Fractionation of Soil Organic Matter into Labile and Stable Fractions

The present study aims to test and evaluate the efficiency of a new modified method of organic matter evaluation. It allows the assessment of the quality and quantity of the primary soil organic matter and the stable organic fractions separately. The new method was tested in six soil samples of different localities in the Czech Republic. This method is based on observing reaction kinetics during the oxidation of soil organic matter and measuring the cation-exchange capacity of stable organic fractions. The results were compared with classical methods, which rely on the isolation of humic substances, determination of the content of humic acids and fulvic acids and their ratio CHA:CFA, quotient E4/6, and fractionation of soil organic matter according to resistance to oxidation. It turned out that the results of the new modified method are more sensitive in comparison with the results obtained by classical procedures. The linear regression demonstrated the dependence between the amounts of soil organic matter determined by the classical method compared with the modified method. Moreover, the new modified method was found to be faster and not demanding on laboratory equipment. The new method has been improved to be easily repeatable, and some shortcomings of the previous method were eliminated. Based on our results and other recent studies, the modified method may be recommended for the practical evaluation of soil organic matter conditions.

Chemical Constituents and Antioxidant Activity of Melothria scabra Naudin Fruits

The fruit of Melothria scabra Naudin is traditionally used by natives of South East Sulawesi and has economic values in the local markets. Nonetheless, little scientific information was gained from this plant to support its development for nutraceutical and pharmaceutical aspects. This study aimed to investigate the phytochemicals contained in the ethanol extract and organic fractions (methanol, ethyl acetate, and hexane) of the fruits using specific reagents and an LC-MS/MS analysis, as well as to evaluate their total phenolics, total flavonoids, and DPPH radical scavenging activity using a dot-blot staining and spectrophotometric assays. Results showed that the fruits of M. scabra contained alkaloids, tannins, flavonoids, terpenoids, and saponins. Six compounds were successfully identified from the ethanol extract of the fruits for the first time that is D-1-[(3-carboxypropyl)amino]-1-deoxyfructose (1), fructose-C3H5NO (2), valine (3), 1β, 3α, 9β-trihydroxyeudesma-5,11(13)-dien-12-oic acid (4), Cucurbitacin B-2-O-α-L-rhamnopyranosyl-β-D-glucopyranoside (5), and 2-heptyl-3-hydroxy-4(H)-quinolone (6). Total phenolics in the extract and organic fractions were in the range of 54.2 ± 2.4 to 259.1 ± 8.4 mg GAE/g, while total flavonoids were in the range of 1.6 ± 0.2 to 22.4 ± 0.2 mg QE/g. The ethanol extract and its organic fractions (methanol and ethyl acetate) were potent radical scavengers with SC50 values ranging from 20.7 to 37.5 µg/mL when compared with ascorbic acid, gallic acid, and quercetin (SC50 of 2.8 to 9.4 µg/mL). This study concludes that M. scabra fruits could be developed as a source of natural antioxidant agents for nutraceuticals and pharmaceuticals purposes.

The Distribution and Migration of 137Cs in Oak (Quercus serrata) and Cedar (Cryptomeria japonica) Forest Organic Fractions

To analyse the 137Cs distribution and migration under various fractions of organic matter layers, this study investigated easily recognizable, originally shaped organic L-fractions, and not easily recognizable, early fermented and fragmented organic F-fractions, of both oak (Quercus serrata) and cedar (Cryptomeria japonica) sampled from Osawa watershed sites at Nihonmatsu City, Fukushima Prefecture, Japan. The organic materials were put on top of soil columns from Field Museum (FM) Tamakyuryo in Hachioji City, Tokyo. The 137Cs vertical distribution in forest soil profiles was analyzed using the relaxation mass depth, ho (kg m−2). Soil columns with both L and F- organic layer fractions of both oak and cedar, labelled as Oak-L, Oak-F, Cedar-L and Cedar-F with four replications (n = 16), were set up by the laboratory column-based method and kept under five months’ incubation period. Soil columns after incubation were sampled at depths of 0–1 cm, 1–2 cm, 2–5 cm and 5–10 cm. Results of 137Cs inventory in the organic fractions showed that 86% (oak and cedar) of the total organic layer fractions 137Cs inventory accumulated within the F-layer, indicating that the transformation of litter is a huge source for potentially mobile 137Cs, especially the oak F-layer (67% 137Cs inventory) and further continuous transfer into the forest soil mineral layers. A higher ho in L treated soils (Oak-L and Cedar-L) compared to the F treatments implied that the low 137Cs amounts penetrated faster and deeper due to their water-soluble nature. Furthermore, Cedar-F showed a higher ho of 24.3 kg m−2 than Oak-F of ho, 14.0 kg m−2, and a significant positive relationship between 137Cs retention and total carbon (TC) (p < 0.05) suggested the influence of soil organic matter on 137Cs penetration and retention. The C/N (carbon nitrogen ratio) results revealed that organic matter fractions of high C/N including 137Cs, as observed in Cedar-F, in which decomposition does not advance, penetrates soil depths while the organic matter fraction of low C/N, observed in Oak-F, showed that decomposition advanced to release 137Cs which was held by adsorption unto the RIP (radiocesium interception potential) of soil surface. In addition, infiltration by water as a transportation process was suggested to largely influence the downward migration and retention of 137Cs at lower depths of Cedar-F.