Ji Chen

• PhD
• Managing Director at Chinese Academy of Sciences

Fractional Vegetation Cover (FVC) and Land Surface Temperature (LST) are critical indicators for assessing grassland ecosystems. Based on global remote sensing data for FVC and LST from 2001 to 2022, this study employs the Mann–Kendall trend test and Spearman correlation analysis to explore the dynamic changes in and spatial distribution patterns o...

The Qinghai–Tibet plateau, with an average altitude of over 4000 m, has low annual average temperatures and a high demand for building heating. This region’s abundant solar energy resources hold substantial practical significance for improving the indoor heat environment and reducing building energy consumption. This paper investigates the impact o...

Aboveground biomass (AGB) serves as a crucial measure of ecosystem productivity and carbon storage in alpine grasslands, playing a pivotal role in understanding the dynamics of the carbon cycle and the impacts of climate change on the Qinghai–Xizang Plateau. This study utilized Google Earth Engine to amalgamate Landsat 8 and Sentinel-2 satellite im...

A retrogressive thaw slump (RTS) is a slope failure formed by slope thaw settlement and retrogressive slump following the thawing of ice‐rich permafrost or the melting of massive ice. Here, we review recent literature on RTSs, one of the main geomorphological landscapes developed in the process of permafrost degradation. The main topics are as foll...

Two-phase closed thermosyphons (TPCTs) have been widely used in permafrost regions because of their good cooling effect. The variation in the inclination angle of TPCTs significantly affects the heat transfer process and temperature distribution inside TPCTs, which is still not fully understood. This study experimentally investigated the heat trans...

The land surface temperature obtained from remote sensing was widely used in the simulation of permafrost mapping instead of air temperature with the rapid development of remote sensing technology. The land surface freezing and thawing index (LFI and LTI), which is commonly regarded as the ground surface freezing and thawing index (GFI and GTI), ca...

The measurement of pile axial load is of great significance to determining pile foundation design parameters such as skin friction and end bearing capacity and analyzing load transfer mechanisms. Affected by the temperature and ice content of frozen ground, the interface contact relationship between pile foundation and frozen soil is complicated, m...

Study region The Tibetan Plateau (TP). Study focus This study evaluated the accuracy of six mainstream gridded precipitation products, including the Asian precipitation dataset by calibrating the GPM-era IMERG (AIMERG), Climate Hazards group InfraRed Precipitation with Stations (CHIRPS), China Meteorological Forcing Dataset (CMFD), ECMWF Re-Analys...

Accurately measuring precipitation is integral for understanding water cycle processes and assessing climate change in the Qinghai—Tibet Plateau (QTP). The Geonor T-200B weighing precipitation gauge with a single Alter shield (Geonor) and the Chinese standard precipitation gauge (CSPG) are widely used for measuring precipitation in the QTP. However...

To improve the rate of formation of carbon dioxide hydrates, tetra-n-butylammonium bromide (TBAB) was compounded with different concentrations of sodium dodecyl sulfate (SDS) and nanographite, and the effects of these mixtures on carbon dioxide hydrate formation were studied. The addition of TBAB alone, as well as mixtures of TBAB and SDS or nanogr...

The hydrothermal relationship between vegetation and seasonal frozen soil is one of the key research contents in the fields of permafrost ecological environment, hydrology and climate change in alpine mountainous areas. Based on the monitoring data of air temperature, precipitation and soil hydrothermal conditions at the depth of 0–5 m from site TS...

The heat emitted in the construction process of cast-in-place (CIP) pile foundations and the subsequent cement hydration process cause a thermal disturbance in the surrounding permafrost and reduce the early load capacity. In this paper, based on monitoring and simulation, the thermal behavior of CIP pile groups in permafrost regions was analyzed....

The temperature difference at the top and bottom of the crushed-rock layer can drive the heat convection inside. Based on this mechanism, crushed-rock structures with different forms are widely used in the construction and maintenance of the Qinghai-Tibet Railway as cooling measures in permafrost regions. To explore the stability of different forms...

Traditional embankment is widely used in the permafrost regions along the Qinghai-Tibet Railway (QTR) because of its simple construction and lower cost. However, this form of embankment has insufficient ability to resist external thermal disturbance. To clarify the thermal characteristics of traditional embankment under climate warming, the ground...

Geonor T-200B weighing precipitation gauge (Geonor) and Chinese standard precipitation gauge (CSPG) are widely used for measuring precipitaion in the Qinghai-Tibet Plateau. However, their measurements must be adjusted due to wetting, evaporation loss and wind-induced undercatch. Some transfer functions had been proposed in previous studies, but the...

The embankment of the Qinghai-Tibet Railway (QTR) has been experiencing severe problems due to permafrost degradation, especially in warm and ice-rich permafrost regions. Based on ground temperature and deformation data of the embankment at location K1497+150 of the QTR in 2006‒2018, the thermal regime and deformation process were analysed. The res...

Permafrost is sensitive to both climate warming and engineering disturbance on the Qinghai–Tibet Plateau (QTP). These factors degrade the stability of infrastructure built on permafrost and reduce its service life. To counter these effects, cooling of the subgrade to lower permafrost temperature forms part of the engineering design on the QTP. Proa...

Cast-in-place pile foundations are widely employed to support basic infrastructures on the Qinghai-Tibet Plateau (QTP). However, concrete hydration heat substantially affects the thermal stabilization of pile foundations in permafrost regions. In this paper, the thermal characteristics of a cast-in-place pile foundation in a warm (>−1 °C) permafros...

Understanding the long‐term role of cooling the underlying permafrost of the crushed rock structure embankment (CRSE) along the Qinghai–Xizang Railway (QXR) is crucial for the railway's safe operation. The thermal regime of the permafrost under the CRSE is analyzed here using monitoring data of soil temperature from 2005 to 2015. The results show t...

Alterations in the permafrost due to a warming climate increases the risk of permafrost thawing, accelerates carbon release, lowers super-permafrost groundwater, strengthens desertification, and destroys infrastructure. The permafrost temperature in six boreholes up to 40 m depth was measured from 2003 to 2015 along the Qinghai–Tibet Railway. Resul...

Alpine meadow degradation is a major environmental problem in the Qinghai-Tibetan Plateau of China. While it is expanding at a rapid pace, quantitative information on the effect of grassland degradation on soil properties remains largely unavailable. This study aimed to evaluate the effect of vegetation cover reduction on soil organic carbon (SOC)...

Changes in soil nutrient availability attributed to climate change and associated permafrost degradation have been reported in several ecosystems. However, little is known about the changes of soil nutrient availability in alpine grassland ecosystems. Based on a comprehensive dataset and random forest models, we investigated soil available nutrient...

Snow cover is characterized by the high albedo, low thermal conductivity, and notable heat transition during phase changes. Thus, snow cover significantly affects the ground thermal regime. A comparison of the snow cover in high latitudes or high-altitude snowy mountain regions indicates that the eastern Tianshan Mountains (China) show a characteri...

Soil nutrient stoichiometry and its environmental controllers play vital roles in understanding soil-plant interaction and nutrient cycling under a changing environment, while they remain poorly understood in alpine grassland due to lack of systematic field investigations. We examined the patterns and controls of soil nutrients stoichiometry for th...

The Tibetan Plateau (TP) has the largest areas of permafrost terrain in the mid- and low-latitude regions of the world. Some permafrost distribution maps have been compiled but, due to limited data sources, ambiguous criteria, inadequate validation, and deficiency of high-quality spatial data sets, there is high uncertainty in the mapping of the pe...

Diatomite is a highly porous media with significant water absorption and retention capacity. In order to investigate the long-term cooling effect of diatomite on a roadbed in a warm permafrost region, a diatomite embankment was constructed in 2003, on National Highway 214, Qinghai-Tibet Plateau. Field data revealed that surface temperature differen...

The Tibetan Plateau (TP) possesses the largest areas of permafrost terrain in the mid- and low-latitude regions of the world. A detailed database of the distribution and characteristics of permafrost is crucial for engineering planning, water resource management, ecosystem protection, climate modelling, and carbon cycle research. Although some perm...

Snow cover significantly influences the moisture and thermal properties of the active layer in permafrost regions. Seasonal snow cover, soil temperature, and moisture were monitored in the northeastern Qinghai-Tibet Plateau (QTP) from December 2012 to February 2015. According to field data, the following conclusions were drawn. (1) The snow season...

On the basis of the Biot’s consolidation theory, a thermo-hydro-mechanical (THM) model was presented for computing the settlement of warm frozen soils under an external load. The proposed model allowed the unfrozen water in the soils to migrate according to the effective stress principle. In addition, the pressure potential due to loading was consi...

An investigation of permafrost in the Gaize area in the west Qinghai-Tibet Plateau in China was conducted in October and November of 2010 and 2011. It was found that mean annual ground temperature was >-1 °C with a permafrost thickness of <60 m in the widespread alpine steppe below an altitude of 5400 m a.s.l. The active layer thickness was usually...

Along the Gonghe-Yushu highway, three typical permafrost embankments, namely insulated board embankment, block-stone embankment and ventilated embankment were utilized. In order to study the process of variation of the underlying permafrost and to compare three measures, the temperature variations of the shallow layer(0-4 m) and deep layer(below 4...

This paper presents an experimental study of the cooling effect of crushed rock-based embankment on slope wetlands along the Chaidaer-Muli Railway. The result shows that only the embankment shady side can be effectively cooled down in a warm permafrost region and the crushed rock-based embankment can cool the entire embankment in a cold permafrost...

The characteristics of the permafrost along National Highway No. 214 (G214) in Qinghai province (between kilometer markers K310 and K670), including the distribution patterns of permafrost and seasonally frozen ground (SFG), ground ice content and mean annual ground temperature (MAGT), were analyzed using a large quantity of drilling and measured g...

The Noah land surface model (LSM) can simulate well the hydrological and thermal processes of permafrost in the Qinghai-Tibet Plateau (QTP) and provides more permafrost metrics than those of statistical empirical models. The aim of this study was to develop a prototype for permafrost modelling by Noah and validate the model with field data. This wa...

In permafrost regions, embankment stability has been destroyed with longitudinal cracks primarily caused by transverse asymmetric settlement. And shady–sunny slope effect is a principal factor which might result in embankment asymmetric settlement. Based on field data of some typical sections along the Chai–Mu Railway (simply called CMR) with obvio...

Zonal alpine meadow is widespread in the source area of the Datong River, northeastern Qinghai-Tibet Plateau, China, and can be divided into typical meadow and swamp meadow, according to variations in the soil moisture content. A total of 56 measurements of the mean annual ground temperature (MAGT) revealed a significant difference in the MAGT of t...

The study analyzed the changes of species diversity indices (richness index, Shannon-Wiener diversity index and Pielou evenness index) along the ground temperature of permafrost based on investigation data from 199 vegetation spots sampled and permafrost temperatures from an equivalent-elevation model in the Datong River source region, northeastern...

Enzyme activities play key roles in the biochemical functioning of soils, in processes such as soil organic matter formation and degradation, and nutrient cycling. They are indicators of soil quality and key to soil ecosystem functioning. In this study, the effect of vegetation communities and soil properties on the activities of invertase, alkalin...

Soil organic carbon (SOC) contents were examined beneath two grassland vegetation communities and cold desert sites in permafrost areas of the central western part of the Qinghai-Tibet Plateau. Mean SOC stocks in the top 150 cm were 7.73 kg m-2 for Stipa roborowskyi communities and 3.72 kg m-2 for Carex moorcroftii communities, but only 1.84 kg m-2...

A large volume of underground gas in the permafrost region of the Qinghai-Tibetan Plateau has been identified. Although many studies were performed to investigate the soil organic carbon dynamics and Earth degassing in volcanic areas, this is the first report of a large amount of non-volcanic CO2 contained in permafrost. The gas was mostly CO2 (81....

Based on the important impact of vegetation on permafrost development, the influence of vegetation on permafrost distribution was studied taking the source region of the Datong River Basin as the study area. Taking the calculated equivalent-elevations together with the measured ground temperatures of permafrost (at 15 m depth) and the vegetation sa...

The current study analyzes the effects of the thermal state of permafrost on the alpine ecosystem based on investigation data from 92 vegetation spots sampled in 2010 and permafrost temperatures from an equivalent-elevation model in the Datong River source region, in the northeastern Qinghai-Tibet plateau in China. The interactions among the permaf...

The Chaidaer-Muli Railway (abb., Chaimu Railway) was constructed in the Qilian Mountains, where middle-latitude swampy permafrost regions are developed. About 20km embankment was equipped with heat pipes. Taking into account the characteristics of local climate, the interaction between heat pipe and ground soils and secondary standard adopted by th...

The source region of the Datong River is an inland watershed and located at the northeastern edge of the Qinghai-Tibetan Plateau. There is relatively plentiful rainfall in the source region. Vegetation, mainly composed of alpine meadow and alpine swamp meadow, developed well and covered mostly the ground surface of the source region. The equivalent...

A primary analysis was applied to analyze the effects of degradation of frozen soil on the alpine vegetation ecosystem based on the investigation data from 92 vegetation plots sampled in 2010 and 30m- normalized difference vegetation index (NDVI) data of these plots across the ground temperature of permafrost in the Datong river source region, on t...

More than half of the recently built 142-km long Chaidaer–Muli Railway (CMR) in northern Qinghai Province, China travels across warm (≥−1°C), ice-rich permafrost in wetlands on the southern flank of the Qilian Mountains. In comparison with the Qinghai–Tibet Railway from Golmud to Lhasa, the CMR traverses mostly across wetlands underlain by more ice...

The Chaimu Railway (CMR) is being constructed for the coal resource transportation in northern Qinghai-Tibet plateau. The total length of the line is 142km. The permafrost in this region is warm, ice-rich and unstable. For the purpose of cooling soil and stabilizing the subgrade, thermosyphon technique was adopted in a quarter of the whole line. Th...

The spatial distribution patterns of permafrost affect the stability of engineering facilities in high-cold regions. A transportation corridor, located in the northeastern Qinghai province of China, and passing through the Qilianshan high-mountain permafrost area is investigated. Two field investigations were carried out and a total of 220 borehole...

There widely exists permafrost over Qinghai-Tibetan Plateau. Many roads have to pass permafrost regions. In northeast edge of the plateau, a section of a road has been suffering from frost heave damage for many years. In 2004, a drilling investigation was carried out. It was found that the section of the road was built on a permafrost island, and t...

Ground-penetrating radar (GPR) has become an important geophysical tool which can provide a wealth of interpretive information about the vertical profile of discontinuous permafrost. A GPR investigation was conducted in October 2006 at the Nalaikh site at the southern boundary of the Siberian discontinuous permafrost region in Mongolia. GPR data we...

The heat transfer performance of hollow bricks with two kinds of thickness under the condition of vertical aperture was studied by steady comparison method. The results show: (1) for the system with the cold end being 0°C, it is cooled more quickly when the cold end is located on the top (mode I) than on the bottom (mode II); (2) when the temperatu...

In permafrost regions, the measures of constructing embankments or installing thermal insulations are in common use to keep the permafrost table under the roadways stable. However, the effectiveness of these measures depends on their adjustment to the mean annual ground temperature and the temperature amplitude in the permafrost under the roadway....