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2017, 9 (6) Online: 01 December 2017 Previous issue Next issue
  • Predictions of future hydrological conditions and contribution of snow and ice melt in total discharge of Shigar River Basin in Central Karakoram, Pakistan
  • Javed Hassan, Rijan Bhakta Kayastha, Ahuti Shrestha, Iram Bano, Sayed Hammad Ali, Haleem Zaman Magsi
  • DOI: 10.3724/SP.J.1226.2017.00511
  • 2017, Vol.9 (6): 511–524 Abstract ( 139) HTML PDF (2396 KB) ( 32 )
  • The high mountains of Hindu-Kush Karakoram and Himalaya (HKKH) contain a large volume of snow and ice, which are the primary sources of water for the entire mountainous population of HKKH. Thus, knowledge of these available resources is very important in relation to their sustainable use. A Modified Positive Degree Day Model was used to simulate daily discharge with the contribution of snow and ice melt from the Shigar River Basin, Central Karakoram, Pakistan. The basin covers an area of 6,921 km2 with an elevation range of 2,204 to 8,611 m a.s.l.. Forty percent of the total area is glaciated among which 20% is covered by debris and remaining 80% by clean ice and permanent snow. To simulate daily discharge, the entire basin was divided into 26 altitude belts. Remotely sensed land cover types are derived by classifying Landsat images of 2009. Daily temperature and precipitation from Skardu meteorological station is used to calibrate the glacio-hydrological model as an input variable after correlating data with the Shigar station data (r=0.88). Local temperature lapse rate of 0.0075 ℃/m is used. 2 ℃ critical temperature is used to separate rain and snow from precipitation. The model is calibrated for 1988~1991 and validated for 1992~1997. The model shows a good Nash-Sutcliffe efficiency and volume difference in calibration (0.86% and 0.90%) and validation (0.78% and 6.85%). Contribution of snow and ice melt in discharge is 32.37% in calibration period and 33.01% is validation period. The model is also used to predict future hydrological regime up to 2099 by using CORDEX South Asia RCM considering RCP4.5 and RCP8.5 climate scenarios. Predicted future snow and ice melt contributions in both RCP4.5 and RCP8.5 are 36% and 37%, respectively. Temperature seems to be more sensitive as compared to other input variables, which is why the contribution of snow and ice in discharge varies significantly throughout the whole century.
  • Comments on thaw-freeze algorithms for multilayered soil, using the Stefan equation
  • ChangWei Xie, William A. Gough
  • DOI: 10.3724/SP.J.1226.2017.00525
  • 2017, Vol.9 (6): 525–533 Abstract ( 34) HTML PDF (1347 KB) ( 24 )
  • The Stefan equation provides a useful and widely used method for predicting the depth of thawing and freezing in a soil where little site-specific information is available. The original Stefan equation was derived for only a homogeneous medium, and some algorithms have been developed for its use in a multilayered system. However, although the Stefan equation was derived more than 100 years ago, there is not a unified understanding for its use in a multilayered system. This paper examines the use of the Stefan equation in multilayered soil, based on comparing three algorithms (JL-algorithm, NM-algorithm, and XG-algorithm). We conclude that the JL and NM algorithms are incorrect, as they arose from flawed mathematical derivations. Both of these algorithms failed to recognize that the thawing depth in a multilayered soil is a piecewise function and not a continuous function of time. This work asserts that the XG-algorithm is a correct and rigorous method to determine the freezing-thawing fronts in multilayered soil.
  • Comparison of precipitation and evapotranspiration of five different land-cover types in the high mountainous region
  • Yong Yang, RenSheng Chen, YaoXuan Song, ChunTan Han, JunFeng Liu, ZhangWen Liu
  • DOI: 10.3724/SP.J.1226.2017.00534
  • 2017, Vol.9 (6): 534–542 Abstract ( 46) HTML PDF (2436 KB) ( 25 )
  • Many rivers originate in high mountainous regions. However, the effects of climate warming on the runoff and water balance in these regions remain unclear due to the lack of observational data from harsh environments, and the variable influences of climate change on alpine land-cover types with different water balances. Using observations and simulations from CoupModel, water-balance values collected at five alpine land-cover types (steppe, shrub meadow, moist meadow, swamp meadow, and moraine) in a small alpine watershed, the Qilian Mountains in Northwest China, from October 2008 to September 2014, were compared. Measured evapotranspiration, multilayer soil temperatures and water contents, and frozen-depth data were used to validate CoupModel outputs. The results show that elevation is the primary influence on precipitation, evapotranspiration, and runoff coefficients in alpine regions. Land-cover types at higher elevations receive more precipitation and have a larger runoff coefficient. Notably, climate warming not only increases evapotranspiration but also particularly increases the evapotranspiration/precipitation ratio due to an upward shift in the optimum elevation of plant species. These factors lead to decrease runoff coefficients in alpine basins.
  • The mass-balance characteristics and sensitivities to climate variables of Laohugou Glacier No. 12, western Qilian Mountains, China
  • JiZu Chen, ShiChang Kang, Xiang Qin, WenTao Du, WeiJun Sun, YuShuo Liu
  • DOI: 10.3724/SP.J.1226.2017.00543
  • 2017, Vol.9 (6): 543–553 Abstract ( 42) HTML PDF (3480 KB) ( 30 )
  • Due to global warming, glaciers on the Tibetan Plateau (TP) are experiencing widespread shrinkage; however, the mechanisms controlling glacier variations across the TP are still rather unclear, especially on the northeastern TP. In this study, a physically based, distributed surface-energy and mass-balance model was used to simulate glacier mass balance forced by meteorological data. The model was applied to Laohugou No. 12 Glacier, western Qilian Mountains, China, during 2010~2012. The simulated albedo and mass balance were validated and calibrated by in situ measurements. The simulated annual glacier-wide mass balances were -385 mm water equivalent (w.e.) in 2010/2011 and -232 mm w.e. in 2011/2012, respectively. The mean equilibrium-line altitude (ELA) was 5,015 m a.s.l., during 2010~2012, which ascended by 215 m compared to that in the 1970s. The mean accumulation area ratio (AAR) was 39% during the two years. Climatic-sensitivity experiments indicated that the change of glacier mass balance resulting from a 1.5 ℃ increase in air temperature could be offset by a 30% increase in annual precipitation. The glacier mass balance varied linearly with precipitation, at a rate of 130 mm w.e. per 10% change in total precipitation.
  • The weak effects of fencing on ecosystem respiration, CH4, and N2O fluxes in a Tibetan alpine meadow during the growing season
  • YiGang Hu, ZhenHua Zhang, ShiPing Wang, ZhiShan Zhang, Yang Zhao, ZengRu Wang
  • DOI: 10.3724/SP.J.1226.2017.00554
  • 2017, Vol.9 (6): 554–567 Abstract ( 39) HTML PDF (2116 KB) ( 27 )
  • Fencing is the most common land-management practice to protect grassland degradation from livestock overgrazing on the Tibetan Plateau. However, it is unclear whether fencing reduces CO2, CH4, and N2O emission. Here, we selected four vegetation types of alpine meadow (graminoid, shrub, forb, and sparse vegetation) to determine fencing effects on ecosystem respiration (Re), CH4, and N2O fluxes during the growing season. Despite increased average monthly ecosystem respiration (Re) for fenced graminoid vegetation at the end of the growing season, there was no significant difference between grazing and fencing across all vegetation types. Fencing significantly reduced average CH4 uptake by about 50% in 2008 only for forb vegetation and increased average N2O release for graminoid vegetation by 38% and 48% in 2008 and 2009, respectively. Temperature, moisture, total organic carbon, C/N, nitrate, ammonia, and/or bulk density of soil, as well as above- and belowground biomass, explained 19%~71% and 6%~33% of variation in daily and average Re and CH4 fluxes across all vegetation types, while soil-bulk density explained 27% of variation in average N2O fluxes. Stepwise regression showed that soil temperature and soil moisture controlled average Re, while soil moisture and bulk density controlled average CH4 fluxes. These results indicate that abiotic factors control Re, CH4, and N2O fluxes; and grazing exclusion has little effect on reducing their emission—implying that climatic change rather than grazing may have a more important influence on the budgets of Re and CH4 for the Tibetan alpine meadow during the growing season.
  • Variations of trace elements and rare earth elements (REEs) treated by two different methods for snow-pit samples on the Qinghai-Tibetan Plateau and their implications
  • YueFang Li, Zhen Li, Ju Huang, Giulio Cozzi, Clara Turetta, Carlo Barbante, LongFei Xiong
  • DOI: 10.3724/SP.J.1226.2017.00568
  • 2017, Vol.9 (6): 568–579 Abstract ( 47) HTML PDF (3200 KB) ( 27 )
  • Although previous investigations of the trace elements in snow and ice from the Qinghai-Tibetan Plateau obtained interesting information about pollution from human activities on the plateau, most were based on traditional acidification methods. To emphasize the influence of the different sample-preparation methods on the records of trace elements and rare earth elements, snow samples were collected from glaciers on the Qinghai-Tibetan Plateau in China and prepared using two methods: traditional acidification and total digestion. Concentrations of 18 trace elements (Al, Ti, Fe, Rb, Sr, Ba, V, Cr, Mn, Li, Cu, Co, Mo, Cs, Sb, Pb, Tl, and U), along with 14 rare earth elements (REEs: La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, and Lu), Y, and Th in the snow samples, were measured using inductively coupled plasma-sector field mass spectrometry (ICP-SFMS). The results showed that the mass fraction of the trace elements (defined as ratio of concentration in the acid-leachable fraction to that in the digested sample) such as Mo, Ti, Al, Rb, and V, varied from 0.06 to 0.5. The mass fraction of other trace elements varied from about 0.6 to more than 0.9; those of the REEs, Y, and Th varied from 0.34 to 0.75. Lower mass fractions will lead to an overestimated contribution of other sources, especially human activities, and the underestimated fluxes of these trace elements (especially REEs, Y, and Th, as well as dust) if the REEs are used as the proxy for the crust dust. The two sample-preparation methods exhibited different REE normalized distribution patterns, REE ratios, and provenance-tracing results. The REE normalized distribution patterns and proxies in the digested samples are more reliable and integrated than those found in traditional acidification method for dust-provenance tracing.
  • Numerical analysis on the thermal regimes of thermosyphon embankment in snowy permafrost area
  • Yan Lu, Xin Yi, WenBing Yu, WeiBo Liu
  • DOI: 10.3724/SP.J.1226.2017.00580
  • 2017, Vol.9 (6): 580–586 Abstract ( 85) HTML PDF (1971 KB) ( 37 )
  • Snow covers the road embankments in winter in high latitude permafrost zones. The effect of snow cover on embankments was simulated based on field measurements of boundary conditions and initial ground temperature profile in Mohe, China. The effect of thermosyphons on the embankment warmed by snow cover was evaluated by numerical simulations as well. The results indicate that the difference of thermal regimes between non-thermosyphon and thermosyphon embankments reaches to 22 m in depth below the ground surface. It is much warmer in the non-thermosyphon embankment body in winter. Affected by the snow cover, heat flux gradually spreads into the deep ground of the subgrade over time. The permafrost table under the slope toe of a thermosyphon embankment is 1.2 m higher than that of a non-thermosyphon embankment in the 20th year. In addition, the permafrost table at the slope toe of a thermosyphon embankment is 26 cm deeper over 20 years. These results indicate that thermosyphons can greatly weaken the warm effect of snow cover. However, thermosyphons cannot avoid the degradation of permafrost under the scenarios of snow cover. Therefore, composite measures need to be adopted to keep embankment stability in snowy permafrost zones.
  • A review on the ambit and prospects of C3 and C4 plants in Nigeria
  • Abdulwakeel Ayokun-nun Ajao, Oludare Oladipo Agboola, Sefiu Adekilekun Saheed
  • DOI: 10.3724/SP.J.1226.2017.00587
  • 2017, Vol.9 (6): 587–598 Abstract ( 25) HTML PDF (2416 KB) ( 18 )
  • Despite the enormous applications of photosynthesis in global carbon budget and food security, photosynthesis research has not been adequately explored as a research focus in Nigeria. Previous works on C3 and C4 plants in Nigeria were mainly on the use of anatomical characteristics to delimit plant species into their respective pathways, with no attention being paid to its applications. In this review, past and present knowledge gaps in this area of study are elucidated. Information used in this review were sourced from referred research articles and books in reputable journals. The results revealed that C3 and C4 plants are distributed among 21 genera and 11 families in Nigeria. In addition there is dearth of informatio such that only three genera have been classified based on diverse photosynthetic pathways with no information found on the physiological and biochemical characterization of these genera. Moreover, further research is also suggested for tackling new challenges in the area of food productivity and climate change.