Coupled effect of temperature and mineral additions facilitates decay of aspen bark

Mineral N and P additions decreased the C:N and increased the Lignin : Cellulose ratios during the long-term incubation of aspen bark and caused a considerable increase in the DecR, k values, TotL-C values, and consequently a decrease of the turnover time. The maximal values of TotL-C were attributed to the SBS-NP treatment at 22 °С and comprised 72% of the initial C content in bark. The turnover time of soil-bark substrates varied from 2 to 7.3 years depending on the treatment and temperature. The increase of the incubation temperature from 2 to 12 °C and from 12 to 22 °C caused a similar effect on the DecR over 12 months of the experiment, and the Q10 in different treatments varied negligibly: from 1.21 to 1.37. The temperature effect was most significant only during the first 1-2 months of experiment, explaining ca. 83% of the mean DecR variance whereas the 'Treatment' factor was attributed for 76-83% of the mean DecR variance in later stages (3-12 months) of decay of aspen bark. A close relationship between the Lig:Cel ratio and DecR was observed during 1-2 months of incubation. We conclude that the effect of mineral additions on the decay rate of aspen bark is more important than the effect of temperature. The coupled effect of N and P additions was more pronounced than the effect of N addition alone.