Soil Air CO2 Concentration Research Articles

Seasonal patterns of soil CO2 efflux and soil air CO2 concentration in a Scots pine forest: comparison of two chamber techniques

AbstractA non‐vented non‐steady state flow‐through chamber and a non‐vented non‐steady state non‐flow‐through chamber technique were used to measure CO2 efflux of a young Scots pine forest on a fertile till soil in southern Finland. Soil temperature, soil moisture and soil CO2 concentration were measured concurrently with CO2 efflux for two and a half successive years. The CO2 efflux showed a seasonal pattern, effluxes ranging from low 0.0–0.1 g CO2 m−2 h−1 in winter to peak values of 2.3 g CO2 m−2 h−1 occurring in late June and in July. The daily average effluxes in July measured by flow through chambers were 1.23 and 0.98 g CO2 m−2 h−1 in 1998 and 1999, respectively. The annual accumulated CO2 efflux was 3117 and 3326 g CO2 m−2 in 1998 and 1999, respectively. The spatial variation in CO2 efflux was high (CV 0.18–0.45) and increased with increasing efflux. Soil air CO2 concentration showed similar seasonal pattern the peak concentrations occurring in July–August. The CO2 concentrations ranged from 580 to 780 µmol mol−1 in the humus layer to 13 620–14 470 µmol mol−1 in the C‐horizon. In winter the soil air CO2 concentrations were lower, especially in deeper soil layers. Drought decreased CO2 efflux and soil air CO2 concentration. The in situ comparison on forest soil between the chamber methods showed the non‐flow‐through chamber to give ∼∼50% lower efflux values than that of the flow‐through chamber. When calibrated against known CO2 efflux ranging from 0.4 to 0.8 g CO2 m−2 h−1 generated with a diffusion box method developed by Widén and Lindroth [Acta Universitatis Agriculturae Suecia Silvestria, 2001], the flow‐through chamber gave equal effluxes at the lower end of the calibration range, but overestimated high effluxes by 20%. Non‐flow‐through chamber underestimated the CO2 efflux by 30%.

A Process-Based Model for Predicting Soil Carbon Dioxide Efflux and Concentration

Decomposition and root respiration processes, important to C cycling in terrestrial ecosystems, are affected by soil temperature, soil moisture, and other soil properties. For studying the effect of these factors on soil CO2 efflux and soil-air CO2 concentration, a dynamic model was developed. In the model, soil was described in successive layers and the processes and soil properties were described separately for each layer. The CO2 in soil layers originated from root and microbial respiration, which were assumed to depend on soil temperature and moisture multiplicatively. The CO2 flux between the layers was driven by diffusion, which depended on CO2 concentration, porosity, and temperature of the layers. The model predictions of CO2 effluxes and soil CO2 concentrations were close to those observed in the field. There was a clear seasonal pattern in the soil CO2 efflux and the soil-air CO2 concentration. According to the model analysis, most of the CO2 was produced in the humus layer throughout the year, but the contribution of deeper layers to total respiration was higher in winter than in summer. The CO2 concentration was strongly dependent on factors affecting the diffusion properties of the soil, that is, the soil porosity and the soil-water content. The CO2 efflux and the soil-air CO2 concentration were overestimated, if the soil-water content was not included in the soil respiration model. The model developed in this study provided a simple and an effective tool for studying the factors affecting soil CO2 efflux and CO2 concentration.

Erosion Effects on Carbon Dioxide Concentration and Carbon Flux from an Ohio Alfisol

Carbon dioxide concentrations in soil both reflect and influence soil biological activity and C flux to the atmosphere. We hypothesized that erosion affects CO2 concentration and C flux from the soil surface because of its effects on soil temperature and water regimes. The soil air concentrations of CO2 and corresponding temperature and water contents were monitored on slight (SLI), moderate (MOD), severe (SEV), and depositional (DEP) phases at 2‐wk intervals between May 1996 and June 1997. The ambient soil CO2 concentration and CO2–C flux were determined using gas chromatograph analyses. Seasonal patterns in soil air CO2 concentrations (ranging from a winter low of 0.56 mL L−1 to a summer high of 20.90 mL L−1) predominated over more subtle differences (20–80% variation) due to erosion phase effects. Significantly greater (by 12–37%) CO2 concentrations for SEV and MOD phases over SLI and DEP were observed mainly during the summer. The effects of the erosion phase on soil CO2 concentrations appeared to be indirect through its impacts primarily on soil temperature and, presumably, soil biological activity. Soil air CO2 concentrations were significantly correlated with soil temperature (R2 = 0.61) and CO2–C (R2 = 0.65) flux from the soil surface but not with soil water content. Both linear and second‐order polynomial regression equations using soil temperature predicted soil CO2 concentration.

Soil Air Carbon Dioxide and Nitrous Oxide Concentrations in Profiles under Tallgrass Prairie and Cultivation

AbstractAssessing the dynamics of gaseous production in soils is of interest because they are important sources and sinks of greenhouse gases. Changes in soil air carbon dioxide (CO2) and nitrous oxide (N2O) concentrations were studied in a Reading silt loam (fine‐silty, mixed, mesic Typic Argiudolls) under prairie and cultivation. Concentrations were measured in situ over a 17‐mo period to a depth of 3 m. Multilevel samplers permitted collection of gases with subsequent measurement by gas chromatography in the laboratory. Soil air N2O concentrations were near atmospheric levels for a majority of the study period in the prairie site (0.184–2.25 µL L−1) but were significantly higher in the cultivated site (0.257–7.56 µL L−1). Annual mean N2O concentrations were 0.403 and 1.09 µL L−1 in the prairie and cultivated sites, respectively. Soil air CO2 annual mean concentrations were 1.56 × 104 and 1.10 × 104 µL L−1 and ranged from 0.096 × 104 to 6.45 × 104 µL L−1 and 0.087 × 104 to 3.59 × 104 µL L−1 in the prairie and cultivated sites, respectively. Concentrations generally increased with depth, with maximum soil air N2O and CO2 concentrations at 1.0 m in the prairie site and 0.5 m in the cultivated site. Nitrous oxide in the cultivated site and CO2 at both sites did not change markedly over winter months, but CO2 and N2O concentrations reached maximums during the summer months and decreased as the year progressed. Although soil air concentrations peaked and decreased faster at shallower depths, deeper depths exhibited relative maximum concentrations for longer time periods.

Experimental soil warming effects on CO2 and CH4 flux from a low elevation spruce–fir forest soil in Maine, USA

AbstractThe effect of soil warming on CO2 and CH4 flux from a spruce–fir forest soil was evaluated at the Howland Integrated Forest Study site in Maine, USA from 1993 to 1995. Elevated soil temperatures (∼5 °C) were maintained during the snow‐free season (May – November) in replicated 15 × 15‐m plots using electric cables buried 1–2 cm below the soil surface; replicated unheated plots served as the control. CO2 evolution from the soil surface and soil air CO2 concentrations both showed clear seasonal trends and significant (P < 0.0001) positive exponential relationships with soil temperature. Soil warming caused a 25–40% increase in CO2 flux from the heated plots compared to the controls. No significant differences were observed between heated and control plot soil air CO2 concentrations which we attribute to rapid equilibration with the atmosphere in the O horizon and minimal treatment effects in the B horizon. Methane fluxes were highly variable and showed no consistent trends with treatment.

Land-use effects on soil methane and carbon dioxide fluxes in forests near Ithaca, New York

:Consumption of atmospheric methane (CH4) and fluxes of carbon dioxide (CO2) were higher for soil in (i) mixed hardwood forest on historically unplowed land than in (ii) 80-year-old mixed hardwood forest and (iii) 80-year-old conifer plantations both established on post-agricultural land, whereas flux rates were lowest in (iv) adjoining agriculture sites, showing that past and present land-use in forest ecosystems affects fluxes of atmospheric CH4 and CO2. Site differences in CH4 fluxes were more pronounced in drier 1993 and 1995 than in wetter 1994, whereas site differences in CO2 fluxes disappeared during winter and during pronounced drought in summer 1995. Seasonal variation in CH4 fluxes in forest sites were related to soil moisture but not CH4 concentrations in soil air. Notably, all four sites occasionally exhibited CH4 efflux to the atmosphere, and studies confirmed the presence of anaerobic CH4-producing microorganisms (methanogens) in the soil, despite well-drained conditions. Seasonal variation in CO2 fluxes in forest sites were related to soil temperature and CO2 concentrations in soil air, but not in the agricultural site that maintained somewhat higher soil CO2 levels. Future studies of soil CH4 and CO2 dynamics should recognize the persistent effects of historical (and recent) changes in land use.

Soil Carbon Dioxide Characteristics under Different Forest Types and after Harvest

AbstractTo characterize soil CO2 under different forest types and several years after a clear‐cut harvest, soil CO2 evolution and soil air CO2 concentrations were measured at three sites in Maine: the Howland Integrated Forest Study (HIFS) site, the Bear Brook Watershed in Maine (BBWM) site, and the Letter E township (Letter E) site. Soil CO2 evolution means ranged from 0.19 to 0.32 g m−2 h−1 among sites, whereas soil air CO2 concentration means ranged from 1023 µL L−1 for the O horizon to 3296 µL L−1 for the C horizon for the 1990 growing season. Soil CO2 evolution and soil air CO2 concentrations were similar under deciduous and coniferous forests and 4 to 6 yr after harvest. Limited multiple‐year data suggest that significant annual variations in temporal patterns of these properties exist as a function of short‐term climatic factors. These data suggest that soil CO2 evolution and soil air CO2 concentrations may be somewhat similar across a diversity of soil types, forest types, and forest conditions at any point in time for northern New England.

Effect of surface and subsurface drip fertigation on sweet corn rooting, uptake, dry matter production and yield

Subsurface (SS) drip fertigation may increase sweet corn ear yield relative to surface (S) fertigation, because immobile nutrients are delivered at the center of the soil-root volume rather than on top of the soil. A container (1 × 1 × 1 m) experiment was conducted on a loessial soil (Haploxeralf) to test this hypothesis. Marketable and total ear yields were higher for tricklers placed 30 cm below the soil surface (3.22 and 4.90 kg m−2, respectively) than on the surface (2.86 and 4.30 kg m−2, respectively). Total fresh weight, dry matter production and plant height during the growing season were also greater for subsurface emitters. Deep trickler position significantly increased P and K content at the center of the root zone. The enhanced concentration apparently stimulated plant rooting which, together with the higher nutrient activity in the soil solution, increased P and K uptake rates, which in turn facilitated the higher dry matter production and commercial yield relative to surface trickler placement. The higher root activity in SS than in S fertigation was reconfirmed by soil air CO2 concentration measurements which showed significant differences between the two treatments during the growth season.

Soil Air Carbon Dioxide Concentrations in a New England Spruce‐Fir Forest

AbstractResearch and modeling efforts to evaluate soil‐soil solution chemical interactions must take into account solution equilibria with soil air CO2. Measurements of soil air CO2 and soil temperature were made in the major horizons of a forest soil in eastern Maine through the 1985 growing season. Soil air CO2 concentration ranged from 0.10 to 0.35%, 0.10 to 1.25%, and 0.20 to 1.20% in the O, B, and C horizons respectively. Peak soil air CO2 concentration occurred in July and early October which coincided with high points in soil temperature during the growing season.