Abstract
The roles of substrate availability and quality in determining temperature sensitivity (Q10) of soil carbon (C) decomposition are still unclear, which limits our ability to predict how soil C storage and cycling would respond to climate change. Here we determined Q10 in surface organic layer and subsurface mineral soil along an elevation gradient in a temperate forest ecosystem. Q10 was calculated by comparing the times required to respire a given amount of soil C at 15 and 25°C in a 350-day incubation. Results indicated that Q10 of the organic layer was 0.22–0.71 (absolute difference) higher than Q10 of the mineral soil. Q10 in both the organic layer (2.5–3.4) and the mineral soil (2.1–2.8) increased with decreasing substrate quality during the incubation. This enhancement of Q10 over incubation time in both layers suggested that Q10 of more labile C was lower than that of more recalcitrant C, consistent with the Arrhenius kinetics. No clear trend of Q10 was found along the elevation gradient. Because the soil organic C pool of the organic layer in temperate forests is large, its higher temperature sensitivity highlights its importance in C cycling under global warming.
Highlights
The roles of substrate availability and quality in determining temperature sensitivity (Q10) of soil carbon (C) decomposition are still unclear, which limits our ability to predict how soil C storage and cycling would respond to climate change
The specific questions we aim to address in this study include: (1) Does Q10 of C decomposition of both the mineral layer and the organic layer support the ‘‘C quality-dependent hypothesis’’? (2) Whether and how does Q10 of the organic layer differ from that of the mineral soil along the elevation gradient?
C:N ratio (p, 0.05) in the organic layer was higher compared to the mineral soil (Fig. 1c)
Summary
The roles of substrate availability and quality in determining temperature sensitivity (Q10) of soil carbon (C) decomposition are still unclear, which limits our ability to predict how soil C storage and cycling would respond to climate change. Q10 in both the organic layer (2.5–3.4) and the mineral soil (2.1–2.8) increased with decreasing substrate quality during the incubation This enhancement of Q10 over incubation time in both layers suggested that Q10 of more labile C was lower than that of more recalcitrant C, consistent with the Arrhenius kinetics. We collected soils from the northern slope of Mountain Changbai in Northeast China[27] (Table 1) to investigate variations of Q10 of decomposition along the elevation gradient Soil samples from both the organic and the mineral layers were incubated for 350 days and Q10 of decomposition was determined by the approach derived from Conant et al.[11] (see Methods).
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