scholarly journals Fate of rice shoot and root residues, rhizodeposits, and microbe-assimilated carbon in paddy soil – Part 1: Decomposition and priming effect

2016 ◽  
Vol 13 (15) ◽  
pp. 4481-4489 ◽  
Author(s):  
Zhenke Zhu ◽  
Guanjun Zeng ◽  
Tida Ge ◽  
Yajun Hu ◽  
Chengli Tong ◽  
...  
Keyword(s):  
Priming Effect ◽  
Nutrient Management ◽  
C Sequestration ◽  
Paddy Soils ◽  
Soil Organic C ◽  
Untreated Soil ◽  
Organic C ◽  
Soil C ◽  
Rice Roots ◽  
Native Soil

Abstract. The input of recently photosynthesized C has significant implications on soil organic C sequestration, and in paddy soils, both plants and soil microbes contribute to the overall C input. In the present study, we investigated the fate and priming effect of organic C from different sources by conducting a 300-day incubation study with four different 13C-labelled substrates: rice shoots (shoot-C), rice roots (root-C), rice rhizodeposits (rhizo-C), and microbe-assimilated C (micro-C). The efflux of both 13CO2 and 13CH4 indicated that the mineralization of C in shoot-C-, root-C-, rhizo-C-, and micro-C-treated soils rapidly increased at the beginning of the incubation and decreased gradually afterwards. The highest cumulative C mineralization was observed in root-C-treated soil (45.4 %), followed by shoot-C- (31.9 %), rhizo-C- (7.90 %), and micro-C-treated (7.70 %) soils, which corresponded with mean residence times of 39.5, 50.3, 66.2, and 195 days, respectively. Shoot and root addition increased C emission from native soil organic carbon (SOC), up to 11.4 and 2.3 times higher than that of the control soil by day 20, and decreased thereafter. Throughout the incubation period, the priming effect of shoot-C on CO2 and CH4 emission was strongly positive; however, root-C did not exhibit a significant positive priming effect. Although the total C contents of rhizo-C- (1.89 %) and micro-C-treated soils (1.90 %) were higher than those of untreated soil (1.81 %), no significant differences in cumulative C emissions were observed. Given that about 0.3 and 0.1 % of the cumulative C emission were derived from labelled rhizo-C and micro-C, we concluded that the soil organic C-derived emissions were lower in rhizo-C- and micro-C-treated soils than in untreated soil. This indicates that rhizodeposits and microbe-assimilated C could be used to reduce the mineralization of native SOC and to effectively improve soil C sequestration. The contrasting behaviour of the different photosynthesized C substrates suggests that recycling rice roots in paddies is more beneficial than recycling shoots and demonstrates the importance of increasing rhizodeposits and microbe-assimilated C in paddy soils via nutrient management.

scholarly journals Fate of rice shoot and root residues, rhizodeposits, and microbe-assimilated carbon in paddy soil: I. Decomposition and priming effect

2016 ◽  
Author(s):  
Zhenke Zhu ◽  
Guanjun Zeng ◽  
Tida Ge ◽  
Yajun Hu ◽  
Chengli Tong ◽  
...  
Keyword(s):  
Organic Carbon ◽  
Soil Organic Carbon ◽  
Priming Effect ◽  
Paddy Soils ◽  
Ch4 Emission ◽  
Untreated Soil ◽  
Organic C ◽  
Soil C ◽  
Rice Roots ◽  
Native Soil

Abstract. The input of recently photosynthesized C has significant implications on soil organic carbon sequestration, and in paddy soils, both plants and soil microbes contribute to the overall C input. In the present study, we investigated the fate and priming effect of organic C from different sources by conducting a 300-d incubation study with four different 13C-labelled substrates: rice shoots (Shoot-C), rice roots (Root-C), rice rhizodeposits (Rhizo-C), and microbe-assimilated C (Micro-C). The efflux of both 13CO2 and 13CH4 indicated that the mineralization of C in Shoot-C-, Root-C-, Rhizo-C-, and Micro-C-treated soils rapidly increased at the beginning of the incubation and then decreased gradually afterwards. In addition, the highest level of C mineralization was observed in Root-C-treated soil (45.4 %), followed by Shoot-C- (31.9 %), Rhizo-C- (7.9 %), and Micro-C-treated (7.7 %) soils, which corresponded with mean residence times of 33.4, 46.1, 62.9, and 192 d, respectively. Furthermore, the cumulative mineralization of native soil organic carbon in Shoot-C-treated soils was 1.48- fold higher than in untreated soils, and the priming effect of Shoot-C on CO2 and CH4 emission was strongly positive over the entire incubation. However, Root-C failed to exhibit a significant priming effect, which suggests that it could potentially be used to mitigate CH4 emission. Although the total C contents of Rhizo-C- (1.89 %) and Micro-C-treated soils (1.9 %) were higher than those of untreated soil (1.8 %), no significant differences in total C emissions were observed. However, the 13C emissions of Rhizo-C- and Micro-C-treated soils gradually increased over the entire incubation period, which indicated that soil organic C-derived emissions were lower in Rhizo-C- and Micro-C-treated soils than in untreated soil, and that rhizodeposits and microbe-assimilated C could be used to reduce the mineralization of native soil organic carbon and to effectively improve soil C sequestration. The contrasting behaviours of the different photosynthesized C substrates suggests that recycling rice roots in paddies is more beneficial than recycling shoots and reveals the importance of increasing rhizodeposits and microbe-assimilated C in paddy soils via nutrient management.

scholarly journals Stability of Woodchips Biochar and Impact on Soil Carbon Stocks: Results from a Two-Year Field Experiment

Forests ◽  
2021 ◽  
Vol 12 (10) ◽  
pp. 1350
Author(s):  
Irene Criscuoli ◽  
Maurizio Ventura ◽  
Katja Wiedner ◽  
Bruno Glaser ◽  
Pietro Panzacchi ◽  
...  
Keyword(s):  
Climate Change ◽  
Field Experiment ◽  
Priming Effect ◽  
Soil Organic C ◽  
Organic C ◽  
Soil C ◽  
Total Soil ◽  
C Stock ◽  
The Stability

Biochar has been shown to improve soil quality and crop yields. Furthermore, thanks to its high carbon content (C) and stable chemical structure, biochar can sequester C in the soil for a long time, mitigating climate change. However, the variability in published biochar stability in the soil makes verifying this trait under different environmental and agricultural conditions necessary. Moreover, most of the published literature refers to short-term incubation experiments, which are considered to not adequately represent long-term dynamics under field conditions. This article reports the results of a field experiment carried out in a vineyard near Merano, northern Italy, where the stability of woodchips biochar in soil, its impact on the total soil C stocks as well as on the original soil organic C (priming effect) were studied over two years. Vineyard soil (Dystric Eutrochrept) was amended with biochar (25 and 50 t ha−1) alone or together with compost (45 t ha−1) and compared with unamended control soil. Two methods assessed the stability of biochar in soil: the isotopic mass balance approach and the quantification of Benzene PolyCarboxylic Acids (BPCAs), molecular markers of biochar. The amount of C in the soil organic matter (SOM-C) was determined in the amended plots by subtracting the amount of biochar-C from the total soil organic C stock, and the occurrence of priming effect was verified by comparing SOM-C values at the beginning and at the end of the experiment. Results did not show any significant biochar degradation for both application rates, but results were characterized by a high variation. The application of 50 t ha−1 of biochar significantly increased soil C stock while no effect of biochar on the degradation of SOM-C was observed. Results were confirmed in the case of biochar application together with compost. It can be concluded that the use of woodchips biochar as a soil amendment can increase soil C content in the medium term. However, further analyses are recommended to evaluate the impact of biochar on climate change mitigation in the long term.

scholarly journals Estimation of carbon inputs to soils from wheat in the Pampas Region, Argentina

2011 ◽  
Vol 47 (Special Issue) ◽  
pp. S39-S42 ◽  
Author(s):  
G. Civeira
Keyword(s):  
C Sequestration ◽  
Plant Production ◽  
Accurate Estimation ◽  
Soil Organic C ◽  
Organic C ◽  
Soil C ◽  
C Stocks ◽  
C Input ◽  
Different Soils ◽  
Pampas Region

Recently soils have gained more attention within the global change debate as the largest terrestrial carbon (C) pool. Different soils and vegetation types have substantial impacts on many of the processes that take place in the ecosystem functioning and thus in soil organic C stocks. An accurate estimation of vegetation C inputs to soils may aid in more precise estimation of the future release or sequestration of soil organic C. Wheat production affects C inputs and thus soil C sequestration in soils. The objective of this research was to evaluate C inputs by wheat, from 1993 to 2002 in the Pampas Region. The estimated C input rate by wheat was greater in the humid subregion than in the semiarid subregion: 0.9 and 0.75 Mg C/ha/year, correspondingly. This pattern agrees with the observation that precipitation constrains plant production in arid to subhumid ecosystems. The average organic C input by wheat into the soils throughout the period was 8.1 Mg C/ha in the humid subregion and, 6.75 Mg C/ha in the semiarid subregion.

Manipulation of rhizosphere organisms to enhance glomalin production and C sequestration: Pitfalls and promises

2014 ◽  
Vol 94 (6) ◽  
pp. 1025-1032 ◽  
Author(s):  
F. L. Walley ◽  
A. W. Gillespie ◽  
Adekunbi B. Adetona ◽  
J. J. Germida ◽  
R. E. Farrell
Keyword(s):  
Plant Growth ◽  
Mycorrhizal Fungi ◽  
Plant Growth Promoting Rhizobacteria ◽  
C Sequestration ◽  
Ionization Mass ◽  
Edge Structure ◽  
Organic C ◽  
Soil C ◽  
N Storage ◽  
C And N

Walley, F. L., Gillespie, A. W., Adetona, A. B., Germida, J. J. and Farrell, R. E. 2014. Manipulation of rhizosphere organisms to enhance glomalin production and C-sequestration: Pitfalls and promises. Can. J. Plant Sci. 94: 1025–1032. Arbuscular mycorrhizal fungi (AMF) reportedly produce glomalin, a glycoprotein that has the potential to increase soil carbon (C) and nitrogen (N) storage. We hypothesized that interactions between rhizosphere microorganisms, such as plant growth-promoting rhizobacteria (PGPR), and AMF, would influence glomalin production. Our objectives were to determine the effects of AMF/PGPR interactions on plant growth and glomalin production in the rhizosphere of pea (Pisum sativum L.) with the goal of enhancing C and N storage in the rhizosphere. One component of the study focussed on the molecular characterization of glomalin and glomalin-related soil protein (GRSP) using complementary synchrotron-based N and C X-ray absorption near-edge structure (XANES) spectroscopy, pyrolysis field ionization mass spectrometry (Py-FIMS), and proteomics techniques to characterize specific organic C and N fractions associated with glomalin production. Our research ultimately led us to conclude that the proteinaceous material extracted, and characterized in the literature, as GRSP is not exclusively of AMF origin. Our research supports the established concept that GRSP is important to soil quality, and C and N storage, irrespective of origin. However, efforts to manipulate this important soil C pool will remain compromised until we more clearly elucidate the chemical nature and origin of this resource.

scholarly journals Proximal sensing for soil carbon accounting

2018 ◽  
Author(s):  
Jacqueline R. England ◽  
Raphael Armando Viscarra Rossel
Keyword(s):  
Bulk Density ◽  
Financial Incentives ◽  
Management Practices ◽  
Ghg Emissions ◽  
Carbon Accounting ◽  
Soil Organic C ◽  
Proximal Sensing ◽  
Organic C ◽  
Soil C ◽  
Cost Efficient

Abstract. Maintaining or increasing soil organic carbon (C) is important for securing food production, and for mitigating greenhouse gas (GHG) emissions, climate change and land degradation. Some land management practices in cropping, grazing, horticultural and mixed farming systems can be used to increase organic C in soil, but to assess their effectiveness, we need accurate and cost-efficient methods for measuring and monitoring the change. To determine the stock of organic C in soil, one needs measurements of soil organic C concentration, bulk density and gravel content, but using conventional laboratory-based analytical methods is expensive. Our aim here is to review the current state of proximal sensing for the development of new soil C accounting methods for emissions reporting and in emissions reduction schemes. We evaluated sensing techniques in terms of their rapidity, cost, accuracy, safety, readiness and their state of development. The most suitable technique for measuring soil organic C concentrations appears to be vis–NIR spectroscopy and for bulk density active gamma-ray attenuation. Sensors for measuring gravel have not been developed, but an interim solution with rapid wet-sieving and automated measurement appears useful. Field-deployable, multi-sensor systems are needed for cost-efficient soil C accounting. Proximal sensing can be used for soil organic C accounting, but the methods need to be standardised and procedural guidelines need to be developed to ensure proficient measurement and accurate reporting and verification. This is particularly important if the schemes use financial incentives for landholders to adopt management practices to sequester soil organic C. We list and discuss the requirements for the development of new soil C accounting methods that are based on proximal sensing, including requirements for recording, verification and auditing.

Site-level simulations of measurable soil fractions with the Millennial V2 soil model

2021 ◽  
Author(s):  
Rose Abramoff ◽  
Bertrand Guenet ◽  
Haicheng Zhang ◽  
Katerina Georgiou ◽  
Xiaofeng Xu ◽  
...  
Keyword(s):  
C Sequestration ◽  
Current Understanding ◽  
Residence Times ◽  
Century Model ◽  
Mineral Association ◽  
Organic C ◽  
Soil C ◽  
Soil Fractions ◽  
Soil Model ◽  
Mean Residence Times

<p>Soil carbon (C) models are used to predict C sequestration responses to climate and land use change. Yet, the soil models embedded in Earth system models typically do not represent processes that reflect our current understanding of soil C cycling, such as microbial decomposition, mineral association, and aggregation. Rather, they rely on conceptual pools with turnover times that are fit to bulk C stocks and/or fluxes. As measurements of soil fractions become increasingly available, it is necessary for soil C models to represent these measurable quantities so that model processes can be evaluated more accurately. Here we present Version 2 (V2) of the Millennial model, a soil model developed in 2018 to simulate C pools that can be measured by extraction or fractionation, including particulate organic C, mineral-associated organic C, aggregate C, microbial biomass, and dissolved organic C. Model processes have been updated to reflect the current understanding of mineral-association, temperature sensitivity and reaction kinetics, and different model structures were tested within an open-source framework. We evaluated the ability of Millennial V2 to simulate total soil organic C (SOC), as well as the mineral-associated and particulate fractions, using three independent data sets of soil fractionation measurements spanning a range of climate and geochemistry in Australia (N=495), Europe (N=176), and across the globe (N=716). Considering RMSE and AIC as indices of model performance, site-level evaluations show that Millennial V2 predicts soil organic carbon content better than the widely-used Century model, despite an increase in process complexity and number of parameters. Millennial V2 also reproduces between-site variation in SOC across gradients of climate, plant productivity, and soil type. By including the additional constraints of measured soil fractions, we can predict site-level mean residence times similar to a global distribution of mean residence times measured using SOC/respiration rate under an assumption of steady state. The Millennial V2 model updates the conceptual Century model pools and processes and represents our current understanding of the roles that microbial activity, mineral association and aggregation play in soil C sequestration.</p>

Site-level simulations of measurable soil fractions with Millennial Version 2

2021 ◽  
Author(s):  
Rose Abramoff ◽  
Bertrand Guenet ◽  
Haicheng Zhang ◽  
Katerina Georgiou ◽  
Xiaofeng Xu ◽  
...  
Keyword(s):  
Meta Analysis ◽  
C Sequestration ◽  
Current Understanding ◽  
Century Model ◽  
Mineral Association ◽  
Microbial Decomposition ◽  
Organic C ◽  
Soil C ◽  
Soil Fractions ◽  
C Stocks

<p>Soil carbon (C) models are used to predict C sequestration responses to climate and land use change. Yet, the soil models embedded in Earth system models typically do not represent processes that reflect our current understanding of soil C cycling, such as microbial decomposition, mineral association, and aggregation. Rather, they rely on conceptual pools with turnover times that are fit to bulk C stocks and/or fluxes. As measurements of soil fractions become increasingly available, soil C models that represent these measurable quantities can be evaluated more accurately. Here we present Version 2 (V2) of the Millennial model, a soil model developed to simulate C pools that can be measured by extraction or fractionation, including particulate organic C, mineral-associated organic C, aggregate C, microbial biomass, and dissolved organic C. Model processes have been updated to reflect the current understanding of mineral-association, temperature sensitivity and reaction kinetics, and different model structures were tested within an open-source framework. We evaluated the ability of Millennial V2 to simulate total soil organic C (SOC), as well as the mineral-associated and particulate fractions, using three soil fractionation data sets spanning a range of climate and geochemistry in Australia (N=495), Europe (N=176), and across the globe (N=730). Millennial V2 (RMSE = 1.98 – 4.76 kg, AIC = 597 – 1755) generally predicts SOC content better than the widely-used Century model (RMSE = 2.23 – 4.8 kg, AIC = 584 – 2271), despite an increase in process complexity and number of parameters. Millennial V2 reproduces between-site variation in SOC across a gradient of plant productivity, and predicts SOC turnover times similar to those of a global meta-analysis. Millennial V2 updates the conceptual Century model pools and processes and represents our current understanding of the roles that microbial activity, mineral association and aggregation play in soil C sequestration.</p>

scholarly journals Evaluation of terrestrial pan-Arctic carbon cycling using a data-assimilation system

2019 ◽  
Vol 10 (2) ◽  
pp. 233-255 ◽  
Author(s):  
Efrén López-Blanco ◽  
Jean-François Exbrayat ◽  
Magnus Lund ◽  
Torben R. Christensen ◽  
Mikkel P. Tamstorf ◽  
...  
Keyword(s):  
The Arctic ◽  
Soil Organic C ◽  
Area Index ◽  
Organic C ◽  
Soil C ◽  
Transit Times ◽  
C Cycle ◽  
C Stocks ◽  
Data Assimilation System ◽  
Assimilation System

Abstract. There is a significant knowledge gap in the current state of the terrestrial carbon (C) budget. Recent studies have highlighted a poor understanding particularly of C pool transit times and of whether productivity or biomass dominate these biases. The Arctic, accounting for approximately 50 % of the global soil organic C stocks, has an important role in the global C cycle. Here, we use the CARbon DAta MOdel (CARDAMOM) data-assimilation system to produce pan-Arctic terrestrial C cycle analyses for 2000–2015. This approach avoids using traditional plant functional type or steady-state assumptions. We integrate a range of data (soil organic C, leaf area index, biomass, and climate) to determine the most likely state of the high-latitude C cycle at a 1∘ × 1∘ resolution and also to provide general guidance about the controlling biases in transit times. On average, CARDAMOM estimates regional mean rates of photosynthesis of 565 g C m−2 yr−1 (90 % confidence interval between the 5th and 95th percentiles: 428, 741), autotrophic respiration of 270 g C m−2 yr−1 (182, 397) and heterotrophic respiration of 219 g C m−2 yr−1 (31, 1458), suggesting a pan-Arctic sink of −67 (−287, 1160) g Cm−2 yr−1, weaker in tundra and stronger in taiga. However, our confidence intervals remain large (and so the region could be a source of C), reflecting uncertainty assigned to the regional data products. We show a clear spatial and temporal agreement between CARDAMOM analyses and different sources of assimilated and independent data at both pan-Arctic and local scales but also identify consistent biases between CARDAMOM and validation data. The assimilation process requires clearer error quantification for leaf area index (LAI) and biomass products to resolve these biases. Mapping of vegetation C stocks and change over time and soil C ages linked to soil C stocks is required for better analytical constraint. Comparing CARDAMOM analyses to global vegetation models (GVMs) for the same period, we conclude that transit times of vegetation C are inconsistently simulated in GVMs due to a combination of uncertainties from productivity and biomass calculations. Our findings highlight that GVMs need to focus on constraining both current vegetation C stocks and net primary production to improve a process-based understanding of C cycle dynamics in the Arctic.

Douglas-fir soil C and N properties a decade after termination of urea fertilization

2001 ◽  
Vol 31 (12) ◽  
pp. 2225-2236 ◽  
Author(s):  
Peter S Homann ◽  
Bruce A Caldwell ◽  
H N Chappell ◽  
Phillip Sollins ◽  
Chris W Swanston
Keyword(s):  
Mineral Soil ◽  
Cellulase Activity ◽  
Douglas Fir ◽  
Soil Organic C ◽  
Total N ◽  
Organic C ◽  
Soil C ◽  
Second Growth ◽  
Heavy Fractions ◽  
Urea Fertilization

Chemical and microbial soil properties were assessed in paired unfertilized and urea fertilized (>89 g N·m–2) plots in 13 second-growth Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco) stands distributed throughout western Washington and Oregon. A decade following the termination of fertilization, fertilized plots averaged 28% higher total N in the O layer than unfertilized plots, 24% higher total N in surface (0–5 cm) mineral soil, and up to four times the amount of extractable ammonium and nitrate. Decreased pH (0.2 pH units) caused by fertilization may have been due to nitrification or enhanced cation uptake. In some soil layers, fertilization decreased cellulase activity and soil respiration but increased wood decomposition. There was no effect of fertilization on concentrations of light and heavy fractions, labile carbohydrates, and phosphatase and xylanase activities. No increase in soil organic C was detected, although variability precluded observing an increase of less than ~15%. Lack of a regionwide fertilization influence on soil organic C contrasts with several site-specific forest and agricultural studies that have shown C increases resulting from fertilization. Overall, the results indicate a substantial residual influence on soil N a decade after urea fertilization but much more limited influence on soil C processes and pools.

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