Effects of degradation severity on the physical, chemical and mechanical properties of topsoil in alpine meadow on the Qinghai-Tibet Plateau, west China

Li, Guorong; Li, Xilai; Chen, Wenting; Li, Jinfang; Hong, Zhu; Hu, Xiasong; Zhou, Huakun; Sun, Haiqun

doi:10.1016/j.catena.2019.104370

Cited by 26 publications

(12 citation statements)

References 40 publications

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“…Changes in precipitation, runoff, and permafrost degradation are the main influencing factors for wetland hydrothermal dynamics in the SAYR (Wang et al, 2001;Wu et al, 2018;Wu et al, 2021). Persistent climate warming has enhanced land surface evaporation, lowered the burial depth of the permafrost table, and has deepened the active layer and the aeration/vadose zone, resulting in a deeper groundwater table, causing the continuously distributed wetlands to become fragmented or even completely disappear (drained) (Li et al, 2016c;Li G. et al, 2020c). With shrinking wetlands, alpine vegetation coverage declined, in turn, resulting in the bare patches of ground surface (blackened soil spots) in grasslands (Yi et al, 2011).…”

Section: Shrinking Of Wetlands and Lakesmentioning

confidence: 99%

Impacts of Permafrost Degradation on Hydrology and Vegetation in the Source Area of the Yellow River on Northeastern Qinghai-Tibet Plateau, Southwest China

Jin

Luo

et al. 2022

Front. Earth Sci.

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Under a persistent warming climate and increasing human activities, permafrost in the Source Area of the Yellow River (SAYR) has been degrading regionally, resulting in many eco-environmental problems. This paper reviews the changes in air temperature and precipitation over the past 60 years and presents the distribution and degradation of alpine permafrost in the SAYR. The review is focused on the permafrost degradation–induced changes in hydrology, wetlands, thermokarst lakes, ponds, and vegetation. Mean annual air temperatures have been rising at an average rate of 0.4°C/10a over the past 60 years, while precipitation has increased only slightly (16 mm/10a). Borehole temperature monitoring at the depth of 15 m shows the permafrost warming rates of 0.01–0.21°C/10a in the Headwater Aera of the Yellow River. As a result of permafrost thaw, the amount of surface waters has declined while groundwater storage has increased. Due to permafrost degradation, the supra-permafrost water table lowers gradually, resulting in a reduction in areal extents of wetlands and lakes in the SAYR. We further renamed the concept of the burial depth of the ecologically-safe supra-permafrost water table, the minimum depth of the groundwater table for sustaining the normal growth of alpine grassland vegetation, for the SAYR to describe the relationship between the lowering permafrost table and succeeding alpine vegetation. Furthermore, we recommended more studies focusing on snow cover and carbon stock and emissions related to permafrost degradation under a warming climate. We also advised to timely establish the long-term monitoring networks for the rapidly changing mountain cryosphere, alpine ecology, alpine hydrology, eco-hydrology, cryo-hydrogeology, and carbon fluxes. Moreover, process-based models should be developed and improved to better simulate and predict the responses of alpine ecosystem changes to the interacting cryospheric and other environmental variables and their ecological and ecohydrological impacts in the SAYR and downstream Yellow River basins. This study can help better manage the ecological and hydrological environments in the Upper Yellow River that are sensitive to changes in the alpine climate and cryosphere.

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Section: Shrinking Of Wetlands and Lakesmentioning

confidence: 99%

Impacts of Permafrost Degradation on Hydrology and Vegetation in the Source Area of the Yellow River on Northeastern Qinghai-Tibet Plateau, Southwest China

Jin

Luo

et al. 2022

Front. Earth Sci.

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“…For the plants of AM, however, the lengths of most of their roots are less than 0.30 m (Figure 2b). Thus, transforming from AS to AM means that deep-rooted plants with dense root systems are gradually replaced by plants with short and sparse root systems [35,[55][56][57][58]. This change indicates that the shallow-rooted plants of AM are more vulnerable to high evaporation, livestock trampling, and human activities in the study area, resulting in further degradation [35].…”

Section: Effect Of Degraded Riparian Vegetation On Tensile Strength O...mentioning

confidence: 99%

“…The average density of the natural soil-root mixture for AS is 18% higher than that of AM (Table 2). This may be attributed to the decreased root number and the dramatically increased pore volume of surface soil (i.e, soil in the 0-0.05 m layer) [58]. Higher bulk density should increase not only bonding forces between particles, which enhances the tensile strength, but also the interfacial contact area of the fiber-matrix structure, which improves the interfacial shear strength and associated friction [24].…”

Section: Effect Of Degraded Riparian Vegetation On Tensile Strength O...mentioning

confidence: 99%

“…In our study, when the AS degenerated to the AM, the rooted soil tensile strength decreased by 67.42% (Table 3). Li et al [58] showed that the shear strength of the root-soil mixture decreases by 36.0% and 52.3% from severely degraded alpine meadows to moderately and slightly degraded alpine meadows, respectively. Thus, degradation of alpine swamp meadows obviously reduces the mechanical properties of the soils and weakens their ability to resist bank failure, wind and water erosion, and other external forces.…”

Section: Effect Of Degraded Riparian Vegetation On Tensile Strength O...mentioning

confidence: 99%

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Impacts of the Degraded Alpine Swamp Meadow on Tensile Strength of Riverbank: A Case Study of the Upper Yellow River

Hong

Gao

et al. 2020

Water

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In the meandering riverbank of the Upper Yellow River (UYR), the native alpine swamp meadow (AS) has continuously degenerated into an alpine meadow (AM) due to climate change and intensified grazing. Its implication on river morphology is still not well known. This study examined this effect by in situ measurings of (1) physical properties of roots and their distribution in the soil-root mixture of the upper bank layer, and (2) the tensile strength in terms of excavating tests for triggering cantilever collapses of AS and AM riverbanks. The results showed that the root number in AS was significantly greater than that in AM, though the root distribution in both was similar. Also, the average tensile strength of individual roots in AS was 31,310 kPa, while that in AM was only 16,155 kPa. For the soil-root mixture, it decreased from 67.39 to 21.96 kPa. The weakened mechanical property was mainly ascribed to the lessened root number and the simpler root structure in the soil-root mixture of AM that reduces its ability to resist the external force. These findings confirmed that healthy AS can enhance bank stability and delay the development of tensile cracks in the riverbank of the meandering rivers in the UYR.

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“…In this paper, natural and saturated soil samples with an area of S = 30 cm 2 and a height of H = 2 cm were prepared in the laboratory by taking the low liquid limit clay in the immersion zone with a ring knife and the mechanical properties of compression and consolidation were tested [31][32][33]. The influence of saturation on the strength and deformation index of low liquid limit clay was analyzed.…”

Section: Introductionmentioning

confidence: 99%

The Effect of the Water Table on the Bearing Capacity of a Shallow Foundation

2022

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Immersion is an important part of reservoir engineering investigation and evaluation. Determining the reasonable and effective burial depth of the critical immersion water table is one of the key scientific issues in the impact assessment of the bearing capacity of reservoir immersion foundations. In this study, basic physical and mechanical property tests were carried out on the soil in the typical immersion area of Xiaonanhai Hydropower Station, and the influence mechanism of saturation on the mechanical properties of building foundation soil and immersion on the bearing capacity of a shallow foundation was obtained. According to the test results, the influence depth of the rising groundwater level on the stability of the building foundation is analyzed, and a method to determine the critical depth of immersion groundwater in the reservoir is proposed. Taking the typical building foundation of Luohuang Town in the immersion area of Xiaonanhai Reservoir as an example, the validity of the critical water depth is further verified. The results show that the safety limit depth of the independent foundation affected by the rise of the water table increases with the increase of the width of the foundation and decreases with the increase of the buried depth of the foundation. Considering the safety limit depth, the critical depth of building immersion is 4.830 m, and without considering the safety limit depth, the critical depth of building immersion is 4.05 m. To a certain extent, it can reduce the impact of water table changes on the bearing capacity of shallow foundations.

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Effects of degradation severity on the physical, chemical and mechanical properties of topsoil in alpine meadow on the Qinghai-Tibet Plateau, west China

Cited by 26 publications

References 40 publications

Impacts of Permafrost Degradation on Hydrology and Vegetation in the Source Area of the Yellow River on Northeastern Qinghai-Tibet Plateau, Southwest China

Impacts of Permafrost Degradation on Hydrology and Vegetation in the Source Area of the Yellow River on Northeastern Qinghai-Tibet Plateau, Southwest China

Impacts of the Degraded Alpine Swamp Meadow on Tensile Strength of Riverbank: A Case Study of the Upper Yellow River

The Effect of the Water Table on the Bearing Capacity of a Shallow Foundation

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