soil inorganic carbon
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Forests ◽  
2022 ◽  
Vol 13 (1) ◽  
pp. 83
Author(s):  
Sihan Wang ◽  
Weiwei Lu ◽  
Fangchao Zhang

Afforestation is a strategy to protect croplands and to sequestrate carbon in coastal areas. In addition, inorganic carbon is a considerable constitute of the coastal soil carbon pool. However, the vertical distribution and controlling factors of soil inorganic carbon (SIC) in plantations of coastal areas have been rarely studied. We analyzed the SIC content as well as physiochemical properties along soil profiles (0–100 cm) in young (YP) and mature (MP) poplar plantations in coastal eastern China. The soil profile was divided into six layers (0–10, 11–20, 21–40, 41–60, 61–80 and 81–100 cm) and a total of 36 soil samples were formed. The SIC content first increased from 0–10 cm (0.74%) to 11–20 cm (0.92%) and then fluctuated in the YP. In contrast, the SIC content increased with increasing soil depth until 40 cm and then leveled off, and the minimum and maximum appeared at 0–10 cm (0.54%) and 81–100 cm (0.98%) respectively in the MP. The soil inorganic carbon density was 12.05 and 12.93 kg m−2 within 0–100 cm in the YP and MP, respectively. Contrary to SIC, soil organic carbon (SOC) first decreased then levelled off within the soil profiles. Compared with the YP, the SIC content decreased 27.8% at 0–10 cm but increased 13.2% at 21–40 cm, meanwhile the SOC content in MP decreased 70.6% and 46.7% at 21–40 cm and 61–80 cm, respectively. The water-soluble Ca2+ and Mg2+ gradually decreased and increased, respectively within the soil profiles. The soil water-soluble Ca2+ increased 18.3% within 41–100 cm; however, the soil water-soluble Mg2+ decreased 32.7% within 21–100 cm in the MP when compared to the YP. Correlation analysis showed that SIC was negatively correlated with SOC, but positively correlated with soil pH and water-soluble Mg2+. Furthermore, structural equation modeling (SEM) indicated that SOC was the most important factor influencing the SIC content in the studied poplar plantations, indicating SOC sequestration promoted the dissolution of SIC. Therefore, our study highlights the trade-off between SIC and SOC in poplar plantations of coastal Eastern China.


2021 ◽  
Author(s):  
Cécile Gomez ◽  
Tiphaine Chevallier ◽  
Patricia Moulin ◽  
Bernard G. Barthès

<p><span>Mid-Infrared reflectance spectroscopy (MIRS, 4000 – 400 cm<sup>-1</sup>) is being considered to provide accurate estimations of soil inorganic carbon (SIC) contents. Usually, the prediction performances by MIRS are analyzed using figures of merit based on entire test datasets characterized by large SIC ranges, without paying attention to performances at sub-range scales. This work aims to <em>1)</em> evaluate the performances of MIR regression models for SIC prediction, for a large range of SIC test data (0-100 g/kg) and for several regular sub-ranges of SIC values (0-5, 5-10, 10-15 g/kg, etc.) and <em>2)</em> adapt the prediction model depending on sub-ranges of test samples, using the absorbance peak at 2510 cm<sup>-1</sup> for separating SIC-poor and SIC-rich test samples. This study used a Tunisian MIRS topsoil dataset including 96 soil samples, mostly rich in SIC, to calibrate and validate SIC prediction models; and a French MIRS topsoil dataset including 2178 soil samples, mostly poor in SIC, to test them. Two following regression models were used: a partial least squares regression (PLSR) using the entire spectra and a simple linear regression (SLR) using the height of the carbonate absorbance peak at 2150 cm<sup>-1</sup>.</span></p><p><span>First, our results showed that PLSR provided <em>1) </em>better performances than SLR on the Validation Tunisian dataset (R<sup>2</sup><sub>test</sub> of 0.99 vs. 0.86, respectively), but <em>2) </em>lower performances than SLR on the Test French dataset (R<sup>2</sup><sub>test</sub> of 0.70 vs. 0.91, respectively). Secondly, our results showed that on the Test French dataset, predicted SIC values were more accurate for SIC-poor samples (< 15 g/kg) with SLR (RMSE<sub>test</sub> from 1.5 to 7.1 g/kg, depending on the sub-range) than with PLSR prediction model (RMSE<sub>test </sub>from 7.3 to 14.8 g/kg, depending on the sub-range). Conversely, predicted SIC values were more accurate for carbonated samples (> 15 g/kg) with PLSR (RMSE<sub>test</sub> from 4.4 to 10.1 g/kg, depending on the sub-range) than with SLR prediction model (RMSE<sub>test</sub> from 6.8 to 14 g/kg, depending on the sub-range). Finally, our results showed that the absorbance peak at 2150 cm<sup>-1</sup> could be used before prediction to separate SIC-poor and SIC-rich test samples (452 and 1726 samples, respectevely). The SLR and PLSR regression methods applied to these SIC-poor and SIC-rich test samples, respectively, provided better prediction performances (<em>R²</em><sub><em>test </em></sub>of 0.95 and <em>RMSE</em><sub><em>test</em></sub> of 3.7 g/kg<sup></sup>). </span></p><p><span>Finally, this study demonstrated that the use of the spectral absorbance peak at 2150 cm<sup>-1</sup> provided useful information on Test samples and helped the selection of the optimal prediction model depending on SIC level, when using calibration and test sample sets with very different SIC distributions.</span></p>


Geoderma ◽  
2020 ◽  
Vol 371 ◽  
pp. 114382
Author(s):  
Patrick Filippi ◽  
Stephen R. Cattle ◽  
Matthew J. Pringle ◽  
Thomas F.A. Bishop

Geosciences ◽  
2020 ◽  
Vol 10 (5) ◽  
pp. 200 ◽  
Author(s):  
Elena A. Mikhailova ◽  
Hamdi A. Zurqani ◽  
Christopher J. Post ◽  
Mark A. Schlautman

Many soil regulating ecosystem services (ES) are linked to Earth’s atmosphere, but associated monetary values often are unknown or difficult to quantify. Atmospheric deposition of calcium (Ca2+) and magnesium (Mg2+) are abiotic flows (wet, dry, and total) from the atmosphere to land surfaces, which potentially can become available to sequester carbon (C) as soil inorganic carbon (SIC). However, these processes typically have not been included in economic valuations of ecosystem services. The primary objective of this study was to demonstrate an approach for valuing non-constrained potential SIC sequestration from atmospheric Ca2+ and Mg2+ deposition based on the concept of the avoided social cost of carbon dioxide emissions (SC-CO2). Maximum monetary values associated with the non-constrained potential SIC sequestration were compiled for the contiguous United States (U.S.) by soil order, land resource region (LRR), state, and region using available deposition data from the National Atmospheric Deposition Program (NRSP-3). For the entire contiguous U.S., an average annual monetary value for the non-constrained potential SIC sequestration due to atmospheric Ca2+ and Mg2+ deposition was $135M (i.e., $135 million U.S. dollars, where M = million = 106). Mollisols, Alfisols, and Entisols were soil orders with the highest average annual monetary values for non-constrained potential SIC sequestration. When normalized by land area, however, Vertisols had the highest average annual monetary values followed by Alfisols and Mollisols for non-constrained potential SIC sequestration. From a more agricultural perspective, the LRRs with the highest average annual monetary values for non-constrained potential SIC sequestration were the Western Range and Irrigated Region (D), the Central Feed Grains and Livestock Region (M), and the Central Great Plains Winter Wheat and Range Region (H). When normalized by area, the LRRS with the highest average annual monetary values were the Southwest Plateaus and Plains Range and Cotton Region (I) and the Florida Subtropical Fruit, Truck Crop and Range Region (U). Among the U.S. states, the highest average annual monetary values for non-constrained potential SIC sequestration were Texas, Kansas, and New Mexico, but when normalized by area the highest values by state were Kansas, Iowa, and Texas. Geographical regions in the contiguous U.S. with the highest average annual monetary values for non-constrained potential SIC sequestration were the South Central, Midwest, and West; when normalized by area, the highest values by region were South Central, Midwest, and Northern Plains. Constraints on maximum monetary values, based on physical, chemical, biological, economic, social, and political limitations, need to be considered and quantified to obtain more precise and accurate accounting of the ES associated with SIC sequestration due to atmospheric Ca2+ and Mg2+ deposition.


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