Salt effects on the soil microbial decomposer community and their role in organic carbon cycling: A review

Rath, Kristin; Rousk, Johannes

doi:10.1016/j.soilbio.2014.11.001

Cited by 426 publications

(260 citation statements)

References 200 publications

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“…Peinemann et al (2005) concluded that in salt-affected soils, mineral-associated OM can be rapidly lost through dispersion and subsequent leaching as dissolved OM, while particulate OM represents a relatively stable fraction as its decomposition is reduced due to inhibited microbial activity. In line with this, previous work revealed in incubation and field studies that the microbial decomposition of soil OM is reduced at elevated salinity (Rath and Rousk, 2015;Rietz and Haynes, 2003), while little is known about the composition of soil microbial communities. Baumann and Marschner (2011) and Pankhurst et al (2001) observed decreased fungi : bacteria ratios at enhanced salinity, while Barin et al (2015) found the opposite, indicating that more research is required to reach firm conclusions.…”

Section: Introductionsupporting

confidence: 53%

“…Microbial communities are sensitive to environmental changes and react to differences in the osmotic and matric potential (Rath and Rousk, 2015;Schimel et al, 2007). Fungi and gram-positive bacteria are thought to be particularly more resistant against drought than gram-negative bacteria due to their ability to produce higher amounts of osmolytes (Schimel et al, 2007).…”

Section: Microbial Community Composition Along the Salinity Gradientmentioning

confidence: 99%

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Organic matter dynamics along a salinity gradient in Siberian steppe soils

et al. 2018

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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 (δ 13 C, 14 C 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 (δ 13 C, 14 C 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 saltaffected soils contribute significantly to the OC storage in the semiarid soils of the Kulunda steppe, while most of the Published by Copernicus Publications on behalf of the European Geosciences Union. 14 N. Bischoff et al.: Organic matter dynamics along a salinity gradient OC is associated with minerals and is therefore effectively s...

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Section: Introductionsupporting

confidence: 53%

Section: Microbial Community Composition Along the Salinity Gradientmentioning

confidence: 99%

Organic matter dynamics along a salinity gradient in Siberian steppe soils

et al. 2018

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“…These adaptations and community shifts could offset some of the inhibiting effect of salinity on the microbial community we document here. Nevertheless, microbial activity remains reduced in soils that experienced high salt concentrations for longer periods of time (12,14,20,23), but it is often unclear to what degree this observed reduction represents a direct effect of salinity. Therefore, our results represent the potential susceptibility of a process to a direct salt exposure in the studied soil, while the degree to which microbial functions can recover from these perturbations remains to be investigated.…”

Section: Discussionmentioning

confidence: 99%

“…0.6 to 700 dS m Ϫ1 in a saturated soil paste [EC e ] [21]). Generally, a soil is described as saline if the EC e is higher than 4 dS m Ϫ1 , but studies of saline soils frequently include soils with a more than 10-fold higher EC e (23). Following the addition of NaCl, soils were incubated at room temperature for 1.5 h before microbial variables were determined.…”

Section: Methodsmentioning

confidence: 99%

“…Instead, responses in processes carried out by the active and growing part of the microbial community can be employed to detect inhibition by exposure to salts. For instance, salt additions have been found to influence and reduce microbial activity, measured as respiration (12,(20)(21)(22)(23) or N transformation rates (22,24). To date, there is a lack of comparative studies on the degree of sensitivity of a comprehensive range of different microbial processes.…”

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Comparative Toxicities of Salts on Microbial Processes in Soil

Rath

Maheshwari

Bengtson

et al. 2016

Appl Environ Microbiol

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Soil salinization is a growing threat to global agriculture and carbon sequestration, but to date it remains unclear how microbial processes will respond. We studied the acute response to salt exposure of a range of anabolic and catabolic microbial processes, including bacterial (leucine incorporation) and fungal (acetate incorporation into ergosterol) growth rates, respiration, and gross N mineralization and nitrification rates. To distinguish effects of specific ions from those of overall ionic strength, we compared the addition of four salts frequently associated with soil salinization (NaCl, KCl, Na 2 SO 4 , and K 2 SO 4 ) to a nonsaline soil. To compare the tolerance of different microbial processes to salt and to interrelate the toxicity of different salts, concentrationresponse relationships were established. Growth-based measurements revealed that fungi were more resistant to salt exposure than bacteria. Effects by salt on C and N mineralization were indistinguishable, and in contrast to previous studies, nitrification was not found to be more sensitive to salt exposure than other microbial processes. The ion-specific toxicity of certain salts could be observed only for respiration, which was less inhibited by salts containing SO 4 2؊ than Cl ؊ salts, in contrast to the microbial growth assessments. This suggested that the inhibition of microbial growth was explained solely by total ionic strength, while ion-specific toxicity also should be considered for effects on microbial decomposition. This difference resulted in an apparent reduction of microbial growth efficiency in response to exposure to SO 4 2؊ salts but not to Cl ؊ salts; no evidence was found to distinguish K ؉ and Na ؉ salts. Soil salinization affects a large area of land globally and has become a major threat to agricultural productivity and food security (1). Due to the wide distribution of salt-affected soils around the world (2, 3), it is important to understand the influence of salinity on the soil microbial community. The soil microbial decomposer community plays an essential role in the decomposition and stabilization of soil organic matter (SOM), as well as the cycling of nutrients vital for plant growth. How substrate during decomposition is allocated to either microbial biomass production or respiration determines the microbial growth efficiency (MGE), which is an important parameter for the C sequestration potential of a soil (4). The potential for soil C storage could be compromised by disturbances or unfavorable environmental conditions that reduce microbial growth efficiencies due to the metabolic burden they place on microbial cells (5).It is generally held that fungus-dominated communities have a higher MGE than communities dominated by bacteria (4). Thus, changes in the relative contribution of bacteria and fungi to the soil microbial community are thought to reflect changes in ecosystem processes, such as decomposition, C sequestration potential, and nutrient cycling (6, 7). It is unclear whether fungi and bacteria are affe...

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