Transformation of Organic Matter of the Larch Forest Soils in the Northern Taiga of Nizhne-Tungusskoe Plateau, Central Siberia

The evaluation of biospheric role of the boreal forests in the accumulation of carbon is connected with the evaluation of organic matter (OM) pool in soils. The research sites were larch forests, they are situated on Nizhne-Tungusskoe Plateau. Larch forests of feather-moss and lichen types (110 and 380 years old) were formed on 'ochric podbur' soils. Litter stocks are 3.5–4.5 kg m^{− 2} with thickness 10–25 cm. Cryomezomorphic northern taiga soils contains 38–73 t (carbon) ha^{− 1}. Pool of fast mineralized OM has average value 38.1 t (carbon) ha^{− 1}, including 20.5 and 6.4 t (Carbon) ha^{− 1} of labile compounds on surface and in the soil, and 11.2 t (carbon) ha^{− 1} of mobile OM. Microbial mass reaches 1.78–3.47 t (carbon) ha^{− 1}, its proportion is 3.6–4.9% of the total OM carbon. Zoomass of feather-moss larch forest is 0.20–0.61 * 10^{− 2}, in lichen larch forest −0.01–0.07 * 10^{− 2} t (carbon) ha^{− 1}. A pool of resistant to biological decomposition and bonded to mineral soil matrix OM is 17.7 t (carbon) ha^{− 1} and it varies from 18.6 to 29.0 in feather-moss larch forest, and from 6.4 to 17.0 t (carbon) ha^{− 1} in lichen larch forest. Two-years field experiment has been performed to determine transformation rates of various plant litter fractions and to clarify the role of soil biota in these processes. The results showed participation of all biota groups in the decomposition of plant residues caused weight loss of larch-needles and root mortmass. Isolation of organic matter from all-size invertebrate groups leads to some decrease of decomposition activity.