Cold Water Extractable Carbon Research Articles

Characterization of Labile Organic Carbon in Different Coastal Wetland Soils of Laizhou Bay, Bohai Sea

Labile organic carbon (LOC) is the most active fraction of soil organic carbon (SOC) with rapid turnover rates, and has been suggested as sensitive indicator of SOC pool under global change. However, the knowledge of LOC pools in coastal wetland soils and their implication for soil carbon reservoir are still scarce. We characterized LOC in soils from two coastal wetlands using cold water extractable carbon (CWC), hot water extractable carbon (HWC), and acid hydrolysable carbon (AHC). Our results indicated that SOC and its labile fractions are higher in Guangrao than that in Changyi. CWC comprised about 24.09–34.86% of SOC for Guangrao and 1.54–2.43% for Changyi. The HWC content was generally higher than CWC, and HWC in Changyi contributed higher proportion to SOC compared with Guangrao wetland. The AHC represented much higher proportion of SOC about 45.94–50.11% in Guangrao and 60.38–65.08% in Changyi, respectively. CWC, HWC and AHC were significantly correlated with each other in profile CB1. Poor correlation among LOC and SOC was observed in GA1, GA2 and CB2. Differences in vegetation and hydrological condition should be considered for obtaining accurate carbon calculation. Relative high proportion of LOC suggests these wetlands might be particularly vulnerable to a warming environment.

Soil Carbon and Nitrogen Fractions of a Grassland in Central Missouri, USA

ABSTRACTQuantification of soil carbon (C) and nitrogen (N) fractions in grasslands is vital for estimating C sequestration and climate change studies. We quantified background soil total carbon (TOC) status, recalcitrant carbon (RC), acid hydrolysable labile carbon (AHC), hot- and cold-water extractable carbon (HWC and CWC, respectively) fractions in the grassland in this study. Soil C fractions were as follows: TOC (11,633 to 15,525 mg C kg−1); RC (11,500 to 15,357 mg C kg−1); AHC (132 to 168 mg C kg−1); HWC (57 to 70 mg C kg−1); and CWC (27 to 33 mg C kg−1). Labile C fractions contributed at most 1.2% to total C. Concentrations of total N ranged from 1072 to 1230 g N kg−1. Recalcitrant C contributed higher amounts (>90%) to total C, indicating the incorporation of C into the stable C fraction. Carbon dioxide (CO2) and nitrous oxide (N2O) fluxes were not significantly correlated with total C.

Effect of organic fertilizers on soil organic carbon and risk trace elements content in soil under permanent grassland

Karabcova H., Pospisilova L., Fiala K., Skarpa P., Bjelkova M. (2015): Effect of organic fertilizers on soil organic carbon and risk trace elements content in soil under permanent grassland. Soil & Water Res., 10: 228–235. The effect of different kinds of organic matter inputs on elemental composition, content, and quality of humic sub stances was studied on permanent grassland during 2008–2013. The experiment included two organic fertilizer types – compost and slurry, both with the range of stocking rates 0.9, 1.4, and 2.0 livestock units (LU)/ha (corresponding to 54, 84, and 120 kg N/ha, respectively), and control without any fertilizer. The soil was sandy-loam, of Cambisol type, with semi natural permanent grassland. Labile forms and total contents of selected trace elements (Co, Cu, Zn, Cd) and macroelements (Ca, Mg, K, P, and N) were measured. Soil organic matter parameters such as total organic carbon (C ox ), humic substances (HS), humic acid (HA), fluvic acid (FA), and labile carbon forms ( hot-water extractable carbon ( C hws ), cold water extractable carbon ( C cws )) were determined. Results showed that the greatest content of P, Ca, Mg, and N in the soil was detected by the CO 2.0 treatment. Furthermore, the positive effect of compost on C ox , C hws , HA, FA, HS, N and macronutrients was observed. The elemental analysis of humic acids showed lower carbon content and higher oxygen content in HA molecule, which indicated young humic acids, with a lower condensation degree. The content and quality of humic substances strongly influenced the total and labile trace elements content in the soil. Additionally, hot water soluble carbon significantly correlated with plant available forms of Zn, Cu, and Cd.

Monthly dynamics of microbial community structure and their controlling factors in three floodplain soils

Seasonal dynamics of microbial community under frequently fluctuating oxidized and reduced conditions in floodplain soils are poorly understood, but are considered to be important for understanding microbial community and carbon cycling dynamics in these ecosystems. We determined the microbial community structure using phospholipid fatty acid analysis (PLFA) of three different floodplain soils (Eutric Gleysol = GLe, Eutric Fluvisol = FLe, and Mollic Fluvisol = FLm) at the Elbe River, Germany, for 17 months. Flood duration, soil moisture, soil temperature were also monitored, and hot and cold water extractable carbon (CHWE, CCWE) were determined. Flood duration seems to have a negative impact on total PLFA biomass which increased in the order GLe < FLe << FLm. All PLFA profiles were dominated by Gram-positive bacteria (GPB) and actinomycetes, respectively, and a low content of fungi and arbuscular mycorrhizal fungi (AMF). In the briefly flooded relatively quickly drained soils (FLe and FLm) Gram-negative bacteria (GNB) were abundant compared to the longer flooded, relatively slow drained soil (GLe). This was also obvious in the significant lowest fungi-bacteria ratio and aerobe-anaerobe ratio of GLe. Non-metric dimensional scaling (NMDS) and canonical discriminant analysis (CDA) as multivariate statistical procedures reveal that FLm could be separated from GLe and FLe probably due to aerobic conditions and available soil organic carbon. The GLe can be discriminated from FLe and FLm mainly due to different flooding durations. The GNB, fungi and AMF were more affected by changes of soil moisture and extractable carbon than the GPB, actinomycetes and anaerobes. We conclude that more stable properties of bulk soil such as the magnitude of soil organic carbon, soil texture, and associated flood duration had a stronger impact on soil microbial community than monthly fluctuations of more dynamic properties, such as soil moisture, soil temperature, and CHWE, CCWE in our soils.

Impact of Atmospheric Nitrogen Deposition on Carbon Dynamics in Two Scots Pine Forest Soils of Northern Germany

The impact of atmospheric N deposition on the dynamics of various carbon fractions was investigated in two Scots pine forest soils (cambisol, podzol) of Northern Germany in microcosm experiments. Total organic carbon (TOC), CO2 emission, microbial carbon (Cmic) as well as organic hot- and coldwater extractable carbon fractions (Chwe, Ccwe) were analyzed before, during, and after soil incubation in microcosms, run in three treatments: 0, +45, and +90 kg N ha−1a−1. On both sites, the N treatment showed no response to total organic carbon (TOC) contents in most of the investigated soil layers. Microbial carbon (Cmic) was significantly increased in the organic layer of both soil types by the N application. Subsequent to the N application, the CO2 emission increased in all mineral soil layers of the cambisol but remained almost unaffected in the podzol. After the N application, a remarkable increase of hotwater extractable C (Chwe) was detected for the organic layer of the cambisol but not for the podzol, whereas coldwater extractable C (Ccwe) concentrations decreased at both sites. The N application did not have a significant impact on the leachate concentrations of total organic carbon (TOC), dissolved organic carbon (DOC), and particulate organic carbon (POC) in the podzol, whereas the concentrations of these C fractions were decreased in the organic layer and the 35–70~cm mineral soil layer of the cambisol. The N treatment changed the contents of most of the investigated C fractions in both soil types and resulted in a considerable C~mobilization. But the processes of the C~mobilization between the cambisol and the podzol were completely different. According to the presented data, the cambisol obtaining moderate atmospheric N loads is much more sensitive to additional N inputs than the podzol that already received high amounts of atmospheric N.