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In the Loess Plateau in Northern China, repeated freeze-thaw (FT) cycles deteriorate the strength and structure of loess as a foundation soil, resulting in the instability or failure of supporting structure. Lignosulfonate is an eco-material, utilized as an effective and nontraditional stabilizer to improve the engineering properties of metastable soils. A series of laboratory tests, including unconfined compression tests, cyclic loading-unloading tests and scanning electron microscopy, on calcium lignosulfonate (CL)- and sodium lignosulfonate (SL)-stabilized loess were performed to investigate the stabilization effect, deterioration mechanisms of the FT cycles, and the resistance to FT cycles. Two traditional stabilizers, quicklime (QL) and sodium silicate (SS), were selected, and the engineering properties of QL- and SS-stabilized loess were compared with those of CL- and SL-stabilized loess. The results showed that the strength values of CL- and SL-stabilized loess specimens decreased by 34.2% and 50% respectively, after 20 FT cycles, whereas those of the traditionally SS- and QL- stabilized specimens decreased by 85.3% and 82.87%, respectively. The elastic moduli of SL- and QL-stabilized loess specimens decreased by 22.1% and 92.0%, respectively. The mean energy dissipations of nontraditionally treated specimens also decreased significantly less than those of traditionally treated specimens. Overall, the results showed CL and SL had better stabilization effects on engineering properties of loess than QL and SS, and their stabilized loess specimens exhibited stronger resistance to FT cycles. The study findings demonstrated the significant potential of lignosulfonate for extensive application in cold loess areas. [ABSTRACT FROM AUTHOR]

Active layer is a key component for permafrost environment studies as many subsurface biological, biogeochemical, ecological, and pedogenic activities prevail in this layer. This study focuses on active layer temperature monitoring in an area with sporadic permafrost at two adjacent sites along China-Russia Crude Oil Pipeline (CRCOP), North-East China. Site T1 is located in disturbed ground on the right-of-way (on-ROW) 2 m away from the center of the oil pipeline. T2 is located in a natural and undisturbed site, around 16.6 m off-ROW. Our objective was to study seasonal variability of the active layer depth and thermal regime from October 2017 to September 2018. The monitoring sites consist of soil temperature probes arranged in a vertical array at different depths at both sites. The following parameters were computed: number of isothermal days (ID), freezing days (FD), thawing days (TD), freezing degree days (FDD), thawing degree days (TDD), number of freeze-thaw days (FTD). The mean air temperature in the monitoring period reached - 3.2°C. The temperature profile indicates that the maximum active layer thickness observed during the study period was 10 m at T1 and 2 m at T2. The majority of the soil temperatures were above or close to 0°C, resulting in great values of TDD, especially in the first 4 m depth. TDD for T1 were predominant and ranged between 600–1160°C·days (0–4 m depth) reflecting the influence of oil temperature from the pipeline. In T2 borehole FDD were predominant for all the soil layer depths resulting in less permafrost degradation. This comparison emphasizes the significant influence of vegetation removal and the dispersed heat from the pipeline on the active layer thickness. [ABSTRACT FROM AUTHOR]

Adequate characterization of soil organic carbon (SOC) fractions is essential to elucidate carbon dynamics in permafrost‐affected ecosystems. SOC and its fractions were investigated across alpine ecosystems, including alpine swamp meadows (ASM), alpine meadows (AM) and alpine steppes (AS), in permafrost regions on the Qinghai–Tibet Plateau (QTP), southwest China. The density separation method was used to separate the SOC into light‐ and heavy‐fraction organic carbon (LFOC and HFOC, respectively). Permafrost soils in the ASM had higher SOC, LFOC, and HFOC contents than in the AM. LFOC and HFOC contents were significantly correlated, but both were more closely related to SOC than to each other. On the ecological gradient from ASM to AS, the thickness of surficial organic horizons decreased while the thickness of mineral materials increased. SOC in the organic horizon and permafrost had high mineralization probability. At soil depths of 0–200 cm in ASM, AM, and AS, the SOC stocks were 123, 71, and 25 kg m−2; LFOC stocks were 70, 49, and 12 kg m−2; and HFOC stocks were 58, 37, and 15 kg m−2, respectively. These results show that SOC fractions vary with vegetation type and active layer thickness, thus making SOC sensitive to changes in environmental conditions. Therefore, the decomposition of SOC in permafrost‐affected soils of the QTP could be accelerated over a degrading permafrost and under a warming climate. [ABSTRACT FROM AUTHOR]

Compacted loess is widely used as fills of road embankments in loess regions of northern China. Generally, densely-compacted loess can satisfy the requirements of embankment strength and post-construction deformation. I lowever, uneven subsidence, pavement cracks and other related damages can affect the integrity of loess subgrade after several years of operation, and even cause some hazards, especially in North China, where the strong freeze-thaw erosion occurs. In this study, cyclic freeze-thaw tests for both densely and loosely compacted loess samples were performed to determine the variation in engineering properties such as volume, void ratio, collapsible settlement, microstructure, and the related mechanisms were addressed. The experimental results showed that an obvious water migration and redistribution occurred within the samples during freeze-thaw cycles. Ice lenses and fissures could be identified in the upper frozen layers of the samples. After freeze-thaw cycles, the dry densities of the nipper layers of samples changed significantly due to strong freeze-thaw erosion. The dry densities decreased for the dense sample and increased for the loose sample. It can be found that dense samples become loose, while loose samples became dense with the increasing number of freeze-thaw cycles. Their related void ratios changed reversely. Both void ratios tended to fall into a certain range, which verified the concept of a residual void ratio proposed by Viklander. The loosening process of densely compacted samples involves the formation of large pores, volume increase and density reduction as well as the related changes in mechanical properties because freeze-thaw cycles may be important contribution to problems of loess road embankments. Adverse effects of freeze-thaw cycles, therefore, should be taken into account in selecting loess parameters for the stability evaluation of road embankment in seasonally frozen ground regions. [ABSTRACT FROM AUTHOR]

On-site monitoring is very important for understanding formation mechanisms of frost hazards frequently occurring in pipeline foundation soils and for designing and deploying according mitigative measures in permafrost regions. Significant thaw subsidence of ground surfaces along the China-Russia Crude Oil Pipeline (CRCOP) from Mo'he to Daqing, Heilongjiang Province, Northeast China have been observed at some segments underlain by ice-rich, warm (>1.0°C) permafrost since the official operation in January 2011. Recent monitoring results of the thermal states of foundation soils at the kilometer post (KP) 304 site along the CRCOP are presented in this paper. The results indicate that during the period from 2012 to 2014, shallow soils (at the depths from 0.8 to 4.0 m from ground surface) has warmed by approximately 1.0°C in the lateral range of 1.2 to 2.1 m away from the pipeline axis, and deeper permafrost (such as at the depth of 15 m, or the depth of zero annual amplitude of ground temperatures) by 0.08°C per year 4 m away from the pipe axis, and 0.07°C per year 5 m away from the pipeline axis. The results indicate an all-season talik has developed around and along the CRCOP. The thaw bulb, with a faster lateral expansion (compared with the vertical growth), enlarges in summer and shrinks in winter. This research will provide important references and bases for evaluating thermal influences of warm pipeline on permafrost and for design, construction, operation and maintenance of pipelines in permafrost regions. [ABSTRACT FROM AUTHOR]

Grazing exclusion (GE) is widely used in the Tibetan Plateau of China to restore degraded grasslands. However, the effects of GE on vegetation and soil properties in alpine meadows are still not well understood. We compared GE with adjacent continuously grazing alpine meadows at five sites to evaluate the impact of GE (10–14 years) on vegetation and soil properties in the permafrost region of the Tibetan Plateau. We collected soil samples at two soil depths (0–20 and 20–40 cm) from GE and adjacent grazing sites. The results showed that GE and Site had significant effects on aboveground biomass and cover, Site but not GE had significant effects on diversity index. GE significantly increased the aboveground biomass and cover in three of the five sites, particularly where vegetation cover was greatest. At each site, GE had inconsistent effects on plant species diversity (a positive effect at one site, no significant effects at three sites, and a negative effect at the other site). No significant differences were found between GE and adjacent grazing grasslands in soil properties (soil organic carbon [SOC], total nitrogen [N], total phosphorus [P], available P, mineral N, microbial biomass carbon [MBC] and nitrogen [MBN] and pH) for both soil depths at each site. A general linear mixed model confirmed that site and sampling depth, rather than GE, significantly affected soil properties (except for MBC). Both total aboveground biomass and cover were positively correlated with soil total P, MBC and MBN, were negatively correlated with available P and pH, and were not significantly correlated with SOC and total N. The results indicate that long-term GE (10–14 years) in alpine meadow did not significantly impact soil properties, and its impact on plant biomass and vegetation cover depends on the vegetation condition of the site. Our results can provide new insights for alpine meadow management in the permafrost region of the Tibetan Plateau. [ABSTRACT FROM AUTHOR]

Abstract: Five new chlorophenolic glucosides, curculigine E (1), curculigine F (2), curculigine G (3), curculigine H (5), curculigine I (6) and one new phenolic glycoside, orcinoside H (4), together with eight known phenolic glycosides (7–14) were isolated from the Curculigo orchioides Gaertn. Their structures were established by spectroscopic techniques (IR, UV, MS, 1D and 2D NMR). The isolated phenolic glycosides were evaluated for antiosteoporotic activity against MC3T3-E1 cell line using MTT assays. Compounds 1, 2, 3, and 5 showed moderate antiosteoporotic activity with the proliferation rate of 10.1–14.1%. [Copyright &y& Elsevier]

• Driving factors of SOC and total N were explored in 28 lucerne fields. • The SOC and total N were mainly explained by soil resources. • Soil P, moisture, and altitude were the key factors affecting SOC and total N. • Plant species diversity positively affected SOC and total N contents. • A strong interaction effect was observed among topography, vegetation and soil on SOC. Lucerne (Medicago sativa L.) is one of the most successfully introduced species for revegetation on the Loess Plateau of China and provides important ecosystem services. However, the driving mechanism of soil organic carbon (SOC) and total nitrogen (TN) in lucerne grasslands remains unclear. This study explored the controlling factors of SOC and TN in lucerne grasslands in the semiarid Loess Plateau. A total of 112 quadrats were employed in 28 lucerne fields. Vegetation characteristics, topographic factors, and soil properties at a 0–20 cm depth were measured in each quadrat. The SOC and TN contents increased with altitude and showed positive correlations with species richness, aboveground biomass of native plants, soil moisture, soil inorganic nitrogen, total soil phosphorus (P), and C:P and N:P ratios. Variations in SOC and TN contents were mainly attributed to soil resources, followed by the interaction of topography, vegetation and soil. Soil P, soil moisture, altitude, and native plant species were the main factors controlling SOC and TN contents in these lucerne grasslands. Results suggest that specific abiotic (soil P and moisture) and biotic (plant species diversity) factors controlled SOC and TN in semiarid lucerne grasslands. These factors should be included in SOC and TN evaluation models to predict the future terrestrial ecosystem carbon and nitrogen dynamics. [ABSTRACT FROM AUTHOR]

A new stigmasterol, (24S)-stigmast-5-en-7beta-ethoxy-3beta-ol (2) together with three known sterols have been isolated from the ethanolic extract of the pericarp of Sphaerophysa salsula (Pall.) DC, and their structures elucidated mainly on the basis of the spectral data and comparison with the literature.