Qinghai-Tibet Plateau Permafrost Research Articles

Changes in the thermal and hydraulic regime within the active layer in the Qinghai-Tibet Plateau

The change trends of air temperature, precipitation and evaporation from 1999 to 2008 shows that the climate in the Qinghai-Tibet Plateau permafrost region had become warmer. The analysis of the systematic active-layer data monitoring network along the Qinghai-Tibet Highway indicated that the active-layer thickness had been increasing and the soil temperature was rising. The soil temperature was rising in winter but not at the end of spring or during the entire summer. With thickening and warming of the active layer, the liquid water content of the active layer had an obvious downward migration and liquid water content in the top horizons decreased, but in the deeper horizons it increased.

Study on thaw consolidation of permafrost under roadway embankment

In order to analyze thaw consolidation of permafrost beneath roadway embankment, the concept of the effective consolidation time is established. A 3-D large strain thaw consolidation model based on Eulerian description is presented and applied to analyze consolidation behaviors of thawed permafrost layer under embankments of the Qinghai-Tibet highway. It is found that thaw consolidation is controlled by several factors, including load, the effective consolidation time as well as the characteristic drainage length. Combination of these factors makes the effect that in the initial operation years of the highway, degree of thaw consolidation increases. After a certain number of years, it decreases mainly due to the increase in the characteristic drainage length and decrease in the effective consolidation time. Pore water then accumulates in the post-thawed domain, which would take some residual consolidation time to dissipate. This explains the phenomenon that in some permafrost areas on the Qinghai-Tibet plateau permafrost has already completely thawed, while settlement of roadway embankment continuously develops.

Numerical simulation of gas production potential from permafrost hydrate deposits by huff and puff method in a single horizontal well in Qilian Mountain, Qinghai province

Based on the geological data of the Qinghai-Tibet plateau permafrost, such as the permafrost ground temperature, the thermal gradient within and below the frozen layer, we numerically investigate the gas production potential from hydrates at the DK-3 drilling site of the Qilian Mountain permafrost, which is located in the north of the Qinghai-Tibet plateau. We employ the huff and puff method using a single horizontal well in the middle of the Hydrate-Bearing Layer (HBL). The simulation results indicate that desirable gas-to-water ratio and energy efficiency can be obtained under suitable injection and production conditions in the huff and puff process. However, the absolute gas production rate remains low during the whole production process. The sensitivity analysis indicates that the gas production performance is strongly dependent on the intrinsic permeability of the hydrate deposits, the sediment porosity, the injection and production rates, the temperature of the injected water, the irreducible water saturation and P01. The relative permeability exponents appear to have limited effect on the gas production behavior using the huff and puff method. The sensitivity analysis also indicates that the production potential of the natural gas hydrate deposit will be better than that of pure methane hydrate in this simulation.

Thermal hazards zonation and permafrost change over the Qinghai–Tibet Plateau

The Qinghai–Tibet Plateau is the largest permafrost region at low latitude in the world. Climate warming may lead to permafrost temperature rise, ground ice thawing and permafrost degradation, thus inducing thermal hazards. In this paper, the ARCGIS method is used to calculate the changes of ground ice content and active layer thickness under different climate scenarios on the Qinghai–Tibet Plateau, in the coming decades, thus providing the basis for hazards zonation. The method proposed by Nelson in 2002 was used for hazards zonation after revision, which was based on the changes of active layer thickness and ground ice content. The study shows that permafrost exhibits different degrees of degradation in the different climate scenarios. The thawing of ground ice and the change from low-temperature to high-temperature permafrost were the main permafrost degradation modes. This process, accompanied with thinning permafrost, increases the active layer thickness and the northward movement of the permafrost southern boundary. By 2099, the permafrost area decreases by 46.2, 16.01 and 8.5% under scenarios A2, A1B and B1, respectively. The greatest danger zones are located mainly to the south of the West Kunlun Mountains, the middle of the Qingnan Valley, the southern piedmont of the Gangdise and Nyainqentanglha Mountains and some regions in the southern piedmont of the Himalayas. The Qinghai–Tibet Plateau permafrost region is in the low-risk category. Climate warming exacerbates the development of thermal hazards. In 2099, the permafrost region is mainly in the middle-risk category, and only a small portion is in the low-risk category.

Responses in leaf functional traits and resource allocation of a dominant alpine sedge (Kobresia pygmaea) to climate warming in the Qinghai-Tibetan Plateau permafrost region

Assessing the influence of warming on leaf traits, carbon, and nutrient concentrations above and below ground to understand how the dominant sedge Kobresia pygmaea (C. B. Clarke) C. B. Clarke may respond and adapt to extant and future climate in the alpine meadow of the Qinghai-Tibetan Plateau. A warming experiment was conducted in the permafrost region of the Qinghai-Tibetan Plateau from 2008 to 2009. Two 2-year warming treatments (T1, annual warming of 2.1°C; T2, annual warming of 4.4°C) were used, and responses of leaf traits and above- and belowground carbon, nitrogen, and phosphorus concentrations of K. pygmaea were examined. The results show that both moderate (T1) and more extensive (T2) warming decreased leaf mass, leaf thickness, and vascular bundle size, and increased the mass-based photosynthetic rate (Amass) and photosynthetic nitrogen use efficiency (PNUE). A moderate warming significantly decreased leaf carbon (C), nitrogen (N), and phosphorus (P), and root C and N concentrations of K. pygmaea. These decreases were even more pronounced under the more extensive warming. The decreases in leaf N and P were significantly larger than the decrease in leaf C concentration. Root P concentration increased more under the extensive than the moderate warming. The observed increase in leaf C:N ratio in the warming treatment indicates that enhanced temperature may increase the long-term nitrogen use efficiency of K. pygmaea leaves. This again suggests that K. pygmaea might adapt well to future climate warming, and that nitrogen might be a more important factor for K. pygmaea dominated alpine meadows under future climate warming.

Climate changes and its impact on tundra ecosystem in Qinghai-Tibet Plateau, China

Alpine ecosystems in permafrost region are extremely sensitive to climate change. The headwater regions of Yangtze River and Yellow River of the Qinghai-Tibet plateau permafrost area were selected. Spatial-temporal shifts in the extent and distribution of tundra ecosystems were investigated for the period 1967-2000 by landscape ecological method and aerial photographs for 1967, and satellite remote sensing data (the Landsat's TM) for 1986 and 2000. The relationships were analyzed between climate change and the distribution area variation of tundra ecosystems and between the permafrost change and tundra ecosystems. The responding model of tundra ecosystem to the combined effects of climate and permafrost changes was established by using statistic regression method, and the contribution of climate changes and permafrost variation to the degradation of tundra ecosystems was estimated. The regional climate exhibited a tendency towards significant warming and desiccation with the air temperature increased by 0.4-0.67A degrees C/10a and relative stable precipitation over the last 45 years. Owing to the climate continuous warming, the intensity of surface heat source (HI) increased at the average of 0.45 W/m(2) per year, the difference of surface soil temperature and air temperature (DT) increased at the range of 4.1A degrees C-4.5A degrees C, and the 20-cm depth soil temperature within the active layer increased at the range of 1.1A degrees C-1.4A degrees C. The alpine meadow and alpine swamp meadow were more sensitive to permafrost changes than alpine steppe. The area of alpine swamp meadow decreased by 13.6-28.9%, while the alpine meadow area decreased by 13.5-21.3% from 1967 to 2000. The contributions of climate change to the degradation of the alpine meadow and alpine swamp was 58-68% and 59-65% between 1967 and 2000. The synergic effects of climate change and permafrost variation were the major drivers for the observed degradation in tundra ecosystems of the Qinghai-Tibet plateau.

Spatial variability of soil moisture at typical alpine meadow and steppe sites in the Qinghai-Tibetan Plateau permafrost region

Permafrost degradation has the potential to significantly change soil moisture. The objective of this study was to assess the variability of soil moisture in a permafrost region using geostatistical techniques. The experiment was conducted in August 2008 in alpine steppe and meadow located in the Qinghai-Tibetan Plateau permafrost region. Four soil depths (0–10, 10–20, 20–30 and 30–40 cm) were analyzed using frequency domain reflectometry, and sampling made of 80 points in a 10 m × 10 m grid were sampled. Soil moisture was analyzed using classical statistics to appropriately describe central tendency and dispersion, and then using geostatistics to describe spatial variability. Classical statistical method indicated that soil moisture in the permafrost region had a normal distribution pattern. Mean surface soil moisture in alpine meadow was higher than that in alpine steppe. The semivariograms showed that soil moisture variability in alpine cold steppe was larger than that in alpine meadow, which decreased with depths. Nugget values in alpine steppe were low (0.1–4.5), in contrast to alpine cold meadow. Soil moisture in alpine steppe had highly structured spatial variability with more than 93.4% spatial heterogeneity, and the range decreased with depth. Soil moisture content in alpine cold meadow had a moderate spatial dependence with a range of 51.3–169.2 m, increasing with depth.

Immunostimulatory activities of Bacillus simplex DR-834 to carp ( Cyprinus carpio)

A bacterial strain, designated DR-834 and producing immunostimulatory activities to carp ( Cyprinus carpio), was isolated from Qinghai–Tibetan Plateau permafrost soil. Cultural characteristic studies suggested that this strain belongs to the genus Bacillus. The nucleotide sequence of the 16S rRNA gene of strain DR-834 exhibited close similarity (99%) with the 16S rRNA gene of Bacillus simplex. Two compounds showing potent activity were isolated from secondary metabolites of the strain through bioassay-guided isolation techniques and identified by spectral data (infrared, nuclear magnetic resonance and mass spectrometry) as: ( 1) 4- trans-hydroxy- l-proline and ( 2) cyclo-( l-Pro-Gly) 2. They were found to be significantly increased the selected innate immune function parameters, serum SOD activity, serum lysozyme activity, serum bactericidal activity, superoxide anion production and phagocytic activity by isolated blood leucocytes. The effects of two compounds on immune-related genes expression were further investigated. The outcomes of real-time quantitative polymerase chain reaction (RQ-PCR) proved that the transcribing level of interleukin 1β (IL-1β) and inducible nitric oxide synthase (iNOS) mRNA in the blood have been augmented by 4- trans-hydroxy- l-proline and cyclo-( l-Pro-Gly) 2. Compounds 1 and 2 administration the challenge with live Aeromonas hydrophila decreased the percentage mortality in the experimental groups with the consequence increase in relative percent survival (RPS) values. Compound 2 produced the highest protection with the RPS values of 87.50, 77.78, 55.56 and 55.56 after 1, 2, 3 and 4 weeks, respectively. The study indicates that the isolated compounds could be positively influence the immune response and protect the heath status of carp against A. hydrophila infection.

Water regime shifts in the active soil layer of the Qinghai–Tibet Plateau permafrost region, under different levels of vegetation

Soil moisture and water cycling in a permafrost active layer are affected in a synergistic manner by both the sequence of soil temperature and changes in vegetative cover. Between 2004 and 2007, the dynamics of soil water content and water movement in the active layer of alpine meadow soils were monitored at sites located in the permafrost region of the Qinghai–Tibetan Plateau, China for four years to examine the synergistic effects of freeze–thaw cycles and levels of vegetation cover. The analysis of variations in monthly and seasonal soil moisture, soil-desiccation index, and soil available indicated that soil moisture exhibited a relatively stable and consistent pattern over the growing season (July–September), independent from the vegetation cover. Greater soil moisture was present in the upper root zone and at the bottom of the soil profile, whereas lower moisture levels occurred in the middle portion of the profile. Irrespective of soil depth, the lower the vegetation cover, the quicker the increase in soil liquid water during the thaw initiation period (May and June), and the quicker its decrease during the freeze initiation period (October and November). In addition, the greater the vegetation cover, the greater the available water content of the upper root zone and the less the water content of the soil layer at 0.60−0.70 m depth below the root zone. Both the soil hydraulic parameters and the spatiotemporal distribution of the water content were subject to the synergistic action of the freeze–thaw cycle and the extent of vegetation cover. The variances in active soil heat transmission and heat-water coupling relationship under the different vegetation covers were considered the main driving factors in the distribution and dynamics of the active soil water regime. The permafrost supports the development of alpine frost meadow ecosystems, and well-ordered, high-cover alpine meadow vegetation favors the protection of permafrost from degradation.

Modeling on Gas Hydrate Formation Conditions in the Qinghai‐Tibet Plateau Permafrost

AbstractBased on the field‐investigated gas geochemistry, the modeling of gas hydrate formation conditions is conducted in the Qinghai‐Tibet plateau permafrost (QTPP) in combination with predecessors' data such as the permafrost ground temperature (T0), the thermal gradient within the frozen layer (G1) and the thermal gradient below the frozen layer (G2). The modeled results show that the permafrost characteristics generally meet the requirements for gas hydrate formation conditions in the study area. Gas composition, temperaturerelated permafrost parameters (e.g. T0,G1,G2) are the most important factors affecting gas hydrate formation conditions in the study area, whose spatial variations may cause the heterogeneity of gas hydrate occurrences. The most probable gas composition to form gas hydrate is the hybrid of methane and weight hydrocarbon gases (ethane and propane). In the predicted gas hydrate locations, the minimal upper depth of gas hydrate occurrence is less than one hundred meters and the maximum lower depth can reach one thousand meters with the thickness up to several hundred meters. Compared with Canadian Mallik gas hydrate field, the QTPP is favorable for gas hydrate formation in aspects of G1, G2 and gas composition, except for relatively thin permafrost, still suggesting great gas hydrate potentials.

Effects of permafrost thawing on vegetation and soil carbon pool losses on the Qinghai–Tibet Plateau, China

Bearing a total organic carbon (TOC) content of 9.3–10.7 kg C/m 2, alpine grassland soils of the Qinghai–Tibet plateau's permafrost region bear a greater organic carbon pool than do grassland soils in other regions of China or than tropical savannah soils. The easily released light fraction organic carbon (LFOC) accounts for 34–54% of the TOC and is particularly enriched in the topsoil (0–0.10 m). The LFOC in the organic carbon pool of alpine cold meadow and alpine cold steppe soils decreased at exponential and quadratic rates, respectively, as the vegetative cover decreased. When the vegetative cover of alpine cold meadows decreased from > 80 dm 2/m 2 to 60 dm 2/m 2, the topsoil TOC and LFOC dropped by 20.4% and 38.4%, respectively. Similarly, when the vegetative cover of alpine cold meadow decreased from 50 dm 2/m 2 to 30 dm 2/m 2 and < 15 dm 2/m 2, the topsoil LFOC content dropped by 60% and 86.7%, respectively. Under climatic warming, the degradation of permafrost and vegetation have resulted in serious soil organic carbon (SOC) loss from the carbon pool. Land cover changes that occurred between 1986 and 2000 are estimated to have resulted in a 1.8 Gg C (120 Mg C/yr) loss in SOC, and a concomitant 65% decrease in the LFOC, in the 0–0.30 m soil layer in the Qinghai–Tibet plateau's permafrost regions. Since the region's ecosystems are quite sensitive to global climate changes, if global warming persists, alpine cold grassland ecosystems are expected to further degrade. Hence, the influence of global climatic change on soil carbon emissions from alpine grasslands should receive more attention.

Phylogenetic diversity of bacteria isolates from the Qinghai-Tibet Plateau permafrost region

The Qinghai-Tibet Plateau in east Asia is a unique and important permafrost environment. However, its microbiology remains largely unexplored to date. In this study, sediment samples were collected from the Qinghai-Tibet Plateau permafrost region, bacteria isolation procedures were performed 8 times, and the samples incubated at 4 degrees C for nearly 3 months. The number of colony forming units (cfu) ranged from 0 to 10(7)/(g dry soil). The quantity of culturable bacteria grew exponentially within the first few weeks, and then slowed gradually to a plateau. Phylogenetic analyses indicated that all the isolates fell into 6 categories: high G+C Gram-positive bacteria, low G+C Gram-positive bacteria, alpha-Proteobacteria, beta-Proteobacteria, gamma-Proteobacteria, and Cytophaga-Flavobacterium-Bacteroides group bacteria. The isolates belong to 19 genera, but the genera Arthrobacter and Pseudomonas were predominant. With the increase in incubation time, the isolated populations changed in terms of both species and their respective quantities. Of the 33 analyzed isolates, 9 isolates related to 8 genera might be new taxa. These results suggest that the Qinghai-Tibet Plateau permafrost region is a specific ecologic niche that accommodates an original microbial assemblage.

Formation Condition and Distribution Prediction of Gas Hydrate in Qinghai-Tibet Plateau Permafrost

Permafrost is one of major geological environments for gas hydrate occurrences. Mean altitude is over 4000m and the permafrost area is about 1.4 x 10(6)km(2) in Qinghai-Tibet Plateau. Based on the thickness of frozen layer and thermal gradient in Qinghai-Tibet Plateau permafrost, the occurrence and distribution of gas hydrate in the low-middle latitude and high altitude permafrost is predicted by using the thermodynamic method of natural gas hydrate stable temperature and pressure. The thermodynamic phase equilibrium of thermogenic and biogenic gas hydrate imply that gas hydrate is buried in depth from similar to 27 to similar to 2070m, and the resource potential of natural gases caged in hydrates are estimated as about 1.2 x 10(11) to 2.4 x 10(14)m(3) in Qinghai-Tibet Plateau permafrost. Gas hydrate is propitious to occur where the frozen layer is thicker and thermal gradient is lower in the permafrost. Seasonal change of air temperature in Qinghai-Tibet Plateau affects only the uppermost sediments 10m and does not affect gas hydrate that is buried below 30m. Under the global warming, gas hydrate will be unstable and degrade in the permafrost. Its distribution area will be gradually reduced and finally disappear in Qinghai-Tibet Plateau permafrost.