Climate change and engineering activities are the leading causes of permafrost temperature increase, active layer thickening, and ground-ice thaw, which trigger changes in the engineering stability of embankments. Based on the important research advances on permafrost changes and frozen soil engineering in Qinghai-Xizang Plateau, the changes in permafrost temperature and active layer thickness, their relationships with climate factors, the response process of engineering activities on permafrost, dynamic change of engineering stability of Qinghai-Xizang Railway, and the cooling mechanism and process of crushed-rock layers are discussed using the monitoring data of permafrost and embankment deformation. Finally, solutions to the key scientific problems of frozen soil engineering under climate change are proposed.

A characteristic of frozen ground is a tendency to form banded sequences of particle-free ice lenses separated by layers of ice-infiltrated soil, which produce frost heave. In permafrost, the deformation of the ground surface caused by segregated ice harms engineering facilities and has considerable influences on regional hydrology, ecology, and climate changes. For predicting the impacts of permafrost degradation under global warming and segregated ice transformation on engineering and environmental, establishing appropriate mathematical models to describe water migration and ice behavior in frozen soil is necessary. This requires an essential understanding of water migration and segregated ice formation in frozen ground. This article reviewed mechanisms of water migration and ice formation in frozen soils and their model construction and introduced the effects of segregated ice on the permafrost environment included landforms, regional hydrological patterns, and ecosystems. Currently, the soil water potential has been widely accepted to characterize the energy state of liquid water, to further study the direction and water flux of water moisture migration. Models aimed to describe the dynamics of ice formation have successfully predicted the macroscopic processes of segregated ice, such as the rigid ice model and segregation potential model, which has been widely used and further developed. However, some difficulties to describe their theoretical basis of microscope physics still need further study. Besides, how to describe the ice lens in the landscape models is another interesting challenge that helps to understand the interaction between soil ice segregation and the permafrost environment. In the final of this review, some concerns overlooked by current research have been summarized which should be the central focus in future study.

Qinghai–Tibet plateau (QTP) is closely related to global climate change, and it has undergone serious permafrost degradation due to global warming in the last decades. It is crucial to measure the active layer thickness (ALT) for characterizing and monitoring the permafrost degradation of QTP. In this paper, an ALT retrieval model based on ground subsidence derived from synthetic aperture radar interferometry (InSAR), land cover types, and groundwater information is proposed. In particular, the surface subsidence is retrieved using the time-series InSAR technique with TerraSAR-X ST mode images. Moreover, groundwater content models with different land covers are constructed based on multilayered assumptions and in situ data. By taking into account the groundwater content profile and land cover types, the ALT is retrieved from deformation with the full season cycle derived by InSAR technique. The experimental results in Beiluhe indicate that the estimated ALT is consistent with field-measured data. The estimated ALT map shows the difference between the alpine meadow and alpine desert areas, with mean ALT of approximately 1.5 m in alpine meadow area and approximately 3 m in alpine desert area. Our results demonstrate that the InSAR technique with high-resolution SAR images can be of great importance for the study of permafrost environments.

Background: The plant tolerance mechanisms to low temperature have been studied extensively in the model plant Arabidopsis at the transcriptional level. However, few studies were carried out in plants with strong inherited cold tolerance.Chorispora bungeanais a subnival alpine plant possessing strong cold tolerance mechanisms. To get a deeper insight into its cold tolerance mechanisms, the transcriptome profiles of chilling-treatedC. bungeanaseedlings were analyzed by Illumina deep-sequencing and compared with Arabidopsis.Results: Two cDNA libraries constructed from mRNAs of control and chilling-treated seedlings were sequenced by Illumina technology. A total of 54,870 unigenes were obtained byde novoassembly, and 3,484 chilling up-regulated and 4,571 down-regulated unigenes were identified. The expressions of 18 out of top 20 up-regulated unigenes were confirmed by qPCR analysis. Functional network analysis of the up-regulated genes revealed some common biological processes, including cold responses, and molecular functions inC. bungeanaand Arabidopsis responding to chilling. Karrikins were found as new plant growth regulators involved in chilling responses ofC. bungeanaand Arabidopsis. However, genes involved in cold acclimation were enriched in chilling up-regulated genes in Arabidopsis but not inC. bungeana.In addition, although transcription activations were stimulated in bothC. bungeanaand Arabidopsis, noCBFputative ortholog was up-regulated inC. bungeanawhileCBF2andCBF3were chilling up-regulated in Arabidopsis. On the other hand, up-regulated genes related to protein phosphorylation and auto-ubiquitination processes were over-represented inC. bungeanabut not in Arabidopsis.Conclusions: We conducted the first deep-sequencing transcriptome profiling and chilling stress regulatory network analysis ofC. bungeana, a subnival alpine plant with inherited cold tolerance. Comparative transcriptome analysis suggests that cold acclimation is not a major chilling tolerance mechanism ofC. bungeana. Activation of protein phosphorylation and ubiquitination may confer chilling tolerance toC. bungeanain a more rapid and flexible way than cold acclimation. Such differences may have contributed to the differences in cold tolerance betweenC. bungeanaand Arabidopsis. The results presented in this paper will be informative for gene discovery and the molecular mechanisms related to plant cold tolerance.