scholarly journals Organic matter dynamics along a salinity gradient in Siberian steppe soils

2017 ◽  
Author(s):  
Norbert Bischoff ◽  
Robert Mikutta ◽  
Olga Shibistova ◽  
Reiner Dohrmann ◽  
Daniel Herdtle ◽  
...  
Keyword(s):  
Organic Matter ◽  
Microbial Community ◽  
Community Composition ◽  
Salinity Gradient ◽  
Microbial Community Composition ◽  
Arid Ecosystems ◽  
Sodic Soils ◽  
Kulunda Steppe ◽  
Salt Affected Soils ◽  
Semi Arid

Abstract. Salt-affected soils will become increasingly important in the next decades as arid and semi-arid ecosystems are predicted to expand as a result of climate change. Nevertheless, little is known about organic matter (OM) dynamics in these soils, though OM is largely controlling soil fertility and represents an important C sink. We aimed at investigating OM dynamics along a salinity and sodicity gradient in soils of the south-western Siberian Kulunda steppe (Kastanozem, Non-sodic Solonchak, Sodic Solonchak) by assessing the organic carbon (OC) stocks, the quantity and quality of particulate and mineral-associated OM in terms of non-cellulosic neutral sugar contents and carbon isotopes (δ13C, 14C activity), and the microbial community composition based on phospholipid fatty acid (PLFA) patterns. Our hypotheses were that (i) soil OC stocks decrease along the salinity gradient, (ii) the proportion and stability of particulate OM is larger in salt-affected Solonchaks as compared to non-salt-affected Kastanozems, and (iii) sodicity reduces the proportion and stability of mineral-associated OM. Against our first hypothesis, OC stocks increased along the salinity gradient with most pronounced differences between topsoils. In contrast to our second hypothesis, the proportion of particulate OM was unaffected by salinity, thereby accounting for only  90 %. Isotopic data (δ13C, 14C activity) and neutral sugars in the OM fractions indicated a comparable degree of OM transformation along the salinity gradient, thus particulate OM was not more persistent under saline conditions. This we attribute to a resilient microbial community composition and function, which was nearly unaffected by salt occurrence, and capable of decomposing OM at a similar rate in salt-affected and non-salt-affected soils. Also our third hypothesis was rejected, as saline-sodic soils contained more than twice as much mineral-bound OC than non-salt-affected soils, what we ascribe to the flocculation of OM and mineral components under higher ionic strength conditions. We conclude that salt-affected soils contribute significantly to the OC storage in the semi-arid soils of the Kulunda steppe while most of the OC is associated to minerals and therefore effectively sequestered in the long-term.

scholarly journals Organic matter dynamics along a salinity gradient in Siberian steppe soils

2018 ◽  
Vol 15 (1) ◽  
pp. 13-29 ◽  
Author(s):  
Norbert Bischoff ◽  
Robert Mikutta ◽  
Olga Shibistova ◽  
Reiner Dohrmann ◽  
Daniel Herdtle ◽  
...  
Keyword(s):  
Organic Matter ◽  
Plant Growth ◽  
Carbon Sink ◽  
Phospholipid Fatty Acid ◽  
Salinity Gradient ◽  
Microbial Community Composition ◽  
Neutral Sugar ◽  
Mineral Components ◽  
Kulunda Steppe ◽  
Salt Affected Soils

Abstract. Salt-affected soils will become more frequent in the next decades as arid and semiarid ecosystems are predicted to expand as a result of climate change. Nevertheless, little is known about organic matter (OM) dynamics in these soils, though OM is crucial for soil fertility and represents an important carbon sink. We aimed at investigating OM dynamics along a salinity and sodicity gradient in the soils of the southwestern Siberian Kulunda steppe (Kastanozem, non-sodic Solonchak, Sodic Solonchak) by assessing the organic carbon (OC) stocks, the quantity and quality of particulate and mineral-associated OM in terms of non-cellulosic neutral sugar contents and carbon isotopes (δ13C, 14C activity), and the microbial community composition based on phospholipid fatty acid (PLFA) patterns. Aboveground biomass was measured as a proxy for plant growth and soil OC inputs. Our hypotheses were that (i) soil OC stocks decrease along the salinity gradient, (ii) the proportion and stability of particulate OM is larger in salt-affected Solonchaks compared to non-salt-affected Kastanozems, (iii) sodicity reduces the proportion and stability of mineral-associated OM, and (iv) the fungi : bacteria ratio is negatively correlated with salinity. Against our first hypothesis, OC stocks increased along the salinity gradient with the most pronounced differences between topsoils. In contrast to our second hypothesis, the proportion of particulate OM was unaffected by salinity, thereby accounting for only < 10 % in all three soil types, while mineral-associated OM contributed > 90 %. Isotopic data (δ13C, 14C activity) and neutral sugars in the OM fractions indicated a comparable degree of OM transformation along the salinity gradient and that particulate OM was not more persistent under saline conditions. Our third hypothesis was also rejected, as Sodic Solonchaks contained more than twice as much mineral-bound OC than the Kastanozems, which we ascribe to the flocculation of OM and mineral components under higher ionic strength conditions. Contrary to the fourth hypothesis, the fungi : bacteria ratio in the topsoils remained fairly constant along the salinity gradient. A possible explanation for why our hypotheses were not affirmed is that soil moisture covaried with salinity along the transect, i.e., the Solonchaks were generally wetter than the Kastanozems. This might cause comparable water stress conditions for plants and microorganisms, either due to a low osmotic or a low matric potential and resulting in (i) similar plant growth and hence soil OC inputs along the transect, (ii) a comparable persistence of particulate OM, and (iii) unaffected fungi : bacteria ratios. We conclude that salt-affected soils contribute significantly to the OC storage in the semiarid soils of the Kulunda steppe, while most of the OC is associated with minerals and is therefore effectively sequestered in the long term.

Organic matter additions to soil and effects on microbially mediated carbon cycling

2020 ◽  
Author(s):  
Rachel hasler ◽  
Mark pawlett ◽  
Jim harris ◽  
Helen bostock ◽  
Marc redmile-gordon
Keyword(s):  
Organic Matter ◽  
Microbial Community ◽  
Carbon Cycling ◽  
Community Composition ◽  
Soil Microbial Community ◽  
Microbial Community Composition ◽  
Soil Microbial ◽  
Horse Manure ◽  
Soil Microbial Community Composition

&lt;p&gt;The type of soil organic amendment selected can have profound implications for carbon cycling processes in soils. Understanding the link between this choice and its effect on the soil microbiome will improve our understanding of the capacity of these materials to improve carbon sequestration and cycling dynamics. Understanding and facilitating the lifestyle strategies of microorganisms processing organic matter is essential to improving our understanding of the terrestrial carbon cycle. This research focuses on utilising organic amendments to alter the indigenous soil microbial community composition and function to improve the capacity of the soil to cycle and store carbon in horticultural soils. &amp;#160;The effects of annual application of various organic fertilisers (peat, bracken, bark, horse manure, garden compost) in a long-term (10year) field experiment were explored. Sampling was completed pre and post application of organic matter within one season (following 10 years of applications) to identify which organic amendment was more effective in producing benefits to plants through improved soil organic matter and which amendments provide the greatest legacy effect on carbon cycling. The response of the soil microbial community composition (phospholipid fatty acid analysis) and carbon functional cycling dynamics (respiration using MicroResp&amp;#8482;) were determined with a view to improving our understanding of the interaction between the materials applied and microbial processes. PCA of the MicroResp&amp;#8482; data identified that all treatments had a different functional profile compared to the control[PM1]&amp;#160; with peat being significantly different from all other treatments. Horse manure and bark differed significantly within a single growing season; prior and post organic matter addition in spring 2019. &amp;#160;Microbial biomass measurements for garden compost and horse manure were significantly higher following organic matter addition compared to all other treatments and the control[PM2]&amp;#160;.&amp;#160; All treatments had a significant effect [PM3]&amp;#160;on hot water extractable carbon and total carbon. Peat had a significantly different effect[PM4]&amp;#160;, when compared to other treatments, on the soil PLFA profile and bark application significantly increased [PM5]&amp;#160;the neutral lipid (NLFA) biomarker 16:1&amp;#969;5. &amp;#160;Bark and horse manure application both significantly increased PLFA fungal biomarker 18:2&amp;#969;6,9. No significant differences were found between the fungal/bacterial ratios of the organic matter additions prior to being added to the soil. These findings show that altering the resources available to the soil microbial community has a significant impact on soil microbial community composition and microbially mediated carbon cycling functionality. Increasing our understanding of how soil functions are altered by land management decisions will enable better informed predictions of the long-term benefits of organic matter applications on carbon sequestration and cycling dynamics.&lt;/p&gt;

scholarly journals Changes in Microbial Community Phylogeny and Metabolic Activity Along the Water Column Uncouple at Near Sediment Aphotic Layers in Fjords

2021 ◽  
Author(s):  
Sven P. Tobias-Hünefeldt ◽  
Stephen R. Wing ◽  
Federico Baltar ◽  
Sergio E. Morales
Keyword(s):  
Organic Matter ◽  
Microbial Community ◽  
Water Column ◽  
Microbial Activity ◽  
Community Composition ◽  
Microbial Community Composition ◽  
Leucine Incorporation ◽  
Metabolic Potential ◽  
Near Surface ◽  
Potential Activity

Abstract Fjords are semi-enclosed marine systems with unique physical conditions that influence microbial community composition and structure. Pronounced organic matter and physical condition gradients within fjords provide a natural laboratory for the study of changes in microbial phylogeny and metabolic potential in response to environmental conditions. Photosynthetic production in euphotic zones sustains deeper aphotic microbial activity via organic matter sinking, augmented by large terrestrial inputs. We profiled microbial functional potential (Biolog Ecoplates), bacterial abundance, heterotrophic production (3H-Leucine incorporation), and prokaryotic/eukaryotic community composition (16S and 18S rRNA amplicon gene sequencing) to link metabolic potential, activity, and community composition to known community drivers. Similar factors shaped metabolic potential, activity and community (prokaryotic and eukaryotic) composition across surface/near surface sites. However, increased metabolic diversity at near bottom (aphotic) sites reflected an organic matter influence from sediments. Photosynthetically produced particulate organic matter shaped the upper water column community composition and metabolic potential. In contrast, microbial activity at deeper aphotic waters were strongly influenced by other organic matter imput than sinking marine snow (e.g. sediment resuspension of benthic organic matter, remineralisation of terrestrially derived organic matter, etc.), severing the link between phylogeny and metabolic potential. Taken together, different organic matter sources shape microbial activity, but not community composition, in New Zealand fjords.

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