch forests of Central Evenkia (64пїЅN, 100пїЅE) at different stages of decomposition and placed in gas-tight boxes. Gas samples were measured in dynamics: at the beginning of the experiment and after 3 hour, 24 hours, after 3 and 6 days of incubation using Picarro G2201-i analyzer. Totally 12 samples were measured. Samples were divided into the three decay classes, based on visual and physical properties. The main basis for division is wood density and presence of bark and branches: decomposition class I - wood has not lost its solidity, stems have bark and branches; decomposition class II - wood has lost some of its solidity, bark easily flakes from wood, but bark and branches are presented on the stems; decomposition class III - wood has almost fully lost its initial solidity, some bark and large branches remain on the stems. It was found that carbon dioxide concentration increased gradually during incubation for logs at all decomposition stages. Coarse woody debris at early stages of decomposition produced 3.3-11.4 ?g CO2 cm-3 h-1 for the decomposition class I and 1.9-6.2 ?g CO2 cm-3 h-1 for the decomposition class II. Flux of carbon dioxide from coarse woody debris at the advanced stage of decomposition (decomposition class III) was significantly higher and comprised 0.9-12.4 ?g CO2 cm-3 h-1. Carbon dioxide emission showed close correlation with temperature, class of decomposition and on type of rot (white or brown rot fungi consortia decomposed logs). Concentration of methane showed gradual increase of its concentration during 6 days incubation (from 1.84 to 2.87 and 3.57 ppm for I and II decomposition classes).Rate of methane increasing was dependent on temperature. If at the temperature +5пїЅC increasing of methane concentration was slow and was observed only for decomposition class I and II, at the temperature +25пїЅC logs of all decomposition classes increased concentration of methane from 1.82-1.84 ppm of the initial measurement to 2.06-2.87 ppm after the 6 days of incubation.

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DOI resolver: doi.org/10.5593/sgem2017/32/s14.107

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