Determination of nine bioactive phenolic components usually found in apple juice by simultaneous UPLC-MS/MS.

The functional food ingredients of apple juice can significantly change during processing, transportation, and storage, thus affecting the quality of the product. A simple and derivation-free analytical method based on ultra-high-performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS) was developed and optimized for the simultaneous determination of functional food ingredients in apple juice bought in the market. Cleanup steps and chromatographic conditions were optimized to remove interference and decrease the matrix effect. The nine target analytes were separated on an Acquity UPLC system equipped with a BEH C18 column and detected by electrospray ionization source (ESI) operating in positive subsection acquisition mode under multiple reaction monitoring (MRM) conditions. The results showed that p-hydroxybenzoic acid, protocatechuate, caffeic acid, chlorogenic acid, epicatechin, phloridzin, hyperoside, procyanidin B2, and rutin could be sufficiently separated for content determination within 6 min. In the concentration range of 20 µg/L-50 mg/L, nine standard samples exhibited a good linear fit with correlation coefficients above .985.

Soil arthropods promote litter enzyme activity by regulating microbial carbon limitation and ecoenzymatic stoichiometry in a subalpine forest.

Soil arthropods are crucial decomposers of litter at both global and local scales, yet their functional roles in mediating microbial activity during litter decomposition remain poorly understood. Here, we conducted a two-year field experiment using litterbags to assess the effects of soil arthropods on the extracellular enzyme activities (EEAs) in two litter substrates (Abies faxoniana and Betula albosinensis) in a subalpine forest. A biocide (naphthalene) was used to permit (nonnaphthalene) or exclude (naphthalene application) the presence of soil arthropods in litterbags during decomposition. Our results showed that biocide application was effective in reducing the abundance of soil arthropods in litterbags, with the density and species richness of soil arthropods decreasing by 64.18-75.45 % and 39.19-63.30 %, respectively. Litter with soil arthropods had a greater activity of C-degrading (ß-glucosidase, cellobiohydrolase, polyphenol oxidase, peroxidase), N-degrading (N-acetyl-ß-D-glucosaminidase, leucine arylamidase) and P-degrading (phosphatase) enzymes than litter from which soil arthropods were excluded. The contributions of soil arthropods to C-, N- and P-degrading EEAs in the fir litter were 38.09 %, 15.62 % and 61.69 %, and those for the birch litter were 27.97 %, 29.18 % and 30.40 %, respectively. Furthermore, the stoichiometric analyses of enzyme activity indicated that there was potential C and P colimitation in both the soil arthropod inclusion and exclusion litterbags, and the presence of soil arthropods decreased C limitation in the two litter species. Our structural equation models suggested that soil arthropods indirectly promoted C-, N- and P-degrading EEAs by regulating the litter C content and litter stoichiometry (e.g., N/P, LN/N and C/P) during litter decomposition. These results demonstrate that soil arthropods play an important functional role in modulating EEAs during litter decomposition.

Responses of soil nematode community within soil aggregates to tea plantation age.

It is increasingly believed that soil nematodes play an important role in the soil community and have a pronounced influence on the evaluation of soil health and the monitoring of soil food web changes. Soil aggregates provide habitable pore space and resource availability for soil organisms. The distribution of soil nematodes, which are relatively small soil fauna, may be related to the degree of soil aggregates. Soil nematode communities were studied with different soil components: large macro-aggregates (> 2 mm), medium macro-aggregates (2-1 mm), small macro-aggregates (1-0.25 mm), and micro-aggregates (< 0.25 mm) extracted from the same crop variety plantings (Sichuan tea) of different ages (19 years, 26 years, 34 years, and 56 years) in Sichuan province, southwestern China, in 2018. The results showed that the tea plantation with 26 years of cultivation was more suitable for the propagation of nematode communities, and the numbers of total nematodes were highest in the > 2 mm fractions. Compared with other tea plantations, the Margalef index (SR) of 26-year-old tea plantation was significantly higher than that within the large and medium macro-aggregates, and the maturity index (MI) was higher in the large and small macro-aggregates in the 26-year-old tea plantation. In the large macro-aggregates, the value of functional metabolic footprints decreased with the tea plantation age. In addition, the functional metabolic footprints increased with the increase in soil aggregate size. Our finding suggests that nematode communities are limited by resource availability and resource quality played an important role in determining nematode communities. Moreover, the soil food web was degenerated with the age of tea cultivation. Therefore, in the study area, it is necessary to pay attention to the rational allocation and application of organic fertilizer in the late stage of tea planting, so as to maintain the soil fertility and soil food web structure of the tea garden.

Roots-Enhanced Preferential Flows in Deciduous and Coniferous Forest Soils Revealed by Dual-Tracer Experiments.

Macropores formed by roots are crucial channels for preferential flows in forest soils that are largely responsible for water percolation and solute leaching. Using dual-tracer experiments (Brilliant Blue FCF and bromide [Br]), this study investigated the preferential flows of water and solutes in a deciduous forest dominated by Bl. and a coniferous forest mainly planted with (L.) Franco. Dye-stained patterns and concentrations of Brilliant Blue and Br were obtained in vertical soil profiles (0-30 cm), whereas stained and unstained roots were collected and analyzed in horizontal soil profiles to a 30-cm soil depth. Brilliant Blue and Br were mainly accumulated in the 0- to 20-cm soil depth, which had greater total root length density than the 20- to 30-cm soil depth ( < 0.05). Only part of the roots facilitated the preferential flows, with finer roots (i.e., diameter <1 mm) contributing the most. More intriguingly, the coniferous forest soil had a greater degree of preferential flows and greater tracer concentrations at deeper soil depth than the deciduous forest soil, suggesting the importance of tree species and forest composition on water and solute transport in forest ecosystems.