Decomposition rate of peat-forming plants at the initial stages of destruction in peat deposits of the oligotrophic bogs “Bakcharskoe” and “Timiryasevskoe”

Abstract

The research presents quantitative estimates of the decomposition rate of plant residues at the initial stages of the decay of four plant species (Eriophorum vaginatum, Carex rostrata, Sphagnum fuscum, Sphagnum angustifolium) in peat deposits of the oligotrophic bogs in the southern taiga subzone of Western Siberia. We also studied the change in the content of total carbon, nitrogen and ash elements in plant residues and the activity of microflora at the initial stages of decomposition. The studies were conducted in the bogs characterized by various hydrothermal conditions. At the initial stage of the decay of peat-forming plants the maximum losses of mass occur in the first month of the experiment and reach 36-52% of the total loss of organic matter during the growing season. Sphagnum fuscum is the most resistant to decomposition. The most intense decomposition of Sphagnum fuscum at the initial stages of decomposition is characteristic for warmer and less humid conditions of the Timiryazevskoe bog. It was revealed that mass losses of organic matter correlate well with total carbon losses. The most intensive decreasing of the total carbon content as well as mass loss of organic matter are observed after the first month of the experiment. The maximal decline of carbon in plant residues was received for Eriophorum vaginatum. During the decomposition of plant residues, the nitrogen content was decreasing, and the most intense nitrogen losses were characteristic for Sphagnum mosses. Nitrogen loss in peat-forming plants during the first month of decomposition varies depending on the locality conditions, but it becomes equal during the later decomposition stages. At the first stages of decomposition of plant residues, both the accumulation and the loss of ash elements were observed in the samples. Both the Bakcharskoe and Timiryazevskoe bogs were characterized by the accumulation of ash elements in plant samples of Eriophorum vaginatum. Dynamics of mass loss and removal of elements are directly related to the activity of microorganisms. The maximum number of microorganisms was found in July and September. Peat and plant samples located in the peat deposit of the Timiryazevskoe bog are more saturated with microorganisms of the nitrogen cycle, and samples from the Bakcharskoe bog are richer in carbon cycle microorganisms. Microorganisms of the lignocellulosic complex were less active as compared with other groups of microorganisms. The number of microorganisms assimilating the mineral forms of nitrogen are on average 1.5 times less than the number of microorganisms assimilating the organic forms. The positive correlation between the nitrogen content and the number of fungi was found. In addition, correlation between the numbers of denitrifiers and oligotrophs was found. It is explained by trophic relationshipsbetween these groups of microorganisms.