scholarly journals Forest Soil Profile Inversion and Mixing Change the Vertical Stratification of Soil CO2 Concentration without Altering Soil Surface CO2 Flux

Forests ◽  
2019 ◽  
Vol 10 (2) ◽  
pp. 192 ◽  
Author(s):  
Xiaoling Wang ◽  
Shenglei Fu ◽  
Jianxiong Li ◽  
Xiaoming Zou ◽  
Weixin Zhang ◽  
...  
Keyword(s):  
Forest Soil ◽  
Soil Profile ◽  
Soil Column ◽  
Soil Surface ◽  
Co2 Flux ◽  
Co2 Concentration ◽  
Co2 Production ◽  
Soil Profiles ◽  
Soil Co2 ◽  
Soil Surface Co2 Flux

In order to gain more detailed knowledge of the CO2 concentration gradient in forest soil profiles and to better understand the factors that control CO2 concentration along forest soil profiles, we examined the soil surface CO2 flux, soil properties and soil profile CO2 concentration in upright (CK), inverted and mixed soil columns with a depth of 60 cm in two subtropical forests in China from May 2008 to December 2009. The results showed that: (1) The SOC (soil organic carbon), TN (total N) and microbial biomass were higher in the deeper layers in the inverted soil column, which was consistent with an increase in CO2 concentration in the deeper soil layer. Furthermore, the biogeochemical properties were homogenous among soil layers in the mixed soil column. (2) CO2 concentration in the soil profile increased with depth in CK while soil column inversion significantly intensified this vertical stratification as the most active layer (surface soil) was now at the bottom. The stratification of CO2 concentration along the soil profile in the mixed soil column was similar to that in CK but it was not intensified after soil was mixed. (3) The soil surface CO2 flux did not significantly change after the soil column was inverted. The surface CO2 flux rate of the mixed soil column was higher compared to that of the inverted soil column but was not significantly different from CK. Our results indicated that the profile soil CO2 production was jointly controlled by soil properties related to CO2 production (e.g., SOC content and soil microbial biomass) and those related to gas diffusion (e.g., soil bulk density and gas molecular weight), but the soil surface CO2 flux was mainly determined by soil surface temperature and may be affected by the intensity of soil disturbance.

scholarly journals Vertical partitioning and controlling factors of gradient-based soil carbon dioxide fluxes in two contrasted soil profiles along a loamy hillslope

2015 ◽  
Vol 12 (15) ◽  
pp. 4637-4649 ◽  
Author(s):  
F. Wiaux ◽  
M. Vanclooster ◽  
K. Van Oost
Keyword(s):  
Co2 Emissions ◽  
Soil Profile ◽  
Temporal Evolution ◽  
Soil Surface ◽  
Slope Position ◽  
Soil Profiles ◽  
Co2 Fluxes ◽  
Soil Co2 ◽  
Soil Co2 Emissions ◽  
Different Depths

Abstract. In this study we aim to elucidate the role of physical conditions and gas transfer mechanism along soil profiles in the decomposition and storage of soil organic carbon (OC) in subsoil layers. We use a qualitative approach showing the temporal evolution and the vertical profile description of CO2 fluxes and abiotic variables. We assessed soil CO2 fluxes throughout two contrasted soil profiles (i.e. summit and footslope positions) along a hillslope in the central loess belt of Belgium. We measured the time series of soil temperature, soil moisture and CO2 concentration at different depths in the soil profiles for two periods of 6 months. We then calculated the CO2 flux at different depths using Fick's diffusion law and horizon specific diffusivity coefficients. The calculated fluxes allowed assessing the contribution of different soil layers to surface CO2 fluxes. We constrained the soil gas diffusivity coefficients using direct observations of soil surface CO2 fluxes from chamber-based measurements and obtained a good prediction power of soil surface CO2 fluxes with an R2 of 92 %. We observed that the temporal evolution of soil CO2 emissions at the summit position is mainly controlled by temperature. In contrast, at the footslope, we found that long periods of CO2 accumulation in the subsoil alternates with short peaks of important CO2 release. This was related to the high water filled pore space that limits the transfer of CO2 along the soil profile at this slope position. Furthermore, the results show that approximately 90 to 95 % of the surface CO2 fluxes originate from the first 10 cm of the soil profile at the footslope. This indicates that soil OC in this depositional context can be stabilized at depth, i.e. below 10 cm. This study highlights the need to consider soil physical properties and their dynamics when assessing and modeling soil CO2 emissions. Finally, changes in the physical environment of depositional soils (e.g. longer dry periods) may affect the long-term stability of the large stock of easily decomposable OC that is currently stored in these environments.

scholarly journals Soil CO2 flux: a method comparison of closed static chambers in a sugarcane field

2012 ◽  
Vol 36 (2) ◽  
pp. 421-426 ◽  
Author(s):  
Walane Maria Pereira de Mello Ivo ◽  
Ignacio Hernán Salcedo
Keyword(s):  
Soil Respiration ◽  
Method Comparison ◽  
Soil Surface ◽  
Co2 Flux ◽  
Soda Lime ◽  
Co2 Absorption ◽  
Soil Co2 ◽  
Soil Co2 Flux ◽  
Absorption Area ◽  
Trapping Solution

A large variety of techniques have been used to measure soil CO2 released from the soil surface, and much of the variability observed between locations must be attributed to the different methods used by the investigators. Therefore, a minimum protocol of measurement procedures should be established. The objectives of this study were (a) to compare different absorption areas, concentrations and volumes of the alkali trapping solution used in closed static chambers (CSC), and (b) to compare both, the optimized alkali trapping solution and the soda-lime trapping using CSC to measure soil respiration in sugarcane areas. Three CO2 absorption areas were evaluated (7; 15 and 20 % of the soil emission area or chamber); two volumes of NaOH (40 and 80 mL) at three concentrations (0.1, 0.25 and 0.5 mol L-1). Three different types of alkaline traps were tested: (a), 80 mL of 0.5 mol L-1 NaOH in glass containers, absorption area 15 % (V0.5); (b) 40 mL of 2 mol L-1 NaOH retained in a sponge, absorption area 80 % (S2) and (c) 40 g soda lime, absorption area 15 % (SL). NaOH concentrations of 0.5 mol L-1 or lower underestimated the soil CO2-C flux or CO2 flux. The lower limit of the alkali trap absorption area should be a minimum of 20 % of the area covered by the chamber. The 2 mol L-1 NaOH solution trap (S2) was the most efficient (highest accuracy and highest CO2 fluxes) in measuring soil respiration.

scholarly journals Field Study on Correlation between CO2 Concentration and Surface Soil CO2 Flux in Closed Coal Mine Goaf

ACS Omega ◽  
2019 ◽  
Vol 4 (7) ◽  
pp. 12136-12145 ◽  
Author(s):  
Yongjun Wang ◽  
Xiaoming Zhang ◽  
Hemeng Zhang ◽  
Kyuro Sasaki
Keyword(s):  
Field Study ◽  
Coal Mine ◽  
Surface Soil ◽  
Co2 Flux ◽  
Co2 Concentration ◽  
Soil Co2 ◽  
Soil Co2 Flux

scholarly journals Explaining CO<sub>2</sub> fluctuations observed in snowpacks

2018 ◽  
Vol 15 (3) ◽  
pp. 847-859
Author(s):  
Laura Graham ◽  
David Risk
Keyword(s):  
Diffusion Model ◽  
Meteorological Data ◽  
Negative Relationship ◽  
Flux Measurement ◽  
Co2 Flux ◽  
Co2 Concentration ◽  
Physical Factors ◽  
Advective Transport ◽  
Soil Co2 ◽  
C Cycle

Abstract. Winter soil carbon dioxide (CO2) respiration is a significant and understudied component of the global carbon (C) cycle. Winter soil CO2 fluxes can be surprisingly variable, owing to physical factors such as snowpack properties and wind. This study aimed to quantify the effects of advective transport of CO2 in soil–snow systems on the subdiurnal to diurnal (hours to days) timescale, use an enhanced diffusion model to replicate the effects of CO2 concentration depletions from persistent winds, and use a model–measure pairing to effectively explore what is happening in the field. We took continuous measurements of CO2 concentration gradients and meteorological data at a site in the Cape Breton Highlands of Nova Scotia, Canada, to determine the relationship between wind speeds and CO2 levels in snowpacks. We adapted a soil CO2 diffusion model for the soil–snow system and simulated stepwise changes in transport rate over a broad range of plausible synthetic cases. The goal was to mimic the changes we observed in CO2 snowpack concentration to help elucidate the mechanisms (diffusion, advection) responsible for observed variations. On subdiurnal to diurnal timescales with varying winds and constant snow levels, a strong negative relationship between wind speed and CO2 concentration within the snowpack was often identified. Modelling clearly demonstrated that diffusion alone was unable to replicate the high-frequency CO2 fluctuations, but simulations using above-atmospheric snowpack diffusivities (simulating advective transport within the snowpack) reproduced snow CO2 changes of the observed magnitude and speed. This confirmed that wind-induced ventilation contributed to episodic pulsed emissions from the snow surface and to suppressed snowpack concentrations. This study improves our understanding of winter CO2 dynamics to aid in continued quantification of the annual global C cycle and demonstrates a preference for continuous wintertime CO2 flux measurement systems.

scholarly journals A field-based method for simultaneous measurements of the δ<sup>18</sup>O and δ<sup>13</sup>C of soil CO<sub>2</sub> efflux

2004 ◽  
Vol 1 (1) ◽  
pp. 1-9 ◽  
Author(s):  
B. Mortazavi ◽  
J. L. Prater ◽  
J. P. Chanton
Keyword(s):  
Isotopic Composition ◽  
Soil Water ◽  
Soil Surface ◽  
Co2 Concentration ◽  
Vertical Gradient ◽  
Co2 Efflux ◽  
Soil Co2 ◽  
Fractionation Factor ◽  
Keeling Plots ◽  
Δ18o And Δ13c

Abstract. Three approaches for determining the stable isotopic composition (δ13C and δ18O) of soil CO efflux were compared. A new technique employed mini-towers, constructed of open-topped piping, that were placed on the soil surface to collect soil-emitted CO2. Samples were collected along a vertical gradient and analyzed for CO2 concentration and isotopic composition. These data were then used to produce Keeling plots to determine the δ18O and δ13C of CO2 emitted from the soil. These results were then compared to the δ18O and δ13C of soil-respired CO2 measured with two other techniques: (1) flux chambers and (2) estimation from the application of the diffusional fractionation factor to measured values of below ground soil CO2 and to CO2 in equilibrium with soil water δ18O. Mini-tower δ18O Keeling plots were linear and highly significant (0.81< r 2 > 0.96), in contrast to chamber δ18O Keeling plots, which showed significant curvature, necessitating the use of a mass balance to calculate the δ18O of respired CO2. In the chambers, the values determined for the δ18O of soil respired CO2 approached the value of CO2 in equilibrium with surficial soil water, and the results were significantly δ18O enriched relative to the mini-tower results and the δ18O of soil CO2 efflux determined from soil CO2. There were close agreements between the three methods for the determination of the δ13C of soil efflux CO2. Results suggest that the mini-towers can be effectively used in the field for determining the δ18O and the δ13C of soil-respired CO2.

Soil surface CO2 flux in a Minnesota peatland

1992 ◽  
Vol 18 (1) ◽  
pp. 37-51 ◽  
Author(s):  
Joon Kim ◽  
Shashi B. Verma
Keyword(s):  
Soil Surface ◽  
Co2 Flux ◽  
Soil Surface Co2 Flux

scholarly journals IN SITE NET PHOTOSYNTHESIS MEASUREMENT OF A PLANT CANOPY IN A SINGLE-SPAN GREENHOUSE

2017 ◽  
Vol 7 (2) ◽  
pp. 1015-1020 ◽  
Author(s):  
Tadashi Takakura ◽  
Haruki Sunagawa ◽  
Maro Tamaki ◽  
Takae Usui ◽  
Naoki Taniai
Keyword(s):  
Heat Flux ◽  
Soil Surface ◽  
Co2 Flux ◽  
Net Photosynthesis ◽  
Co2 Concentration ◽  
Plant Canopy ◽  
Canopy Photosynthesis ◽  
Plant Cultivation ◽  
On Line ◽  
Co2 Balance

Using newly developed sensor units that were more compact and accurate than earlier units (Takakura et al., 2009), this study was conducted to estimate the net photosynthesis of a plant canopy in a practical greenhouse during plant cultivation. Net photosynthesis and the ventilation flow rate are two unknowns in this greenhouse system, with adequate growth of bitter gourd plants. Environmental conditions related to evapotranspiration from the canopy and CO2 flux from the soil surface were measured respectively using the developed sensor units and a box-type CO2 concentration sensor. Heat flux from the soil was also measured. Two equations were solved: one for CO2 balance and one for water vapor balance. On-line monitoring of net photosynthesis is possible using simple and inexpensive sensors, but the obtained data of the canopy photosynthesis were scattered because of frequent changes in the ventilation amount. Furthermore, improved sensor units revealed that the evapotranspiration of the canopy was linearly related to net solar radiation in the greenhouse.

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