Estimate of temperature effect on the decomposition rate of peat-forming plants in a long-term laboratory experiment

Abstract

The aim of the study. To quantify the effect of the temperature on the decay rate of the modern peat-forming plants of oligotrophic bogs in the southern taiga subzone of Western Siberia in a long-term laboratory experiment.

The study location and time. Samples of the prevalent peat-forming plants (Chamaedaphne calyculata Moench., Eriophorum vaginatum L. and Sphagnum fuscum Klinggr.) were collected on the oligotrophic bog "Bakcharskoye" (Bakcharsky district, Tomsk region, 56°26' N, 84°50' E) in September 2017. To assess the dynamics of the decomposition rate of plant substrates, laboratory experiment was conducted from November 2017 to April 2018.

Methodology. The rate of decomposition (DecR, µg C / g of substrate / hour) of plant substrates of the main peat-forming plants was estimated in the 6-month laboratory experiment by the control of the СО₂ emission rate at 2, 12 and 22 °C. Humidity of plant samples corresponded to 90% of their water-holding capacity. Measurements of DecR were taken 3-5 times per week during the 1-st month of the experiment and 1 times per week for the next 5 months. The effect of temperature on the DecR value was estimated using the temperature coefficient Q₁₀.

Main results. The highest СО₂ emission rate from all plant samples was recorded at 22 °C in the first 2-3 weeks of the experiment, whereas the maximum values ​​of the СО₂ emission at 2 °C rate were observed only 1-2 weeks after the start of incubation of samples. C. calyculata demonstrated the most significant C(CO₂) losses for the 6 months of the experiment at 22 °C  whereas E. vaginatum - at 12 ° C (21% and 23%of initial C content, respectively). The maximum values of the temperature coefficient Q₁₀ were found for E. vaginatum in the temperature range of 2–12 °C, and for C. сalyculata - in the range of 12–22 °C.

Conclusion. Temperature and type of plant material had a pronounced effect on the dynamics of DecR of prevalent peat-forming plants during the incubation experiment. Excepting E. vaginatum, all plant samples at a moisture of 90% of their water holding capacity were characterized by the highest total losses of С (СО₂) during the whole experiment at a temperature of 22 °С.  Sphagnum fuscum showed the highest resistance to decomposition. The temperature coefficient Q₁₀ also depended on the type of plant sample and the temperature range for which the measurement was performed.