scholarly journals Carbon and nitrogen cycling on intertidal mudflats of a temperate Australian estuary. III. Sources of organic matter

2004 ◽  
Vol 280 ◽  
pp. 55-72 ◽  
Author(s):  
PLM Cook ◽  
AT Revill ◽  
LA Clementson ◽  
JK Volkman
Keyword(s):  
Organic Matter ◽  
Nitrogen Cycling ◽  
Carbon And Nitrogen ◽  
Intertidal Mudflats ◽  
Carbon And Nitrogen Cycling ◽  
Australian Estuary

scholarly journals Potential consequences of water limitation and drought-induced tree mortality on carbon and nitrogen cycling

2020 ◽  
Author(s):  
Emily F. Solly ◽  
Astrid C. H. Jaeger ◽  
Johan Six ◽  
Martin Hartmann
Keyword(s):  
Organic Matter ◽  
Nitrogen Cycling ◽  
Scots Pine ◽  
Tree Mortality ◽  
Soil Microbe ◽  
Water Limitation ◽  
Carbon And Nitrogen ◽  
Carbon And Nitrogen Cycling ◽  
Plant Soil ◽  
Alpine Valleys

<p>Water limiting conditions for the growth and physiology of trees as well as episodes of tree mortality triggered by drought have recently been documented in several bioregions across the world. In parallel to these major vegetation alterations, the impact of water scarcity also has prominent effects on soil processes mediated by the microbiome such as the transformation of organic matter, heterotrophic respiration, microbial uptake as well as nutrient mineralization. Although currently little explored, shifts in the interplay occurring between tree functioning and soil microbial processes may be crucial during tree mortality events and may feed back on ecosystem carbon and nitrogen cycling. We will present a multidisciplinary setup to mechanistically explore how water limitation acts synergistically on the interplay between trees and soil microorganisms, with potential consequences for ecosystem biogeochemical fluxes.</p><p>The experimental setup focusses on a key temperate forest species, Scots pine (<em>Pinus sylvestris</em> L.), which is currently facing high mortality rates in several inner-Alpine valleys of Europe due to drier climatic conditions during parts of the year. We make use of small scale mesocosms featuring young trees and soil collected from a drought-affected natural forest. The mesocosms are treated with different levels of water availability under controlled conditions. Plant growth and physiological changes related to water limitation are investigated in parallel to various soil properties. State-of-the-art isotopic labelling techniques are used to trace alterations in carbon and nitrogen transfers within the plant-soil-microbe continuum. We will specifically test whether extended periods of drought suppress the flux of carbon from plants to soil and lead plants to invest more in the maintenance of fine root systems. Moreover, we will follow the potential changes in the rates of decomposition, mineralization and incorporation of plant debris into soil organic matter over time and link them to potential alterations of the soil microbiota. These experimental observations will be validated by measurements in drought-affected Scots pine forests in inner-Alpine valleys. We expect the outcomes of this work to advance the fundamental understanding of the alterations occurring in the plant-soil-microbe system related to drought as well as to improve the detection of mechanisms leading to Scots pine mortality.</p>

scholarly journals Microbial Community Diversity Associated with Carbon and Nitrogen Cycling in Permeable Shelf Sediments

2006 ◽  
Vol 72 (9) ◽  
pp. 5689-5701 ◽  
Author(s):  
Evan M. Hunter ◽  
Heath J. Mills ◽  
Joel E. Kostka
Keyword(s):  
Organic Matter ◽  
Nitrogen Cycling ◽  
Rrna Genes ◽  
Column Experiments ◽  
Ssu Rrna ◽  
Carbon And Nitrogen ◽  
Carbon And Nitrogen Cycling ◽  
In Situ Conditions ◽  
Shelf Sediments

ABSTRACT Though a large fraction of primary production and organic matter cycling in the oceans occurs on continental shelves dominated by sandy deposits, the microbial communities associated with permeable shelf sediments remain poorly characterized. Therefore, in this study, we provide the first detailed characterization of microbial diversity in marine sands of the South Atlantic Bight through parallel analyses of small-subunit (SSU) rRNA gene (Bacteria), nosZ (denitrifying bacteria), and amoA (ammonia-oxidizing bacteria) sequences. Communities were analyzed by parallel DNA extractions and clone library construction from both sediment core material and manipulated sediment within column experiments designed for geochemical rate determinations. Rapid organic-matter degradation and coupled nitrification-denitrification were observed in column experiments at flow rates resembling in situ conditions over a range of oxygen concentrations. Numerous SSU rRNA phylotypes were affiliated with the phyla Proteobacteria (classes Alpha-, Delta-, and Gammaproteobacteria), Planctomycetes, Cyanobacteria, Chloroflexi, and Bacteroidetes. Detectable sequence diversity of nosZ and SSU rRNA genes increased in stratified redox-stabilized columns compared to in situ sediments, with the Alphaproteobacteria comprising the most frequently detected group. Alternatively, nitrifier communities showed a relatively low and stable diversity that did not covary with the other gene targets. Our results elucidate predominant phylotypes that are likely to catalyze carbon and nitrogen cycling in marine sands. Although overall diversity increased in response to redox stabilization and stratification in column experiments, the major phylotypes remained the same in all of our libraries, indicating that the columns sufficiently mimic in situ conditions.

scholarly journals Composition of dissolved organic matter within a lacustrine environment

2011 ◽  
Vol 8 (2) ◽  
pp. 146 ◽  
Author(s):  
Margaret V. McCaul ◽  
David Sutton ◽  
André J. Simpson ◽  
Adrian Spence ◽  
David J. McNally ◽  
...  
Keyword(s):  
Organic Matter ◽  
Dissolved Organic Matter ◽  
Nitrogen Cycling ◽  
Substantial Contribution ◽  
Chemical Characteristics ◽  
Carbon And Nitrogen ◽  
Carbon And Nitrogen Cycling ◽  
Lake System ◽  
Environmental Processes ◽  
Transformation Mechanisms

Environmental contextFreshwater dissolved organic matter is a complex chemical mixture central to many environmental processes, including carbon and nitrogen cycling. Questions remain, however, as to its chemical characteristics, sources and transformation mechanisms. We studied the nature of dissolved organic matter in a lake system and found that it is influenced by anthropogenic activities. Human activities can therefore influence the huge amounts of carbon sequestered in lakes as dissolved organic matter. AbstractFreshwater dissolved organic matter (DOM) is a complex mixture of chemical components that are central to many environmental processes, including carbon and nitrogen cycling. However, questions remain as to its chemical characteristics, sources and transformation mechanisms. Here, we employ 1- and 2-D nuclear magnetic resonance (NMR) spectroscopy to investigate the structural components of lacustrine DOM from Ireland, and how it varies within a lake system, as well as to assess potential sources. Major components found, such as carboxyl-rich alicyclic molecules (CRAM) are consistent with those recently identified in marine and freshwater DOM. Lignin-type markers and protein/peptides were identified and vary spatially. Phenylalanine was detected in lake areas influenced by agriculture, whereas it is not detectable where zebra mussels are prominent. The presence of peptidoglycan, lipoproteins, large polymeric carbohydrates and proteinaceous material supports the substantial contribution of material derived from microorganisms. Evidence is provided that peptidoglycan and silicate species may in part originate from soil microbes.

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