Bolstering fitness via CO2 fixation and organic carbon uptake: mixotrophs in modern groundwater

AbstractCurrent understanding of organic carbon inputs into ecosystems lacking photosynthetic primary production is predicated on data and inferences derived almost entirely from metagenomic analyses. The elevated abundances of putative chemolithoautotrophs in groundwaters suggest that dark CO2 fixation is an integral component of subsurface trophic webs. To understand the impact of autotrophically fixed carbon, the flux of CO2-derived carbon through various populations of subsurface microbiota must first be resolved, both quantitatively and temporally. Here we implement novel Stable Isotope Cluster Analysis to render a time-resolved and quantitative evaluation of 13CO2-derived carbon flow through a groundwater community in microcosms stimulated with reduced sulfur compounds. We demonstrate that mixotrophs, not strict autotrophs, were the most abundant active organisms in groundwater microcosms. Species of Hydrogenophaga, Polaromonas, Dechloromonas, and other metabolically versatile mixotrophs drove the production and remineralization of organic carbon. Their activity facilitated the replacement of 43% and 80% of total microbial carbon stores in the groundwater microcosms with 13C in just 21 and 70 days, respectively. The mixotrophs employed different strategies for satisfying their carbon requirements by balancing CO2 fixation and uptake of available organic compounds. These different strategies might provide fitness under nutrient-limited conditions, explaining the great abundances of mixotrophs in other oligotrophic habitats, such as the upper ocean and boreal lakes.

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Chemical Transport Facilitated by Multiphase Flow Systems1

Water Science & Technology ◽

10.2166/wst.1985.0078 ◽

1985 ◽

Vol 17 (9) ◽

pp. 1-12 ◽

Cited By ~ 11

Author(s):

Carl G. Enfield

Keyword(s):

Organic Carbon ◽

Boundary Conditions ◽

Transport Equation ◽

Fluid Phase ◽

Chemical Transport ◽

Facilitated Transport ◽

Organic Fraction ◽

Dispersive Transport ◽

Transformation Of Variables ◽

The Impact

Relatively immobile chemicals have been observed moving significantly faster than anticipated from hydrophobic theory. A theory is developed considering transport in three mobile fluid phases which can be used to describe this facilitated transport. The convective dispersive transport equation is solved utilizing a transformation of variables which permits utilizing existing solutions covering a wide variety of boundary conditions. The impact of the facilitated transport is demonstrated for one case where the soils organic carbon is 10%. If 2% of the fluid phase is an organic fraction, the theory developed projects that hydrophobic theory may underestimate mobility by more than 100 times. At concentrations of dissolved organic carbon normally observed in nature (5 - 10 mg/l), a measurable increased mobility is anticipated for the very immobile compounds like dioxins.

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From the Ground Up: Prairies on Reclaimed Mine Land—Impacts on Soil and Vegetation

Land ◽

10.3390/land9110455 ◽

2020 ◽

Vol 9 (11) ◽

pp. 455

Author(s):

Rebecca M. Swab ◽

Nicola Lorenz ◽

Nathan R. Lee ◽

Steven W. Culman ◽

Richard P. Dick

Keyword(s):

Organic Carbon ◽

Soil Organic Carbon ◽

Soil Properties ◽

Plant Community ◽

Prairie Restoration ◽

Native Plant ◽

Soil Microbial ◽

Prairie Restorations ◽

Mine Lands ◽

The Impact

After strip mining, soils typically suffer from compaction, low nutrient availability, loss of soil organic carbon, and a compromised soil microbial community. Prairie restorations can improve ecosystem services on former agricultural lands, but prairie restorations on mine lands are relatively under-studied. This study investigated the impact of prairie restoration on mine lands, focusing on the plant community and soil properties. In southeast Ohio, 305 ha within a ~2000 ha area of former mine land was converted to native prairie through herbicide and planting between 1999–2016. Soil and vegetation sampling occurred from 2016–2018. Plant community composition shifted with prairie age, with highest native cover in the oldest prairie areas. Prairie plants were more abundant in older prairies. The oldest prairies had significantly more soil fungal biomass and higher soil microbial biomass. However, many soil properties (e.g., soil nutrients, β-glucosoidase activity, and soil organic carbon), as well as plant species diversity and richness trended higher in prairies, but were not significantly different from baseline cool-season grasslands. Overall, restoration with prairie plant communities slowly shifted soil properties, but mining disturbance was still the most significant driver in controlling soil properties. Prairie restoration on reclaimed mine land was effective in establishing a native plant community, with the associated ecosystem benefits.

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Organic mulching promotes soil organic carbon accumulation to deep soil layer in an urban plantation forest

Forest Ecosystems ◽

10.1186/s40663-020-00278-5 ◽

2021 ◽

Vol 8 (1) ◽

Author(s):

Xiaodan Sun ◽

Gang Wang ◽

Qingxu Ma ◽

Jiahui Liao ◽

Dong Wang ◽

...

Keyword(s):

Organic Carbon ◽

Soil Organic Carbon ◽

Carbon Content ◽

Fine Roots ◽

Soil Layer ◽

Carbon Accumulation ◽

Bulk Soil ◽

Organic Mulch ◽

The Impact ◽

Soc Fractions

Abstract Background Soil organic carbon (SOC) is important for soil quality and fertility in forest ecosystems. Labile SOC fractions are sensitive to environmental changes, which reflect the impact of short-term internal and external management measures on the soil carbon pool. Organic mulching (OM) alters the soil environment and promotes plant growth. However, little is known about the responses of SOC fractions in rhizosphere or bulk soil to OM in urban forests and its correlation with carbon composition in plants. Methods A one-year field experiment with four treatments (OM at 0, 5, 10, and 20 cm thicknesses) was conducted in a 15-year-old Ligustrum lucidum plantation. Changes in the SOC fractions in the rhizosphere and bulk soil; the carbon content in the plant fine roots, leaves, and organic mulch; and several soil physicochemical properties were measured. The relationships between SOC fractions and the measured variables were analysed. Results The OM treatments had no significant effect on the SOC fractions, except for the dissolved organic carbon (DOC). OM promoted the movement of SOC to deeper soil because of the increased carbon content in fine roots of subsoil. There were significant correlations between DOC and microbial biomass carbon and SOC and easily oxidised organic carbon. The OM had a greater effect on organic carbon fractions in the bulk soil than in the rhizosphere. The thinnest (5 cm) mulching layers showed the most rapid carbon decomposition over time. The time after OM had the greatest effect on the SOC fractions, followed by soil layer. Conclusions The frequent addition of small amounts of organic mulch increased SOC accumulation in the present study. OM is a potential management model to enhance soil organic matter storage for maintaining urban forest productivity.

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Dynamics of soil organic carbon in the steppes of Russia and Kazakhstan under past and future climate and land use

Regional Environmental Change ◽

10.1007/s10113-021-01799-7 ◽

2021 ◽

Vol 21 (3) ◽

Author(s):

Susanne Rolinski ◽

Alexander V. Prishchepov ◽

Georg Guggenberger ◽

Norbert Bischoff ◽

Irina Kurganova ◽

...

Keyword(s):

Climate Change ◽

Land Use ◽

Organic Carbon ◽

Land Use Change ◽

Soil Organic Carbon ◽

Arable Land ◽

Future Climate ◽

Future Climate Change ◽

Climate Scenarios ◽

The Impact

AbstractChanges in land use and climate are the main drivers of change in soil organic matter contents. We investigated the impact of the largest policy-induced land conversion to arable land, the Virgin Lands Campaign (VLC), from 1954 to 1963, of the massive cropland abandonment after 1990 and of climate change on soil organic carbon (SOC) stocks in steppes of Russia and Kazakhstan. We simulated carbon budgets from the pre-VLC period (1900) until 2100 using a dynamic vegetation model to assess the impacts of observed land-use change as well as future climate and land-use change scenarios. The simulations suggest for the entire VLC region (266 million hectares) that the historic cropland expansion resulted in emissions of 1.6⋅ 1015 g (= 1.6 Pg) carbon between 1950 and 1965 compared to 0.6 Pg in a scenario without the expansion. From 1990 to 2100, climate change alone is projected to cause emissions of about 1.8 (± 1.1) Pg carbon. Hypothetical recultivation of the cropland that has been abandoned after the fall of the Soviet Union until 2050 may cause emissions of 3.5 (± 0.9) Pg carbon until 2100, whereas the abandonment of all cropland until 2050 would lead to sequestration of 1.8 (± 1.2) Pg carbon. For the climate scenarios based on SRES (Special Report on Emission Scenarios) emission pathways, SOC declined only moderately for constant land use but substantially with further cropland expansion. The variation of SOC in response to the climate scenarios was smaller than that in response to the land-use scenarios. This suggests that the effects of land-use change on SOC dynamics may become as relevant as those of future climate change in the Eurasian steppes.

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Impact of crop residue management on crop production and soil chemistry after seven years of crop rotation in temperate climate, loamy soils

PeerJ ◽

10.7717/peerj.4836 ◽

2018 ◽

Vol 6 ◽

pp. e4836 ◽

Cited By ~ 20

Author(s):

Marie-Pierre Hiel ◽

Sophie Barbieux ◽

Jérôme Pierreux ◽

Claire Olivier ◽

Guillaume Lobet ◽

...

Keyword(s):

Organic Carbon ◽

Crop Production ◽

Crop Residue ◽

Crop Residues ◽

Conventional Tillage ◽

Residue Management ◽

Temperate Climate ◽

Reduced Tillage ◽

Crop Residue Management ◽

The Impact

Society is increasingly demanding a more sustainable management of agro-ecosystems in a context of climate change and an ever growing global population. The fate of crop residues is one of the important management aspects under debate, since it represents an unneglectable quantity of organic matter which can be kept in or removed from the agro-ecosystem. The topic of residue management is not new, but the need for global conclusion on the impact of crop residue management on the agro-ecosystem linked to local pedo-climatic conditions has become apparent with an increasing amount of studies showing a diversity of conclusions. This study specifically focusses on temperate climate and loamy soil using a seven-year data set. Between 2008 and 2016, we compared four contrasting residue management strategies differing in the amount of crop residues returned to the soil (incorporation vs. exportation of residues) and in the type of tillage (reduced tillage (10 cm depth) vs. conventional tillage (ploughing at 25 cm depth)) in a field experiment. We assessed the impact of the crop residue management on crop production (three crops—winter wheat, faba bean and maize—cultivated over six cropping seasons), soil organic carbon content, nitrate (${\mathrm{NO}}_{3}^{-}$), phosphorus (P) and potassium (K) soil content and uptake by the crops. The main differences came primarily from the tillage practice and less from the restitution or removal of residues. All years and crops combined, conventional tillage resulted in a yield advantage of 3.4% as compared to reduced tillage, which can be partly explained by a lower germination rate observed under reduced tillage, especially during drier years. On average, only small differences were observed for total organic carbon (TOC) content of the soil, but reduced tillage resulted in a very clear stratification of TOC and also of P and K content as compared to conventional tillage. We observed no effect of residue management on the ${\mathrm{NO}}_{3}^{-}$ content, since the effect of fertilization dominated the effect of residue management. To confirm the results and enhance early tendencies, we believe that the experiment should be followed up in the future to observe whether more consistent changes in the whole agro-ecosystem functioning are present on the long term when managing residues with contrasted strategies.

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Modelling long-term soil organic carbon dynamics under the impact of land cover change and soil redistribution

CATENA ◽

10.1016/j.catena.2016.12.008 ◽

2017 ◽

Vol 151 ◽

pp. 63-73 ◽

Cited By ~ 7

Author(s):

Samuel Bouchoms ◽

Zhengang Wang ◽

Veerle Vanacker ◽

Sebastian Doetterl ◽

Kristof Van Oost

Keyword(s):

Organic Carbon ◽

Soil Organic Carbon ◽

Land Cover ◽

Land Cover Change ◽

Carbon Dynamics ◽

Soil Redistribution ◽

The Impact ◽

Soil Organic Carbon Dynamics

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Effect of Tillage Systems on Soil Organic Carbon and Soil Quality in a Purple Paddy Soil

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.183-185.1190 ◽

2011 ◽

Vol 183-185 ◽

pp. 1190-1194

Author(s):

Jun Ke Zhang ◽

Qing Ju Hao ◽

Chang Sheng Jiang ◽

Yan Wu

Keyword(s):

Organic Carbon ◽

Soil Quality ◽

Paddy Soil ◽

Conventional Tillage ◽

Water Infiltration ◽

Purple Soil ◽

Tillage Systems ◽

Field Station ◽

No Till ◽

The Impact

The impact of conservation tillage practices on carbon sequestration has been of great interest in recent years. This experiment analyzed the organic carbon status of soils sampled at depth increments from 0 to 60 cm after 20 years in a purple paddy soil. The tillage experiment was established in the Key Field Station for Monitoring of Eco-Environment of Purple Soil of the Ministry of Agriculture of China, located in the farm of Southwest University (30°26′N, 106°26′E), Chongqing. In this paper, five tillage treatments including conventional tillage with rice only system (DP), conventional tillage with rotation of rice and rape system (SL), no-till and ridge culture with rotation of rice and rape system (LM), no-till and plain culture with rotation of rice and rape system (XM) and tillage and ridge culture with rotation of rice and rape system (LF) were selected as research objectives to measure SOC storage and stratification ratio of SOC (CSR). The SOC storage under different tillage systems was calculated based on an equivalent soil mass. The CSR can be used as an indicator of soil quality because surface organic matter is essential to erosion control, water infiltration, and the conservation of nutrients. Results showed that in soil under no-till SOC was concentrated near the surface, while in tilled soil SOC decreased equably with the increase of soil depth. The difference of SOC contents between the five tillage systems was the largest in the top soil and the lowest in the bottom soil. The order of SOC storage was LM (158.52 Mg C•ha-1) >DP (106.74 Mg C•ha-1) >XM (100.11 Mg C•ha-1) >LF (93.11 Mg C•ha-1) >SL (88.59 Mg C•ha-1), LM treatment was significantly higher than the other treatments. The CSR of 0-10/50-60 cm was 2.65, 2.70 and 2.14 under LM, XM and LF treatments, while 1.54 and 1.92 under DP and SL treatments. We considered CSR>2 indicate an improvement in soil quality produced by changing from tillage to no-tillage, as well as changing from plane to ridge. Overall, long-term LM treatment is a valid strategy for increasing SOC storage and improving soil quality in a purple paddy soil in Southwest China.

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Aerosol distribution over Europe: a model evaluation study with detailed aerosol microphysics

Atmospheric Chemistry and Physics ◽

10.5194/acp-8-1591-2008 ◽

2008 ◽

Vol 8 (6) ◽

pp. 1591-1607 ◽

Cited By ~ 36

Author(s):

B. Langmann ◽

S. Varghese ◽

E. Marmer ◽

E. Vignati ◽

J. Wilson ◽

...

Keyword(s):

Organic Carbon ◽

Rural Areas ◽

Regional Scale ◽

Evaluation Study ◽

Emission Data ◽

Aerosol Model ◽

Fire Emissions ◽

Elevated Ozone ◽

Emission Fluxes ◽

The Impact

Abstract. This paper summarizes an evaluation of model simulations with a regional scale atmospheric climate-chemistry/aerosol model called REMOTE, which has been extended by a microphysical aerosol module. Model results over Europe are presented and compared with available measurements in surface air focusing on the European distribution and variability of primary and secondary aerosols. Additionally, model results obtained with detailed aerosol microphysics are compared to those based on an aerosol bulk mass approach revealing the impact of dry deposition fluxes on atmospheric burden concentration. An improved determination of elevated ozone and sulfate concentrations could be achieved by considering a diurnal cycle in the anthropogenic emission fluxes. Deviation between modelled and measured organic carbon concentrations can be mainly explained by missing formation of secondary organic aerosols and deficiencies in emission data. Changing residential heating practices in Europe, where the use of wood is no longer restricted to rural areas, need to be considered in emission inventories as well as vegetation fire emissions which present a dominant source of organic carbon.

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