Improved methodology to quantify the temperature sensitivity of the soil heterotrophic respiration in croplands
Citation
Delogu, E., Le Dantec, V., Mordelet, P., Ceschia, E., Aubinet, M., Buysse, P., Pattey, E. (2017). Improved methodology to quantify the temperature sensitivity of the soil heterotrophic respiration in croplands. Geoderma, [online] 296 18-29. http://dx.doi.org/10.1016/j.geoderma.2017.02.017
Plain language summary
Soil microbes usually release carbon dioxide in the atmosphere during decomposition of soil organic matter. Because soil respiration measurements include both microbial and crop root respiration, being able to estimate the soil microbial respiration alone is essential to determining an accurate terrestrial carbon budget. Soil microbial respiration from cultivated agricultural fields is usually modeled using temperature dependence equations, which varies according to soil properties and climate. The temperature sensitivity is expressed as a function of the base rate of microbial respiration (at 0oC) and the respiration change rate for a 10°C temperature increment. The team of scientists from France, Belgium and Canada developed a methodology to better quantify these two parameters, and verified its performance using seven sets of one-year soil respiration datasets collected in wheat fields in three mid-latitude European sites and one North American site under contrasting climate conditions. Soil respiration chambers and eddy flux towers were used to acquire the soil respiration measurements. The research found that coherent results among the sites were obtained for a common respiration change rate for a 10°C temperature increment value of 2.2. This value provided model results that were similar to the base rates of microbial respiration for other sites over time and is consistent with other reported works. It reflected the strong relationship between the base rate of microbial respiration and the slow decomposing carbon in the top 30-cm soil layer. The model is a useful tool to predict daily soil microbial respiration over multiple sites.
Abstract
Soil heterotrophic respiration (RH) is usually modeled using simple temperature dependence equations where the temperature sensitivity of RH could vary for different soils and climate conditions. The temperature sensitivity is expressed as a function of the base rate of heterotrophic respiration (RH − 0) and the respiration change rate over a 10 °C temperature shift (Q10). A methodology was developed to better quantify these two parameters, and was validated using seven contrasting year-site soil respiration datasets collected in wheat fields. The data were acquired using soil respiration chambers and eddy flux towers in three mid-latitude European sites and one North American site. The first step consisted in parameterizing and initializing a semi-mechanistic process-based model then validating the prediction performance using 2/3 of the datasets. The coefficient of determinations between the predictions and the observations of daily soil respiration (Rs) was 0.71 and was 0.73 for its heterotrophic component (RH). The second step consisted in using the daily semi-mechanistic model predictions of RH for each growing season and site to calibrate a simple empirical model describing RH response to soil temperature and water content. It was shown with the contrasting years-sites that coherent results were only obtained when a common average Q10 value was determined prior to fit the base rate of heterotrophic respiration coefficient. Using a common Q10 value of 2.2 provided more stable RH − 0 for each site over time. It reflected the strong relationship between the RH − 0 and the slow decomposing C in the first 30-cm soil layer. The simple empirical model, which was validated using 1/3 of the data, explained between 42% and 92% of the variability of RH over the different sites.