Decomposition Rate of Peat-Forming Plants in Oligotrophic Bogs of the Southern Taiga Subzone of Western Siberia: Assessment of the Effect of Water Table Level and Peat Deposit Temperature

The decomposition rate of four species of peat-forming plants typical of bog phytocenoses in the southern taiga subzone of Western Siberia—Sphagnum fuscum, Chamaedaphne calyculata, Eriophorum vaginatum, and Sphagnum angustifolium—was determined in the 3-yr field experiment. The research was performed by the method of partially isolated samples on the Timiryazevskoe and Bakcharskoe bogs, differing in their hydrological regime and temperature condition. Regardless of the chemical composition of the peat-forming plants, their decomposition was characterized by the most significant mass loss over the first year of studies. By the end of the third year, the destruction of plant residues was slowed down, and the decomposition constant value for all the studied plant species decreased by 1.2–2.8 times. The decomposition of peat-forming plants was the slowest under wetter conditions of the Bakcharskoe bog, where the mass losses of all the species studied, except for Eriophorum vaginatum, were 1.2–1.6 times lower than on the Timiryazevskoe bog. Over the three years of the experiment, the total mass loss and the decomposition constant value significantly differed for S. fuscum and Chamaedaphne calyculata, as well as for two sphagnum species (S. fuscum and S. angustifolium). Positive correlations between the mass loss of peat-forming plants (except for S. angustifolium) and the sums of temperatures of the peat deposit, exceeding 0, 5, and 10°C, were revealed. The lowering of the water table level resulted in a significant increase in the intensity of the decomposition processes for all the studied plant species, except for Eriophorum vaginatum.