Table of Content

15 March 2012, Volume 29 Issue 2 Previous Issue    Next Issue

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Spatiotemporal Variation of Vegetation Coverage Index in North China during the Period from 1982 to 2006 SUN Yan-Ling, GUO Peng 2012, 29 (2):  187-193.  Abstract ( 1846 )   PDF (2146KB) ( 980 )   In this paper, the spatiotemporal variation of normalized difference vegetation index (NDVI) values in north China was analyzed based on the GIMMS data during the period of 1982-2006. The preliminary results were as follows: (1) The average annual NDVI curves of vegetation were unidomal in north China. The NDVI peaks of vegetation occurred in summer, the NDVI peak in Beijing was the highest, then in Hebei Province, and it was the lowest in Inner Mongolia. The NDVI peak of forests was higher than that of grasslands and farmland; (2) In recent 25 years, the average annual NDVI in north China was increased. The average annual NDVI in Hebei Province was increased significantly, and the trend was the most significant (P<0.01).The average annual NDVI in Beijing was also increased significantly. In different land cover types, the highest increase of average annual NDVI occurred over farmland, than over grasslands, and it was the slowest in forests; (3) Based on the spatial trend analysis, the proportion of NDVI increase in the study area was 15.96%, and that of NDVI decrease was 11.86%. In different provinces, the NDVI  increase occurred mainly in Hebei Province, and the NDVI decrease occurred mainly in Inner Mongolia. In three land cover types, NDVI in farmland was increased more significantly than that in forests and grasslands; (4) Based on the background of warming and drying climate in north China, human activities were the main causes resulting in the NDVI variation. References | Related Articles | Metrics

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Response of Growth and Biomass Allocation of Haloxylon persicum Seedlings to Different Salt Treatments LU Hai-Ying, ZHANG Yuan-Ming 2012, 29 (2):  194-202.  Abstract ( 1565 )   PDF (2400KB) ( 809 )   Haloxylon persicum Bunge ex Boiss. et Buhse, a perennial shrub, is an important species in sand fixation and ecosystem regeneration in desert. In this study, the response of growth and biomass allocation of the species under different salt treatments was evaluated. Three kinds of salt (NaCl, Na2SO4 and compound salt mixed by NaCl and Na2SO4 with equal mol ratio) and six salt gradients 〔0 (CK), 50, 100, 200, 300 and 500 mmol/L〕 were designed in the study. Morphological characteristics, dynamic change of biomass accumulation and biomass allocation in the seedlings under different salt treatments were determined. It is confirmed that salt kind and salt content could significantly affect the biomass accumulation, biomass allocation and morphological characteristics of H. persicum seedlings. The results are as follows: (1) The morphological structure of assimilating branches under different salt treatments was different. Root length was promoted under moderate salt concentration, but it was restricted under high salt treatment. The height, stem diameter and biomass accumulation of  H. persicum seedlings were positively correlated with treating time and salt concentration. Compared with the contrast, the biomass of H. persicum seedlings under 500mmol/L compound salt (mixed by NaCl and Na2SO4) treatment after 70 days was decreased by 77%, 87% and 78%, the aboveground biomass by 78%, 87% and 74%, and the underground biomass by 75%, 81% and 76%, respectively; (3) Rootshoot ratio was increased with the time under all treatments, but it was different from different treatments. There was no significant difference in rootshoot ratio between the contrast and all the NaCl or compound salt treatments after 25 days, but the rootshoot ratio was increased under high salt concentration of Na2SO4. Rootshoot ratio was in an increase trend with increasing salt concentration regardless what kinds of salt; (4) There was an obviously allometric relationship between aboveground biomass and underground biomass, and the accumulating rate of underground biomass was higher than that of aboveground biomass. Additionally, saline treatments did not change the allometric parameter (a)significantly. The results demonstrated that the response of H. persicum seedlings varied with salt kinds, content and treatment time. Under salt stress, the response of H. persicum seedlings to Na2SO4 was faster than to NaCl and compound salt, such response trended to a similarity with the time. References | Related Articles | Metrics

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Effects of Seed Dressing with 4 PGPR Strains on Growth and Grain Yield of Broad Bean (Vicia faba L.) under Drought Stress WU Xing-Xing, WU Yi-Xin, ZHAO Zheng-Long, Rainer BORRISS, MAO Zi-Chao, CHEN Xiao-Hua, HE Yue-Qiu 2012, 29 (2):  203-207.  Abstract ( 2072 )   PDF (495KB) ( 1009 )   Four PGPR strains, B9601Y2, FZB42, B2 and B9 were used for dressing seeds of broad bean at the concentration of 5×108 CFU/mL before seeding. Under serious drought during whole growth period, all these strains could enhance the growth of broad bean in comparison with negative control: obviously earlier seed germination, higher plant at seedling stage, increasing weight of above and underground parts and more pod number. The pods after dressing seeds of broad bean with B9601Y2, FZB42, B2 and B9 were increased by 0.65, 0.50, 0.05 and 0.33, the fruiting pods per plant were 0.68, 0.53, 0.08 and 0.28, the pod weights were 4.56 g, 3.36 g, 2.13 g and 0.36 g, the seeds per plant were 1.18, 1.55, 0.80 and 0.15 g, the weights per 100seeds were 5.28 g，5.75 g, 3.72 g and 2.50 g, the grain yield of broad bean were 14.49%, 12.04%, 6.28% and 2.21%, respectively. References | Related Articles | Metrics

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Response of Growth of Salix gordejevii Seedling to Sand Burial Depth in the Semiarid Aeolian Sand Field MIAO Chun-Ping, LI Xue-Hua, JIANG De-Ming 2012, 29 (2):  208-212.  Abstract ( 1898 )   PDF (1035KB) ( 1146 )   Sand-burial controlled experiment was conducted to investigate the response of Salix gordejevii seedling growth, and the sand burial depths were varied from 0, 10 and 20 to 40 cm. The results show that the mortality of S. gordejevii was increased with increasing sand burial depth. There were some significant differences in the stem height, relative height growth rate, biomass allocated to roots, stems and leaves as well as the rootshoot ratio of seedlings in 4 treatments. There was no significant sand burial effect on absolute height growth rate and biomass accumulation. Slight sand burying promoted the growth of stem. With the increase of sand burial depth, the stem growth could be increased, but the relative height growth rate was decreased. The root biomass was increased to absorb water and nutrient under slight sand burial depth. More biomass was allocated to shoots with the increase of sand burial depth. These results reveal that the defense of S. gordejevii seedlings was increased by stem growing and biomass allocation so as to maintain photosynthesis by stem growing or allocating more biomass to shoots.   References | Related Articles | Metrics

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Study on Windbreak Effect of Artemisia ordosica  Community over Different Vegetation Coverage WEI Bao, DING Guo-Dong, WU Bin, ZHANG Yu-Qing 2012, 29 (2):  213-217.  Abstract ( 1585 )   PDF (1404KB) ( 969 )   In traditional study, wind velocity, aerodynamic roughness, friction velocity, drag coefficient and other parameters are often used to evaluate the restriction effect of vegetation on wind erosion, but the studies on wind energy dissipation of vegetation using boundary layer displacement thickness and momentum loss thickness are relatively insufficient. In this paper, the windbreak effect of Artemisia ordosica community over different vegetation coverage was quantitatively studied after carrying out a field investigation in southwestern marginal zone of the Mu Us Sandy land. Artemisia ordosica was selected in the study, its initial coverage was 60%, it was artificially decreased down to 50%, 40% and 30%, and the wind velocities at 0.1, 0.5, 1.0, 2.0, 3.0, 4.0, 5.0 and 6.0 m were recorded. When the coverage of Artemisia ordosica community was increased from 30% to 60%, wind profile did not change significantly, and the values of wind profile equation, aerodynamic roughness, boundary layer displacement thickness and momentum loss thickness were similar. As those parameters did not show a regular change with changing vegetation coverage, it is believed that vegetation coverage and windbreak effect of Artemisia ordosica community are similar. References | Related Articles | Metrics

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Preliminary Study on Leskeaceae (Musci) in Xinjiang, China Mamtimin Sulayman, Anwar Abdurehim 2012, 29 (2):  218-221.  Abstract ( 1748 )   This paper is based on 105 specimens collected from Xinjiang Uygur Autonomous Region. The classification results show that there are 8 species of Leskeaceae in Xinjiang. They are Lescuraea Bruch & Schimp. in B. S. G. ［3 species: L. incurvata (Hedw.) Lawton, L. radicosa (Mitt.) Moeck. and L. saxicola (Schimp. in B. S. G.) Mol. in Lor.］, Leskea Hedw. (1 species: L. polycarpa Hedw.), Leskeella (Brid.) Loeske (1 species: L. nervosa (Brid.) Loeske), Lindbergia (C. Müll) Broth. ［1 species: L. sinensis (C. Müll) Broth.］,  Pseudoleskeella Kindb. ［2 species: P. catenulata (Brid. ex Schrad.) Kindb. and P. tectorum (Brid. )Kindb.］. Among them, the genus Leskea Hedw., Leskea polycarpa Hedw. and L. radicosa (Mitt.) Moeck. are newly reported in this region. According to the studied specimens, the habitat and the geographic distribution of these species are discussed. The studied specimens are stored in the herbarium of College of Life Science, Xinjiang University． References | Related Articles | Metrics

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Causes of Surface Energy Imbalance and Its Possible Solutions LI Hong yu, ZHANG Qiang, ZHAO Jian hua 2012, 29 (2):  222-232.  Abstract ( 2497 )   PDF (2238KB) ( 1844 )   Surface energy imbalance is a difficulty in the study on land surface interaction. A series of experiments related to surface energy imbalance have been conducted in different climate zones and underlying surfaces in the world. Over the past two decades, some systematic progresses on this issue have been made. This paper summarizes the research achievements of surface energy balance in land surface process experiments conducted over different underlying surfaces, introduces the statistical methods to characterize surface energy imbalance, and discusses the possible causes resulting in energy imbalance. Heat storage in upper soil layer and energy storage due to plant photosynthesis and temperature variation of canopy and air has an effect on surface energy balance. Vertical sensible advection is also discussed as a cause resulting in surface energy imbalance. Because of footprint differences of energy components, heterogeneous surface has an impact on representation of measurements, and it also induces local circulations and largescale eddy. Together with the nighttime inadequate turbulent mixing, the inconsistent atmospheric status makes some troubles to the flux measurements. After data quality control is processed strictly, three schemes are put forward to solve the energy imbalance, heat flux advection correction for singlepoint EC system, spatial averaging of flux observations for multipoint one and the replacement of EC system by LAS with  larger measurement footprint. It is suggested that the nighttime EC latent heat flux be substituted by the PenmanMonteith modeled flux in cases of insufficient turbulent mixing. A simple discussion is made by a comparison between the EC water vapor flux and the actual surface evaporation observed by the weighing evaporation instrument and the weighing evaporation instrument as a possible test method, and it is proposed to calculate surface latent heat flux. References | Related Articles | Metrics

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Change and Causes of the Riverlake Marshes along the Green Corridor at the Lower Reaches of the Qarqan River LI Li, ZENG Qing-Wei, ZHOU Hui-Zhen, WANG Ai-Hua, LIU Chang, CHI Yao-Bin, WANG Zhi-Yong 2012, 29 (2):  233-237.  Abstract ( 1887 )   PDF (2027KB) ( 1036 )   River green corridor is a narrow barrier region along an inland river in arid region, it has two remarkable characteristics, one is that the soil moisture content in the corridor is higher than that in surrounding desert, and the other is that the landscape types are quite different from those in around environment. As an important landscape type in river green corridor in arid region in northwest China, marsh plays an important role in climatic regulation, water conservation and purification, maintenance of biological diversity, etc. The Qarqan River has the highest annual runoff volume in the southeast Tarim Basin and maintains the entironment of the green corridors in the east Taklimakan Desert and along the Tarim River. Because of its dramatic change, the riverlake marsh change in the green corridor along the Qarqan River attracts more and more attentions in recent years. So we monitored the dynamic change of the riverlake marshes using multispectral RS images from different satellites, such as Beijing1, HJ, CBERS-2 and Landsat TM during the period from 2000 to 2010. The results show that the area of the river lake marshes was enlarged at first, then it was reduced and followed by enlargement again since the year of 2000, and the monthly variation was also distinct in 2010. The monitoring area was 141 km2 in the year of 2005, and it was enlarged to 393 km2 in the year of 2010. Moreover, the meteorological, social and economic data, such as annual temperature, annual precipitation, annual cultivated land area and annual GDP in Ruoqiang County and Qiemo County in recent 50 years, were analyzed, and the correlations among the annual runoff volume of the Qarqan River and these factors were computed using quantitative analysis. The quantitative analysis was combined with the statistic data of glacier change in the Muztag Mountain during the period from 2000 to 2010 after analyzing the RS data and the water conservancy policy of Xinjiang government at all levels. The main causes resulting in the riverlake marsh change could be summarized as follows: Climate change was the key factor bringing about the riverlake marsh increase and the entironment maintenance in the green corridor of the Qarqan River, and temperature increase resulted in the glacier melting and the increase of annual precipitation and water resources supply. The increasing human activities, such as the expansion of cultivated land and economic development, require more water resources but result in the reduction of river lake marshes. However, the implementation of the projects of water conveyance for saving the ecology and the water conservancy policy reduced these negative impacts. References | Related Articles | Metrics

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Dynamic Monitoring on Gully Head Erosion on Weiliantan Terrance in Longyangxia Reservoir Area MA Yu-Feng, YAN Ping, LI Shuang-Quan, ZHAN Xiu-Li 2012, 29 (2):  238-244.  Abstract ( 1758 )   PDF (1381KB) ( 1060 )   The gully head of south branch gully on Weiliantan Terrance in Longyangxia Reservoir area was monitored by laser 3D scanner, Trimble 4700 differential GPS and submeter differential GPS. After surveying the gully head erosion for 4 years (2006-2010) in field work and analyzing the meteorological data, this paper estimated primarily the erosion amount, and discussed the erosion causes and the gully head development. The results show that the fragmented form of the bank at the gully head in 2006 provided a favorable terrain for erosion in the following years. After 3 years, the erosion area was enlarged significantly, especially in the tension crack zone of the south bank. The scanning data during the period from 2007 to 2010 revealed that the headward erosion was the most serious in 2009. The tension cracks were resulted in by the repeated alternation of freezingthawing and wettingdrying process, which not only strengthened soil erosion in rainy season, but also intensified the erosion of gully head through destroying soil structure and causing soil collapse. The obvious increase of gully headward erosion did not occur in the years when there was more frequency erosive rainfall, but it could be easily caused by flood disaster under heavy rainfall, and flood disaster was an important power for the gully head erosion. References | Related Articles | Metrics

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RSbased Monitoring of Glacier Change in the Beidahe River Basin in the Qilian Mountains YAN Dong-Hai, LI Zhong-Qin, GAO Wen-Yu, WANG Pu-Yu, DONG Zhi-Wen 2012, 29 (2):  245-250.  Abstract ( 1948 )   PDF (2878KB) ( 1223 )   In this paper, the change of glaciers in the Beidahe River Basin in the Qilian Mountains in recent 47 years was studied using the topographic map in 1956 and the ASTER image data in 2003 so as to ascertain the glacial boundaries in these two years under the support of RS and GIS means. The results show that area of the 372 glaciers in the basin was reduced by 33.56 km2 in recent 47 years, 0.09 km2 per glacier in average, the change rate was -15.42%, and the total shrinkage of the glacier terminals was 51 015 m. The analyzed results revealed that the melting of small glaciers was faster than that of large ones. After comparing and analyzing the data of average annual temperature and summer temperature as well as annual precipitation, it was considered that the significant temperature increase was the main cause resulting in the rapid shrinkage of glaciers in the Beidahe River Basin. After carrying out a comparative study on glacier shrinkage in west China, it was found that the glacial melting rate in the Beidahe River Basin was higher than that in north Xinjiang but lower than that in the Heihe River Basin and other distributary basins. It was conferred preliminarily that the shrinkage of glaciers might be jointly caused by climate change and the factors of glaciers themselves.  References | Related Articles | Metrics

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Study on Variation of Net Radiation in the Dunhuang Gobi WANG Chao- , WEI Zhi-Gang- , LI Zhen-Chao- , LIU Hui- , WEI Hong 2012, 29 (2):  251-256.  Abstract ( 1828 )   In this paper, the probability distribution, daily and annual variation of net radiation and its change under typical weather conditions were analyzed based on the fieldobserved data at Shangdunzi Gobi Experiment Station in Dunhuang during the period from December 2008 to December 2009. The results are as follows: (1) There was an obvious peak distribution of net radiation in the range of -100-0 W/m2, and the average annual net radiation was 43.88 W/m2; (2) There was an obvious daily variation of net radiation, the net radiation was positive in daytime but negative at night, its maximum occurred at midday, and its minimum occurred at sunset. Seasonal difference of net radiation was obvious, the net radiation was the highest in summer and the lowest in winter; (3) Net radiation was quite different under different weather conditions including sunny, cloudy and sandstorm days. References | Related Articles | Metrics

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Study on Aridity Trend in China in 20th Century MENG Meng, ZONG Mei-Juan 2012, 29 (2):  257-261.  Abstract ( 1731 )   In this paper, the values of aridity index in China were calculated using the time series 2.0 climatic datasets from Climatic Research Unit of University of East Anglia and the Holdridge potential evapotranspiration method. On which the dynamic change of values of aridity index in China in the 20th century was analyzed. Moreover, the results were interpolated in GIS software, and then they were formed as the digital maps of AI distribution in China. The results show that there was a notable reduction of humid climate area in China in the 20th century, semihumid climate area was enlarged considerably, dry climate area was enlarged significantly, and the drought trend was significant. Temperature increase and precipitation decrease in China leaded to a reduction of surface moisture and a disadvantage for moisture accumulation over land surface. These are the important factors of producing and aggravating ariditification. References | Related Articles | Metrics

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A Modeling Study on Drought Trend in the Sino-Mongolian Arid and Semiarid Regions in the 21st Century LI Xin-Zhou, LIU Xiao-Dong 2012, 29 (2):  262-272.  Abstract ( 1671 )   PDF (4310KB) ( 1551 )   Using a regional climate model (RegCM3) nested in oneway mode within the Community Climate System Model (CCSM3), some high resolution numerical experiments were conducted under the SRES A2, A1B and B1 scenarios for the 21st century, and the drought characteristics and their possible trends in the Sino-Mongolian arid and semiarid regions were analyzed. The results show that the precipitation and surface temperature have an obvious increasing trend under all scenarios. There is no clear drying trend in the 21st century based on the analyzed results of precipitation. Considering from the Palmer Drought Severity Index (PDSI), however, the signals of precipitation and temperature reveal that the drought area may be expanded continuously. The proportions of extremely severe, severe and moderate drought areas are increased, which are all significant at significance level of 95%. The extremely severe drought area was expanded by higher than 3% under all the scenarios in the late-21st century compared with that in the mid-21st century. Compared with mid-21st century and modern time, the drought areas will be enlarged by 8% and 11.51% under A2, 12.48% and 18.34% under A1B, and 9.73% and 10.82% under B1 in the late-21st century, respectively. The change of both precipitation and temperature must be taken into account in predicting climate change in arid and semiarid regions so as to more accurately reflect the characteristics of drought and drying trend.   References | Related Articles | Metrics

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Mesoscale Atmospheric Numerical Simulation and Its Progress HUANG Jing, ZHANG Qiang 2012, 29 (2):  273-283.  Abstract ( 3987 )   PDF (1318KB) ( 2356 )   In this paper, several aspects of mesoscale atmospheric numerical simulation were summed up briefly. Firstly, MM5, RAMS and WRF were taking as the cases to introduce their dynamic framework, physical processes and applications. Furthermore, the characteristics of several current well-known mesoscale numerical models were compared. Secondly, cumulus parameterization schemes, planetary boundary layer parameterization schemes and land surface parameterization schemes were respectively discussed in detail. Cumulus parameterization schemes were divided into convective adjustment, large-scale water vapor flux convergence and mass flux, and their characteristics, advantages and disadvantages were summarized. Planetary boundary layer parameterization schemes were mainly consisted of the bulk planetary boundary layer parameterization scheme, high-resolution planetary boundary layer parameterization scheme and large eddy simulation. The development of land surface process parameterization, nonuniform land surface parameterization and currently major land surface models were discussed. The objective analysis methods and three main kinds of data assimilation methods were analyzed. Finally, some problems which are needed to study were pointed out, and the development of mesoscale atmospheric numerical simulation was prospected. It is hoped to synthetically analyze these issues so as to promote the application of  mesoscale atmospheric numerical simulation in the future. References | Related Articles | Metrics

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Study on Occurrence Pattern and Trend of Drought in East Qinghai Province YANG Fang, LIU Lu 2012, 29 (2):  284-288.  Abstract ( 1681 )   PDF (982KB) ( 1169 )   In this paper, the characteristics, formation causes, spatiotemporal distribution, disaster mechanism and degree of drought in east Qinghai Province were analyzed based on the investigated results and the data of climate change in the study area. The results show that, affected by global warming, the air temperature has been in an increase trend since the 1970s, the precipitation increase was not significant, annual runoff volumes of the rivers were slightly reduced, drought occurred frequently, and it is difficult to alleviate drought in near future. Consequently, soil erosion, landslides, avalanches and other geological disasters, agriculture biological disasters and a series of ecological problems would be induced. The development pattern and trend of drought in east Qinghai Province along with climate change were discussed. References | Related Articles | Metrics

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Study on the Change of Extreme Events of Hightemperature and HeavyPrecipitation in Shanxi Province in Recent 48 Years WANG Yong-Mei, ZHANG Hong-Yu, GUO Xue, LIU Hui-Li, LI Run-Chun 2012, 29 (2):  289-295.  Abstract ( 1699 )   PDF (2158KB) ( 1124 )   In this paper, the events of extreme high-temperature and extreme heavy-precipitation in Shanxi Province were analyzed using Mann-Kendall test and wavelet analysis based on the daily highest temperature and precipitation data observed by 68 meteorological stations. The results show that the increase of extreme high-temperature was significant with an increase rate of 5.9 d/10 a, it was not so high before the mid-1990s but significant since 1997. Moreover, the extreme heavy-precipitation days were decreased in recent 48 years, but the trend was not obvious. There was a sharp change of extreme high-temperature days in 2001, and the extreme high-temperatures days were increased significantly since 2001. The increase of extreme high-temperature days was closely related to climate warming, and it was strongly affected by high sea temperature in Nino_3, strong latitudinal circulation over Eurasia and large-area Western Pacific High. The increase of extreme heavy-precipitation days was closely related to the low sea temperature in Nino_3 and strong East Asian Monsoon. References | Related Articles | Metrics

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Analysis on Change of Daily Extreme Precipitation Frequency and Intensity in Gansu Province in Summer during the Period of 1959-2008 MA Zhong-Hua, ZHANG Bo , WANG Xing-Mei , ZOU Yue, ZHANG Ya-Ning 2012, 29 (2):  296-302.  Abstract ( 1749 )   PDF (3899KB) ( 1033 )   In this paper, the changes of periodic and distributional characteristics of daily extreme precipitation frequency and intensity in summer were analyzed using the ArcGIS and Matlab 7.0 data software platform, complex Morlet wavelet analysis and Mann-Kendall test based on the data of daily precipitation in Gansu Province in summer during the period of 1959-2008. The results show that there were mainly the 19-year and 8-year periodicities of extreme precipitation frequency and mainly the 11-year and 19-year ones of extreme precipitation intensity. There were also the obvious differences in extreme precipitation and spatial distribution of total precipitation in summer in the southeastern region of the province. Moreover, the extreme precipitation frequency was in a decreasing trend, but the extreme precipitation intensity was in an increasing trend. References | Related Articles | Metrics

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Spatiotemporal Variation of Winter Heat Resources in the Urumqi-Changji Region Based on GIS PU Zong-Chao, ZHANG Shan-Qing, BIN Jian-Hua, DOU Xin-Ying, LI Jing-Lin 2012, 29 (2):  303-311.  Abstract ( 1759 )   PDF (3272KB) ( 930 )   Based on the data of average daily temperature and annual extreme minimum temperature at 16 meteorological stations in the Urumqi-Changji region during the period of 1961-2009, this paper analyzes the spatiotemporal change and sharp change of the first day of daily mean temperature stabilized at ≤ 0 ℃ and ≥ 0 ℃, duration of average daily temperature ≤0 ℃, negative accumulated temperature in winter, average monthly temperature in January and extreme minimum temperature using the methods of Mann-Kendall test, three-dimensional and quadratic trend surface simulation and inverse-distance square weighting residual error revising based on GIS. The main results are as the follows: (1) The winter heat resources was quite different from different regions in the Urumqi-Changji region. Generally, the first day of daily mean temperature stabilized at ≤0 ℃was earlier in mountains than that in plains and valleys, but the first day of daily mean temperature stabilized at ≥0 ℃ was later in mountains than that in plains and valleys. The continuous duration of average daily temperature ≤0 ℃ was longer in mountains than that in plains and valleys, and longer in the eastern part than that in the western part of the Urumqi-Changji region. Affected by winter inversion, the negative accumulated temperature in winter, average monthly temperature in January and extreme minimum temperature were increased from plains to mid-mountain zone about 2 100 m a. s. l., and their maximums occurred at this altitude; (2) under global warming, winter heat resources was in a significant increase trend in the Urumqi-Changji region in recent 49 years, the first day of daily mean temperature stabilized at ≤0 ℃ was sharply postponed in 1994 , the continuous duration of daily average temperature ≤0 ℃ was sharply shortened in 2004, negative accumulated temperature in winter was sharply decreased in 1988, and the average monthly temperature in January and the extreme minimum temperature were sharply increased in 1973 and 2004 respectively. The increase of various winter heat elements before and after their sharp change was higher in plains than that in mountains, and higher in city-dense regions than that in peripheral regions. Effects of winter heat resources increase may be advantageous to agriculture and livestock production in the Urumqi-Changji region. Therefore, some managing and technical measures should be taken so as to promote the sustainable development of agricultural and livestock production.   References | Related Articles | Metrics

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Validation and Assessment of Cloud Obscuration Reduction of Snow Cover Products in Arid Areas in China WANG Zeng-Yan, CHE Tao 2012, 29 (2):  312-319.  Abstract ( 1505 )   PDF (1675KB) ( 1015 )   Cloud coverage in daily snow cover products is a main obstacle in using Moderate Resolution Imaging Spectroradiometer (MODIS). In this study, the multitemporal and multisensor combination approaches are applied to reduce cloud obscuration with Aqua Advanced Microwave Scanning Radiometer for NASA’S Earth Observing System (AMSR-E)  snow depth products introduced as the auxiliary data to develop 6 new kinds of snow cover products. Different snow cover duration days(SCD) maps are developed from these combined products. The results are as follows: (1) MODIS and AMSR-E 4-day thresholdcombined snow cover product performed well in algorithm efficiency, cloud-reducing effect and capability in maintaining relatively high spatiotemporal resolutions; (2) Under all weather conditions, the overall, snow and land accuracies of the resulted cloud-free products were 96%, 80% and 99%, and they were significantly higher than 64%, 32% and 70% of the original MODIS Terra and Aqua combination product, respectively; (3) The SCD map generated from this product could not only maintain a high spatial resolution of the original MODIS product, but also could precisely reflect the spatial distribution of the snow cover status in the study area. References | Related Articles | Metrics

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Research on Change of Surface Water Vapor in the Tianshan Mountains under Global Warming YAO Jun-Qiang, YANG Qing, ZHAO Ling 2012, 29 (2):  320-327.  Abstract ( 1848 )   PDF (3057KB) ( 952 )   In this paper, the change of surface water vapor was analyzed using the linear trend estimation, anomaly analysis, Mann-Kendall sharp change test and power spectrum analysis based on the data of water vapor pressure at 44 meteorological stations in the Tianshan Mountains during the period from 1961 to 2009. The results show that the change trend of surface water vapor in the Tianshan Mountains was significant, and the average change trend was 0.015. There were the obvious inter-annual and inter-decadal differences in variation and change trend of annual and seasonal surface water vapor, the highest increase occurred in the late-1990s, the minimum in the late-1970s and mid-1980s, and the maximum in the early 21st century. The increase trend of surface water vapor was the most significant in summer, then in autumn and winter, and the minimum increase occurred in spring. Sharp changes of the annual and seasonal surface water vapor occurred in 1986 (especially in summer and autumn), 1980 (winter) and 1996 (spring). The test shows that all the sharp changes were significant( r=0.05).The power spectrum analysis shows that there were the obvious periodicities in annual and seasonal surface water vapor change. The obvious annual periodicities of surface water vapor change were for 3.2 years and 2.9 years; the summer ones for 2.9 years and 2.3 years, and autumn ones for 3.6 years and 3.2 years. The change trend and sharp change of surface water vapor in the Tianshan Mountains were similar to the change trends of mean annual temperature and precipitation, westerly circulation, Qinghai-Tibetan Plateau circulation NAO and the time of their sharp changes. The correlation between annual precipitation and water vapor was the closest, and followed by temperature and other factors.  References | Related Articles | Metrics

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Response of Stable Carbon Isotope of Larix sibirica Ledeb. Tree rings  to Climate Change ZHANG Rui-Bo, YUAN Yu-Jiang, WEI Wen-Shou, SHANG Hua-Ming, YU Shu-Long, ZHANG Tong-Wen, CHEN Feng, FAN Zi-Ang, QIN Li 2012, 29 (2):  328-334.  Abstract ( 1967 )   PDF (1543KB) ( 934 )   Stable isotopes in tree rings are the important approaches in climate reconstruction and in studies on tree response to environmental factors in the past, such as the maximum latewood density, tree ring width and other tree ring parameters. In this paper, the tree ring samples of Larix sibirica Ledeb. collected in south slope of the Altay Mountains in 2009 were used to develop the treering width chronology and stable carbon isotope series based on the standard Dendrochronology methods and stable carbon isotope research achievements. It can establish the detrend series (DS) of stable carbon isotope of tree rings to eliminate atmospheric CO2 effect from original δ13C. The stable carbon isotope series values of L. sibirica tree rings varied in a range of -22.8‰--25.4‰, The average value was -24.0‰, and the coefficient of variation was -0.017. Width chronology and stable carbon isotope detrend series were compared with monthly climatic factors (mean temperature, mean maximum temperature, mean minimum temperature, precipitation, relative humidity and sunshine duration) at Fuyun Meteorological Station. Correlation analysis revealed that there was a strong positive correlation between the stable carbon isotope detrend series and the mean temperature and mean maximum temperature but a negative one between it and the relative humidity in growing season. The correlation coefficient between the detrend series of stable carbon isotope and the monthly maximum temperature in June and July was as high as 0.611 (P<0.000 001), that between it and the monthly relative humidity in June and July was -0.493 (P<0.001), and that between it and monthly precipitation in July was -0.459 (P<0.01). The response of stable carbon isotope of L. sibirica tree rings to temperature and relative humidity in growing season was the most sensitive. The main factor affecting stable carbon isotope of L. sibiricawas the monthly maximum temperature in June and July. References | Related Articles | Metrics

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Response of Riparian Vegetation to the Change of Groundwater Level at Middle and Lower Reaches of the Shiyang River LIU Hu-Jun, LIU Shi-Zeng, LI Yi, YANG Zi-Hui, LI Yin-Ke, ZHANG Ying-Hua, GUO Chun-Xiu, LIU Shu-Juan 2012, 29 (2):  335-341.  Abstract ( 2456 )   PDF (1057KB) ( 1156 )   Located in a zone of 36°29′-39°27′ N and 101°41′-104°16′ E, the Shiyang River Basin is one of the inland river basins where the environment is strongly disturbed by human activities, and its degeneration is resulted in. It is an important reference to study the relationship between water conditions of riverbank and riparian vegetation for revealing ecological management and regenerating entironment in the Shiyang River Basin. In September and October 2009, the vegetation, soil and water conditions were investigated in the riparian region, the study area was divided into two types, i.e. the regions with and without runoff, and then the data were analyzed. In addition, the groundwater level was observed every two months during the period of 2009-2010. The analyzed results show that there was a positive correlation between groundwater level and distance away from the river channel. The types and richness of plant communities of the riparian vegetation in the Shiyang River Basin were reduced with the increase of distance away from the river channel. In the riparian region with runoff, the change of groundwater level responded to the runoff volume at a belt of 130 m in width. The belt width of riparian vegetation, decided by distribution of the types of plant communities, vegetation coverage and groundwater level at riparian zone, was about 500 m at the middle and lower reaches of the Shiyang River. At a zone 500 m in width away from the river channel, the types and richness of plant communities of the riparian vegetation were more than that in a zone further than 500 m, soil moisture content was higher, total salt content was lower, and the vegetation coverage was higher. At the riparian region without runoff, there was a positive correlation between the depth of groundwater level and the distance away from the river channel. The riparian plant species might be found in a zone 200 m in width away from the dried-up river channel. Although stream flow was cut off at the lower reaches, the river landforms were benefit to water storage and plant growth. Vegetation at the riparian region of the study area could be classified into 12 communities and 29 sub-communities in 5 vegetation types. The riparian plant communities responded to the groundwater level. References | Related Articles | Metrics

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Research on Hydraulic Lifting of Populus euphratica Seedling Roots in Desert Riparian Forest Area SU Rui, LI Wei-Hong, HAO Xing-Ming, GUO Bin, ZHU Cheng-Gang 2012, 29 (2):  342-346.  Abstract ( 1801 )   PDF (1352KB) ( 702 )   Plant hydraulic lifting is a phenomenon that the roots in deep wet soil uptake water from subsoil and carry water though the transport tissues to the roots in topsoil and into dry topsoil around them when transpiration is lower at night. The method in which the roots were separated into those in topsoil and subsoil was used to study the hydraulic lifting of Populus euphratica seedling roots in their whole growing season. The results are as follows; (1) There is a hydraulic lifting function in roots of P. euphratica seedlings; (2) Hydraulic lifting occurred from 21:00  to 6:00 am next morning. The total uptake water volumes of the seedling roots of 3 P. euphratica plants in growing season were 2.78, 2.31 and 2.46 kg, and their average daily volumes were 0.022 6, 0.018 7 and 0.020 kg, respectively; (3) The proportion of hydraulic lifting water volume of P. euphratica seedling roots varied in a range of 13%-20% of evaporation from topsoil. During the period from June to August when transpiration was significant, the average daily hydraulic lifting water volume was also high; (4) There was a significant correlation between root biomass and hydraulic lifting water volume in subsoil. References | Related Articles | Metrics

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Effect of Biological Soil Crust on Soil Temperature in the Mu Us Sand Land YANG Yong-Sheng, BU Chong-Feng, GAO Guo-Xiong 2012, 29 (2):  352-359.  Abstract ( 1596 )   PDF (3747KB) ( 1248 )   Soil temperature affects strongly the crop growth, soil watersalt transport, biological activity and quantity, and soil carbon balance. In order to study the differences of biological crust and bare sand soil temperature in Mu Us Sand Land, some sunny days were selected to conduct the experiments in Gechou Ditch in the Mu Us Sand Land located in Shenmu County, north Shaanxi Province during the period from September to November 2010. The results are as follows: (1) The change trend of soil temperature at the same depth was the same in both the plots of biological soil crust and bare sand; From 6:00 to 21:00（every 3 hours）,the soil temperature curves were “\”, micro“(”， obvious “(”, “/”, micro “)” and “\”; (2) Biological crust cover decreased significantly the topsoil temperature (P<0.01); (3) The change range of topsoil temperature in both the biological crust and bare sand plots was the highest, and it was decreased with the increase of soil depth. The effect of biological crust on soil temperature at the same depth was more significant. From the perspective of vertical profile, biological crust decreased the soil temperature and its change range; (4) Biological crust enhanced the sensitivity of soil temperature at depth of 0-25 cm to air temperature. The study results showed that the change of soil temperature was affected by many factors, and the previous achievement that the effect of biological crust on soil temperature was judged with the biological crust color was not reliable. The effect of biological crust on soil temperature is probably caused by that biological crust changes the topsoil structure and moisture conditions. Soil moisture evaporation, soil chemical properties, etc., especially the temperature effect of biological crust on these processes, should be paid more attention to in the future. References | Related Articles | Metrics

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Evapotranspiration of a Filmmulched Cotton Field under Drip Irrigation in North Xinjiang LIU Jing-Xian, ZHOU Shi-Qiao, JIN Lu-Sheng, WANG Jin, Yang-Jing-Hui 2012, 29 (2):  360-368.  Abstract ( 1524 )   PDF (1739KB) ( 875 )   Evapotranspiration including evaporation and transpiration is a main expenditure of water budget at farmland, and it plays an important role in agricultural water management, especially in arid region. In Xinjiang, as a cotton growing area in arid region, water-saving irrigation of cotton is significant for agricultural production. Previous studies on evapotranspiration of cotton reported the total monthly or growth-stage values, however, the daily observations were unavailable. As a method with high time resolution, the eddy covariance has been widely used in measuring evapotranspiration. In this paper, the values of evapotranspiration in the whole cotton growing season were calculated and analyzed based on the observations by eddy covariance at a cotton field under drip irrigation with plastic film in North Xinjiang during the period from June 2009 to June 2010. Under the clear and cloudless terms, daily variation of evapotranspiration was highly consistent with net radiation at each cotton growth stage. The evapotranspiration was affected by net radiation during the period from sowing to emergence and at seedling and boll opening stages, and also by leaf area index at squaring, flowering and boll formation stages. Under the present irrigation regime, soil moisture content could meet the water demand for evapotranspiration in the whole cotton growing season except at boll opening stage. Daily mean evapotranspiration was 1.8, 1.7, 3.7, 3.8 and 1.2 mm/d during the period from sowing to emergence and at seedling, squaring, flowering, boll formation and boll opening stages, respectively. The total evapotranspiration in the whole cotton growing season amounted to 514.3 mm. References | Related Articles | Metrics

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Impacts of Different Temperature Conditions on Population Crash of Aphis gossypii in Midsummer MA Ji-Hong, 吕Zhao-Zhi , GAO Gui-Zhen, XIA De-Ping 2012, 29 (2):  369-374.  Abstract ( 1684 )   PDF (933KB) ( 975 )   In order to research the relationship between fluctuant high temperature and population crash of Aphis gossypii in midsummer, the mortalities of Aphis gossypii under different fluctuant thermal regimes were investigated in laboratory, and Aphis gossypii population abundance in field, affected by climatic factors, were analyzed. The results showed that the impacts of high temperature (30 ℃, 34 ℃, 38 ℃ and 42 ℃), exposure hours (2 and 6 h/d), exposure days (1-5 days) and interactions among these parameters on the mortality were extremely significant. The mortality of Aphis gossypii was increased with the increase of high temperature (>30 ℃) under the same treatments of exposure hours and days and the same high temperature treatment. The longer the high temperature continued, the higher of mortality of Aphis gossypii was. The mortality of Aphis gossypii was not significantly affected by fluctuant high temperature when temperature was lower than 38 ℃ (2 h/d). The date of population crash of Aphis gossypii in field coincided with the occurrence of high temperature (from July 31 to August 4). The diurnalnocturnal fluctuation of high temperature in field was consistent with the hightemperature thermal regimes which resulted in an increase of mortality of Aphis gossypii (24 ℃ 18 h/34 ℃ 6 h lasted for 4 days and 24 ℃ 18 h/38 ℃ 6 h lasted for 3 days). The results suggested that fluctuant high temperature played an important role in population crash of Aphis gossypii in midsummer. The results can be used to explain that the population crash of Aphis gossypii occurs usually in midsummer, but the mechanism should be further researched. References | Related Articles | Metrics

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Optimized Planning Model of Field Watersaving Irrigation and Its Application —A Case Study in Hotan Prefecture，Xinjiang WANG Xin, BAI Dan, WANG Quan-Jiu 2012, 29 (2):  375-378.  Abstract ( 1606 )   PDF (364KB) ( 1155 )   In this paper, an optimized planning model of field water-saving irrigation was developed based fully on considering the minimum increase of annual cost of field water-saving irrigation projects, regional water resources types, available field irrigation water volume, crop planting structure, status of water-saving irrigation and feasibility of all the water-saving irrigation ways so as to satisfy the demand of crop irrigation water supply. The model was used to work out an optimized planning scheme of field water-saving irrigation in Hotan Prefecture, Xinjiang in 2020. The model can be used to provide a scientific basis for working out a rational field water-saving irrigation planning and achieve a rational redistribution of water and land resources in the prefecture. References | Related Articles | Metrics