Interdependencies between temperature and moisture sensitivities of CO<sub>2</sub> emissions in European land ecosystems

Abstract

Abstract. Soil respiration is one of the largest terrestrial fluxes of carbon dioxide (CO 2 ) to the atmosphere. Hence, small changes in soil respiration rates could have large effects on atmospheric CO 2 . In order to assess CO 2 emissions from diverse European soils with different land-use types and climate (soil moisture and temperature), we conducted a laboratory incubation experiment.Emission measurements of CO 2 under controlled conditions were conducted using soil monoliths of nine sites from a European flux network (ÉCLAIRE). The sites are located all over Europe -from the United Kingdom in the west to Ukraine in the east, and from Italy in the south to Finland in the north -and can be separated according to four land-use types (forests, grasslands, arable lands and one peatland). Intact soil cores were incubated in the laboratory in a two-way factorial design, with temperature (5, 10, 15, 20 and 25 • C) and water-filled pore space (WFPS; 5, 20, 40, 60 and 80 %) as the independent variables, while CO 2 flux was the response variable. The latter was measured with an automated laboratory incubation measurement system.Land use generally had a substantial influence on carbon dioxide fluxes, with the order of CO 2 emission rates of the different land-use types being grassland > peatland > forest/arable land (P < 0.001). CO 2 efflux responded strongly to varying temperature and moisture content with optimum moisture contents for CO 2 emissions between 40 and 70 % WFPS and a positive relationship between CO 2 emissions and temperature. The relationship between temperature and CO 2 emissions could be well described by a Gaussian model. Q 10 values ranged between 0.86 and 10.85 and were negatively related to temperature for most of the moisture contents and sites investigated. At higher temperatures the effect of water and temperature on Q 10 was very low. In addition, under cold temperatures Q 10 varied with moisture contents, indicating a stronger prospective effect of rain events in cold areas on temperature sensitivity. At both coniferous forest sites we found a strong increase in the temperature sensitivity at a moisture range between 20 and 40 % WFPS.We developed a new approach to calculate moisture sensitivity (MS) of CO 2 efflux. MS was calculated as the slope of a polynomial function of second degree. Moisture sensitivities were highest under dry and wet conditions. In addition we found a positive relationship between MS of CO 2 efflux and temperature for both arable lands.

Soil Greenhouse Gas Fluxes, Environmental Controls, and the Partitioning of N2O Sources in UK Natural and Seminatural Land Use Types

“…Soil temperature explained most of the variability (47%) of soil respiration across land use types, with an additional 13% explained by soil moisture and bulk density, which confirms the findings of several previous studies on the controls of soil CO 2 respiration in terrestrial ecosystems (Carter et al, 2012;Gritsch et al, 2015;Imer et al, 2013;Luo et al, 2012;Schaufler et al, 2010;Skiba et al, 2013). The temperature dependence of soil respiration can be explained by the stimulation of biological activity (plant roots and microbial communities) with increasing temperature, and this was evident within all the investigated land use types as indicated by the MLR analysis (Table 2).…”

“…Global methane emission controls include soil moisture or water table depth, soil carbon content, soil temperature and pH, and vegetation composition (Carter et al, 2012;Levy et al, 2012;Turetsky et al, 2014), but the relative importance of these controls varies depending on the spatial and temporal scales investigated (Dise, 1993;Levy et al, 2012) and also the ecosystem type. Soil temperature and moisture are also postulated as universal controls of respiratory CO 2 production across ecosystems (Gritsch, Zimmermann, & Zechmeister-Boltenstern, 2015).…”

Temperature Response of Respiration Across the Heterogeneous Landscape of the Alaskan Arctic Tundra

“…These fixed Q 10 values are widely used in ecosystem models (Foereid et al, ; Mahecha et al, ; Potter et al, ). Conversely, several studies have suggested that Q 10 is variable, with values ranging from 1 to more than 12 (Gritsch et al, ; Hamdi et al, ) and reaching 4.5 in Arctic tundra ecosystems (Ueyama et al, ). Globally, Q 10 seems to be amplified in Arctic ecosystems in comparison to temperate and tropical regions, perhaps due to an inverse correlation with mean annual temperature across biomes (Bekku et al, ; Zhou et al, ).…”

Effect of sieving and sample storage on soil respiration and its temperature sensitivity (Q10) in mineral soils from Germany

“…After pre-incubation at 4°C for 6 days, soil samples were sequentially set to 5°C, 10°C, 15°C, 20°C, and 25°C by controlling the temperature of the water bath of the Respicond system. Samples were kept at each temperature for 24 h (see also Gritsch et al 2015). The first 12 h after each temperature rise were treated as equilibration time.…”

“…The authors criticized that sample preprocessing like sieving and storage might alter microbial biomass, microbial activity, microbial community composition, and the availability of substrate. However, storage is mostly inevitable for practical reasons (e.g., Gritsch et al 2015;Lefèvre et al 2014;Meyer et al 2017) and sieving (mostly to < 2 mm) is a common practice to remove roots, plant residues, and rock fragments and to ensure homogenization of the soil (e.g., Conant et al 2008;Fierer et al 2006;Wang et al 2016). Only few studies on Q10 were conducted using undisturbed and/or fresh samples (e.g., Miller and Geisseler 2018;Reichstein et al 2005) An alteration of SR and Q10 by sieving and storage might be straightforward if all soils were similarly affected.…”