scholarly journals Microbial Decomposition of Organic Matter Derived from Phytoplankton Cellular Components in Seawater

2004 ◽  
Vol 19 (2) ◽  
pp. 128-136 ◽  
Author(s):  
Yuka Ohnishi ◽  
Minoru Fujii ◽  
Shinichiro Murashige ◽  
Atsushi Yuzawa ◽  
Hitoshi Miyasaka ◽  
...  
Keyword(s):  
Organic Matter ◽  
Microbial Decomposition ◽  
Decomposition Of Organic Matter ◽  
Cellular Components

scholarly journals Root exudate input stimulates peatland recalcitrant DOC decomposition by r-strategic taxa of Gammaproteobacteria and Bacteroidetes

2020 ◽  
Author(s):  
Jiří Mastný ◽  
Jiří Bárta ◽  
Eva Kaštovská ◽  
Tomáš Picek
Keyword(s):  
Organic Matter ◽  
Community Composition ◽  
Plant Community ◽  
Root Exudates ◽  
Early Stage ◽  
Gene Copy Number ◽  
Gene Copy ◽  
Plant Community Composition ◽  
Microbial Decomposition ◽  
Decomposition Of Organic Matter

Abstract Background In peatlands, decomposition of organic matter is limited by harsh environmental conditions and low decomposability of the plant material. Increased microbial decomposition of organic matter in peatland ecosystems may become an important phenomenon in the near future after the expected shift in plant community composition from Sphagnum to vascular plants due to climate change. Such a change in plant community composition will lead to increased root exudates flux to the soil and stimulation of microbial growth and activity. The aim of our study was to evaluate the effect of root exudates on the decomposition of recalcitrant dissolved organic carbon (DOC) and identify the microorganisms responsible for this process. Results Decomposition of recalcitrant DOC was stimulated by a high levels of 13 C labelled root exudates addition whereas it was suppressed by a low levels of root exudates addition. Recalcitrant DOC decomposition was positively related to the exudate C/N ratio as a result of enhanced “microbial nutrient mining” due to a deepening of microbial nutrient limitation. The early stage of incubation immediately following the exudate addition was characterized by the preferential use of the added compounds at the expense of recalcitrant DOC. At the same time, r-strategic bacteria (identification based on average 16SrRNA gene copy number) belonging to mainly to Gammaproteobacteria and Bacteriodete s phyla relatively increased within the microbial community. At the later stage, this more abundant bacterial community was replaced by a less abundant community composed of bacteria mostly belonging to Alphaproteobacteria and Acidobacteria . The most important taxa with the potential to decompose complex compounds were indentified: Mucilaginibacter ( Bacteriodete s), Burkholderia and Pseudomonas ( Gammaproteobacteria ) among r-strategists and Bryocella and Candidatus Solibacter ( Acidobacteria ) among K-strategists. Conclusions Increased inputs of root exudates, with a higher C/N ratio, may stimulate decomposition of peatland recalcitrant DOC. In this, bacteria were found to be more important than fungi. Our experiment indicates that r-strategic bacteria as well as K-strategists can be important in stimulated decomposing of recalcitrant peatland DOC.

scholarly journals Nitrate addition stimulates microbial decomposition of organic matter in salt marsh sediments

2019 ◽  
Vol 25 (10) ◽  
pp. 3224-3241 ◽  
Author(s):  
Ashley N. Bulseco ◽  
Anne E. Giblin ◽  
Jane Tucker ◽  
Anna E. Murphy ◽  
Jonathan Sanderman ◽  
...  
Keyword(s):  
Organic Matter ◽  
Salt Marsh ◽  
Microbial Decomposition ◽  
Nitrate Addition ◽  
Decomposition Of Organic Matter ◽  
Marsh Sediments ◽  
Salt Marsh Sediments

scholarly journals What is recalcitrant soil organic matter?

2010 ◽  
Vol 7 (4) ◽  
pp. 320 ◽  
Author(s):  
Markus Kleber
Keyword(s):  
Organic Matter ◽  
Soil Organic Matter ◽  
Microbial Ecology ◽  
Organic Molecules ◽  
Global Scale ◽  
Critical Discussion ◽  
Environmental Drivers ◽  
Microbial Decomposition ◽  
Decomposition Of Organic Matter ◽  
Logistical Problem

Environmental context.On a global scale, soils store more carbon than plants or the atmosphere. The cycling of this vast reservoir of reduced carbon is closely tied to variations in environmental conditions, but robust predictions of climate–carbon cycle feedbacks are hampered by a lack of mechanistic knowledge regarding the sensitivity of organic matter decomposition to rising temperatures. This text provides a critical discussion of the practice to conceptualise parts of soil organic matter as intrinsically resistant to decomposition or ‘recalcitrant’. Abstract.The understanding that some natural organic molecules can resist microbial decomposition because of certain molecular properties forms the basis of the biogeochemical paradigm of ‘intrinsic recalcitrance’. In this concept paper I argue that recalcitrance is an indeterminate abstraction whose semantic vagueness encumbers research on terrestrial carbon cycling. Consequently, it appears to be advantageous to view the perceived ‘inherent resistance’ to decomposition of some forms of organic matter not as a material property, but as a logistical problem constrained by (i) microbial ecology; (ii) enzyme kinetics; (iii) environmental drivers; and (iv) matrix protection. A consequence of this view would be that the frequently observed temperature sensitivity of the decomposition of organic matter must result from factors other than intrinsic molecular recalcitrance.

scholarly journals Annual Variations of the 14C Content of Soil CO2

Radiocarbon ◽  
1986 ◽  
Vol 28 (2A) ◽  
pp. 338-345 ◽  
Author(s):  
Helmut Dörr ◽  
K O Münnich
Keyword(s):  
Organic Matter ◽  
Soil Co2 ◽  
Transfer Velocity ◽  
Microbial Decomposition ◽  
Vertical Transfer ◽  
Annual Variations ◽  
Decomposition Of Organic Matter ◽  
Ca 50 ◽  
Carbon Reservoir ◽  
Slow Turnover

A 6-year and a 2-year record of 14C measurements of soil CO2 in two soils are presented and discussed. The annual 14C variation of soil CO2 is controlled by the seasonally varying contribution of root respiration and of microbial decomposition of organic matter producing soil CO2. The Δ14C soil CO2 difference between summer and winter is ca 50‰ in a soil where turnover of organic matter is fast (τ = 2.5a) and ca 100‰ in a soil of slow turnover (τ = 60a). A simple model describing the movement and turnover of organic matter is derived, giving the depth distributions of organic carbon and of 14C. The model needs a subdivision of the carbon reservoir into at least two reservoirs with residence times of τ1 = la and τ2 = 100a, respectively, and with a vertical transfer velocity in the order of 0.6mm/a.

Chemical complexity matters: differential mobilization of mineral-associated organic matter driven by functionally distinct rhizodeposits

2020 ◽  
Author(s):  
Tobias Bölscher ◽  
Hui Li ◽  
Mariela Garcia Arredondo ◽  
Zoe G. Cardon ◽  
Carolyn M. Malmstrom ◽  
...  
Keyword(s):  
Organic Matter ◽  
Mineral Dissolution ◽  
Model Systems ◽  
Microbial Decomposition ◽  
Storage Mechanism ◽  
Chemical Complexity ◽  
Decomposition Of Organic Matter ◽  
First Results ◽  
Fe Hydroxide ◽  
The Stability

<p>Protective mineral-organic associations are the quantitatively most important soil carbon storage mechanism, but their vulnerability to environmental change is largely uncertain. While it is well established that root growth can promote (or “prime”) the microbial decomposition of organic matter (OM), our mechanistic knowledge of the ability of roots to destabilize OM protected within mineral-organic associations remains limited. Here we examined how the composition of root-derived compounds (rhizodeposits) affects the stability of mineral-organic associations.</p><p>In model systems, we first tested the ability of functionally distinct low-molecular weight compounds (ligands, reductants, simple sugars) commonly observed in the rhizosphere to cause the mobilization and mineralization of isotopically labeled OM from different mineral types (Fe and Al hydroxides). Our results showed that all compounds stimulated mobilization and mineralization of previously mineral-associated OM. However, OM bound to Al hydroxide was less susceptible to mobilization than OM bound to Fe hydroxide. Further, sugars and reductants revealed a greater mobilization potential than ligands for both mineral types, suggesting that OM mobilization in soils may be microbially mediated, rather than driven by direct mineral dissolution. In complementary pot experiments, we investigated the effect of rhizodeposition on the mobilization of mineral-associated OM. We grew <em>Avena sativa</em> in soils amended with isotopically-labeled mineral-organic associations and followed mobilization dynamics over four weeks. First results indicated that rhizodeposition dynamics dictate the mobilization and mineralization of mineral-associated OM. Together, our results suggest a strong mechanistic linkage between the composition and functionality of rhizodeposits and their ability to destabilize mineral-associated OM.</p>

Penetration of pea radicles into saturated soil cores related to organic matter amendments

Soil Research ◽  
1981 ◽  
Vol 19 (3) ◽  
pp. 343
Author(s):  
P Willoughby ◽  
ST Willatt
Keyword(s):  
Organic Matter ◽  
Saturated Soil ◽  
Root Penetration ◽  
Soil Cores ◽  
Soil Matrix ◽  
Microbial Decomposition ◽  
Pea Seedlings ◽  
Decomposition Of Organic Matter ◽  
Different Depths ◽  
Incubation Temperatures

The radicles of pea seedlings penetrated to different depths in saturated cores prepared from Goulburn Valley orchard soil according to the amount and type of organic matter added to the soil. Additions of ground straw and glucose restricted the penetration of the roots when grown for 4 days at constant temperature. Longer incubation times and higher incubation temperatures imposed on the cores before growing the seedlings further restricted the roots in the presence of added peat, straw or glucose. The restrictions to root penetration can be attributed to poor oxygen supply into the saturated soil matrix and to phytotoxins produced by the microbial decomposition of organic matter contained in the soil cores. The results suggest that structural units in an irrigated soil should not be larger than about 6 mm in diameter if roots are to fully exploit the soil volume.

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