Rapid laboratory measurement of the temperature dependence of soil respiration and application to changes in three diverse soils through the year
Determining the temperature dependence of soil respiration is needed to test predictive models such as Arrhenius-like functions and macro-molecular rate theory (MMRT). We tested a method for rapid measurement of respiration using a temperature gradient block, cooled at one end (~2 °C) and heated at the other (~50 °C) that accommodated 44 tubes containing soil incubated at roughly 1 °C increments. Gas samples were taken after 5 h incubation and analysed for CO2. The temperature gradient block allowed rapid assessment of temperature dependence of soil respiration with the precision needed to test models and explore existing theories of how temperature and moisture interact to control biochemical processes. Temperature response curves were well fitted by MMRT and allowed calculation of the temperature at which absolute temperature sensitivity was maximal (Tinf). We measured temperature response of three soils at seven moisture contents and showed that the absolute rate and sensitivity of respiration was partly dependent on adjusted moisture content. This result implied that comparisons between soils need to be made at a common moisture content. We also measured potential changes in the temperature dependence (and sensitivity) of respiration for three different soils collected at one site throughout a year. Tinf ranged from 43 to 51 °C for the three soils. Tinf and temperature sensitivity were not dependent on soil type collected but was partly dependent on time of year of collection. Temporal changes in temperature response suggested that the microbial communities may tune their metabolisms in response to changes in soil temperatures.
KeywordsRespiration Temperature Arrhenius Soil Carbon
Funding from University of Waikato, Landcare Research Core funding (Ministry of Business, Innovation and Employment’s Science and Innovation Group), DairyNZ, Marsden Fund of New Zealand (08-UOW-57), and New Zealand Agricultural Greenhouse Gas Research Centre. Ray Littler provided sage advice on statistical analysis. Jack Pronger, Katharyn Woods and anonymous reviewers provided useful comments on drafts.
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