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Does the temperature sensitivity of decomposition of soil organic matter depend upon water content, soil horizon, or incubation time?
Author(s) -
Reichstein Markus,
Subke JensArne,
Angeli Andrew C.,
Tenhunen John D.
Publication year - 2005
Publication title -
global change biology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 4.146
H-Index - 255
eISSN - 1365-2486
pISSN - 1354-1013
DOI - 10.1111/j.1365-2486.2005.001010.x
Subject(s) - soil respiration , q10 , environmental science , soil science , soil organic matter , rhizosphere , organic matter , water content , bulk soil , soil water , growing season , soil horizon , humus , agronomy , respiration , chemistry , geology , botany , biology , geotechnical engineering , organic chemistry , paleontology , bacteria
Several studies have shown multiple confounding factors influencing soil respiration in the field, which often hampers a correct separation and interpretation of the different environmental effects on respiration. Here, we present a controlled laboratory experiment on undisturbed organic and mineral soil cores separating the effects of temperature, drying–rewetting and decomposition dynamics on soil respiration. Specifically, we address the following questions:1 Is the temperature sensitivity of soil respiration ( Q 10 ) dependent on soil moisture or soil organic matter age (incubation time) and does it differ for organic and mineral soil as suggested by recent field studies. 2 How much do organic and mineral soil layers contribute to total soil respiration? 3 Is there potential to improve soil flux models of soil introducing a multilayer source model for soil respiration?Eight organic soil and eight mineral soil cores were taken from a Norway spruce ( Picea abies ) stand in southern Germany, and incubated for 90 days in a climate chamber with a diurnal temperature regime between 7 and 23°C. Half of the samples were rewetted daily, while the other half were left to dry and rewetted thereafter. Soil respiration was measured with a continuously operating open dynamic soil respiration chamber system. The Q 10 was stable at around 2.7, independent of soil horizon and incubation time, decreasing only slightly when the soil dried. We suggest that recent findings of the Q 10 dependency on several factors are emergent properties at the ecosystem level, that should be analysed further e.g. with regard to rhizosphere effects. Most of the soil CO 2 efflux was released from the organic samples. Initially, it averaged 4.0 μmol m −2 s −1 and declined to 1.8 μmol m −2 s −1 at the end of the experiment. In terms of the third question, we show that models using only one temperature as predictor of soil respiration fail to explain more than 80% of the diurnal variability, are biased with a hysteresis effect, and slightly underestimate the temperature sensitivity of respiration. In contrast, consistently more than 95% of the diurnal variability is explained by a dual‐source model, with one CO 2 source related to the surface temperature and another CO 2 source related to the central temperature, highlighting the role of soil surface processes for ecosystem carbon balances.