Dominant extracellular enzymes in priming of SOM decomposition depend on temperature

Abstract

Decomposition of soil organic matter (SOM) is operated by microbial extracellular enzymes and is dependent on temperature. It remains unclear how input of labile organics interacts with temperature on SOM decomposition. Soil samples collected from a temperate forest were incubated for 3months to quantify SOM decomposition and its priming induced by input of 14C-labelled glucose at five temperatures (from 3 to 31°C with an interval of 7°C). The activities of eight extracellular enzymes were measured four times during the incubation. Increasing temperature accelerated SOM decomposition with a temperature sensitivity (Q10) value ranging from 1.3 to 4.4. Response of priming to temperature was mediated by the activity and variety of extracellular enzymes temporally: (1) priming increased with increasing temperature at the initial stage; (2) subsequently, priming at lower temperature gradually exceeded those at higher temperature; and (3) finally, priming at high temperature was higher than at low temperatures. At higher temperatures (17–31°C), N-acquiring enzymes (leucine amino peptidase and N-acetyl-β-d-glucosaminidase) dominated at the early stage of priming, but C-acquiring enzymes (β-glucosidase and xylanase) dominated at later stages. Priming exhibited a hysteresis at low temperatures (3–17°C) with C-acquiring enzyme (β-galactosidase) dominating at the initial stage, C-and P-acquiring enzymes (α-glucosidase and phosphomonoesterase) at the middle stage, and C-acquiring enzymes (β-galactosidase and xylanase) at the later stage. Consequently, microbial extracellular enzymes were produced in terms of nutrient availability over time depended on temperature. Such acclimation of microbial extracellular enzymes to temperature and nutrient availability should be considered to predict responses of C cycling to global change.