The article assesses the influence of permafrost weathering on the rate of destruction of technogenic land forms, as exhibited on as illustrated by the railway embankment of the Amur-Yakut mainline in the Sakha Republic (Yakutia). Studies were carried out on a railway section more than 375 km long. The subsidence rate of the embankment slopes and structural excavations was determined using laboratory methods that simulate various mechanisms of temperature (with a transition through 0 °C) impact on rocks. For the first time, a quantitative assessment of the influence of cryogenic weathering on the stability of the railway in the region belonging to the northern building-climatic zone is given. For the territory under consideration, embankment rocks were experimentally determined to undergo more than 100 freezing and thawing cycles during a year. Under the existing climatic conditions, cryogenic weathering actively affects the embankment of the railway to a depth of 30 cm. Most of the embankment deformations detected during field observations are due to defects in the integrity of this particular layer. The size of the disintegrating layer of particular types of rock comprising the railway embankment has been established as reaching 10 cm per year. In 5 years following the formation of embankments comprising the upper structure of the railroad tracks, the physical and mechanical properties of rocks, which initially had a tensile strength for uniaxial compression in the range of 40-70 MPa, were reduced by more than 50%. According to the authors, the establishment of regional cryohypergenesis features is universal in nature and can be applied to solving a wide range of tasks related to the assessment and prediction of the degree of cryogenic transformation of rocks having different structural properties.
Hydrological circulation, as the most basic material cycle and active natural phenomenon on earth, exerts a significant influence on climate change. The mid-Holocene is an important period to better understand modern environmental change; however, little research has focused on its quantitative simulation of paleo-hydrological process. In this research, we first collected chronological evidence and sediment records from six Holocene sedimentary sections in the Shiyang River Basin to reconstruct the mid-Holocene environment and terminal paleo-lake area. Secondly, we comprehensively analyzed modern pollen combinations and their propagation characteristics in surface soil, air, river and lacustrine sediments in the Shiyang River Basin, and combined the pollen records, as well as quantitatively reconstructed the millennial-scale vegetation zones. Finally, based on the land-cover adjustment results during the mid-Holocene, we successfully used the Soil and Water Assessment Tool (SWAT) model, a modern distributed hydrological watershed model, to simulate mid-Holocene runoff in the basin. Results show that the reconstructed climate in the basin was warmer and moister than that in recent times. Vegetation types in the mid-Holocene mainly consisted of sub-alpine shrub distributed between 2,550 m and 2,750 m, forest at an elevation of 2,550-2,750 m, steppe at an elevation of 1,550-2,150 m and desert steppe below 1,550 m. The upstream, midstream, downstream and average annual runoff of the mid-Holocene in the basin were 16.76×108 m3, 22.86×108 m3, 9.00×108 m3 and 16.20×108 m3 respectively, compared to 15.61×108 m3 of modern annual runoff. Also, the area of terminal paleo-lake in the mid-Holocene was 628 km2. Thus, this study provides a new quantitative method for paleo-hydrological simulation.
Based on observational data of arid, semi-arid and semi-humid areas in Northwest China, the characteristics of surface-water heat transfer and land-surface parameters were compared and analyzed. The results show that the annual mean net radiation was largest in the semi-humid area, followed by the semi-arid area, and then the arid area: 77.72 W/m2, 67.73 W/m2, and 55.47 W/m2, respectively. The annual mean sensible heat flux was largest in the arid area, followed by the semi-arid and semi-humid areas, while latent heat flux showed the reverse. The annual mean sensible heat flux in arid, semi-arid, and semi-humid areas was 85.7 W/m2, 37.59 W/m2, and 27.55 W/m2, respectively. The annual mean latent heat flux was 0 W/m2, 26.08 W/m2, and 51.19 W/m2, respectively. The annual mean soil-heat flux at the 5-cm soil layer in arid, semi-arid, and semi-humid areas was 1.00 W/m2, 0.82 W/m2, and -1.25 W/m2, respectively. The annual mean surface albedo was largest in the arid area, followed by the semi-humid area; and the smallest was in the semi-arid area: 0.24, 0.21, and 0.18, respectively. The annual mean Bowen ratio in the semi-arid area was about 2.06, and that in semi-humid area was about -0.03. The annual mean soil thermal conductivity in the arid, semi-arid, and semi-humid areas was 0.26 W/(m?k), 1.15 W/(m?k), and 1.20 W/(m?k), respectively.
Lakes have received considerable attention as long-term sinks for organic carbon (C) at regional and global scales. Previous studies have focused on assessment and quantification of carbon sinks, and few have worked on the relationship between millennial-scale lake C sequestration, hydrological status and vegetation, which has important scientific significance in improving our understanding of lake C stocks and storage mechanisms. Here, we present a comprehensive study of pollen records, organic geochemical proxies, lake-level records, sediment accumulation rate (SAR) and organic C accumulation rate (CAR) in China since the Holocene. We also include numerical climate classification and lake-level simulations, to investigate variations of lake C sequestration, hydrological status and vegetation during the Holocene. Results indicate that the evolution of lake C accumulation showed an out-of-phase relationship with hydrological status and vegetation in China. Lake C accumulation exhibited an overall trend of increasing from the early to late Holocene in response to gradually increasing terrestrial organic matter input. However, China as a whole experienced the densest vegetation cover in the middle Holocene, corresponding to the mid-Holocene optimum of a milder and wetter climate. Optimal hydrological conditions were asynchronous in China; for example, early Holocene in Asian monsoon dominated areas, and middle Holocene in westerlies controlled regions. Our synthesis indicated that climate change was the main factor controlling the long-term variability in lake C accumulation, hydrologic conditions, as well as vegetation, and human influences were usually superimposed on the natural trends.
Lilium davidii var. unicolor (Lanzhou lily) is an important economic crop in the northwest cold and arid regions of China. Effective regulation of tiller-bulb development and plant growth is the key to improving yield and quality of the lily. This study attempted to evaluate the effect of gibberellic acid (GA3) on tiller-bulb development and plant growth of Lanzhou lily by applying GA3 at various concentrations (0 mg/L, 10 mg/L, 30 mg/L, 60 mg/L, and 100 mg/L) before planting and in the seedling period. Results showed that the 60-mg/L GA3 application had an inhibiting effect on tiller-bulb formation and increased the ratios of single and double bulbs but decreased the ratios of bulbs with three or more tiller bulbs, as compared to the control (CK) and other GA3 treatments. The difference in flower number did not reach significant levels among the treatments. The tillering-related endogenous hormones IAA (indole-3-acetic acid) and Z (zeatin) content decreased, while IAA/Z increased with the 60-mg/L GA3 treatment during tiller initiation. And also, the shoot-bulb number and total daughter-bulb number decreased significantly with the 60-mg/L GA3 treatment. Furthermore, the 10-mg/L GA3 application promoted growth of Lanzhou lily significantly and resulted in an increase in plant height; bulb diameter; bulb circumference; and biomass of shoots, bulbs, fibrous roots, and the whole plant. Therefore, GA3 application is promising as a new regulation method for inhibiting tiller-bulb development and promoting bulb growth in Lanzhou lily production.
