Long‐term half‐hourly measurement of soil CO₂ concentration and soil respiration in a temperate deciduous forest

Abstract

We conducted a field experiment in a cool‐temperate deciduous forest to investigate the dynamic behavior of soil CO2 and the vertical distribution of soil respiration. Soil CO2 concentration (C) was measured half‐hourly at four depths for 6 months in 2000 with infrared gas analyzers installed below ground. Using C profiles, soil surface CO2 efflux (F0), CO2 production rates of the topsoil (PA), and CO2 flux from the subsoil to topsoil (FCA) were evaluated half‐hourly by applying Fick's first law. Some remarkable short‐term and long‐term variations were found in C, F0, PA, FCA, and the contribution of topsoil respiration to total soil respiration (PA/F0), which include (1) rapid increase in C and decrease in F0 and PA due to rainwater infiltration, (2) diurnal variation in C coupled with that of the atmosphere, (3) diurnal variation in F0 and PA similar to that of topsoil temperature, (4) decrease in C, F0, and PA following soil drying in August, (5) linearly increasing FCA between late May and mid‐September, and (6) decrease in PA/F0 from around 0.9 during summer to 0.3 in November. The variation of PA was mainly controlled by soil temperature at −0.07 m between 7° and 17°C, although PA did not respond well to soil temperature above and below this temperature range. Above 17°C, PA increased linearly with soil moisture, and moisture variation accounted for the PA decrease in August. Neither temperature nor moisture explained the PA behavior below 7°C. Subsoil respiration (FCA) showed an exponential relationship with soil temperature at −1 m.

Influences of snow cover and soil-frost on ground surface flux and soil gas concentration of CO2 in an agricultural land in northern Japan

“…Such temporary increases were often observed after a rain event. The temporary increase in CO2 concentration was also observed at other study sites using successive measurements with CO2 sensors installed in soil (e.g., Hirano et al, 2003;Chen et al, 2005;Desutter et al, 2008). The temporal increase also lasted several days in these studies.…”

“…Some studies have measured soil CO2 concentrations (e.g., van Bochove et al, 2001;Hirano et al, 2003;Chen et al, 2005;Maljanen et al, 2007;DeSutter et al, 2008;Muhr et al, 2009;Liang et al, 2010). These studies revealed seasonal variations in CO2 concentrations; the CO2 concentrations peaked in summer and had been increasing during the snow-covered period, which suggests that the stored CO2 in the soil during the winter might be released to the atmosphere after the Full Paper J.…”

Measurement depth effects on the apparent temperature sensitivity of soil respiration in field studies

“…Davidson et al (1998) predicted that Q 10 values would increase with temperature measurement depth, and recognized that this complicates comparisons between studies. Recently, several field studies with multiple temperature measurement depths have been published (Xu and Qi, 2001;Hirano et al, 2003;Tang et al, 2003;Gaumont-Guay et al, 2006;Khomik et al, 2006;Shi et al, 2006;Wang et al, 2006;Pavelka et al, 2007). All of them show an increase of apparent Q 10 with depth.…”

Frontiers and challenges in soil respiration research: from measurements to model-data integration

“…The second method to measure soil respiration involves automated soil CO 2 concentration profiles using gas wells (Hirsch et al 2004;Risk et al 2002a) or solid state CO 2 sensors (Hirano et al 2003). With soil CO 2 concentrations profiles, the location of production of CO 2 within the soil profile can be determined (Hashimoto and Komatsu 2006;Risk et al 2002b), but the calculation of soil respiration is dependent on the proper estimate of multiple physical factors such as: (1) variation in soil water content that change CO 2 diffusivity in the soil (Šimůnek and Suarez 1993); and (2) the proper estimation of tortuosity, soil texture, bulk density and porosity which are difficult to determine in rocky soils or water saturated soils (Jassal et al 2005;Pumpanen et al 2008;Turcu et al 2005).…”