Soil respiration partitioning in afforested temperate peatlands

Abstract

Understanding and quantifying soil respiration and its component fluxes are necessary to model global carbon cycling in a changing climate as small changes in soil CO2 fluxes could have important implications for future climatic conditions. A soil respiration partitioning study was conducted in eight afforested peatland sites in southwest Ireland. Using trenched points, annual soil CO2 emissions, and the contributions of autotrophic and heterotrophic respiration as components of total soil respiration, were estimated. Nonlinear regression models were evaluated to determine the best predictive soil respiration model for each component flux, using soil temperature and water table level as explanatory variables. Temporal variation in soil CO2 efflux was driven by soil temperature at 10 cm depth, with all treatment points also affected by water table level fluctuations. The effect of water table level on soil respiration was best accounted for by incorporating a water level Gaussian function into the soil-temperature-soil-respiration model. Mean autotrophic respiration was 44% of mean total soil respiration, varying between 1100-2049 g CO2 m -2 year -1 . Heterotrophic respiration was divided between peat respiration and litter respiration, which accounted for 35 and 21% of total soil respiration, respectively. While peat respiration varied between 774-1492 g CO2 m -2 year -1 , litter respiration varied between 514-1013 g CO2 m -2 year -1 . Although the extrapolation of these results to other sites should be done with caution, the empirical models developed for the entire dataset in this study are a useful tool to predict and simulate CO2 emissions in afforested peatland in temperate climates.

Soil carbon balance of afforested peatlands in the maritime temperate climatic zone

“…A similar effect of the temperature, rainfall and WTD conditions on soil CO 2 emissions was found by Wilson et al (2016) when developing C EF for peatlands managed for peat extraction in the same climatic zone. In addition, Jovani‐Sancho et al (2018) showed that R H fluxes increased with deeper WTD (greater aerobic conditions in the peat) and that this CO 2 efflux was maximum when WTD was −66 cm. This would support the present results.…”

“…While continuous soil T was averaged for hourly and daily values, WTD gaps between consecutive measurements were filled by linear interpolation. For a full description of the soil respiration chamber and the measurements method see Jovani‐Sancho et al (2018).…”

“…Jovani‐Sancho et al (2018) developed site‐specific R H models by multiple nonlinear regression analysis using mean hourly R H , soil T and WTD values for each site (mean of seven subsites) and sampling event. After comparing several models, the same authors reported that Equations (2) and (3) were the best models to simulate hourly R H effluxes at site S38 and at all the other sites respectively,where y is the measured soil CO 2 efflux rate, T is the measured soil temperature at 10 cm depth, a i and b i are fitted parameters greater than 0 obtained by nonlinear regression analysis, WTD is the measured water table level, c i , d i and WTD i are specific‐fitted parameters determined using least squares nonlinear regression (Table S1).…”

“…The same authors concluded that it was likely that the soda‐lime method used to measure soil respiration may have underestimated soil CO 2 fluxes because this method is not as reliable as infrared‐absorption methods. Reported soil respiration values for afforested peatlands in oceanic climates and forestry‐drained peatlands in boreal regions vary between 4.5 and 11.1 t C ha −1 year −1 (Jovani‐Sancho et al, 2018; Mäkiranta et al, 2008; Minkkinen et al, 2018; Ojanen et al, 2010; Yamulki et al, 2013). Soil R H is commonly measured in partitioning studies of soil respiration using trenching techniques and portable soil respiration chambers (Byrne & Kiely, 2006; Ferréa et al, 2012; Jovani‐Sancho et al, 2018; Mäkiranta et al, 2008; Saiz et al, 2006).…”

“…Reported soil respiration values for afforested peatlands in oceanic climates and forestry‐drained peatlands in boreal regions vary between 4.5 and 11.1 t C ha −1 year −1 (Jovani‐Sancho et al, 2018; Mäkiranta et al, 2008; Minkkinen et al, 2018; Ojanen et al, 2010; Yamulki et al, 2013). Soil R H is commonly measured in partitioning studies of soil respiration using trenching techniques and portable soil respiration chambers (Byrne & Kiely, 2006; Ferréa et al, 2012; Jovani‐Sancho et al, 2018; Mäkiranta et al, 2008; Saiz et al, 2006). Although more accurate methods with less soil disturbance effects exist to separate R H from total soil respiration, such as C isotope techniques, these methods are expensive and difficult to implement in the field or over large areas (Kuzyakov, 2006).…”