Changes in temperature sensitivity of forest litter during decomposition along an altitudinal gradient in temperate mountains – A reciprocal litter transplantation study

Abstract

The aim of this study was to assess the effects of the factors controlling the temperature sensitivity of litter decomposition, which is essential for predicting the rate of soil carbon loss in in the context of global climate changes. It based on the translocation of forest litter in a field experiment conducted in the Western Carpathians. Litterbags were used to expose litter originating from different altitudes (i.e., 600, 900, and 1200 m a.s.l.) at the altitude where it was collected and at two other altitudes on five different mountains. Litterbags were collected after 6, 10, and 24 months of exposure. The respiration rate of litter was measured in the laboratory, and Q10 coefficients were evaluated for two temperature ranges: lower (Q10L; 5 °C–15 °C) and higher (Q10H; 15 °C–25 °C). We tested whether litter Q10 values correlated with experimental factors, as well as soil and microbial community properties. After 24 months of exposure, the litter mass decreased to half of its initial mass. The general linear model (GLM) constructed for Q10 (R2adj = 77.3 %; p < 0.0001) indicated, that Q10L values were higher than Q10H values (2.19 ± 0.58 and 1.52 ± 0.31, respectively) and increased strongly with time (1.56 ± 0.36, 1.73 ± 0.45, and 2.36 ± 0.60, consecutively). There was a significant interaction between the temperature range and time, indicating that Q10L increased more over time than Q10H. Other interaction between temperature range and litter origin indicated that Q10L increased with the altitude of the litter origin, whereas Q10H did not change. The proportion of fungi in the microbial biomass correlated positively with Q10. Our results were consistent with the kinetic theory of higher temperature sensitivity for more decomposed organic matter. The conclusion that litter Q10L is more responsive to environmental conditions than Q10H has important implications for estimating soil carbon emissions.