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15 March 2018, Volume 35 Issue 2 Previous Issue    Next Issue

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Dynamic Parameterization and Simulation of Surface Albedo in Maize Cropland Mulched by Plastic Film in Arid Region 2018, 35 (2):  461-470.  Abstract ( 395 )   PDF (6025KB) ( 1097 )   Based on the observed data of surface albedo in maize cropland mulched by plastic film in an arid region from June 1 to July 24, 2015, the variation of surface albedo during the vegetation growth period and the relationship between surface albedo and soil moisture content were analyzed. It was found that the surface albedo variation and the correlation between surface albedo and soil moisture content were significantly different from that on underlying surface without mulching plastic film, thus a corresponding dynamic parameterization scheme of surface albedo was established. Furthermore, the modified dynamic parameterization scheme of surface albedo was applied to the land surface process model CoLM, and three simulation tests were carried out to analyze and verify the accuracy and applicability of the new scheme on cropland underlying surface mulched by plastic film. The numerical simulation results showed that the three tests could reflect the daily variation trend of land surface process, but the comparison revealed that the simulation performance of the new model was the best, because the simulation capability of the upward shortwave and longwave radiation was obviously increased, and the simulated results of soil temperature and soil moisture content in shallow soil were improved to some extent. Hence, the dynamic parameterization method of surface albedo could significantly facilitate the land surface process simulation capability on cropland underlying surface mulched by plastic film in arid region, and it could be referred in further developing and improving the land surface process models in the future. References | Related Articles | Metrics

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Spatiotemporal Variation of Drought in the Qaidam Basin 2018, 35 (2):  387-394.  Abstract ( 411 )   PDF (2524KB) ( 844 )   Using the measured precipitation and temperature data from the meteorological stations in and around the Qaidam Basin, the values of standardized precipitation index (SPI) and the standardized precipitation evapotranspiration index (SPEI) were calculated to describe the drought characteristics in the study area at different time scales. However, limited by the sparse distribution of stations, these two indexes were insufficient in evaluating the drought features in the region. Based on the globally distributed scPDSIpm data sets, in this study the Palmer drought severity index (PDSI) was used to analyze the characteristics of drought evolution and spatiotemporal distribution of drought in the whole study area. Results are as follows: (1) It could be seen that the effect of temperature on drought was significant at inter-annual scale but not at monthly or seasonal scale; (2) The correlation coefficients between PDSI index and the SPEI and SPI indices were higher than 0.7. In addition, PDSI was more suitable for evaluating drought in the areas without observed data; (3) As a whole, drought was the most serious in the central Qaidam Basin, and the occurring frequency of drought was low in the eastern marginal zone and the northwestern part of the study area. However, the situation had been greatly improved since 2000. This study has important guiding significance for evaluating the suitability of different drought indexes and drought evaluation in ungauged basins. References | Related Articles | Metrics

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Spatiotemporal distribution pattern of vegetation communities in the middle section of the Qilian Mountains 2018, 35 (2):  346-353.  Abstract ( 505 )   PDF (1782KB) ( 844 )   It is a precondition of regenerating ecological environment to fully understand the spatial and temporal distribution pattern of vegetation communities. In this paper, a vegetation classification was carried out based on the LANDSAT images in 4 years of 1976, 1991, 2001 and 2016. The classified results were used to get three landscape indexes, i.e., the mean patch area (MNA), fractal dimension (Fd) and aggregation index (AI), which were used to analyze the degree and driving forces of vegetation habitat change. Based on the classification for 2001 and 2016, the vegetation distribution in 2031 was predicted by CA-Markov model. The results showed that human activities were the main factors resulting in the change of vegetation communities. The distribution of vegetation communities was changed a lot during the period of 1976-2016, the areas of forests and grasslands were reduced by 91 km2 and 169 km2 respectively. From 1976 to 2001, the MNAs of forests, shrubberies and grasslands were reduced by 1.22 km2, 0.14 km2 and 0.16 km2, the AIs of forests, shrubberies and grasslands were decreased by 2.79, 0.03 and 8.77, and the Fds of forests, shrubberies and grasslands were increased by 0.013, 0.001 and 0.005, respectively. The degree of vegetation community fragmentation was serious. But from 2001 to 2016, the MNAs of forests, shrubberies and grasslands were enlarged by 0 km2，0.13 km2 and 0.02 km2, the AIs of forests, shrubberies and grasslands were increased by 2.38, 0.21 and 6.55, and the Fds of a forests, shrubberies and grasslands were decreased by 0.005, 0.002 and 0.002, respectively. The habitat of vegetation communities was gradually regenerated after 2001. The predicted areas of forests, shrubberies and grasslands in 2031 were 409 km2, 486 km2 and 550 km2 respectively, which nearly equaled to those in 1976. A significant effect of ecological conservation policy had been achieved. References | Related Articles | Metrics

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Research Progress of Community Structure and Ecological Functions of Phyllosphere Microorganisms 2018, 35 (2):  340-345.  Abstract ( 592 )   PDF (723KB) ( 571 )   Phyllosphere and rhizosphere of plants are two unique and complex ecosystems with rich microbial components, and play an important role in promoting plant growth, enhancing plant disease resistance and stress resistance. Over the past decades, rhizosphere attracted many microbiologists and botanists, especially some research progresses were achieved at the aspects of rhizospheric microorganisms in promoting plant growth and enhancing the effect and mechanism of plant disease resistance. Comparatively speaking, the study on phyllosphere microorganisms was much more behind that on rhizospheric microorganisms. Initially, the study on phyllosphere microorganisms was focused on plant pathogenic microorganisms, so the progress of researching phyllosphere microorganisms was slow due to the limitation of technical conditions. The research on phyllosphere microorganisms was developed rapidly since the 21st century along with the development of molecular biological technique, especially the application of high-throughput sequencing technology. Recently, numerous studies proved that only a few of phyllosohere microorganisms were pathogenic, and most of them benefited plants by improving nutrients, promoting plant growth, and improving disease and stress resistance, thus a very important role of structuring plant communities and sustaining their functions was played. The objectives of this review are as follows: (1) To introduce the definition of phyllosphere and the development of the methodology related to phyllosphere microorganisms as well as their biological functions and mechanisms; and (2) To provide future perspectives in understanding microorganisms. References | Related Articles | Metrics

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Spatial Variation of Soil Bulk Density, Saturated Hydraulic Conductivity and Soil Water Content in a Slope-gully unit of the Northern Loess Plateau 2018, 35 (2):  315-324.  Abstract ( 982 )   PDF (1635KB) ( 655 )   Gully is an important kind of erosional landform in the watershed of northern Loess Plateau and has a profound effect on the surface processes such as hydrological, vegetational, geomorphologic and ecological et al. To clarify the response of three soil physical parameters (soil bulk density, BD; saturated hydraulic conductivity, Ks; soil water content, SWC) to gully topography, slope position and soil depth, we layouted three sampling transects in the bottom, edge and nearby bank of an erosional gully, with the sampling site numbers set as 40. At every site, undisturbed soil cores were sampled at three soil depth layers: 0~10 cm, 10~20 cm and 20~30 cm, they were regarded as surface, sub-surface and shallow layers, respectively. Based on the constant water-head method and drying method, we obtained the data of BD, Ks and SWC. The results showed: (1) three topography condition had significant or highly significant effect on BD, Ks and SWC, and the three parameters showed wave-like trend along the slope length. The BD on the gully edge and bank slightly decreased with the increase of slope length. With exception to soil surface on the gully edge, SWC on down slope was significantly higher than middle and upper slope; (2) On the gully edge and bank, the variation trend of Ks and BD with the depth layer was different from that on the gully bottom; (3) At every depth layer, SWCs on the gully edge and bank were significantly different from those on the gully bottom; and SWC on the gully edge was always lower than that on the gully bank. The results above mentioned indicated that the spatial pattern of BD, Ks and SWC on the slope was changed by the distribution of gully, the influence of different topography conditions of the slope-gully unit on the soil physical parameters could not be neglected. References | Related Articles | Metrics

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Chemical Characteristics of Summer Precipitation in Yushugou River basin, Hami, Eastern Tianshan 2018, 35 (2):  277-286.  Abstract ( 520 )   PDF (1664KB) ( 602 )    As an effective means to study the atmospheric chemical composition change, atmospheric precipitation chemistry could accurately reflect the local atmospheric environmental quality and pollution condition. The precipitation chemistry features far away from human colonies can reflect the background value of atmospheric chemistry, and help to study the atmosphere chemical conversion, transmission and the formation process and mechanism of acid rain. Restricted by precipitation seasonal distribution and the conditions of observation in the river basin, the pH, EC and ion composition of precipitation were analyzed in the Yushugou River basin in EasternTianshan from May to August 2013. The ionic sources were simultaneously investigated. The results showed that the precipitation was neutral with mean pH of 6.8. It suggested that there was no acid rain during the sampling period in study area. The EC ranged from 3.79-239 μs/cm and it was obviously affected by amount of precipitation. With the increase of rainfall, the under cloud wash action diluted the conductive ions in precipitation, at the same time, precipitation conductivity decrease correspondingly. The concentration orders of cations and anions are Ca2+> NH4+>Na+>K+>Mg2+ and SO42->NO3->Cl->F-, respectively. The order of the cationic was exactly the same as that of the elements order in the crust and different from the order of cation concentration in the seawater (Na+ > Mg2+> Ca2+ > K+). It may be due to its geographic location. The Yushugou River basin is located in arid inland areas distributing a large area of desert sand, which makes the ion concentration sequence in the atmospheric precipitation be controlled by terrigenous material. The SO42-/NO3- ratio (1.76) indicated that SO42- was the main acid-causing substance in precipitation. The source of the different ion in summer precipitation is different. SO42-、NO3-、F- and NH4+ mainly comes from man-made sources, such as burning coal, vehicle emissions, and agricultural production activities. Cl- almost came from the sea salt source and crust source has little impact on it. The source of sodium affected by sea salt meanwhile quite part was from terrigenous. Ca2+ and K+ come from the non-sea-salt, which were mainly affected by the earthcrust and human activities. In the study area， there were four precipitation conveying paths which were northwest, southwest, southeast, and north four paths. Northwest path air masses originated from western Russia and Kazakhstan by the way of western Xinjiang. Path moisture originated from Mongolia passed across western Inner Mongolia with low population density, relatively underdeveloped economy, meanwhile industrial agricultural activity was frequent. The human activities exist in northwest pass. Through Northwestern and northern path there was a large area of desert with alkaline soil. It brought a large amount of alkaline substances to the atmosphere where alkaline substances could neutralize the acid precipitation. Southwest path water vapor was from southwest inland areas in China, passing along the eastern Qinghai-Tibet Plateau. The vegetation in southwest inland was in good condition and less affected by human activities. Along the southeast path air mass from the Midwest region in China, the vegetation coverage is very low, so the precipitation was greatly influenced by terrigenous. By studying the chemical characteristics of atmospheric precipitation in the river basin, this paper discussed material source of the precipitation. This research will provide data for further studies of water cycle mechanism in this mountain basin. References | Related Articles | Metrics

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Characteristics of water cycle in atmosphere in the arid region of northwestern China 2018, 35 (2):  269-276.  Abstract ( 705 )   PDF (942KB) ( 868 )   The arid region of northwestern China is one of the most sensitively response to global change. Global warming accelerated water cycle, caused by obviously changes of the water cycle in atmospheric. Based on the data analysis and newest research results, this paper analyzes the Characteristics of water cycle in atmosphere and related scientific problems in the arid region of northwestern China. The original daily temperature, precipitation and relative humidity data were collected from 96 meteorological stations in the region and analyzed by a Mann – Kendall test and linear trend. The analysis results show thatthe water vapor and precipitation experienced experienced a “sharply” increase in the late 1980's, however, this sharp increasing trend has turned to an apparent decrease since the 21st century. The eastern northwest water vapor and precipitation decrease obviously, caused by the monsoon intensity weaken. The northwest of Xinjiang and northwest of the Hexi Corridor were sensitive to the water vapor change.The increased stations of the precipitation accounted for 95.9%, and have the elevation-depending wetting, especially in the Tianshan Mountain and Qilian Mountain. The precipitation trend increases signi?cantly with elevation except for the altitude from 500 to 1500 m, the highest correlation appears above 1500 m, increases by 13 mm/decade with each 1000 m. With the elevation increasing every 1000 m, precipitation tendency rate increases by 7 mm/decade from 1000 to 2000 m and increases by 10 mm/decade from 2000 to 4000 m. Average water vapor balance is 2.8×1011 m3, but the precipitation cycle rate is low, middle troposphere water net income increase significantly. Actual evaporation showed a weak decrease trend in the northwest arid region, and the Tianshan Mountain area decreased significantly, while Qilian Mountain region increased significantly. Summer precipitation is given priority to with westerlies water vapor transport, but the low latitude water vapor transport is particularly important when the large scale precipitation process occurred. References | Related Articles | Metrics

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Study on atmospheric circulation characteristics of precipitation anomalies in arid region of Central Asia 2018, 35 (2):  249-259.  Abstract ( 974 )   PDF (3035KB) ( 1065 )   As climate transition zone between Mediterranean climate region and East Asian monsoon region, arid region of Central Asia (including five Central Asian countries and Xinjiang province of China) which is influenced by high, middle and low latitude circulations has different synoptic-climatic characteristics from that of Europe and East Asia while its climate characteristics also varies greatly within the region. Central Asia has unique and complicated topography and ecosystem patterns like deserts, oasis, glaciers and basins, forming a highly representative meteorological disaster-breeding environment under the influence of multiple-background, multiple-factor and multiple-scale. This area has abundant solar-heat energy, large evaporation and dramatic temperature changes. Besides, its precipitation is scarce and has extremely uneven distribution with high value in the western and middle parts of Tianshan Mountains. Over the last one hundred years, Central Asia has experienced a warm and wet trend. Central Asia low value system together with the high, middle and low latitude circulation systems linked by West Asia westerly jet stream have contributed to the interdecadal and interannual variations of precipitation in Xinjiang. However, due to the insufficient construction of integrated meteorological observation network, the studies concerning regional featured circulation system, regularity and mechanism of disastrous weathers, high resolution regional numerical model, impacts of land-atmosphere interaction on regional weather and climate change prediction are still inadequate. Correspondingly, to carry out those studies has essential scientific significance and strategic value for the sustainable social and economic development in Silk Road Economic Belt. References | Related Articles | Metrics

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Driving factors causing the change of runoff volume of the Balager River in Inner Mongolia BAI Yong, GAO Rui-zhong, WANG Xi-xi, LIU Ting-xi, WANG Wei-na 2018, 35 (2):  296-305.  doi: 10.13866/j.azr.2018.02.06 Abstract ( 875 )   PDF (4761KB) ( 698 )   The Balager River Basin is a typical inland drainage basin and is located in a grassland plateau in China, where the grassland degeneration and the change of hydrological process are caused by many factors. It is very important to quantitatively analyze the variation of runoff volume, climate change and human activities for the reasonable utilization of water resources and conservation of grassland eco-environment. In this paper, the double cumulative curve, departure accumulation, improved Mann-Kendall trend test method and change rate of cumulative slope were used to quantitatively calculate and analyze the characteristics and main driving factors causing the change of runoff volume at different scales based on the hydrological, meteorological and socioeconomic data in the Balager River Basin during the period from 1959 to 2015. The following results were concluded (1) The shift point of runoff volume occurred in 1998. The runoff volume was changed under the influence of precipitation before 1998 (named as the reference period), while there were the double influences of climate change and human activities on runoff volume after 1998 (named as the variable period); (2) The annual, wet-seasonal and dry-seasonal runoff volumes were holistically decreased, but there was no significant precipitation variation; (3) Although there was no significant variable trend of precipitation (p= 0.428) at annual scale, the runoff volume was deceased significantly (p= 0.042). The runoff volume in the reference period was higher than that in the variable period when the precipitation was similar; (4) Both the runoff volume (p= 0.117) and precipitation (p = 0.077) decreased slightly in wet season, while the runoff volume in dry season (p = 0.003) decreased significantly but the precipitation (p = 0.286) did not. No matter in wet season or dry season, the average runoff volume in the reference period was higher than that in the variable period; (5) The monthly precipitation and runoff volume in the whole time series, reference period and variable period fluctuated similarly. The precipitation in July (107mm) was the highest, but the corresponding runoff volume (1.7mm) was not the highest. The highest runoff volume (2.963mm) occurred in April because of the melting of accumulated snow cover in winter; (6) Compared the climate factors in the reference period with those in the variable period, the variable ranges of temperature, precipitation and wind speed were 65.12%, -16.97% and -13.3% separately, while the fluctuations of other climate factors were less than 5%. So the temperature, precipitation and wind speed were the main climate factors affecting the runoff volume; (7) In the study area, the primary industry, sheep number and population increased by 3.8 times, 12.06% and 9% separately; (8) The contribution rates of runoff volume reduction due to climate change and human activities were 28.86% and 71.14% respectively, so human activities were the main driving forces causing the change of runoff volume. The study results can provide the references for analyzing the ecological hydrological change, water resources utilization and conservation in the process of socio-economic development in grassland watershed in semiarid area of north China. References | Related Articles | Metrics