Elevated CO2 increases plant growth but reduces soil C storage under N limiting conditions

2020 ◽  
Author(s):  
Lucia M. Eder ◽  
Enrico Weber ◽  
Johannes Rousk ◽  
Marion Schrumpf ◽  
Sönke Zaehle
Keyword(s):  
Plant Growth ◽  
Root Exudation ◽  
Beech Forest ◽  
Coarse Roots ◽  
Soil System ◽  
Soil C ◽  
N Nutrition ◽  
N Limitation ◽  
C Storage ◽  
C And N

<p>Rising atmospheric CO<sub>2</sub> concentrations may induce or aggravate nitrogen (N) limitation to plant growth. To overcome this limitation, plants may invest their newly assimilated carbon (C) into N acquiring strategies, such as root growth, root exudation or C allocation to mycorrhizal symbionts. These shifts in C allocation can increase the turnover of soil organic matter by stimulating microbial activity. As these processes are poorly quantified, their net effects on ecosystem C storage remain uncertain.</p><p>To gain a better quantitative understanding of these processes, we assessed the effect of elevated CO<sub>2</sub> on plant C and N allocation in a mesocosm experiment. For four months of one growing season, 64 saplings of Fagus sylvatica L. were grown in a natural beech forest topsoil. Plants were exposed to near ambient (390 ppm) or elevated (560 ppm, eCO<sub>2</sub>) CO<sub>2</sub> concentrations at two levels of continuous <sup>13</sup>CO<sub>2</sub> enrichment (δ<sup>13</sup>C +50 or +150‰). At the end of the experiment, we determined dry biomass, C and N concentrations and isotopic compositions for all leaves, buds, twigs, stems and fine and coarse roots for all plants. For all plants, C and N budgets and the amount of newly incorporated C were evaluated.</p><p>We found a positive effect of eCO<sub>2</sub> on tree growth, with the highest growth response in fine root biomass. In both CO<sub>2</sub> treatments, newly fixed C was preferentially allocated to roots compared to other plant compartments, but under eCO<sub>2</sub>, we found a shift in C allocation patterns towards higher belowground C allocation. These results suggest enhanced plant investments into belowground resource acquisition. Decreased N concentrations in all plant organs of these trees under eCO<sub>2</sub> may indicate plant N limitation and suggest that the effect of increased belowground C allocation was insufficient to fulfil the plants N demand. Still, the observed increase in C allocation to microbial biomass in these soils may be a mechanism to enhance plant N nutrition. CO<sub>2</sub> concentrations also affected C allocation within the whole plant-soil-system: Under eCO<sub>2</sub>, more C was stored in tree biomass and less C was stored in soils. Overall, there was no effect of CO<sub>2</sub> treatment on total mesocosm C. We will discuss these findings with regard to the N mining hypothesis.</p>

Post-thinning soil organic matter evolution and soil CO2 effluxes in temperate radiata pine plantations: impacts of moderate thinning regimes on the forest C cycle

2012 ◽  
Vol 42 (11) ◽  
pp. 1953-1964 ◽  
Author(s):  
Irene Fernandez ◽  
Juan Gabriel Álvarez-González ◽  
Beatríz Carrasco ◽  
Ana Daría Ruíz-González ◽  
Ana Cabaneiro
Keyword(s):  
Organic Matter ◽  
Soil Organic Matter ◽  
Radiata Pine ◽  
Soil Samples ◽  
Mitigation Strategies ◽  
Change Scenario ◽  
Soil C ◽  
C Storage ◽  
C Cycle ◽  
C And N

Forest ecosystems can act as C sinks, thus absorbing a high percentage of atmospheric CO2. Appropriate silvicultural regimes can therefore be applied as useful tools in climate change mitigation strategies. The present study analyzed the temporal changes in the effects of thinning on soil organic matter (SOM) dynamics and on soil CO2 emissions in radiata pine ( Pinus radiata D. Don) forests. Soil C effluxes were monitored over a period of 2 years in thinned and unthinned plots. In addition, soil samples from the plots were analyzed by solid-state 13C-NMR to determine the post-thinning SOM composition and fresh soil samples were incubated under laboratory conditions to determine their biodegradability. The results indicate that the potential soil C mineralization largely depends on the proportion of alkyl-C and N-alkyl-C functional groups in the SOM and on the microbial accessibility of the recalcitrant organic pool. Soil CO2 effluxes varied widely between seasons and increased exponentially with soil heating. Thinning led to decreased soil respiration and attenuation of the seasonal fluctuations. These effects were observed for up to 20 months after thinning, although they disappeared thereafter. Thus, moderate thinning caused enduring changes to the SOM composition and appeared to have temporary effects on the C storage capacity of forest soils, which is a critical aspect under the current climatic change scenario.

Comparison of carbon and nitrogen storage in mineral soils of graminoid and shrub tundra sites, western Greenland

2016 ◽  
Vol 2 (4) ◽  
pp. 165-182 ◽  
Author(s):  
Chelsea L. Petrenko ◽  
Julia Bradley-Cook ◽  
Emily M. Lacroix ◽  
Andrew J. Friedland ◽  
Ross A. Virginia
Keyword(s):  
Vegetation Type ◽  
Mineral Soil ◽  
Biotic Interactions ◽  
The Arctic ◽  
Soil C ◽  
N Storage ◽  
C Storage ◽  
Arctic Soils ◽  
C Pools ◽  
C And N

Shrub species are expanding across the Arctic in response to climate change and biotic interactions. Changes in belowground carbon (C) and nitrogen (N) storage are of global importance because Arctic soils store approximately half of global soil C. We collected 10 (60 cm) soil cores each from graminoid- and shrub-dominated soils in western Greenland and determined soil texture, pH, C and N pools, and C:N ratios by depth for the mineral soil. To investigate the relative chemical stability of soil C between vegetation types, we employed a novel sequential extraction method for measuring organo-mineral C pools of increasing bond strength. We found that (i) mineral soil C and N storage was significantly greater under graminoids than shrubs (29.0 ± 1.8 versus 22.5 ± 3.0 kg·C·m−2 and 1.9 ± .12 versus 1.4 ± 1.9 kg·N·m−2), (ii) chemical mechanisms of C storage in the organo-mineral soil fraction did not differ between graminoid and shrub soils, and (iii) weak adsorption to mineral surfaces accounted for 40%–60% of C storage in organo-mineral fractions — a pool that is relatively sensitive to environmental disturbance. Differences in these C pools suggest that rates of C accumulation and retention differ by vegetation type, which could have implications for predicting future soil C pool storage.

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.

Texture effects on carbon stabilisation and storage in New Zealand soils containing predominantly 2 : 1 clays

Soil Research ◽  
2016 ◽  
Vol 54 (1) ◽  
pp. 30 ◽  
Author(s):  
Denis Curtin ◽  
Michael H. Beare ◽  
Weiwen Qiu
Keyword(s):  
New Zealand ◽  
Clay Fraction ◽  
Clay Content ◽  
Soil C ◽  
Particle Size Fractions ◽  
C Storage ◽  
Physico Chemical ◽  
Wide Range ◽  
Mass Proportion ◽  
C And N

Developing strategies to sequester carbon (C) in soils requires an understanding of the key factors that influence C stabilisation. Although fine mineral particles, especially clay, play a key role in stabilising soil organic matter (SOM), the relationship between SOM and texture is often not strong. We examined the role of the fine mineral fraction in C storage in sedimentary soils in New Zealand. Soils, representing two soil Orders (Brown and Recent) and different land use histories (total of 58 soils; 0–15 cm depth) were sampled. The concentration of C (and N) in four particle size fractions (<5, 5–20, 20–50, >50 µm) was determined (soils fractionated after dispersion by sonication). The soils had a wide range of textures and SOM; the mass proportion of clay (<5 µm) ranged from 10 to 60 g 100 g–1 and soil C from 16 to 45 g kg–1. Across both soil Orders and all land uses (dairy, sheep or beef, arable and vegetable cropping), the majority of soil C (57 to 66%) was stored in the clay fraction. However, there was no correlation (R2 = 0.02; P > 0.05) between the C concentration in whole soil and clay content. The concentration of C in the clay fraction, which varied over a wide range (35 to 135 g kg–1 clay), decreased as the mass proportion of clay increased. A similar trend in C concentration was observed for the fine (5–20 µm) silt fraction. Because of this inverse relationship between the mass of the fine fractions and their C concentration, there was little change in amount of stable C (defined as C in the <20 µm fraction) as the mass proportion of fine (<20 µm) particles increased. Differences in pyrophosphate extractable aluminium explained part of the variability in C concentration in the fine fractions; however, we were unable to identify any specific physico-chemical factor that would account for the relatively low C concentrations observed in the <5 and 5–20 µm fractions of fine-textured soils. We concluded that such soils may be under-saturated and potential may exist to store additional stable C.

scholarly journals Mineralisation, leaching and stabilisation of <sup>13</sup>C-labelled leaf and twig litter in a beech forest soil

2011 ◽  
Vol 8 (8) ◽  
pp. 2195-2208 ◽  
Author(s):  
A. Kammer ◽  
F. Hagedorn
Keyword(s):  
Leaf Litter ◽  
Mineral Soil ◽  
Soil Surface ◽  
Field Studies ◽  
Beech Forest ◽  
Organic C ◽  
Soil C ◽  
C Storage ◽  
Swiss Jura ◽  
C Mineralisation

Abstract. Very few field studies have quantified the different pathways of C loss from decomposing litter even though the partitioning of C fluxes is essential to understand soil C dynamics. Using 0.75 kg m−2 of 13C-depleted leaf (δ13C = −40.8 ‰) and 2 kg m−2 of twig litter (δ13C = −38.4 ‰), we tracked the litter-derived C in soil CO2 effluxes, dissolved organic C (DOC), and soil organic matter of a beech forest in the Swiss Jura. Autotrophic respiration was reduced by trenching. Our results show that mineralisation was the main pathway of C loss from decomposing litter over 1 yr, amounting to 24 and 31 % of the added twig and leaf litter. Contrary to our expectations, the leaf litter C was mineralised only slightly (1.2 times) more rapidly than the twig litter C. The leaching of DOC from twigs amounted to half of that from leaves throughout the experiment (2 vs. 4 % of added litter C). Tracing the litter-derived DOC in the soil showed that DOC from both litter types was mostly removed (88–96 %) with passage through the top centimetres of the mineral soil (0–5 cm) where it might have been stabilised. In the soil organic C at 0–2 cm depth, we indeed recovered 4 % of the initial twig C and 8 % of the leaf C after 1 yr. Much of the 13C-depleted litter remained on the soil surface throughout the experiment: 60 % of the twig litter C and 25 % of the leaf litter C. From the gap in the 13C-mass balance based on C mineralisation, DOC leaching, C input into top soils, and remaining litter, we inferred that another 30 % of the leaf C but only 10 % of twig C could have been transported via soil fauna to soil depths below 2 cm. In summary, over 1 yr, twig litter was mineralised more rapidly relative to leaf litter than expected, and much less of the twig-derived C was transported to the mineral soil than of the leaf-derived C. Both findings provide some evidence that twig litter could contribute less to the C storage in these base-rich forest soils than leaf litter.

Total belowground carbon and nitrogen partitioning of mature black spruce displaying genetic × soil moisture interaction in growth

2012 ◽  
Vol 42 (11) ◽  
pp. 1939-1952 ◽  
Author(s):  
John E. Major ◽  
Kurt H. Johnsen ◽  
Debby C. Barsi ◽  
Moira Campbell
Keyword(s):  
Fine Roots ◽  
Root Biomass ◽  
Black Spruce ◽  
Soil Depth ◽  
C Sequestration ◽  
Nitrogen Partitioning ◽  
Coarse Roots ◽  
Soil C ◽  
Coarse Root ◽  
C And N

Total belowground biomass, soil C, and N mass were measured in plots of 32-year-old black spruce ( Picea mariana (Mill.) Britton, Sterns & Poggenb.) from four full-sib families studied previously for drought tolerance and differential productivity on a dry and a wet site. Stump root biomass was greater on the wet than on the dry site; however, combined fine and coarse root biomass was greater on the dry than on the wet site, resulting in no site root biomass differences. There were no site differences in root distribution by soil depth. Drought-tolerant families had greater stump root biomass and allocated relatively less to combined coarse and fine roots than drought-intolerant families. Fine roots (<2 mm) made up 10.9% and 50.2% of the belowground C and N biomass. Through 50 cm soil depth, mean total belowground C mass was 187.2 Mg·ha–1, of which 8.9%, 3.4%, 0.7%, and 87.0% were from the stump root, combined fine and coarse roots, necromass, and soil, respectively. Here, we show that belowground C sequestration generally mirrors (mostly from stump roots) aboveground growth, and thus, trends in genetic and genetic × environment productivity effects result in similar effects on belowground C sequestration. Thus, tree improvement may well be an important avenue to help stem increases in atmospheric CO2.

Carbon Accumulation and Partitioning Above and Belowground under Coppiced and Replanted Eucalypt Plantations

2021 ◽  
Author(s):  
Rodinei F Pegoraro ◽  
Ivo R Silva ◽  
Ivan F Souza ◽  
Roberto F Novais ◽  
Nairam F Barros ◽  
...  
Keyword(s):  
Genetic Material ◽  
Carbon Accumulation ◽  
Sink Strength ◽  
Large Contribution ◽  
Forest Residues ◽  
Coarse Roots ◽  
Soil C ◽  
C Storage ◽  
Eucalypt Plantations ◽  
C Stocks

Abstract The extent to which the C sink strength of eucalypt plantations can be affected by coppicing or replanting remains unclear. To address this issue, we evaluated variations in C stocks under coppiced or replanted eucalypt stands formed by clones or seedlings. For each field assessment (0 [T0], 2.5, 3.5, 4.5, 5.5 and 7.0 years [at harvest]), tree biomass, litterfall, and soil C stocks (0–120 cm depth) were determined. At harvest, debarked stemwood productivity was similar under coppice or replanting, about 50.0 Mg C ha–1. Generally, coppiced stands favored subsoil C storage (40–100 cm), whereas replanted stands favored soil C accrual in topsoil (0–20 cm), depending on the genetic material. Relative to T0, soil C increased about 2.14, 1.91, and 1.84 Mg C ha–1 yr–1 under coppice, replanting with seedlings and clones, respectively. Coarse root biomass under these stands were about 17.3, 13.4, and 9.5 Mg C ha–1, respectively, equivalent to 50% of total harvest residues. Hence, inputs from coarse roots could represent a large contribution to soil C over multiple rotations under coppiced or replanted stands. Otherwise, short-term C losses can be high where stumps and coarse roots are harvested, especially following successive coppice cycles. Study Implications: Our findings have important implications for forest managers growing eucalypt plantations aiming to maximize C accumulation. Both coppiced and replanted stands can fix up to 50 Mg C ha−1 only in debarked stemwood over 7 years, with a comparatively higher C storage in coarse roots under coppice. Despite the increasing demand for forest residues in bioenergy production, harvesting stumps and coarse roots should be avoided, especially upon replanting eucalypt stands after successive coppice cycles.

Exploiting inter-organismal chemical communication for improved inoculants

2006 ◽  
Vol 86 (4) ◽  
pp. 951-966 ◽  
Author(s):  
Fazli Mabood ◽  
Elizabeth J Gray ◽  
Kyung D Lee ◽  
Donald L Smith
Keyword(s):  
Plant Growth ◽  
Recent Work ◽  
Plant Growth Promoting Rhizobacteria ◽  
Direct Stimulation ◽  
Soil C ◽  
Fuel Prices ◽  
C Storage ◽  
Plant Growth Promoting ◽  
Adverse Environmental Conditions ◽  
Cell Densities

The combination of rising fossil fuel prices and a need to reduce greenhouse gas emissions will lead to expanded use of crop inoculants (bio-fertilizers) both for increased production of biomass (for bio-fuels and soil C storage) and to reduce production of nitrous oxide, through increased reliance on biological nitrogen fixation. Over the last century inoculants have been improved through strain selection, improved carriers (including sterile carriers), and increased cell densities. During the last few decades our understanding of signalling between symbiotic bacteria and plants has expanded enormously, with the signalling between rhizobia and their legume hosts being the model system. Recent work has shown that adverse environmental conditions can inhibit this signalling and that addition of plant-to-microbe signals into inoculants can help overcome this. This is also true of addition of the microbe-to-plant signals that act as the return signals of this system; however, they have also been shown to cause a general and direct stimulation of plant growth that is not yet well understood. Finally, very recent work has shown that some of the plant growth-promoting rhizobacteria produce novel signal compounds that stimulate plant growth. This is a time of rapid increase in understanding with regard to plant-microbe signalling; the use of these signals in commercial inoculants offers a new wave in innovations for this industry at a time when there is great need. Key words: Inoculants, rhizobacteria, rhizobia, signalling

scholarly journals Nitrate uptake and carbon exudation – do plant roots stimulate or inhibit denitrification?

2020 ◽  
Author(s):  
Pauline Sophie Rummel ◽  
Reinhard Well ◽  
Birgit Pfeiffer ◽  
Klaus Dittert ◽  
Sebastian Floßmann ◽  
...  
Keyword(s):  
Soil Moisture ◽  
Plant Growth ◽  
Nitrate Uptake ◽  
N Uptake ◽  
Root Exudation ◽  
Mineral N ◽  
Double Labeling ◽  
Organic C ◽  
C And N

Abstract Background and aims Plant growth affects soil moisture, mineral N and organic C availability in soil, all of which influence denitrification. With increasing plant growth, root exudation may stimulate denitrification, while N uptake restricts nitrate availability. Methods We conducted a double labeling pot experiment with either maize (Zea mays L.) or cup plant (Silphium perfoliatum L.) of the same age but differing in size of their shoot and root systems. The 15N gas flux method was applied to directly quantify N2O and N2 fluxes in situ. To link denitrification with available C in the rhizosphere, 13CO2 pulse labeling was used to trace C translocation from shoots to roots and its release by roots into the soil. Results Plant water and N uptake were the main factors controlling daily N2O + N2 fluxes, cumulative N emissions, and N2O production pathways. Accordingly, pool-derived N2O + N2 emissions were 30–40 times higher in the treatment with highest soil NO3− content and highest soil moisture. CO2 efflux from soil was positively correlated with root dry matter, but we could not detect any relationship between root-derived C and N2O + N2 emissions. Conclusions Root-derived C may stimulate denitrification under small plants, while N and water uptake become the controlling factors with increasing plant and root growth.

scholarly journals Alteration of soil carbon and nitrogen pools and enzyme activities as affected by increased soil coarseness

2017 ◽  
Vol 14 (8) ◽  
pp. 2155-2166 ◽  
Author(s):  
Ruzhen Wang ◽  
Linyou Lü ◽  
Courtney A. Creamer ◽  
Feike A. Dijkstra ◽  
Heyong Liu ◽  
...  
Keyword(s):  
Microbial Biomass ◽  
Enzyme Activities ◽  
Organic C ◽  
Soil C ◽  
N Limitation ◽  
Soil C And N ◽  
C And N ◽  
Microbial C ◽  
Sandy Grasslands ◽  
Acid Phosphomonoesterase

Abstract. Soil coarseness decreases ecosystem productivity, ecosystem carbon (C) and nitrogen (N) stocks, and soil nutrient contents in sandy grasslands subjected to desertification. To gain insight into changes in soil C and N pools, microbial biomass, and enzyme activities in response to soil coarseness, a field experiment was conducted by mixing native soil with river sand in different mass proportions: 0, 10, 30, 50, and 70 % sand addition. Four years after establishing plots and 2 years after transplanting, soil organic C and total N concentrations decreased with increased soil coarseness down to 32.2 and 53.7 % of concentrations in control plots, respectively. Soil microbial biomass C (MBC) and N (MBN) declined with soil coarseness down to 44.1 and 51.9 %, respectively, while microbial biomass phosphorus (MBP) increased by as much as 73.9 %. Soil coarseness significantly decreased the enzyme activities of β-glucosidase, N-acetyl-glucosaminidase, and acid phosphomonoesterase by 20.2–57.5 %, 24.5–53.0 %, and 22.2–88.7 %, used for C, N and P cycling, respectively. However, observed values of soil organic C, dissolved organic C, total dissolved N, available P, MBC, MBN, and MBP were often significantly higher than would be predicted from dilution effects caused by the sand addition. Soil coarseness enhanced microbial C and N limitation relative to P, as indicated by the ratios of β-glucosidase and N-acetyl-glucosaminidase to acid phosphomonoesterase (and MBC : MBP and MBN : MBP ratios). Enhanced microbial recycling of P might alleviate plant P limitation in nutrient-poor grassland ecosystems that are affected by soil coarseness. Soil coarseness is a critical parameter affecting soil C and N storage and increases in soil coarseness can enhance microbial C and N limitation relative to P, potentially posing a threat to plant productivity in sandy grasslands suffering from desertification.

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