To determine how the change of hydrothermic regime influences on the rate of decomposition of the organic matter of above- and underground plant residues and of the forest soil humus the method of field experiment was used. Observation were realized in the 80-year pine forests (54oN,92oE): in the sedge-bracken pine forest on the dark-grey forest soil and in the grass-cowberry pine forest on soddy-pine soil. Two soil substratums were used for experiment: loam - it means 10-cm layer of humus accumulative horizon of dark-grey soil, containing 6,59% carbon of humus and 3,59% carbon of mortmass, and loamy sand one - it means 4-cm layer humus horizon of soddy-pine soil, containing 1,90% carbon of humus and 6,10% carbon of mortmass. The experiment lasted for 11 years. Under current climatic conditions the 80-year pine forests where the experiment was carried out play the role of sink for carbon. The increase of the average daily air temperature in July by 2.4oC, of July temperature from 8 to 20 o'clock by 3.1 - 3.4 and of August temperature by 1.2 - 1.5 degrees caused the intensive humus mineralization in the loam substratum and the loss of 48 - 51% of its primary supply. Humus mineralization was followed by decrease of saturation of <0,001mm fraction of the loam by carbon. Decomposition rate of plant residues changed moderately. As a result, the overall mineralization of organic matter of plant residues and soil (the layer 0-10sm) will make 20826 kgCha-1 and ecosystem of the sedge-bracken pine forest on high humus dark-grey soils transforms into carbon source.
Dr. Estella F. Vedrova Institute of Forestry Russian Academy of Sciences Siberian Branch Krasnoyarsk, 660036, Akademgorodok RUSSIA Phone: (7) (391-2) 433686 Fax: (7) (391-2) 433686 E-mail: dndr@ifor.krasnoyarsk.su