Temperature sensitivity of organic matter mineralization as affected by soil edaphic properties and substrate quality

Abstract

Warming in ecosystems simultaneously changes soil temperatures and inputs of organic matter into soils. Soil chemical properties and exogenous substrate inputs both have significant effects on the temperature sensitivity (Q10) of mineralization. In this study, three soil types (Cambisol, Chernozem and Luvisol) were collected from natural forests at three latitudes in temperate China, whereas the vegetation types are mixed broadleaf-conifer, broadleaf and conifer respectively. The soils differed in soil organic carbon (SOC) contents in the order Chernozem (8.5%), Luvisol (6%), Cambisol (3.6%). The soils were incubated for 40 days at three temperatures (5, 15, and 25 °C). Glucose and maize leaf powder were added as exogenous substrates. To add the same amounts of soluble carbon glucose and maize leaf powder were added at the rate of 2 and 4 mg C g−1 soil, respectively. Independent of substrate addition, the Chernozem had the highest cumulative CO2 efflux under all temperature treatments. Maize addition accelerated cumulative CO2 efflux more than glucose in most treatments. The Q10 value was higher (P < 0.05) in the Chernozem (1.29 ∼ 1.49) than the Cambisol (1.17 ∼ 1.28) and the Luvisol (1.10 ∼ 1.29), both in the treatments and the control. Soil Q10 was positively correlated (P < 0.001) with DOC and mineral N content, but negatively correlated (P < 0.001) with the MBC/MBN ratio. However, the effect of exogenous substrate addition on Q10 varied between the different soil types. Addition of both substrates reduced Q10 by 8.7 ∼ 13.4% in the Chernozem and by 10 ∼ 14.0% in the Luvisol, whereas maize input increased (P < 0.05) Q10 by 7.6% in the Cambisol. These results suggested that DOC, mineral N and MBC/MBN ratio significantly influenced Q10, whereas the effects of exogenous substrates on soil respiration and Q10 were highly dependent on SOC content and substrate type.