scholarly journals Soil organic carbon in a toposequence in the semiarid of Paraíba, Brazil

2020 ◽  
Vol 9 (5) ◽  
pp. e164953365
Author(s):  
Cheila Deisy Ferreira ◽  
Francisco Tibério de Alencar Moreira ◽  
Patrícia Carneiro Souto ◽  
Lyanne dos Santos Alencar ◽  
César Henrique Alves Borges

Organic carbon is a sensible indicator to evaluate the environmental quality of the soil. The objective of this study was to evaluate the organic carbon content of the soil in a toposequence in Serra do Teixeira, municipality of Teixeira, PB. Soil samples were collected in the upper third (UT), upper middle third (UMT), lower middle third (LMT) and lower third (LT) on three depths (0-5, 5-10 and 10-20 cm), with five replicates for each depth, resulting in a total of 60 samples. The organic carbon was evaluated using the methodology of Walkey-Black. Physical and chemical soil analysis were also carried out. The highest mean of carbon content was found in the first 5 cm (19.83 g dm-3), significantly differing from the other depths. It was also observed that the mean content of soil organic carbon on LMT was significantly higher than the other thirds, with 19.39 g dm-3. It is concluded that the highest contents of organic carbon are found on the most superficial layer of the soil. The organic carbon content variations found along the toposequence indicates influence of the relief and the anthropic action.

2021 ◽  
Vol 24 ◽  
pp. e00367
Author(s):  
Patrick Filippi ◽  
Stephen R. Cattle ◽  
Matthew J. Pringle ◽  
Thomas F.A. Bishop

2021 ◽  
Author(s):  
Christoph Rosinger ◽  
Michael Bonkowski

AbstractFreeze–thaw (FT) events exert a great physiological stress on the soil microbial community and thus significantly impact soil biogeochemical processes. Studies often show ambiguous and contradicting results, because a multitude of environmental factors affect biogeochemical responses to FT. Thus, a better understanding of the factors driving and regulating microbial responses to FT events is required. Soil chronosequences allow more focused comparisons among soils with initially similar start conditions. We therefore exposed four soils with contrasting organic carbon contents and opposing soil age (i.e., years after restoration) from a postmining agricultural chronosequence to three consecutive FT events and evaluated soil biochgeoemical responses after thawing. The major microbial biomass carbon losses occurred after the first FT event, while microbial biomass N decreased more steadily with subsequent FT cycles. This led to an immediate and lasting decoupling of microbial biomass carbon:nitrogen stoichiometry. After the first FT event, basal respiration and the metabolic quotient (i.e., respiration per microbial biomass unit) were above pre-freezing values and thereafter decreased with subsequent FT cycles, demonstrating initially high dissimilatory carbon losses and less and less microbial metabolic activity with each iterative FT cycle. As a consequence, dissolved organic carbon and total dissolved nitrogen increased in soil solution after the first FT event, while a substantial part of the liberated nitrogen was likely lost through gaseous emissions. Overall, high-carbon soils were more vulnerable to microbial biomass losses than low-carbon soils. Surprisingly, soil age explained more variation in soil chemical and microbial responses than soil organic carbon content. Further studies are needed to dissect the factors associated with soil age and its influence on soil biochemical responses to FT events.


PLoS ONE ◽  
2021 ◽  
Vol 16 (1) ◽  
pp. e0245040
Author(s):  
Feng Zhang ◽  
Shihang Wang ◽  
Mingsong Zhao ◽  
Falv Qin ◽  
Xiaoyu Liu

Soil organic carbon content has a significant impact on soil fertility and grain yield, making it an important factor affecting agricultural production and food security. Dry farmland, the main type of cropland in China, has a lower soil organic carbon content than that of paddy soil, and it may have a significant carbon sequestration potential. Therefore, in this study we applied the CENTURY model to explore the temporal and spatial changes of soil organic carbon (SOC) in Jilin Province from 1985 to 2015. Dry farmland soil polygons were extracted from soil and land use layers (at the 1:1,000,000 scale). Spatial overlay analysis was also used to extract 1282 soil polygons from dry farmland. Modelled results for SOC dynamics in the dry farmland, in conjunction with those from the Yushu field-validation site, indicated a good level of performance. From 1985 to 2015, soil organic carbon density (SOCD) of dry farmland decreased from 34.36 Mg C ha−1 to 33.50 Mg C ha−1 in general, having a rate of deterioration of 0.03 Mg C ha−1 per year. Also, SOC loss was 4.89 Tg from dry farmland soils in the province, with a deterioration rate of 0.16 Tg C per year. 35.96% of the dry farmland its SOCD increased but 64.04% of the area released carbon. Moreover, SOC dynamics recorded significant differences between different soil groups. The method of coupling the CENTURY model with a detailed soil database can simulate temporal and spatial variations of SOC at a regional scale, and it can be used as a precise simulation method for dry farmland SOC dynamics.


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