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2018, 10 (5) Online: 19 November 2018 Previous issue Next issue
  • Study of thermal properties of supraglacial debris and degree-day factors on Lirung Glacier, Nepal
  • Mohan Bahadur Chand,Rijan Bhakta Kayastha
  • DOI: 10.3724/SP.J.1226.2018.00357
  • 2018, Vol.10 (5): 357–368 Abstract ( 213) HTML ( 25) PDF (4797 KB) ( 123 )
  • The extensive debris that covers glaciers in the ablation zone of the Himalayan region plays an important part in regulating ablation rates and water availability for the downstream region. The melt rate of ice is determined by the amount of heat conducted through debris material lying over the ice. This study presents the vertical temperature gradients, thermal properties in terms of thermal diffusivity and thermal conductivity, and positive degree-day factors for the debris-covered portion of Lirung Glacier in Langtang Valley, Nepal Himalaya using field-based measurements from three different seasons. Field measurements include debris temperatures at different debris thicknesses, air temperature, and ice melt during the monsoon (2013), winter (2013), and pre-monsoon (2014) seasons. We used a thermal equation to estimate thermal diffusivity and thermal conductivity, and degree-day factors (DDF) were calculated from cumulative positive temperature and ice melt of the measurement period. Our analysis of debris temperature profiles at different depths of debris show the daily linear gradients of ?20.81 °C/m, 4.05 °C/m, and ?7.79 °C/m in the monsoon, winter, and pre-monsoon seasons, respectively. The values of thermal diffusivity and thermal conductivity in the monsoon season were 10 times greater than in the winter season. The large difference in these values is attributed to surface temperature and moisture content within the debris. Similarly, we found higher values of DDFs at thinner debris for the pre-monsoon season than in the monsoon season although we observed less melting during the pre-monsoon season. This is attributed to higher cumulative temperature during the monsoon season than in the pre-monsoon season. Our study advances our understanding of heat conductivity through debris material in different seasons, which supports estimating ice melt and discharge from glacierized river basins with debris-covered glaciers in the Himalayan region.

  • Comparison of temperature extremes between Zhongshan Station and Great Wall Station in Antarctica
  • AiHong Xie,ShiMeng Wang,YiCheng Wang,ChuanJin Li
  • DOI: 10.3724/SP.J.1226.2018.00369
  • 2018, Vol.10 (5): 369–378 Abstract ( 122) HTML ( 15) PDF (4839 KB) ( 32 )
  • Although temperature extremes have led to more and more disasters, there are as yet few studies on the extremes and many disagreements on temperature changes in Antarctica. Based on daily minimum, maximum, and mean air temperatures (Tmin, Tmax, Tmean) at Great Wall Station (GW) and Zhongshan Station (ZS), we compared the temperature extremes and revealed a strong warming trend in Tmin, a slight warming trend in Tmean, cooling in Tmax, a decreasing trend in the daily temperature range, and the typical characteristic of coreless winter temperature. There are different seasonal variabilities, with the least in summer. The continentality index and seasonality show that the marine air mass has more effect on GW than ZS. Following the terminology of the Fifth Assessment Report of the Intergovernmental Panel on Climate Change (IPCC AR5), we defined nine indices of temperature extremes, based on the Antarctic geographical environment. Extreme-warm days have decreased, while extreme-warm nights have shown a nonsignificant trend. The number of melting days has increased at GW, while little change at ZS. More importantly, we have found inverse variations in temperature patterns between the two stations, which need further investigation into the dynamics of climate change in Antarctica.

  • Numerical simulation of the climate effect of high-altitude lakes on the Tibetan Plateau
  • YinHuan Ao,ShiHua Lyu,ZhaoGuo Li,LiJuan Wen,Lin Zhao
  • DOI: 10.3724/SP.J.1226.2018.00379
  • 2018, Vol.10 (5): 379–391 Abstract ( 68) HTML ( 6) PDF (5751 KB) ( 38 )
  • Lakes regulate the water and heat exchange between the ground and the atmosphere on different temporal and spatial scales. However, studies of the lake effect in the high-altitude Tibetan Plateau (TP) rarely have been performed until recently, and little attention has been paid to modelling of frozen lakes. In this study, the Weather Research and Forecasting Model (WRF v. 3.6.1) is employed to conduct three numerical experiments in the Ngoring Lake Basin (the original experiment, an experiment with a tuned model, and a no-lake experiment) to investigate the influences of parameter optimization on the lake simulation and of the high-altitude lake on the regional climate. After the lake depth, the roughness lengths, and initial surface temperature are corrected in the model, the simulation of the air temperature is distinctly improved. In the experiment using a tuned model, the simulated sensible-heat flux (H) is clearly improved, especially during periods of ice melting (from late spring to early summer) and freezing (late fall). The improvement of latent-heat flux (LE) is mainly manifested by the sharp increase in the correlation coefficient between simulation and observation, whereas the improvement in the average value is small. The optimization of initial surface temperature shows the most prominent effect in the first year and distinctly weakens after a freezing period. After the lakes become grassland in the model, the daytime temperature clearly increases during the freezing and melting periods; but the nocturnal cooling appears in other stages, especially from September to October. The annual mean H increases by 6.4 times in the regions of the Ngoring Lake and the Gyaring Lake, and the LE declines by 56.2%. The sum of H and LE increases from 71.2 W/m2 (with lake) to 84.6 W/m2 (no lake). For the entire simulation region, the sum of H and LE also increases slightly. After the lakes are removed, the air temperature increases significantly from June to September over the area corresponding to the two lakes, and an abnormal convergence field appears; at the same time, the precipitation clearly increases over the two lakes and surrounding areas.

  • Comparison of precipitation products to observations in Tibet during the rainy season
  • Zhuo Ga,Za Dui,Duodian Luozhu,Jun Du
  • DOI: 10.3724/SP.J.1226.2018.00392
  • 2018, Vol.10 (5): 392–403 Abstract ( 39) HTML ( 6) PDF (7662 KB) ( 22 )
  • Precipitation is an important component of global water and energy transport and a major aspect of climate change. Due to the scarcity of meteorological observations, the precipitation climate over Tibet has been insufficiently documented. In this study, the distribution of precipitation during the rainy season over Tibet from 1980 to 2013 is described on monthly to annual time scales with meteorological observations. Furthermore, four precipitation products are compared to observations over Tibet. These datasets include products derived from the Asian Precipitation-Highly-Resolved Observational Data (APHRO), the Global Precipitation Climatology Centre (GPCC), the University of Delaware (UDel), and the China Meteorological Administration (CMA). The error, relative error, standard deviation, root-mean-square error, correlations and trends between these products for the same period are analyzed with in situ precipitation during the rainy season from May to September. The results indicate that these datasets can broadly capture the temporal and spatial precipitation distribution over Tibet. The precipitation gradually increases from northwest to southeast. The spatial precipitation in GPCC and CMA are similar and positively correlated to observations. Areas with the largest deviations are located in southwestern Tibet along the Himalayas. The APHRO product underestimates, while the UDel, GPCC, and CMA datasets overestimates precipitation on the basis of monthly and inter-annual variation. The biases in GPCC and CMA are smaller than those in APHRO and UDel with a mean relative error lower than 10% during the same periods. The linear trend of precipitation indicates that the increase in precipitation has accelerated extensively during the last 30 years in most regions of Tibet. The CMA generally achieves the best performance of these four precipitation products. Data uncertainty in Tibet might be caused by the low density of stations, complex topography between the grid points and stations, and the interpolation methods, which can also produce an obvious difference between the gridded data and observations.

  • Altitude pattern of carbon stocks in desert grasslands of an arid land region
  • Rong Yang,JunQia Kong,ZeYu Du,YongZhong Su
  • DOI: 10.3724/SP.J.1226.2018.00404
  • 2018, Vol.10 (5): 404–412 Abstract ( 48) HTML ( 3) PDF (4973 KB) ( 75 )
  • For estimating the altitude-distribution pattern of carbon stocks in desert grasslands and analyzing the possible mechanism for this distribution, a detailed study was performed through a series of field vegetation surveys and soil samplings from 90 vegetation plots and 45 soil profiles at 9 sites of the Hexi Corridor region, Northwestern China. Aboveground, belowground, and litter-fall biomass-carbon stocks ranged from 43 to 109, 23 to 64, and 5 to 20 g/m2, with mean values of 80.82, 44.91, and 12.15 g/m2, respectively. Soil-carbon stocks varied between 2.88 and 3.98 kg/m2, with a mean value of 3.43 kg/m2 in the 0–100-cm soil layer. Both biomass- and soil-carbon stocks had an increasing tendency corresponding to the altitudinal gradient. A significantly negative correlation was found between soil-carbon stock and mean annual temperature, with further better correlations between soil- and biomass-carbon stocks, and mean annual precipitation. Furthermore, soil carbon was found to be positively correlated with soil-silt and -clay content, and negatively correlated with soil bulk density and the volume percent of gravel. It can be concluded that variations in soil texture and climate condition were the key factors influencing the altitudinal pattern of carbon stocks in this desert-grassland ecosystem. Thus, by using the linear-regression functions between altitude and carbon stocks, approximately 4.18 Tg carbon were predicted from the 1,260 km2 of desert grasslands in the study area.

  • Comparison of two classification methods to identify grain size fractions of aeolian sediment
  • YanZai Wang,YongQiu Wu,MeiHui Pan,RuiJie Lu
  • DOI: 10.3724/SP.J.1226.2018.00413
  • 2018, Vol.10 (5): 413–420 Abstract ( 81) HTML ( 4) PDF (5099 KB) ( 15 )
  • Grain-size class-Std (GSCStd) and Grain-size class-dD (GSCdD) methods are simple statistical approaches for classifying bulk grain-size distributions (GSDs) into grain-size fractions. Although these two methods were developed based on similar statistical principles, the classification difference between these two methods has not been analyzed. In this study, GSCStd and GSCdD methods are conducted in thirteen grain-size data sequences to examine the applicability for identifying grain size fractions. Results show that, application of the GSCStd method is equivalent to that of the GSCdD method in identifying finer grain-size fractions, and the difference between the two methods mainly comes from the identification of coarse grain-size fractions. Thus, finer grain-size fractions are recommended for use in research of surface aeolian and paleo-aeolian sediments. In addition, our results do not completely agree with previous studies, coarser grain-size fractions in our case suggest that the GSCdD method may not be more applicable than the GSCStd method.

  • Effect of slow-release iron fertilizer on iron-deficiency chlorosis, yield and quality of Lilium davidii var. unicolor in a two-year field experiment
  • Yang Qiu,ZhongKui Xie,XinPing Wang,YaJun Wang,YuBao Zhang,YuHui He,WenMei Li,WenCong Lv
  • DOI: 10.3724/SP.J.1226.2018.00421
  • 2018, Vol.10 (5): 421–427 Abstract ( 59) HTML ( 1) PDF (4283 KB) ( 24 )
  • Iron deficiency chlorosis of Lilium davidii var. unicolor is often the case in practice in alkaline soils of northwest region of China. It is difficult to control iron chlorosis because of high cost and short effective work time of conventional iron fertilizers. In this study, a 2-year field experiment was conducted to evaluate the effects of two slow-release fertilizers on the suppression of iron deficiency chlorosis, soil chemical properties, and the yield and quality of L. davidii var. unicolor. Results show that both coated slow-release iron fertilizers and embedded slow-release iron fertilizer effectively controlled iron-deficiency chlorosis. The application of slow-release iron fertilizers significantly increased plant height and chlorophyll content of L. davidii var. unicolor at different growth stages. Furthermore, coated iron fertilizer application significantly increased starch, protein, soluble sugar and vitamin C content of L. davidii var. unicolor, and it also significantly improved total amino acid content, with increases in essential amino acids (Trp, Leu, Lys, Phe, Val, and Thr contents) and in nonessential amino acids (Asp, Glu, Cit, Ihs, Acc, Ala, Pro, and Cys contents). It was concluded that application of coated slow-release iron fertilizer could be a promising option for suppression of iron deficiency chlorosis and deserves further study.

  • Transcriptomic comparison to identify rapidly evolving genes in Braya humilis
  • YuMing Wei,XiaoFei Ma,PengShan Zhao
  • DOI: 10.3724/SP.J.1226.2018.00428
  • 2018, Vol.10 (5): 428–435 Abstract ( 43) HTML ( 4) PDF (4412 KB) ( 14 )
  • The Brassicaceae species Braya humilis shows broad adaptation to different climatic zones and latitudes. However, the molecular adaptation mechanism of B. humilis is poorly understood. In China, B. humilis is mainly distributed on the Qinghai-Tibetan Plateau (QTP) and in the adjacent arid region. Previous transcriptome analysis of B. humilis has revealed that 39 salt and osmotic stress response genes are subjected to purifying selection during its speciation. To further explore the adaptation mechanism of B. humilis to an arid environment, OrthoMCL program was employed in this study and 6,268 pairs of orthologous gene pairs with high confidence were obtained betweenB. humilis and Arabidopsis thaliana. A comparative evolutionary analysis based on nonsynonymous to synonymous substitution ratio (Ka/Ks) was then conducted. There were 64 pairs exhibiting a Ka/Ks ratio more than 0.5 and among which, three instrumental candidate genes, T2_20487, T2_22576, and T2_13757, were identified with strong selection signatures (Ka/Ks >1). The corresponding A. thaliana orthologs are double-stranded RNA-binding domain protein, MADS-box family protein, and NADH-dehydrogenase subunit 6, which is encoded by mitochondria genome. This report not only demonstrates the adaptation contribution of fast evolving nuclear genes, but also highlights the potential adaptive value of mitochondria gene to the speciation and adaptation of B. humilis toward the extreme environment in an arid region.

  • Sociodemographic characteristics, cultural biases, and environmental attitudes: An empirical application of grid-group cultural theory in Northwestern China
  • FangLei Zhong,AiJun Guo,XiaoJuan Yin,JinFeng Cui,Xiao Yang,YanQiong Zhang
  • DOI: 10.3724/SP.J.1226.2018.00436
  • 2018, Vol.10 (5): 436–446 Abstract ( 39) HTML ( 2) PDF (4595 KB) ( 17 )
  • Natural resource-management studies have become increasingly attentive to the influences of human factors. Among these, cultural biases shape people's responses to changes in natural resource systems. Several studies have applied grid-group cultural theory to assess the effects of multiple value biases among stakeholders on natural resource management. We developed and administered a questionnaire in the Heihe River Basin (n = 364) in northwestern China to investigate the appropriateness of applying this theory in the Chinese context of natural resource management. The results revealed various cultural biases among the respondents. In descending order of prevalence, these biases were hierarchism (46.98%), individualism (26.65%), egalitarianism (18.96%), and fatalism (2.78%), with the remaining respondents (4.67%) evidencing no obvious bias. Our empirical study revealed respondents' worldviews and the influence of sociodemographic characteristics on cultural biases, as theoretically posited. Among the variables examined, age had a positive and significant effect across all biases except individualism. The correlation of income to all cultural biases was consistently negative. Only education had a negative and significant effect across all biases. Women were found to adhere to egalitarianism, whereas men adhered to individualism and hierarchism. Thus, grid-group cultural theory was found to be appropriate in the Chinese context, with gender, age, education, and income evidently accounting for cultural biases. Relationships between environmental attitudes and cultural biases conformed with the hypothesis advanced by grid-group cultural theory. This finding may be of value in explaining individuals' environmental attitudes and facilitating the development and implementation of natural resource-management policies.