Table of Content

15 November 2012, Volume 29 Issue 6 Previous Issue    Next Issue

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GISbased Spatializing Method for Estimating Snow Cover Depth in Northeast China and Its Nabes ZHAO Xiao-Meng, LI Dong-Liang, CHEN Guang-Yu 2012, 29 (6):  927-933.  Abstract ( 1719 )   PDF (1541KB) ( 1109 )   In this study, five climate zones were delimited using the rotated empirical orthogonal function (REOF)  method base on the data of snow cover depth and other meteorological factors, observed by 122 meteorological stations in northeast China in recent 50 years. A database of three terrain factors (longitude, latitude and altitude) and three microterrain factors (slope, exposure and openness) was derived using digital elevation model (DEM) and GIS to simulate snow cover depth in northeast China with the mathematical theorem of trend simulation and stepwise regression. The results showed that there was a positive correlation between the macroterrain factors and the snow cover depth. Snow cover depth was thick in the Da Xing'an Mountains and Xiao Xing'an Mountains in northeast China, and it was increased with the increase of altitude and latitude. Delimitation of the climate zones reveals that the microterrain factors could increase their effects on snow cover depth, gives prominence to local features of snow cover depth distribution, and reduce the relative errors. References | Related Articles | Metrics

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Analysis on Change of Solar Radiation in the Central Shiyang River Basin YANG Yong-Long, QING Ji-Zu, QIAN Li, LIU Ming-Chun, DING Wen-Kui 2012, 29 (6):  934-940.  Abstract ( 1687 )   PDF (2144KB) ( 920 )   In this study, the change of solar radiation and its affecting factors in the central Shiyang River Basin during the period of 2007-2010 was comprehensively analyzed based on the solar radiation data and considering the underlaying surface and weather conditions using the mathematical statistics. The results showed that the average annual global radiation, reflected radiation, floor longwave radiation, atmosphere longwave radiation and net radiation in recent years were 6 030.9, 1 596.1, 11 764.7, 8 892.8 MJ·m-2and 1 563 MJ·m-2 respectively. The curve of radiation was unimodal, radiation was high in summer (from June to August) but low in winter (from December to January or February). Surface albedo was decreased with the increase of vegetation coverage, its maximum value in winter was 0.329, and its minimum one in autumn (from September to November) was 0.241. The curves of all other radiation forms on sunshine days were unimodal except the approximate beeline of atmosphere longwave radiation. The peak value of floor longwave radiation delayed generally for 1-2 hours than that of global radiation. The daily variation of shortwave radiation and longwave radiation was complicated under both overcast and rainy or snowy weather conditions. An extreme high value of global radiation (159 W·m-2) occurred after a gustiness rainfall in spring and summer because of the high atmospheric transparency. Cloudage impacted directly radiation. Atmosphere longwave radiation on sunshine days was lower than that on cloudy and rainy days and overcast, a sharp change of net radiation occurred around sunrise and sundown, but cloud could reduce the change extent. References | Related Articles | Metrics

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Analysis on Identification Characters of Storm Cells for Early Warning of Hail and Thunder Storms in the  Northeast Qinghai-Tibetan Plateau ZHU Ping, XIAO Jian-She, FU Yang 2012, 29 (6):  941-948.  Abstract ( 1621 )   PDF (2603KB) ( 906 )   After selecting the strong storm cells with early warning significance, in this study the identification characteristics of storm cells of both hail and thunder storms before local convection were compared and analyzed based on the data of CINRAD/CD radar detection over the northeast Qinghai-Tibetan Plateau during the period from June to August of 2006-2011 so as to achieve an early warning of hail and thunder storms. Generally, the height of strong echo center of thunder storm is low and even lower than the 0 ℃height, but the 45dBz echo (H45) height was 1/2 higher than that of 18 dBz (H18), and its HDBZM is lower than 3.5 km. The HDBZM of the cells of hail storm was higher than 3 km, and the echo height of 30 dBz (H30) was higher than the 0 ℃height. A early warning of hail storm could be issued when a sharp increase of vertically integrated liquid water content (VIL) of hailstorm cell occurred, the value was≥6 kg•m-2, the maximum value of VIL≥15 kg•m-2, and the VIL density was higher than 2.2 g•m-3. An early warning of hail weather accompanying with rainfall could also be issued when the value of H45-H0 was≥0.5 km, and the value of VIL above the 0 ℃height was ≥3.8 kg•m-2. These earlywarning characteristic parameters of storm cell were verified with the daytoday radar data in September 2011, and they can be used to identify the storm types and issue the earlywarning information of strong convection weather. References | Related Articles | Metrics

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Effect of ENSO Events on Climate and Climatic Disasters in the Hexi Corridor, Gansu Province YANG Long, ZHAO Jing-Bo 2012, 29 (6):  949-955.  Abstract ( 1960 )   PDF (4207KB) ( 1251 )   In this paper, the variation of air temperature, precipitation and drought and flood disasters which were affected by ENSO events in the Hexi Corridor was analyzed based on the data of air temperature and precipitation in Dunhuang, Jiuquan, Zhangye and Wuwei cities in the Hexi Corridor in recent 58 years. The results showed that the annual air temperature in the corridor was in an increase trend in fluctuation way, and its increase rate was 0.3 ℃/10 a; annual precipitation was slightly increased, and its increase rate was 2.3 mm/10 a. The occurring frequency of regional drought and flood disasters in recent 58 years was 50%. The wavelet analysis revealed that there were the 4-5year periodicity of slight flood and drought disasters, 13-14year periodicity of moderate ones, 18-19year periodicity of serious ones, and 26-27year periodicity of extremely serious ones. The effect of ENSO events on mean annual air temperature was more significant than that on mean annual precipitation, air temperature in the El Nino years was obviously increased, and the precipitation was slightly increased; in the La Nina years, the air temperature was distinctly decreased, and the mean annual precipitation was increased by 10.5 mm. There was a significant correlation between the ENSO events and the regional drought and flood disasters, the regional drought and flood disasters occurred mainly around the years of ENSO events, especially in the years of successional ENSO events. References | Related Articles | Metrics

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Spatiotemporal Climate Change in the Hedong Region in Gansu Province in Recent 54 Years ZHAO Yi-Fei, ZHANG Bo, WANG Bao-Long, HE Xu-Qiang, JIN Sheng-Li, YIN Hai-Xia 2012, 29 (6):  956-964.  Abstract ( 1958 )   PDF (3511KB) ( 1056 )   In this paper, the spatiotemporal and sharp changes of average annual and seasonal temperature and precipitation in the Hedong region of Gansu Province in recent 54 years were analyzed based on the temperature and precipitation data collected from 26 meteorological stations during the period from 1957 to 2010. The results were as follows: the temperature was significantly increased by 0.26 ℃/decade in the Hedong region, especially since the 1990s, and its curve was unimodal; On the whole, average annual temperature was spatially in an increase trend, especially in the northern and central regions of the east Gansu Plateau. Seasonal temperature was also in an increase trend, especially in winter. Average annual precipitation was decreased by 12.01 mm/10 a in recent 54 years, and its curve was unimodal. There was an obvious difference in seasonal precipitation: summer precipitation was the highest, followed by spring one, and winter one was the least. Spatially, precipitation was in a decrease trend in the most regions, and especially the decrease in the southeast was more significant than that in the northwest. In addition, it was found that a sharp change of temperature occurred in the Hedong region in 1997. On the contrary, the abrupt change in precipitation was not obvious. The influence of temperature increase and precipitation decrease in agricultural production was also discussed. It is necessary to strengthen the research work, propose the appropriate measures, make full use of the positive factors, and control and reduce the negative factors. It is considered that the agricultural development in the Hedong region will be sustained and stabilized. References | Related Articles | Metrics

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Change of Extreme Temperature and Precipitation Events in Gansu Province in Summer in Recent 51 Years KONG Xiang-Wei, TAO Jian-Hong 2012, 29 (6):  965-971.  Abstract ( 1609 )   PDF (2780KB) ( 825 )   In this paper, the characteristics and trends of rainstorm events, severe drought events and anomalous maximum and minimum temperature events were investigated based on the daily data observed by 35 meteorological stations in Gansu Province and the reanalysis monthly data in summer (from June to August) during the period from 1960 to 2010, and the data were derived from National Climate Center and National Center for Environmental Prediction/National Center for Atmospheric Research (NCEP/NCAR). The main results show that the absolute intensity of rainstorm was lower than the relative intensity. The frequency of rainstorm events in summer was about 0.1 time a year in the Hexi Corridor in recent 51 years. In the Hedong region, however, the rainstorm frequency was in a decrease trend before the mid-1970s, and then the change trend was not significant. The variation of rainstorm intensity in these two areas was not significant, and the seasonal distribution was relatively dispersed. Rainstorm events occurred 10 days earlier compared with that after the mid1980s. Severe drought events were sharply increased from 1991. The frequency of extremely high temperature was significantly increased but that of extremely low temperature decreased from the mid-1990s. References | Related Articles | Metrics

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Research Progress in Atmospheric Nitrogen Deposition CHANG Yun-Hua, LIU Xue-Jun, LI Kai-Hui, 吕Jin-Ling , SONG Wei- 2012, 29 (6):  972-979.  Abstract ( 3569 )   PDF (1244KB) ( 3364 )   Atmospheric nitrogen(N) deposition refers to the processes by which N components are removed from atmosphere and then deposited on the earth surface. Nowadays N deposition is wellknown to be one of key components of global N biogeochemical cycles. Along with the aggravated anthropogenic perturbation (fossil fuel combustion, nitrogen fertilizer application, livestock and poultry production, e.g.), large amount of reactive N (Nr) species are emitted into atmosphere and subsequently deposited back to global, terrestrial and aquatic ecosystems, existing as a source of nutrient and acid, where they have been altering the natural N cycling profoundly. Moreover, excessive anthropogenic Nr deposition may exert the direct or indirect detrimental environmental effects, e.g. soil acidification, water eutrophication, biodiversity degradation, human health issues, etc. Emerging from an agricultural benchmark to increasing industrialization and urbanization, China was identified as one of the three N deposition hotspots. This paper reflected on the research history of N deposition, in addition, several main research progresses were involved in: responses of different ecosystems to N saturated, economic cost assessment on N deposition, improvement on N monitoring and analysis, research progresses on organic N and current situation in China, consideration of N deposition into integrated cropland nutrient management and its perspective, and the last but not the least, the development of monitoring network presently. In view of the complexity of N research, establishing national monitoring network in parallel to modeling works should attract more attention in the future. References | Related Articles | Metrics

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Study on Stream Power of Muddy and Sandy Drainage Channels in SalineAlkaline Land in Pingluo County of Ningxia FAN Xiao-Li, WANG Sui-Ji, DU Jun, WAN Shu-Qin 2012, 29 (6):  980-983.  Abstract ( 1277 )   PDF (858KB) ( 878 )   Irrigation and drainage channels play an important role in developing irrigation projects in farmland, and also an active role in controlling water logging and salinealkaline disasters. In this study, a flume experiment was carried out to analyze the gross and specific stream power of the drainage channels, and two channels in Pingluo County of Ningxia Hui Autonomous Region were separately paved with saline soil and sand. The stability and erosion of these drainage channels were analyzed based on the characteristics of stream power. The results showed that, under the given conditions, the gross stream power of the muddy drainage channel was much lower than that of the sandy one, and it could be quickly reduced to achieve a balance of the channel. The experiment also revealed that the stability of muddy channel was higher than that of the sandy one. Therefore, it is suggested to take muddy channel in developing and improving saline soil in Pingluo County. References | Related Articles | Metrics

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Study on Ecological Water Requirements along the Mainstream Channel of the Tarim River LIU Xin-Hua, XU Hai-Liang, LING Hong-Bo, BAI Yuan, FU Jin-Yi, DAI Yue 2012, 29 (6):  984-991.  Abstract ( 1511 )   PDF (1243KB) ( 1287 )   In this study, the sequential clustering method was used to discriminate the significant sharp change of human activities in the mainstream area of the Tarim River during the period of 1957-2006. The lowest and suitable monthly ecological water requirements at the Xinquman, Usuman and Qara hydrological sections were calculated. The results showed that the disturbance of human activities on water resources in the mainstream area of the Tarim River was increased in recent 50 years. Runoff of the mainstream of the Tarim River was basically natural before the year of 1976, but a sharp increase of human activities occurred in 1976. The lowest annual ecological water requirements at the Xinquman, Usuman and Qara hydrological sections were 17.68×108 m3, 10.02×108 m3 and 3.29×108 m3, and the suitable ones were 35.65×108 m3, 18.23×108 m3 and 7.00×108 m3, respectively. The health of ecosystems in the mainstream area of the Tarim River could be ensured if the lowest ecological water requirements at these hydrological sections could be maintained at 5.33×108 m3, 3.77×108 m3 and 1.32×108 m3 during the general water consumption period from October to next March and at 28.99×108 m3, 13.70×108 m3 and 5.09×108 m3 during the sensitive water consumption period from April to September. References | Related Articles | Metrics

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Study on the Change of Lake Area and Its Causes in the Mapangyong Co Basin in Tibet LA Ba, BIAN Duo, CI Zhen, LA Ba-Zhuo-Ma, CHEN Tao 2012, 29 (6):  992-996.  Abstract ( 3609 )   PDF (1292KB) ( 1188 )   This paper investigated the change of area of the Mapangyong Co Lake and Laang Co Lake in Pulan County, Tibet Autonomous Region and its response to climate change based on the topographic map in 1975, TM satellite remote sensing data in the years of 1990, 1999-2009 and climatic data including air temperature, precipitation, snowcover days, evaporation, etc. in recent 35 years (1975-2009). Results indicate that the areas of both the Mapangyong Co Lake and Laang Co Lake were reduced at first and then enlarged. Holistically, the areas of these two lakes were in a reduction. Areas of the Mapangyong Co Lake and Laang Co Lake were reduced to 415.44 km2 and 261.36 km2 in 2009, and they were reduced by 1.56 km2 and 11.01 km2, respectively. Furthermore, the areas of modern glaciers near the lakes were also reduced due to climate warming. According to the statistical results of meteorological data in Pulan County during the period of 1975-2009, the decrease of precipitation was the dominant factor resulting in the reduction of lake areas, and then the slight increase of evaporation and the melt of modern glaciers. References | Related Articles | Metrics

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Effects of Longterm Enclosure on Spatial Variation of Soil Organic  Carbon Content in the Bayanbulak Subalpine Steppe SU Jian-Hong, ZHU Xin-Ping, WANG Xin-Jun, JIA Hong-Tao, ZHAO Cheng-Yi, HU Yu-Kun, LI Li-Jun 2012, 29 (6):  997-1002.  Abstract ( 1565 )   PDF (1022KB) ( 1049 )   In this study, the longterm fenced sample plots located in the Bayanbulak Steppe in the central Tianshan Mountains were focused, classical statistics and geostatistics were used to study the effects of longterm enclosure on the spatial variation of soil organic carbon content in the subalpine steppe. The results were as follows: (1) Longterm enclosure can increase soil organic carbon content, the average organic carbon content was 40.76 g/kg in soil layer of 0-20 cm in depth inside the fenced steppe, and it was 38.50 g/kg outside the fenced steppe; the average organic carbon content was 20.98 g/kg in soil layer of 20-40 cm inside the fenced steppe, and it was 18.70 g/kg outside. Soil organic carbon content inside the fenced steppe was higher than that outside at horizontal direction; (2) Variation degree of soil organic carbon content inside the fenced steppe was significantly higher than that outside. There was a moderate spatial correlation between organic carbon contents in the upper and lower soil layers no matter inside or outside the fenced steppe, and the variation degree of organic carbon content in the upper soil layer was higher than that in the lower soil layer; (3) Spatially, the distribution of soil organic carbon was different from different places, the soil organic carbon content in spatial distribution inside the fenced steppe was higher than that outside. From the spatial interpolation map, it was found that, if the soil organic carbon content in soil layer of 0-20 cm was high both inside and outside the fenced steppe, the soil organic carbon content in soil layer of 20-40 cm was oppositely low References | Related Articles | Metrics

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Effects of Crop Residue Returning to Field and Fertilizer  Application on Soil Respiration in Wheat/rape Field HE Xiang-nan, HUANG Gao-Bao, HUANG Peng 2012, 29 (6):  1003-1008.  Abstract ( 1684 )   PDF (1225KB) ( 910 )   Based on the threeyear field experiment in wheat/rape field in the Hexi Oasis Irrigation Area, the values of soil respiration rate were estimated with the EGM-4 soil respiration measurement system under different fertilizer application levels and ways and crop residue returning to field. The results showed that, throughout the observation period, the maximum value of soil respiration rate (152.06-199.58 mg•m-2•h-1) occurred in late August, and the minimum one (12.67-19.01 mg•m-2•h-1) occurred in midOctober. The curve of daily variation of soil respiration rate was unimodal, the maximum value occurred during the period of 12:00-14:00, and the minimum value appeared around 4:00. The soil respiration rate was significantly reduced under high crop stubble harvest without till, especially during the rape growth period. The soil respiration rate was significantly decreased under the different fertilizer application levels and in the case that N and P fertilizers were reduced by 15%. Under the treatment measures in the experiment, there was an extremely significant positive correlation between soil respiration rate and soil temperatures at soil layers of 5 cm and 10 cm in depth and also the soil moisture content at soil layer of 30 cm in depth. Furthermore, the correlation of soil respiration rate with soil moisture content in soil layer of 0-30 cm was higher than that with soil temperature. There was a negative correlation between soil respiration rate and soil porosity, but their correlation was not significant. References | Related Articles | Metrics

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Effects of Shelter Forest on Soil Physicochemical Properties of Farmland in the Horqin Sand Land WANG Yong-Fang, BAO Hui-Juan, HAI Chun-Xing, YIN Shan 2012, 29 (6):  1009-1013.  Abstract ( 1534 )   PDF (654KB) ( 972 )   In order to explore the effects of shelter forest on farmland in different landforms, in this study the lump farmland and meadow farmland in Naiman Banner in the Horqin Sand Land were selected to carry out a comparative analysis on soil physicochemical properties of the farmland with or without shelter forest. The results were as follows: (1) Soil physicochemical properties of farmland with shelter forest were better than those of farmland without shelter forest; (2) The effect of shelter forest on lump farmland was higher than that on meadow farmland, it was obvious at all the three sample plots of lump farmland, especially at sample plot 1 and sample plot 2, but the effect of shelter forest on meadow farmland was obvious at sample plot 1 only. References | Related Articles | Metrics

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Research Progress in Effect of Soil Moisture Content on Soil Respiration GAO Jin-Chang, SU Yong-Hong 2012, 29 (6):  1014-1021.  Abstract ( 1774 )   PDF (941KB) ( 1529 )   The largest carbon source and carbon sink of terrestrial ecosystems is soil. Soil respiration is an important component of global carbon cycle, and also a key process of regulating and controlling global carbon cycle and climate change. Moreover, it is an important issue of carbon budget in carbon cycle and a crucial field in global change ecology. Since soil moisture is an important disturbance to soil respiration, it is necessary to study the effects of soil moisture from different sources on soil respiration so as to accurately estimate soil respiration, especially in arid and semiarid regions. In this paper, the responses of soil respiration to soil moisture from different sources including precipitation, irrigation and groundwater as well as the processes of soil respiration were compared and analyzed. The results could be referred in further study on soil respiration in the future. References | Related Articles | Metrics

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Evaluation on Dustholding Capabilities of Photosynthetic Organs of Ten Shrub Species in Hinterland of the Taklimakan Desert LI Sheng-Yu, GU Feng, QIU Yong-Zhi, JIN Zheng-Zhong, LI Ying-Gang, GAO Xiao-Yang 2012, 29 (6):  1022-1031.  Abstract ( 1855 )   PDF (2919KB) ( 889 )   In this paper, the photosynthetic organs stained with dust on the whole plants of 10 shrub species planted in Tazhong Botanical Garden in the hinterland of the Taklimakan Desert were sampled, and their dustholding capabilities were analyzed using the multiple indices in mass subtraction method. The results were as follows: (1) Dustholding capabilities of plant photosynthetic organs are closely related to the environment. The plants growing in the desert hinterland can hold more dust by their photosynthetic organs than those growing in the peripheral regions of the desert; (2) Though photosynthetic organs of Haloxylon ammodendron and Calligonum caput-medusae degenerated into the assimilative branches with extremely degenerated leaves similar to needles of coniferous species, their dust holding capabilities are higher than those of coniferous species mentioned in other paper. The dustholding capabilities of photosynthetic organs of H. ammodendron are higher than those of C. caput-medusae because of its assimilative branches with shorter knot spacing and more leaves; (3) Though leaves of Tamarix plants also degenerated extremely, they have the excellent dustholding capabilities by their photosynthetic organs, higher than H. ammodendron and C. caput-medusae, and even higher than broadleaved shrubs and broadleaved trees, because of their photosynthetic organ surface characteristics (such as the relatively bigger leaf size, abundant tomenta and salt secretion), a mass of leaves, and greater photosynthetic organ density of crown. Therefore, the dustholding capabilities of these Tamarix plants mentioned in this paper are distinctly different; (4) Photosynthetic organs of the whole plants, unit weight and unit surface area can only represent the dustholding capabilities in some aspects, but dustholding amount of unit volume crown can represent the dustholding capabilities of photosynthetic organs of plants more holistically. The dustholding capabilities of photosynthetic organs of 10 shrub species are in an order of Tamarix austromongolica > T. elongata > T. juniperina > T. androssowii > T. hispida > T. hohenackeri > T. ramosissma > T. taklamakanensis > H. ammodendron > C. caput-medusae. These results may provide a scientific basis for tree species selection and distribution in landscaping and shelterbelt construction and dustholding effect evaluation, and also a reference in studying the correlation between plants and soils in arid regions. References | Related Articles | Metrics

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Response of Fungialgae Symbiotic Lichen Crusts to Grazed  Livestock Disturbance in the Gurbantunggut Desert WU Nan, ZHANG Yuan-Ming, PAN Hui-Xia 2012, 29 (6):  1032-1038.  Abstract ( 1658 )   PDF (1454KB) ( 864 )   Biological soil crusts (BSCs) occur extensively in the southern part of the Gurbantunggut Desert, and serve as one of the important biological factors relating to sand surface fixation. As a winter rangeland, the desert is trampled by grazed livestock widely. Lichen crusts are the main type of BSCs in the southern part of the Gurbantonggut Desert and serve as one kind of the important nitrogen resources. They are also one of the sensitive biomonitors of desert ecosystem health, habitat heterogeneity and humaninduced disturbances. This study investigated the effect of trampling on cover of BSCs. The results were as follows: (1) The local disturbance rate mainly ranged from 10% to 20%, which was a relatively safe range against wind erosion; (2) The total coverage of BSCs was decreased due to the grazed livestock disturbance. The response of BSCs to grazing disturbance was different. Holistically, trample of grazed livestock reduced the coverage of dominant crusts, especially the lichen crusts. When disturbance rate was exceeded 30%, the average coverage of lichen crusts was lower than 30%. Because of the destroyed structure of fungalalgae symbiont, the quantity of fungi was increased (P<0.05). Contrast to the reduction of lichen crusts, more bare sand appeared with the increasing disturbance rate; (3) Grazing disturbance reduced soil organic matter content, soil bulk density and ion contents. There was an extremely significant positive correlation between soil bulk density and lichen crust coverage (P<0.01). References | Related Articles | Metrics

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Study on Daily Change and Midday Depression of Photosynthesis of Alhagi pseudoalhagi and Vigna radiata under Salt Stress Wu-Mu-Ti-Han-?Ka-Ke-Mu, HAI Li-Li-?Ku-尔Ban, CHEN Qi-Jun, WANG Xue-Chen 2012, 29 (6):  1039-1045.  Abstract ( 1739 )   PDF (2290KB) ( 783 )   This experiment was designed to investigate the factors affecting the daily change of photosynthesis in the salttolerant leguminous plant Alhagi pseudoalhagi by comparing with saltsensitive Vigna radiata. The plants were cultivated in a greenhouse and subjected to 0 (controlled), 50, 100 and 200 mmol•L-1 NaCl treatments for 2  weeks.The daily change of photosynthesis, chlorophyll content and expression of Rubisco large subunit gene were measured. The results showed that the curves of controlled plants of both A. pseudoalhagi and V. radiata were unimodal, while the response of photosynthetic daily change with increasing salinity was different between the saltsensitive plant V. radiata and the salttolerant one A. pseudoalhagi. For A. pseudoalhagi, the rates of Pn in 50-200 mmol•L-1 NaCltreated plants increased faster than that in the untreated control plants, and there was no significant difference among other treatments in the max peak of Pn values. The increase of photosynthetic rate of V. radiata was faster in the controlled plants than that in salinity treatments, and salttreated plants had a lower photosynthetic rate than the untreated plants. There was no midday depression for A. pseudoalhagi in 50-100 mmol•L-1 and V. radiata[ in 50 mmol•L-1 NaCl, which was observed in A. pseudoalhagi 200 mmol•L-1 treatment and in V. radiata 100 mmol•L-1 treatment. In A. pseudoalhagi, the ‘midday depression’ was mainly caused by decreased Gs under severe salt stress, while in V. radiata, the contribution of the inhibition of Rubisco to the Pn‘midday depression’ was more significant than that of the Gs. In V. radiata, the expression of rbcL was decreased with increasing salt stress, and in A. pseudoalhagi, the expression of rbcL was increased at 50 and 100 mmol•L-1, however, it was decreased at 200 mmol•L-1 NaCl. References | Related Articles | Metrics

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Study on Water Holding Capacity of Litters in Shelterbelt  along the Tarim Desert Highway ZHANG Dong-Dong, JIN Zheng-Zhong, XU Xin-Wen, LI Sheng-Yu, LEI Jia-Qiang, WANG Yong-Dong, WANG Ying-Ju 2012, 29 (6):  1046-1053.  Abstract ( 1404 )   PDF (2557KB) ( 896 )   In this study, the storage, water holding capacity and water absorption rate of litters in shelterbelts with different ages along the Tarim Desert Highway were studied using the methods of typical sampling and soaking extraction. The results showed that the litter storage in shelterbelts with four different ages was in an order of 13-year-old shelterbelt (42.3 t•hm-2)>6yearold one (39.6 t•hm-2)>10-year-old one (39.1 t•hm-2)>7-year-old one (16.2 t•hm-2)．The water holding capacity of the undecomposed litters in shelterbelts along the desert highway was in an order of Haloxylon>Tamarix>Calligonum, and that of the semidecomposed litters was in an order of Tamarix>Haloxylon>Calligonum. The maximum water holding capacity of litters in the semidecomposed layer was higher than that in the undecomposed layer. There was a logarithmic relationship between water holding capacity of litters with different decomposition degrees and watering time, and the optimal fitting relation equation was W=b+a lg t, but a power function relationship between water absorption rate and watering time, and the formula was V=ktn. The water absorption rate was decreased sharply within the first one hour, and reduced stably after 4 hours. Water sorption of litters was decreased gradually. References | Related Articles | Metrics

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Variation of Stomatal Length and Stomatal Density in Leaves of Rhododendrons with Elevation XU Hao-Jie, YANG Tai-Bao, ZENG Biao 2012, 29 (6):  1054-1058.  Abstract ( 2090 )   PDF (1538KB) ( 1148 )   This paper investigated the stomatal length (SL) and stomatal density (SD) of Rhododendron lapponicum and R. anthopogonoides collected from different altitudes ranging from 2 600 to 3 100 m in Xinglong Mountains. The factors affecting the variations of SL and SD at different altitudes were also analyzed using the data of air temperature, CO2 concentration and terrain. The results showed that SL was decreased but SD increased significantly in leaves of R. lapponicum with the increase of altitude. SL in leaves of R. anthopogonoides was increased at first and then decreased, and SD was opposite. Air temperature and CO2 concentration were strongly affected by altitude. R. lapponicum acclimatizes mainly the change of temperature and CO2 concentration by increasing SL and decreasing SD in its leaves, while R. anthopogonoides acclimatizes mainly the change of air temperature, CO2 concentration and soil moisture content by increasing SL and decreasing SD in its leave. References | Related Articles | Metrics

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Application of Combination of Two bifurcation Method and Multi bifurcation Method in Developing an Identification Key of Tree Species Classification A Case Study in Developing the “Identification Key of Classification of Landscape Tree Species in Urumqi” MAI Mai-Ti-Jiang-?Tu-尔Xun, DI Li-Xia-Ti-?Ha-Si-Mu, ZHANG Sheng 2012, 29 (6):  1059-1068.  Abstract ( 1827 )   PDF (1078KB) ( 888 )   In this paper, a case study on the development of “Identification Key of Classification of Landscape Tree Species in Urumqi” was carried out, and the difficulties in applying the traditional identification key were discussed. The “Identification Key of Classification of Landscape Tree Species in Urumqi” was developed based on the field survey, literature identification and firsthand information from teaching, [WTBX]etc.[WTBZ] by combining the twobifurcation method and multibifurcation method. Classification key of landscape tree species in the cities in north China was discussed, and the traditional classification key of landscape tree species was modified in this paper. The advantages of this method are as follows: (1) It is not limited by the species level or location in system, and easy to use; (2) It becomes much more easy for the classification by combining the twobifurcation method and multibifurcation method together, and also spends less space; (3) The identification of landscape tree species will not be limited because the simple, popular and stable characteristics were selected in this key, and there are no the tree species identification difficulties from the lack of plant organs. This classification key will bring much more convenient to teaching and scientific research to the local professional colleges, universities and scientific institutions, and will become as a basic mean and important reference in this area. References | Related Articles | Metrics

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Study on Frost Resistance of Watertight Bentonite ZHOU Chun-Sheng, SHI Hai-Bin, YU Jian 2012, 29 (6):  1069-1076.  Abstract ( 1416 )   PDF (1875KB) ( 874 )   In order to investigate the applicability of watertight bentonite in arid and cold areas, the antifreezing properties of three kinds of bentonite, collected from different places, were studied. Results showed that, after Yellow River water was frozen and thawed for 31 timers, the free expansion volume, average EC value and shear stress of bentonite were increased by 32.8%, 27.7% and 40.6%, but the cumulative filtrating volume, filtration loss and thickness of filtered bentonite cake were decreased by 23.5%, 23.4% and 15.4 %, respectively. On the other hand, the results of ANOVA showed that the effects of freezingthawing process on the free expansion volume, EC value of solution, shear stress and cumulative filtrating volume were significant(F＞F0.01); the microstructure parameters of bentonite varied in a range from 86.02 μm to 372.12 μm, the pores were dominated by the plate and irregular shapes, the F value varied in a range from 0.12 to 0.40, and the fractal dimension of pore surface in a range of 1.18-1.21. References | Related Articles | Metrics

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Study on Dynamic Properties of Gobi Surface with  Different Gravel Coverage ZHANG Ke-Cun, ZHANG Wei-Min, QU Jian-Jun, AN Zhi-Shan, TAN Li-Hai 2012, 29 (6):  1077-1082.  Abstract ( 1689 )   PDF (1859KB) ( 900 )   In order to understand the dynamic properties of Gobi surface, some wind tunnel experiments were conducted on the Gobi surface with different gravel coverage on the top of the Mogao Grottoes in Dunhuang, Gansu Province, China. The study results showed that gravel coverage of Gobi surface affected directly the amount and distribution of roughness elements, such as the wind speed profile, friction velocity, roughness degree and shear stress. Friction velocity was increased in a linear way with the increase of wind speed in the wind tunnel, but the dynamic roughness was decreased in a fluctuation way. Wind speed near Gobi surface was gradually decreased with the increase of gravel coverage, but the friction velocity, dynamic roughness and shear stress were increased in a linear way. When the gravel coverage was increased to 35%, the dynamic roughness, friction velocity and shear stress on the Gobi surface were 0.30 cm, 0.93 cm/s and 1.11 N/cm respectively. The results in this paper can be used to guide the design of sandcontrol structures both in our study area and other Gobi regions where it suffers from windblown sand. References | Related Articles | Metrics

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Study on Distribution of Microrelieves on Steep Slopes in a Loess Hilly gully Region KUANG Gao-Ming, ZHU Qing-Ke, ZHAO Lei-Lei, CHANG Cun, ZHENG Xue-Liang 2012, 29 (6):  1083-1088.  Abstract ( 1613 )   PDF (1600KB) ( 965 )   Soil moisture content is the main factor affecting vegetation conservation and regeneration in the loess hillygully region, but it is low in steep slope. Microrelief affects strongly the soil moisture content in slope. A field measurement of the terrain parameters was carried out with a 3dimentional laser scanning total station in the Hejia Valley in Wuqi County, Shaanxi Province. The distribution of gullies, shallow gullies, platforms, scarps and collapses on steep slope was researched based upon Arc GIS 9.2. The results showed that the proportions of area of microrelieves varied in a range of 18%-30% of the total steep slope area and 23.13% in average. The proportions of area of different microrelieves were in an order of gully (8.44%)>platform (6.66%)>shallow gully (5.00%)>scarp (1.53%)>collapse (1.52%). Exposure and slope were the main topographic factors affecting the proportions of area of gullies, shallow gullies and collapses, the proportion of area of scarp was mainly affected by slope, and there was no obvious effect of exposure and slope on the proportion of area of gentle platform. Exposure affected the proportions of area of microrelieves on steep slope, proportions of the microrelieves were in an order of sunny slope ＞semisunny slope＞semishaded slope＞shaded slope, and the proportions of area of collapse, gully and shallow gully on sunny slope and semisunny slope were higher than those on semishaded slope and shaded slope, however, there was an opposite result for the proportion of area of scarp. The proportions of area of scarp, gully and shallow gully were decreased with the increase of slope, but the proportion of area of collapse was increased with the increase of slope. References | Related Articles | Metrics

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Carbonate Content and Pollen Conservation in Lacustrine Sediments at Different Locations of the Zhuye Lake GUO Chen-Lu, LI Yu, CHENG Ying, YU Da-Qi, ZHANG Cheng-Qi 2012, 29 (6):  1089-1093.  Abstract ( 1675 )   PDF (1168KB) ( 901 )   Pollen is a proxy to be used to reconstruct paleoclimate and paleovegetation. According to the available previous research achievements, there are some different points of view in recognizing the Holocene climate and environmental changes indicated by pollen in the Zhuye Lake region. Lacustrine carbonate sediments can be used to reveal the alkaline sedimentary environment, but the alkaline environment can corrode pollen seriously and impact pollen conservation. According to the relationship between carbonate and pollen concentration in lacustrine sediments, it can be explored that whether the regional pollen conservation was affected by carbonate. The results showed that the high carbonate content and the high pollen concentration corresponded with each other in the Zhuye Lake region during the Holocene. Climate was warm and wet in the Zhuye Lake region during the period of lake expansion, and there was a large amount of pollen input, although the alkaline environment corroded pollen seriously and affected pollen conservation. Therefore, the alkaline sedimentary environment was not enough to change pollen concentration. The different midHolocene pollen assemblages at different locations of the lake basin were not resulted in by pollen conservation. References | Related Articles | Metrics

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Analysis on Extreme Climate Events Recorded in [WTHX]Tamarix[WTHZ] spp. Dune  and Their Affecting Factors in the Lop Nur Lake Region ZHAO Juan, ZHAO Yuan-Jie, XIA Xun-Cheng 2012, 29 (6):  1094-1099.  Abstract ( 1549 )   PDF (2429KB) ( 875 )   Some veracious dating and environmental information was recorded in the laminas of the [WTBX]Tamarix[WTBZ] sp. dunes in the Lop Nur Lake region, and the laminas are as good as tree rings for dating and revealing the ancient environmental conditions. In this paper, the correlations among the proxy environmental indicators and the extreme climate events, recorded by the C/N, δ13C, δD, δ18O, etc., were analyzed. The results revealed that there were the good correlations among the proxy environmental indicators and the extreme climate events in the Lop Nur Lake region. On which the extreme climate events and their affecting factors in the Lop Nur Lake region were lucubrated. References | Related Articles | Metrics

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Study on Wind blown Sand Characteristics at Different  Directions near the Surface in the Frontier of an  Oasis desert Ecotone in Qira County, Xinjiang YANG Xing-Hua, HE Qing, HUO Wen, CHENG Yu-Jing 2012, 29 (6):  1100-1104.  Abstract ( 1530 )   PDF (1113KB) ( 1016 )   Aeolian sand transport is serious in many arid regions in the world, and it is considered to be as a significant part of global biogeochemical cycles. Furthermore, windblown sand brings often disasters. Therefore, widespread attention has been paid to the significance of aeolian sand transport in many fields, such as geomorphology, climatology, meteorology, ecology and environmental science. Windblown sand direction is a base for both studying the formation and evolution of aeolian geomorphology and carrying out the sand damage control measures. In this study, a statistical analysis on windblown sand direction in an oasisdesert ecotone in Qira County, located in the south marginal zone of the Tarim Basin, was carried out during the period from 2010 to 2011. Some preliminary conclusions are as follows: (1) In the study area, the wind directions of sanddriving wind are mainly W and WNW, and the change of wind direction is comparatively simple; (2) In the study area, the wind directions at which the values of sediment discharge are high are dominated by NW, WNW, W, SW and WSW, and the occurring frequency is as high as 68.3%. An aeolian sediment discharge of 96 kg passing through a height extent of 0-40 cm and 1cm width occurred. The annual resultant windblown sand amount is 45.9 kg, and the resultant windblown sand direction is 102.5°; (3) In the study area, the windblown sand potential and resultant windblown sand potential are 43.2 VU and 31.04 VU respectively. There is a considerable difference between the direction of windblown sand potential and the measured sediment discharge. It is recognized that windblown sand is a complex process, and various factors affecting windblow sand, such as wind speed, wind direction and underlying surface, should be comprehensively considered and researched. References | Related Articles | Metrics

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Climate Change and Its Impact to Maize Yield in Heilongjiang Province WANG Xiu-Fen, YANG Yan-Zhao, YOU Fei 2012, 29 (6):  1105-1111.  Abstract ( 1445 )   PDF (1719KB) ( 948 )   Climate change affects regional crop production. Heilongjiang Province is one of the most important grainproducing provinces in China, and its maize production plays an important role in local and national food security. Moreover, Climate change has occurred in Heilongjiang Province in 30 years (1980-2009). Based on the 30year observational data from 30 meteorological stations, in this study the climate change at different maize growing stages was researched, and the correlations between maize yield per unit area and climate factors at different maize growing stages were analyzed. The results showed that the average temperature, maximum temperature and minimum temperature were all increased at different maize growing stages in recent 30 years, and spatially their increase amplitudes were increased from east to west. Temporally, sunshine duration and reference crop evapotranspiration were also in an increase trend at all other growing stages except at the sowing and seedling stages, and their change amplitudes were increased from southwest to northeast. Spatial change of precipitation was different from different maize growing stages. There was a positive correlation between the maize meteorological yield and the minimum temperature at panicle and corncob stages, but a negative one between the maize meteorological yield and the maximum temperature at anthesis stage. References | Related Articles | Metrics

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Study on Agricultural Structural Adjustment Based on  Food Security in the Ogan River Basin TANG Hong, YANG De-Gang, MU Kan-Re-Mu-?Nai-Mai-Ti, WANG Fei, LIU Yun-Tong- 2012, 29 (6):  1112-1120.  Abstract ( 1356 )   PDF (2244KB) ( 794 )   Based on the data of cultivated land use in the Ogan River Basin in Xinjiang in recent 30 years, in this paper the conditions and pressure of cultivated land resources were researched, and the factors affecting land use benefits were analyzed. On the premise of food security baseline, the reasonable space of agricultural structural adjustment was discussed. The results were as follows: (1) The cultivated land area in the Ogan River Basin trended to be enlarged in recent 30 years, but the per capita cultivated land area trended to be reduced, and the situation was different from different stages and counties. Cultivated land was in surplus in this basin all the time, and the surplus was increased in a fluctuation way; (2) Land use structure affected the benefits of cultivated land to some extent, the higher the proportion of graincrop sown area was, the lower the per capita agricultural gross output value and annual per capita net income of rural households would be. It was effective for increasing agricultural output to adjust the agricultural structure and reduce the proportion of graincrop sown area; (3) Considering the control of cultivated land and 30% storageconsumption ratio of grain, it was predicted that the proportion of graincrop sown area in 2015 and 2020 will be lower than that in 2009, and there will be a certain space to adjust the agricultural structure. Because of the difference among counties, the predicted values were adjusted to be more reasonable. The implementation of grain growing subsidy policy should be strengthened so as to improve the positivity of farmers to grow grain crops. References | Related Articles | Metrics