Soil temperature dynamics and freezing processes for biocrustal soils in frozen soil regions on the Qinghai–Tibet Plateau

Geoderma ◽  
2022 ◽  
Vol 409 ◽  
pp. 115655
Author(s):  
Jiao Ming ◽  
Yunge Zhao ◽  
Qingbai Wu ◽  
Hailong He ◽  
Liqian Gao
Keyword(s):  
Soil Temperature ◽  
Frozen Soil ◽  
Tibet Plateau ◽  
Temperature Dynamics ◽  
Qinghai Tibet Plateau

scholarly journals Impacts of changes in vegetation cover on soil water heat coupling in an alpine meadow of the Qinghai-Tibet Plateau, China

2009 ◽  
Vol 13 (3) ◽  
pp. 327-341 ◽  
Author(s):  
W. Genxu ◽  
H. Hongchang ◽  
L. Guangsheng ◽  
L. Na
Keyword(s):  
Heat Flux ◽  
Soil Temperature ◽  
Soil Water ◽  
Vegetation Cover ◽  
Alpine Meadow ◽  
Root Zone ◽  
Frozen Soil ◽  
Tibet Plateau ◽  
Permafrost Region ◽  
Qinghai Tibet Plateau

Abstract. Alpine meadow is one of the most widespread grassland types in the permafrost regions of the Qinghai-Tibet Plateau, and the transmission of coupled soil water heat is one of the most crucial processes influencing cyclic variations in the hydrology of frozen soil regions, especially under different vegetation covers. The present study assesses the impact of changes in vegetation cover on the coupling of soil water and heat in a permafrost region. Soil moisture (θv), soil temperature (Ts), soil heat content, and differences in θv−Ts coupling were monitored on a seasonal and daily basis under three different vegetation covers (30, 65, and 93%) on both thawed and frozen soils. Regression analysis of θv vs. Ts plots under different levels of vegetation cover indicates that soil freeze-thaw processes were significantly affected by the changes in vegetation cover. The decrease in vegetation cover of an alpine meadow reduced the difference between air temperature and ground temperature (ΔTa−s), and it also resulted in a decrease in Ts at which soil froze, and an increase in the temperature at which it thawed. This was reflected in a greater response of soil temperature to changes in air temperature (Ta). For ΔTa−s outside the range of −0.1 to 1.0°C, root zone soil-water temperatures showed a significant increase with increasing ΔTa−s; however, the magnitude of this relationship was dampened with increasing vegetation cover. At the time of maximum water content in the thawing season, the soil temperature decreased with increasing vegetation. Changes in vegetation cover also led to variations in θv−Ts coupling. With the increase in vegetation cover, the surface heat flux decreased. Soil heat storage at 20 cm in depth increased with increasing vegetation cover, and the heat flux that was downwardly transmitted decreased. The soil property varied greatly under different vegetation covers, causing the variation of heat conductivity and water-heat hold capacity in topsoil layer in different vegetation cover. The variation of heat budget and transmitting in soil is the main factor that causes changes in soil thawing and freezing processes, and θv−Ts coupling relationship under different vegetation fractions. In addition to providing insulation against soil warming, vegetation in alpine meadows within the permafrost region also would slow down the response of permafrost to climatic warming via the greater water-holding capacity of its root zone. Such vegetation may therefore play an important role in conserving water in alpine meadows and maintaining the stability of engineering works constructed within frozen soil of the Qinghai-Tibet Plateau.

scholarly journals Impacts of changes in vegetation cover on soil water heat coupling in an alpine meadow, Qinghai-Tibet Plateau, China

2008 ◽  
Vol 5 (4) ◽  
pp. 2543-2579
Author(s):  
W. Genxu ◽  
H. Hongchang ◽  
L. Yuanshou ◽  
W. Yibo
Keyword(s):  
Heat Flux ◽  
Soil Temperature ◽  
Soil Water ◽  
Vegetation Cover ◽  
Alpine Meadow ◽  
Root Zone ◽  
Frozen Soil ◽  
Tibet Plateau ◽  
Permafrost Region ◽  
Qinghai Tibet Plateau

Abstract. Alpine meadow is one of the most widespread grassland types in the permafrost regions of the Qinghai-Tibet Plateau. The transmission of coupled soil water heat is one of the most important processes influencing cyclic variations in the hydrology of frozen soil regions, especially under conditions of changing vegetation cover. The present study assesses the impact of changes in vegetation cover on the coupling of soil water and heat in a permafrost region. Soil moisture (θv), soil temperature (Ts), soil heat content, and differences in θv−Ts coupling were monitored on a seasonal and daily basis under three different densities of vegetation cover (30, 65, and 93%) upon both thawed and frozen soils. Regression analysis of θv vs. Ts plots under different levels of vegetation cover indicates that soil freeze-thaw processes were significantly affected by changes in vegetation cover. With decreasing vegetation cover upon an alpine meadow, the difference between air temperature and ground temperature (ΔTa−s) also decreased. A decrease in vegetation cover also resulted in a decrease in the Ts at which soil froze and an increase in the temperature at which it thawed; this was reflected in a greater response of soil temperature to changes in air temperature (Ta). For ΔTa−s outside the range of −0.1 to 1.0°C, root zone soil-water temperatures showed a significant increase with increasing ΔTa−s; however, the magnitude of this relationship was dampened with increasing vegetation cover. At the time of maximum water content in the thawing season, the soil temperature decreased with increasing vegetation. Changes in vegetation cover also led to variations in θv−Ts coupling. With increasing vegetation cover, the surface heat flux increased, along with the amplitude of its variations. Soil heat storage at 20 cm depth also increased with increasing vegetation cover, and the downward transmitted of heat flux decreased. In addition to providing insulation against soil warming, vegetation in alpine meadows within the permafrost region also slows down the response of permafrost to climatic warming via the greater water-holding capacity of its root zone. Such vegetation may therefore play an important role in conserving water in alpine meadows and maintaining the stability of engineering works constructed within frozen soil of the Qinghai-Tibet Plateau.

Heat Effect Analysis of Buried Oil Pipeline in the Qinghai-Tibet Plateau

2014 ◽  
Vol 501-504 ◽  
pp. 211-217
Author(s):  
Wei Bo Liu ◽  
Wen Bing Yu ◽  
Xin Yi ◽  
Lin Chen
Keyword(s):  
Temperature Field ◽  
Frozen Soil ◽  
Operating Conditions ◽  
Tibet Plateau ◽  
Soil Mechanic ◽  
Insulation Layer ◽  
Effect Analysis ◽  
Oil Pipeline ◽  
Permafrost Table ◽  
Qinghai Tibet Plateau

The Geermu-Lasa oil pipeline was located in the Qinghai-Tibet Plateau permafrost regions. The building and operating of pipeline will change the temperature field of soil around it, which can lead to changes of frozen soil mechanic properties, and this will induces deformation or even fracture of pipeline. These phenomena will affect the normal transportation of oil. In this paper, temperature field around the pipelines were analyzed due to different pipe diameters and different insulation layer thicknesses in the way of finite element method. The rule of thawing and freezing of soil around the pipeline in an annual cycle was obtained. Artificial permafrost table variations under the pipeline were also obtained due to different operating conditions. For 30cm diameter pipeline with 7cm insulation layer, its artificial permafrost table depth change value is just 0.48m after 30-year running. These analysis results can provide references to the construction of the new Geermu-Lasa oil pipeline.

scholarly journals Analysis on the Temporal and Spatial Characteristics of the Shallow Soil Temperature of the Qinghai-Tibet Plateau

2021 ◽  
Author(s):  
Yujie Li ◽  
Cunjie Zhang ◽  
Zhenchao Li ◽  
Liwei Yang ◽  
Xiao Jin ◽  
...  
Keyword(s):  
Soil Temperature ◽  
Observational Data ◽  
Temperature Increase ◽  
Soil Layer ◽  
Tibet Plateau ◽  
Shallow Soil ◽  
Increasing Trend ◽  
Temporal And Spatial ◽  
Region 10 ◽  
Qinghai Tibet Plateau

Abstract Shallow soil refers to the soil layer within 50 cm underground. Shallow soil temperature (ST) affects many processes that occur in the soil. Therefore, the study of shallow ST is of great significance in understanding energy, hydrological cycles and climate change. This work collected the observational data from 141 meteorological stations on the Qinghai-Tibet Plateau from 1981 to 2020, analyzed the ST as well as its temporal and spatial change characteristics at different levels. The results show that: 1) The shallow ST has a gradually increasing trend from north to south, from west to east. From the perspective of time characteristics, the increasing trend is obvious. The temperature increase of 0–20 cm (the surface layer of the shallow soil) is roughly the same. The average annual is 9.15–9.57 ℃, the interdecadal variabilities are 0.49–0.53 K/10a. The average annual of 40 cm (the bottom layer) is 8.69 ℃, the interdecadal variability reaches by 0.98 K/10a; 2) Judging from the 12 regions of 20 cm, the temperature increase trend is obvious, but there are certain regional differences. The average value ranges from 4.3 ℃ (region 4, Qaidam Plateau) to 18.1 ℃ (region 10, Southeast Qinghai-Tibet Plateau), the difference is nearly 14 K. The standard deviation ranges from 0.38 K (region 10) to 0.82 K (region 11, Northern Qiangtang Plateau); 3) The results of the reanalysis data are lower than the observational data. This work is significant for understanding the characteristics of the ST evolution and the land-atmosphere interaction on the Qinghai-Tibet Plateau.

scholarly journals PIC v1.3: comprehensive R package for computing permafrost indices with daily weather observations and atmospheric forcing over the Qinghai–Tibet Plateau

2018 ◽  
Vol 11 (6) ◽  
pp. 2475-2491 ◽  
Author(s):  
Lihui Luo ◽  
Zhongqiong Zhang ◽  
Wei Ma ◽  
Shuhua Yi ◽  
Yanli Zhuang
Keyword(s):  
Ground Surface ◽  
R Package ◽  
Frozen Soil ◽  
Tibet Plateau ◽  
Trend Test ◽  
Active Layer Thickness ◽  
Permafrost Degradation ◽  
Spatial Trends ◽  
The Impact ◽  
Qinghai Tibet Plateau

Abstract. An R package was developed for computing permafrost indices (PIC v1.3) that integrates meteorological observations, gridded meteorological datasets, soil databases, and field measurements to compute the factors or indices of permafrost and seasonal frozen soil. At present, 16 temperature- and depth-related indices are integrated into the PIC v1.3 R package to estimate the possible trends of frozen soil in the Qinghai–Tibet Plateau (QTP). These indices include the mean annual air temperature (MAAT), mean annual ground surface temperature (MAGST), mean annual ground temperature (MAGT), seasonal thawing–freezing n factor (nt∕nf), thawing–freezing degree-days for air and the ground surface (DDTa∕DDTs∕DDFa∕DDFs), temperature at the top of the permafrost (TTOP), active layer thickness (ALT), and maximum seasonal freeze depth. PIC v1.3 supports two computational modes, namely the stations and regional calculations that enable statistical analysis and intuitive visualization of the time series and spatial simulations. Datasets of 52 weather stations and a central region of the QTP were prepared and simulated to evaluate the temporal–spatial trends of permafrost with the climate. More than 10 statistical methods and a sequential Mann–Kendall trend test were adopted to evaluate these indices in stations, and spatial methods were adopted to assess the spatial trends. Multiple visual methods were used to display the temporal and spatial variability of the stations and region. Simulation results show extensive permafrost degradation in the QTP, and the temporal–spatial trends of the permafrost conditions in the QTP are close to those of previous studies. The transparency and repeatability of the PIC v1.3 package and its data can be used and extended to assess the impact of climate change on permafrost.

scholarly journals Assessing the simulated soil hydrothermal regime of the active layer from the Noah-MP land surface model (v1.1) in the permafrost regions of the Qinghai–Tibet Plateau

2021 ◽  
Vol 14 (3) ◽  
pp. 1753-1771
Author(s):  
Xiangfei Li ◽  
Tonghua Wu ◽  
Xiaodong Wu ◽  
Jie Chen ◽  
Xiaofan Zhu ◽  
...  
Keyword(s):  
Soil Temperature ◽  
Snow Cover ◽  
Land Surface ◽  
Tibet Plateau ◽  
Cold Bias ◽  
Surface Model ◽  
Model Parameters ◽  
Hydrothermal Regime ◽  
Qinghai Tibet Plateau ◽  
Permafrost Regions

Abstract. Extensive and rigorous model intercomparison is of great importance before model application due to the uncertainties in current land surface models (LSMs). Without considering the uncertainties in forcing data and model parameters, this study designed an ensemble of 55 296 experiments to evaluate the Noah LSM with multi-parameterization (Noah-MP) for snow cover events (SCEs), soil temperature (ST) and soil liquid water (SLW) simulation, and investigated the sensitivity of parameterization schemes at a typical permafrost site on the Qinghai–Tibet Plateau (QTP). The results showed that Noah-MP systematically overestimates snow cover, which could be greatly resolved when adopting the sublimation from wind and a semi-implicit snow/soil temperature time scheme. As a result of the overestimated snow, Noah-MP generally underestimates ST, which is mostly influenced by the snow process. A systematic cold bias and large uncertainties in soil temperature remain after eliminating the effects of snow, particularly in the deep layers and during the cold season. The combination of roughness length for heat and under-canopy (below-canopy) aerodynamic resistance contributes to resolving the cold bias in soil temperature. In addition, Noah-MP generally underestimates top SLW. The runoff and groundwater (RUN) process dominates the SLW simulation in comparison to the very limited impacts of all other physical processes. The analysis of the model structural uncertainties and characteristics of each scheme would be constructive to a better understanding of the land surface processes in the permafrost regions of the QTP as well as to further model improvements towards soil hydrothermal regime modeling using LSMs.

scholarly journals Thermal impacts of engineering activities on permafrost in different alpine ecosystems in Qinghai-Tibet Plateau, China

2016 ◽  
Author(s):  
Qingbai Wu ◽  
Zhongqiong Zhang ◽  
Siru Gao ◽  
Wei Ma
Keyword(s):  
Soil Temperature ◽  
Climate Warming ◽  
Tibet Plateau ◽  
Alpine Ecosystems ◽  
Railway Ballast ◽  
Alpine Meadows ◽  
Engineering Construction ◽  
Cooling Effects ◽  
Qinghai Tibet Plateau ◽  
Vegetation Layer

Abstract. Climate warming and engineering activities have various impacts on the thermal regime of permafrost in alpine ecosystems of the Qinghai–Tibet Plateau. Using recent observations of permafrost thermal regimes along the Qinghai–Tibet Highway and Railway, the change of such regimes beneath embankments constructed in alpine meadows and steppes are studied. The results show that alpine meadows on the Qinghai–Tibet Plateau can have a controlling role within engineering construction effects on permafrost beneath embankments. The artificial permafrost table (APT) beneath embankments is predominantly controlled by alpine ecosystems, but the change rate of APT is not closely related with those ecosystems; it is mainly related with cooling effects of railway ballast and heat absorption effects of asphalt pavement. Variation of soil temperature beneath embankments is independent of alpine ecosystems, but variation of mean annual soil temperature with depth is closely related to those ecosystems. The vegetation layer in alpine meadows can have an insulation role within engineering activity effects on permafrost beneath embankments. This insulation role is an advantage for alleviating permafrost temperature rise in the short term, but a disadvantage in the long term because of climate warming, suggesting that vegetation layer in alpine meadow should be removed upon initiating engineering construction.

scholarly journals Effects of the Freezing–Thawing Cycle Mode on Alpine Vegetation in the Nagqu River Basin of the Qinghai–Tibet Plateau

Water ◽  
2019 ◽  
Vol 11 (10) ◽  
pp. 2122 ◽  
Author(s):  
Zihao Man ◽  
Baisha Weng ◽  
Yuheng Yang ◽  
Xiaoyan Gong ◽  
Meng Li ◽  
...  
Keyword(s):  
Climate Change ◽  
River Basin ◽  
Frozen Soil ◽  
Root Cell ◽  
Frequency Mode ◽  
Tibet Plateau ◽  
Alpine Vegetation ◽  
Soil Ecosystem ◽  
Thawing Cycle ◽  
Qinghai Tibet Plateau

The freezing–thawing cycle is a basic feature of a frozen soil ecosystem, and it affects the growth of alpine vegetation both directly and indirectly. As the climate changes, the freezing–thawing mode, along with its impact on frozen soil ecosystems, also changes. In this research, the freezing–thawing cycle of the Nagqu River Basin in the Qinghai–Tibet Plateau was studied. Vegetation growth characteristics and microbial abundance were analyzed under different freezing–thawing modes. The direct and indirect effects of the freezing–thawing cycle mode on alpine vegetation in the Nagqu River Basin are presented, and the changing trends and hazards of the freezing–thawing cycle mode due to climate change are discussed. The results highlight two major findings. First, the freezing–thawing cycle in the Nagqu River Basin has a high-frequency mode (HFM) and a low-frequency mode (LFM). With the influence of climate change, the LFM is gradually shifting to the HFM. Second, the alpine vegetation biomass in the HFM is lower than that in the LFM. Frequent freezing–thawing cycles reduce root cell activity and can even lead to root cell death. On the other hand, frequent freezing–thawing cycles increase microbial (Bradyrhizobium, Mesorhizobium, and Pseudomonas) death, weaken symbiotic nitrogen fixation and the disease resistance of vegetation, accelerate soil nutrient loss, reduce the soil water holding capacity and soil moisture, and hinder root growth. This study provides a complete response mechanism of alpine vegetation to the freezing–thawing cycle frequency while providing a theoretical basis for studying the change direction and impact on the frozen soil ecosystem due to climate change.

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