North Shaanxi Research Articles

Research on the prediction of tar potential and maceral recognition based on artificial neural network: A case study of tar-rich coal from north Shaanxi, China

The high tar yield of tar-rich coal is ascribable to the complex interplay and coupling effects among various factors, which pose a significant challenge to its tar yield prediction owing to its intricate formation mechanism. This study employed artificial neural networks to predict the tar potential and maceral recognition considering the case of tar-rich coal in northern Shaanxi Province. A deep neural network model based on the U-Net architecture was utilised for high-precision quantitative analysis of macerals. In addition, traditional instrumental analyses were conducted to acquire fundamental coal quality parameters, such as industrial analysis, elemental analysis, and tar yield data. Subsequently, key features closely related to tar yield were carefully selected through correlation analysis. Finally, multiple statistical regression (MSR), backpropagation neural networks (BPNN), and convolutional neural networks (CNNs) were employed to construct a tar yield prediction model. Experimental results revealed that the hydrogen-rich feature parameters (Vad, Hd, and V) in tar-rich coal exhibited the most pronounced influence on tar yield. In terms of maceral recognition, U-Net performed exceptionally well, achieving an average accuracy of 72.16%, with the prediction accuracy for the four main macerals (vitrinite, inertinite, carbonate minerals, and sulfide minerals) surpassing 90.00%. With respect to the tar yield prediction, the neural network predictive models surpassed the MSR predictive models in terms of performance. Both the BPNN and CNN prediction models had a coefficient of determination greater than or equal to 0.95, especially for the Group CNN prediction model optimised by group convolution, which had a coefficient of determination as high as 0.98, an average absolute error as low as 0.18%, and a root mean square error of only 0.24%. The application of neural networks in deciphering the maceral and tar-producing characteristics of tar-rich coal can significantly enhance the associated analytical efficiency and precision.

Experimental and theoretical study on molecular structure construction of Hongliulin coal

A suitable model can reflect the properties of coal well. In this study, the properties of HongLiuLin (HLL) coal were studied through industrial analysis, XPS, 13C NMR and FTIR. The results show the coal has middle-rank bituminous coal characteristics, and the ratio of aromatic bridge carbon to aromatic peripheral carbon is 0.16. Benzene and naphthalene ring are the main components of the aromatic structure. N and S exist in pyrrole nitrogen and fatty sulfur, respectively. The hypothesis method was used to deduce the molecular formula C130H73O21NS of the coal model. The stability of the carbon skeleton was improved through the Van Der Waals (VDW) forces in non-bonding energy. Verification of NMR, FTIR and density was completed based on quantum chemistry and molecular mechanics. The coal model energy level orbitals analysis shows that the LUMO and HOMO orbitals are located in the aromatic functional groups. This work provides a reference for further research on the nature of coal in north Shaanxi and improving the utilization rate of coal.

Soil C:N:P Stoichiometric Characteristics and Soil Quality Evaluation under Different Restoration Modes in the Loess Region of Northern Shaanxi Province

Vegetation restoration is essential for the stability of the ecological system structure and function in the loess region of North Shaanxi Province. Natural and artificial restoration are the primary modes for vegetation recovery and soil quality improvement in this region. In this study, two adjacent watersheds with similar ecological environment conditions but different restoration modes were selected for research; one watershed is restored naturally (He Gou watershed), and the other is restored artificially (Chai Gou watershed). According to the study of soil stoichiometric characteristics and soil quality after the vegetation restoration in these two watersheds, the results showed: (1) Compared with the natural restoration, artificial restoration was more effective in increasing the content of soil organic carbon and total nitrogen, however, the total phosphorus content of the soil in the natural restoration mode was higher than that in the artificial restoration mode. (2) The ratios of soil C:N, C:P, and N:P showed a decreasing trend with the increase of soil depth at these two restoration modes. (3) In the 0–60 cm soil layer, the soil quality under the artificial restoration mode was better than that of the natural restoration, especially for the soil layer beneath 20 cm. (4) The minimal data set on the soil quality evaluation in the study area included soil organic carbon, capillary water holding quantity, available potassium, soil water content and available phosphorus. It showed a linear relation with the total index data set (y = 0.829x + 0.058, R2 = 0.76) and can reflect the soil quality more sensitively than the total indicator data set.

Isotopic characteristics and vapor sources of atmospheric precipitation in the loess region of North Shaanxi, China

To explore the hydrogen and oxygen stable isotopes and vapor sources of atmospheric precipitation in the loess region of north Shaanxi, we collected 107 samples of precipitation during 2018 to 2020 in the Dingbian County, Shaanxi Province. After measuring δ18O and δ2H of precipitation, we analyzed the isotopic characteristics and vapor sources of precipitation in different seasons. There was obvious seasonal variability in δ18O and δ2H, in that they were more depleted in the wet season (June-September) but more enriched in the dry season (April-May, October-November). In addition, the deuterium excess values were high in the dry season but low in the wet season. The local meteoric water line was regressed as δ2H=7.35δ18O+4.19 (R2=0.96, P<0.01) with slope and intercept lower than that of the global meteoric water line, indicating an impact of evaporation on isotope fractionation. There was temperature effect in the precipitation isotopes for the whole year and for the dry season, while the precipitation isotopes in the wet season were affected by the combined effects of temperature and rainfall amount. The HYSPLIT model showed that the dry season water vapor mainly came from the Atlantic Ocean and the polar Arctic Ocean, while the wet season vapor mainly came from the Indian Ocean and Pacific subject to the Westerly.

The metabolic diversity of soil microbial community in the petroleum exploitation area of Northern Shaanxi, China

In order to explore the changes of soil chemical properties and microbial metabolic diversity under different petroleum pollution levels, conventional soil detection technology and Biolog® technology were used to study the soil chemical properties and microbial community characteristics of the clean soil in the north Shaanxi oilfield under four different petroleum pollution gradients. The results showed that the soil after petroleum pollution had higher total organic carbon content, higher carbon nitrogen ratio and lower total nitrogen content. Petroleum had a significant effect on the metabolic capacity of soil microbial communities from carbon sources and their utilization patterns. There were significant differences in microbial community metabolism in petroleum-contaminated soils at different concentrations, with a decreasing trend with increasing contamination. At the same time, the microbial activity that could utilize carboxylic acid compounds and polymers was higher in the contaminated soil, while the microbial activity that utilized amino acids and carbohydrates was higher in the clean soil. With the increase of pollutant concentration, the metabolic pattern of soil microbial community to carbon sources changed from sugar-based to polymers-based. This indicates that oil pollution has changed the use of some preferred carbon sources by soil microorganisms, and long-term pollution will stabilize the carbon sources available to microorganisms and promote the development of microbial communities that prefer polymeric substances as carbon sources. This provides theoretical guidance and data support for the bioremediation and treatment of petroleum-contaminated soil in loess hilly areas.

Evaluation of land ecosystem health in Shaanxi Province, Northwest China based on PSR Model.

Based on the pressure-state-response (PSR) model and entropy method, we analyzed the health status of land ecosystem and the temporal and spatial variations from 2009 to 2017 in ten cities and one district in Shaanxi Province. The driving factors affecting the health of the land ecosystem was examined. Results showed that during 2009-2017, the overall health of the land ecosystem in Shaanxi Province was improved, which was lower during 2009-2014 and being obviously improved after 2014. The health level of land ecosystems in Xi'an, Baoji, Weinan and Hanzhong was high and with substantial variation, while that in Yan'an, Yulin, and Ankang was low and stable, decreasing in order of South Shaanxi, Guanzhong region and North Shaanxi. Overall, the pressure, state and response indices of the land ecosystem in Shaanxi Province increased during 2014-2017 with a gentle growth, which were basically flat after 2014. Those results indicated that the land ecosystem in Shaanxi Province was at a stable and healthy state. Population growth, urbanization level, fertilizer load per unit of arable land, forest coverage rate, industrial wastewater discharge compliance rate and comprehensive utilization rate of industrial solid waste were the main driving factors for the health of land ecosystems in Shaanxi. Controlling the use of fertilizers and pesticides, optimizing the structure of land use and improving land use efficiency are necessary strategies to promote the construction of ecological civilization and implement the red line of ecological protection for Shaanxi Province.

Study on the bearing structure and stability of overlying strata: an interval gob in shallow buried coal mining of Northwest China

The bearing structural characteristics of overlying strata in overlying gobs are the main factor in inducing dynamic disasters in roof in close-distance coal seam group mining. In the present work, the bearing structure and stability characteristics of overlying strata in the shallow-buried interval gob (SBIG) of Yushenfu mining area in north Shaanxi Province, China, have been studied by numerical and physical similarity simulations and theoretical analyses. Research results showed that the instability of gob temporary coal pillars (TCP) led to the rotary instability of basic roof, increasing the stress arch in overlying strata with the expansion of the failure range of overlying rocks giving rise to increases of arch height and superimposition of adjacent stress arches. This way, “trapezoid-semicircular arch” caving of overlying strata was performed. “W-shaped voussoir beam” bearing structure was formed by the fracture of the basic roof of gob and “double arch bridge” bearing structure was created by interval coal pillar (ICP) and fracture rock. In this work, the bearing structure model of interval gob overlying rock “W-shaped voussoir beam + double arch bridge” was established. On the basis of “voussoir beam structure,” the stability of “double arch bridge” type bearing structure formed by the rotation of broken rock block on the top of the basic roof of the interval gob was analyzed. When the support capacity of coal pillar was weakened or the overlying strata were changed, the stability of asymmetrical stress inclined arch equilibrium structure was lost. The stress distribution of “double arch bridge” structure overlying the interval type gob was analyzed by numerical simulation, and the stress transfer law of pier column in floor was obtained. It was found that with the decrease of the width of pier pillar, the “double arch bridge” structure became asymmetric, and the change characteristics of stress inclined arch height were decreased. The arch roof transferring to pier side was divided into prevention and control areas of roof dynamic disaster in the mining of lower coal seams. The purpose of this paper was to provide theoretical guidance for dynamic pressure prevention and control of mining under shallow interval gob.

Characteristics and Sources of PM2.5 Pollution in Typical Cities of the Central Plains Urban Agglomeration in Autumn and Winter

To study the characteristics of PM2.5 pollution and the potential sources of its main components in the central plain urban agglomeration in autumn and winter, PM2.5 samples were collected continually in the four typical cities of Zhengzhou, Luoyang, Anyang, and Xinxiang from October 2018 to January 2019. X-ray fluorescence spectrometry, carbon analysis methods, and ion chromatography were used to determine 18 kinds of inorganic elements, organic carbon (OC)/elemental carbon (EC), and 9 kinds of water-soluble inorganic ions. According to the daily PM2.5 concentration, three pollution levels were divided, and the comparative analysis for the spatial and temporal variation of PM2.5 and its main components, i.e., NO3-, OC, and 18 kinds of inorganic elements, were studied via the calculation of the nitrogen oxidation rate (NOR), secondary organic carbon (SOC), and enrichment factor. The emission sources and their contribution rates of PM2.5 pollution level in the four cities were calculated by a chemical mass balance (CMB) model; the potential pollution sources of PM2.5 and its main components, NO3- and OC, in the four cities were analyzed by a backward trajectory model (HYSPLIT) and potential source contribution factor method (PSCF). The results showed that the means of PM2.5 in Zhengzhou, Luoyang, Anyang, and Xinxiang were (82.1±45.5), (84.7±39.8), (96.8±46.1), and (81.1±36.6) μg·m-3, respectively, during the sampling period, and the maximum daily mean values were 3.3, 2.6, 3.0, and 2.3 times, respectively, of the Chinese national secondary standard; the main components of PM2.5 in the four cities were NO3- and SOC, and the concentration of NO3-, the ratio of NO3-/EC, and NOR all increased significantly with the rising of pollution levels, generally showing that the mean values of NO3-/EC and NOR of Zhengzhou and Luoyang were a little higher than those of Anyang and Xinxiang; the concentration of SOC, the proportion of SOC in OC, and the ratio of SOC/EC all increased with the rising of pollution levels. From the concentration and enrichment degree of inorganic elements, As was the highest in Zhengzhou; Mn and Fe were the highest in Luoyang; Zn, Ni, and Cr were the highest in Anyang; and Cu and Pb were the highest in Xinxiang. Secondary nitrate, secondary sulfate, organic matter, coal combustion, motor vehicle, dust, biomass burning, and industrial processes were the main PM2.5 pollution sources in the four cities, with the highest contribution rate of secondary nitrate in Zhengzhou (37.7%), the highest contribution rate of vehicle sources in Xinxiang (14.1%), and a relatively high contribution rate of industrial process source in Luoyang (7.0%) and Anyang (6.8%). The northwest direction of airflow contributed 51.6%, 49.2%, 49.6%, and 46.3% of the total airflow in Zhengzhou, Luoyang, Anyang, and Xinxiang, respectively. From the potential pollution area of each city, the Zhengzhou area was mainly concentrated in Henan province, the Luoyang area was mainly concentrated in the south of Henan province and Fen-wei plain, and the Anyang and Xinxiang areas were mainly concentrated in Henan province and the Beijing-Tianjin-Hebei transport belt. The pollution levels of OC in Anyang and Xinxiang were also affected by the northwest Anhui, southwest Shandong, southeast Shanxi, and north Shaanxi.

Land use structure of typical county with conversion of farmland to forests in loess areas of Northern Shaanxi

Loess Plateau is the key construction area of ecological environment restoration in China. Since implementing the project of converting farmland to forests, the land use structure and existing problems in the loess area of northern Shaanxi have received extensive attention. Land use structure is the area and proportion of all kinds of land within a certain area, which determines the play of regional functions and land use benefits. This work took Wuqi County, Loess District, Northern Shaanxi, the demonstration county of national project of converting farmland to forests. Based on the land use data of Wuqi County in Loess Ddistrict of north Shaanxi Province in 2009, this work carried out the quantitative analysis and discussion of land use quantitative structure in this area by means of quantitative geographical model and GIS spatial analysis and by using indexes such as diversification, centralization and combination coefficient of ground class. The results show that the quantity and structure of land use in Wuqi County are diversified, the concentration is low, and the complete degree of land use type is high. Additionally, the land combination type is mainly forestland-grassland, and the overall function needs to be improved. This study can provide reference for the quantitative analysis of land use structure in similar areas and counties.

Geographical variations in maternal lifestyles during pregnancy associated with congenital heart defects among live births in Shaanxi province, Northwestern China

In this study, we aimed to explore regional differences in maternal lifestyle during pregnancy related to congenital heart defects (CHD) in Shaanxi province, Northwestern China. A large-scale epidemiologic survey of birth defects among infants born during 2010–2013, was conducted in Shaanxi province. Non-spatial and geographic weighted logistic regression models were used for analysis. The spatial model indicated that passive smoking frequency was positively associated with CHD for 43.3% of participants (P < 0.05), with the highest OR in North Shaanxi and the lowest in South Shaanxi. Approximately 49.2% of all mothers who ever drink tea were more likely to have an infant with CHD (P < 0.05), with the highest OR values observed in North and Central Shaanxi. Additionally, maternal alcohol intake frequency ≥ 1/week was significantly correlated with CHD among about 24.7% of participants (P < 0.05), with OR values ranging from 0.738 (Central Shaanxi) to 1.198 (North Shaanxi). The rates of unhealthy maternal lifestyles during pregnancy associated with CHD differed in various areas of the province. The role of geographical variations in these factors may provide some possible clues and basis for tailoring site-specific intervention strategies.

Contribution of biogenic sources to secondary organic aerosol in the summertime in Shaanxi, China

A revised Community Multi-scale Air Quality (CMAQ) model with updated secondary organic aerosol (SOA) yields and a more detailed description of SOA formation from isoprene (ISOP) oxidation was applied to study the spatial distribution of SOA, its components and precursors in Shaanxi in July of 2013. The emissions of biogenic volatile organic compounds (BVOCs) were generated using the Model of Emissions of Gases and Aerosols from Nature (MEGAN), of which ISOP and monoterpene (MONO) were the top two, with 1.73 × 109 mol and 1.82 × 108 mol, respectively. The spatial distribution of BVOCs emission was significantly correlated with the vegetation coverage distribution. ISOP and its intermediate semi-volatile gases were up to ∼7.0 and ∼1.4 ppb respectively in the ambient. SOA was generally 2–6 μg/m3, of which biogenic SOA (BSOA) accounted for as high as 84% on average. There were three main BVOCs Precursors including ISOP (58%) and MONO (8%) emit in the studied domain, and ISOP (9%) transported. The Guanzhong Plain had the highest BSOA concentrations of 3–5 μg/m3, and the North Shaanxi had the lowest of 2–3 μg/m3. More than half of BSOA was due to reactive surface uptake of ISOP epoxide (0.2–0.7 μg/m3, ∼19%), glyoxal (GLY) (0.2–0.5 μg/m3, ∼11%) and methylglyoxal (MGLY) (0.4–1.4 μg/m3, ∼32%), while the remaining was due to the traditional equilibrium partitioning of semi-volatile components (0.1–1.2 μg/m3, ∼25%) and oligomerization (0.2–0.4 μg/m3, ∼12%). Overall, SOA formed from ISOP contributed 1–3 μg/m3 (∼80%) to BSOA.

Vertical distribution and migration of plutonium in the Loess Plateau, North Shaanxi, China

The vertical distribution and migration behavior of 239+240Pu in a soil core in northern Loess Plateau in Shaanxi Province was investigated. The results showed that the 239+240Pu activity concentration was in the range of 0.02–0.75 mBq/g. The measured atom ratios of 240Pu/239Pu in the soil profile varied from 0.179 to 0.201 and were consistent with the typical global fallout. The inventory of 239+240Pu was 66 Bq/m2 in the sampling site and the proportion of Pu in the first 10 cm top layer accounted for around 75%. The apparent convection velocity and effective dispersion coefficient were 0.19 cm/year and 0.12 cm2/year by the convection dispersion equation model, respectively. Further investigation is still highly required to clarify the dominant factors that control Pu migration.

ESP Simulation Study on the DC Grounding Electrode in Chinese Shanbei Converter Station Based on ANSYS

When the UHVDC project was put into operation, the grounding current of DC grounding electrode may have a great influence on the transformer near the pole. The calculation of earth surface potential (ESP) distribution was a problem to be considered in the planning and design stage. In this paper, the calculation method of the current field of DC transmission grounding electrode was deduced. The grounding electrode project of Chinese North Shaanxi converter station was referred, and the layered model of 6 layers of ground soil was established. The potential distribution in the range of 0-100 km of the earth electrode was calculated by using ANSYS. The calculation results show that the distance between the ground electrode and the ground electrode decreases faster than that of the ground electrode. The distribution of earth surface potential within the range of 2 km of the earth electrode should be studied emphatically, and the potential distribution of the substations and power plants that have been built and planned has been calculated. The method presented in this paper could provide reference for the debugging of HVDC transmission monopole.

Factors Affecting the Spatial and Temporal Variations in Soil Erodibility of China

AbstractSoil erosion occurs extensively across China, leading to severe degradation of the land and ecosystem services. However, the spatial and temporal variations in soil erodibility (k) and the distribution of soil erosion across land use types and slopes remain unclear. We synthesized the results from 325 sites published in 152 literatures to analyze the factors affecting the k, such as land use type, climate, topography, soil, and vegetation restoration age. The results showed that areas with slopes &gt;25° had a larger k factor (k = 0.1047) than did those with slope &lt;6° (k = 0.0637) or 6–25° (k = 0.0832). The k from 2006 to 2011 (k = 0.0725) was higher than that from 1999 to 2005 (k = 0.058) and that from 2012 to 2016 (k = 0.0631). The k value initially increased with vegetation restoration age and then gradually decreased. Land use also had an impact on the k factor, with the k factor of cropland (k = 0.0697) being higher than that of grassland (k = 0.0663) but lower than that of forest (k = 0.0967). Across China, North Shaanxi, Heilongjiang, and South Guizhou, which are located in the Loess Plateau in Northwest China, the Black Soil region of Northeast China, and the Karst areas in Southwest China, respectively, were the three most severely eroded regions due to hydraulic erosion, frost‐thaw erosion, and high‐intensity erosion, respectively. Overall, the most important factors affecting the k were soil characteristics, followed by topography and climate. Among them, soil nitrogen and precipitation were the two most critical factors influencing the k.

The Temperature Vegetation Dryness Index (TVDI) Based on Bi-Parabolic NDVI-Ts Space and Gradient-Based Structural Similarity (GSSIM) for Long-Term Drought Assessment Across Shaanxi Province, China (2000–2016)

Traditional NDVI-Ts space is triangular or trapezoidal, but Liu et al. (2015) discovered that the NDVI-Ts space was bi-parabolic when the study area was covered with low biomass vegetation. Moreover, the numerical value of the indicator was considered in most of the study when the drought conditions in the space domain were evaluated. In addition, quantitatively assessing the spatial-temporal changes of the drought was not enough. In this study, first, we used MODIS NDVI and Ts data to reexamine if the NDVI-Ts space with “time” and a single pixel domain is bi-parabolic in the Shaanxi province of China, which is vegetated with low biomass to high biomass. This is compared with the triangular NDVI-Ts space and one of the well-known drought indexes called the temperature-vegetation index (TVX). The results demonstrated that dry and wet edges exhibited a parabolic shape again in scatter plots of Ts and NDVI in the Shaanxi province, which was linear in the triangular NDVI-Ts space. The Temperature Vegetation Dryness Index (TVDIc) was obtained from bi-parabolic NDVI-Ts andTVDIt was obtained from the triangular NDVI-Ts space and TVX were compared with 10-cm depth relative soil moisture. By estimating the 10-cm depth soil moisture, TVDIc was better than TVDIt, which were all apparently better than TVX. Second, combined with MODIS data, the drought conditions of the study area were assessed by TVDIc between 2000 to 2016. Spatially, the drought in the Shaanxi Province between 2000 to 2016 were mainly distributed in the northwest, North Shaanxi, and the North and East Guanzhong plain. The drought area of the Shaanxi province accounted for 31.95% in 2000 and 27.65% in 2016, respectively. Third, we quantitatively evaluated the variation of the drought status by using Gradient-based Structural Similarity (GSSIM) methods. The area of the drought conditions significantly changed and moderately changed at 5.34% and 40.22%, respectively, between 2000 and 2016. Finally, the possible reasons for drought change were discussed. The change of precipitation, temperature, irrigation, destruction or betterment of vegetation, and the enlargement of opening mining, etc., can lead to the variations of drought.

Regional topographic classification in the North Shaanxi Loess Plateau based on catchment boundary profiles

Topographic classification and mapping are fundamental topics in geomorphology and have many promising applications. This study aimed to achieve landform classification using the catchment boundary profile (CBP) in the area of the North Shaanxi Province. CBPs were extracted, and seven indices were proposed and calculated to describe the profile features. Spatial maps of these indices were generated by interpolating 81 sample areas in the North Shaanxi Province of China. Finally, a topographic regional map was generated through multi-resolution segmentation after integrating the spatial maps of the seven indices. Results showed that the CBP indices were typical and representative to describe the terrain characteristics in the North Shaanxi Province and revealed their diverse spatial patterns. The investigated area was classified into 14 topographic units. The requirements of maximizing internal homogeneity while minimizing external homogeneity in terms of morphological characteristics were satisfied through the analysis of the terrain texture, topographic features, and land surface parameters. A comparison with the reference map showed that the regional classification differed from the geomorphologic map, given the different classification systems. However, the regional classification provided new knowledge of topographic features and spatial patterns in the macro scale. A comparison with other classification method indicated the advantage of the CBP-based method, which could distinguish the landforms of loess tableland, loess ridge, and loess hill that are the typical characteristics of loess landforms. The sensitivity analysis revealed that the differences in CBP indices, except for roughness and fractal dimension (FD) from different landforms, would increase with the digital elevation model (DEM) resolution becoming coarser, which indicates that the CBP-based method could be applied on a coarser resolution DEM if the differences of roughness and FD from different landforms could be identified at this coarse DEM level.

Effects of land use types on deep soil water content in the loess hilly area of the north Shaanxi Province, China

This study explored the differences of soil water content at 0-20 m soil depth at three locations, including economical plantation in Mizhi, reforestation area in Shenmu, and wind break and sand fixation forest district of Yuyang, and for clarifying the impacts of different land use types on deep soil water distribution and storage characterization, as well as its eco-environmental effect on the loess hilly area. The results showed that in the soil profile of 0-20 m, land use patterns had a significant impact on soil moisture distribution. There were significant differences of soil water sto-rage for the economical plantation, pruning Ziziphus jujuba plantation ＞ Z. jujuba plantation with 587.9 mm difference. There was no significant difference in soil water storage between Caragana korshinskii plantation and degraded artificial vegetation or between pine forests and natural grass field, degraded artificial grassland ＞ C. korshinskii plantation with 98.8 mm difference at Shenmu, and natural grassland ＞ Pinus sylvestris var. mongolica plantation with 7.5 mm difference at Yuyang. The pruning Z. jujuba tree reduced soil water consumption and was beneficial to sustainable use of soil water due to the decreased crown width and thus reduced transpiration. There were no obvious differences of soil water content between C. korshinskii plantation and degraded artificial grassland due to the historical alfalfa planting which was characterized by high water consumption due to its deep root distribution and large biomass. In contrast, P. sylvestris var. mongolica plantation and na-tural grassland had similar and low averaged soil water contents with 3.4% and 3.6%, respectively, mainly due to the sandy soil texture and weak soil water holding capacity. In addition, with increa-sing soil depth, soil water content increased in this area, indicating the effect of plants on water moisture of deep soil was very limited. Except for the underlying control of soil texture on soil water content in the soil profile, different vegetation played a key role in the dynamics of soil water content due to the difference of root zones. It was very important to choose the suitable type of vegetation regarding the protection and sustainable use of deep soil water.

Evaporation stage of paleo-saline lake in North Shaanxi salt basin China: insight from fluid inclusions in halite

Fluid inclusions within halite from the Mizhi cores in the North Shaanxi Basin were studied to restore the ancient sedimentary environment, and to discuss the material supply on this basis. Fluid inclusion analyses include fluid inclusion petrography to examine their characteristics and types, hydrogen and oxygen isotopic compositions of trapped fluids, and package play flow components. This study shows that halite recrystallization occurred in the North Shaanxi Basin from fluid mixing of fresh and brine waters during transgressions. Hydrogen and oxygen isotopic compositions of halite inclusions show that precipitation of halite was supplied by multiple provenances, including thermal fluids. The study on the fluid compositions in the Ordovician halite inclusions indicates that the ancient sea water could allow the precipitation of the potassium magnesium salt rocks at that time, but the frequent transgressions influenced the preservation of the potassium magnesium salt rocks. Therefore, using the available data, this study proposes that the deposition of the MajiagouV member in the North Shaanxi Basin was supplied by transgressive sea water and thermal fluids. In addition, the frequent transgression during the Majiagou deposition affected the preservation of the potassium magnesium salt.

Geographical boundary and climatic analysis of Pinus tabulaeformis in China: Insights on its afforestation

Pinus tabulaeformis, as an endemic species in China, is one of the main tree species for afforestation. For rational cultivation planning and conservation, it is necessary to understand the geographical boundaries and the ecological characteristics of P. tabulaeformis, and to explore its priority afforestation areas. In this study, maximum entropy modeling (MaxEnt) was used to identify and prioritize suitable habitats of P. tabulaeformis, based on 13 climatic variables and GlobCover 2009 data. The results show that the MaxEnt model performs better than random prediction, with an average test area under the curve (AUC) value of 0.93 (0.91–0.94). Precipitation of wettest month (PWM), annual biotemperature (ABT), mean temperature of the coldest month (MTCM), annual mean temperature (AMT), precipitation of driest month (PDM), coldness index (CI), annual precipitation (AP), and mean temperature of the warmest month (MTWM) are identified as dominant variables which explain 94.6% of variability the geographical distribution of P. tabulaeformis. Climatic conditions of P. tabulaeformis in the core area of its distribution are as follows: PWM, 100–246mm; ABT, 3.0–4.7°C; MTCM, −20.2 to −1.1°C; AMT, 2.9–14.7°C; PDM, 2–11mm; CI, −49.4–0°C; AP, 431–1122mm; and MTWM, 19.6–31.2°C. The suitable areas for afforestation are 2.6×104km2 (patches with an area >1km2), 1.6×104km2 (patches with an area >10km2), and 1.2×104km2 (patches with an area >100km2), which are mainly located in north Shaanxi, south Ningxia, and the middle of Gansu and Liaoning provinces with serious landscape fragmentation caused by human agricultural activities. Our simulation results can improve our understanding of the geographical and ecological characteristics of P. tabulaeformis and provide prediction of priority areas for afforestation of this species under current and future climate change scenarios in China.

Factors affecting runoff and sediment yield on the semiarid loess area in Northern Shaanxi Province, China

The semiarid loess area in north Shaanxi Province is one of the most serious areas of water erosion in China. The Chinese government initiated the project “Grain-for-Green” for soil erosion control in 1999, with significant effect. Vegetation, rainfall, soil, and topography are the most dominant natural factors affecting soil erosion; therefore, the aim of this research was to investigate the effects of these four factors on runoff and soil loss at the runoff-plot scale over five years and use the Gray relational analysis methods to compare the impacts of these factors. Five runoff-measuring sites were established in five different vegetation types. The results show that the relative impacts of the four factors on runoff were: rainfall > soil > topography > vegetation, and the relative impacts of the factors on sediment yield were soil > runoff > rainfall > topography > vegetation. We also analyzed the weights of these four factors on runoff and sediment yield during the wettest year alone. For that year, the relative weights of the factors on runoff were topography > rainfall > soil > vegetation, and the relative weights of the factors on sediment yield were runoff > soil > rainfall > topography > vegetation.