Semi-arid Area Of Northwest China Research Articles

Modeling the effects of the plastic-mulched cropland over the arid and semi-arid areas of China on the East Asian regional climate

Arid and semi-arid areas of Northwest China are extremely sensitive to climate change. Plastic mulch is a technology used worldwide to inhibit soil evaporation and increase crop yield. The properties of plastic film are significantly different from the soil. Plastic mulch not only alters the physical attributes of the underlying surface, but also blocks the energy and mass exchanges between the land surface and the atmosphere. This latter situation has not been depicted in current regional climate models. This study couples a detailed plastic mulch layer submodel considering the effects of the plastic mulch on the radiation and heat transfer into the regional climate model RegCM4.5 to explore the effects of plastic mulch on East Asian regional climate over Northwest China. Results suggest that the plastic film covering cropland can enhance the near surface sensible heat transfer, accelerate the rise of near surface air temperature, and reduce the water vapor supply of convective process. Meanwhile, the rainfall is reduced in Northwest China and most areas south of the Yangtze River, while the precipitation is improved from Sichuan and Chongqing to North and Northeast China when the cropland underlying surface is covered by the plastic film. Moreover, the cyclone of the lower troposphere in Northwest China is strengthened and the air pressure is weakened, which promotes the subtropical high to the northwest, thus East Asian summer monsoon is influenced because of the plastic film mulching.

Effects of Weeding Frequency on the Yield and Quality of Glycyrrhiza uralensis Fisch in an Arid and Semi-Arid Area of Northwest China

Weeds interfere with agricultural production activities worldwide and have a very serious impact on agriculture and animal husbandry. Identifying a safe and reliable weed control strategy may increase the yield and production net income, and improve crop quality. Licorice is one of the most popular traditional Chinese herbal medicines and has been used for over 2000 years in China. Liquiritin and glycyrrhizic acid are crucial active ingredients. A field experiment was carried out to explore the effects of weeding frequency on the yield and quality of Glycyrrhiza uralensis Fisch in an arid and semi-arid area of northwest China. The experiment consisted of seven treatments: (1) no weeding, marked as WF0, and (2)–(7) artificial weeding using a hoe once every 1, 2, 4, 6, 8 and 10 weeks after emergence, marked as WF1, WF2, WF4, WF6, WF8 and WF10, respectively. We found that a higher weeding frequency resulted in greater plant height, photosynthesis, yield and quality. The highest yield was obtained when the WF1 treatment was applied, while the cost of weeding was high among all treatments. The concentrations of liquiritin and glycyrrhizic acid were increased by 53.24% and 36.57%, with the highest nitrogen metabolism enzymatic activities and quality observed when the WF4 treatment was applied. The WF4 treatment resulted in the largest increase in the net income among all treatments in both growing seasons, with respective increases of up to 71.39% and 78.81%. These findings suggest that weeding once every four weeks could be an effective and sustainable measure to control weeds in an arid and semi-arid area.

Study and application of coupling relationship between water-salt-resistivity-soil structure in saline soils in arid and semi-arid areas of northwest China

Widespread saline soils in Northwest China pose a serious threat to the region's ability to use infrastructure safely because they are prone to soil structure damage when subjected to external environmental fluctuations, which in turn affects the stability of the foundations for buildings. The non-destructive approach of measuring resistivity can be used to swiftly reflect the subsoil body's state and make assumptions about its safety. However, the electrical resistivity of the underground soil body can be used to quickly identify unstable areas because the resistivity is influenced by the water content, salt content, and structural characteristics of the soil body. To do this, it is necessary to understand the coupling relationship between various factors. In this study, we first constructed samples with various water, salt, and soil structure characteristics, and then used indoor tests, such as soil resistivity measurement and thermogravimetric analysis, to analyze the multiple factors affecting the resistivity characteristics of the soil. The relationship between soil resistivity and actual saline soil diseases in Northwest China was then further discussed in conjunction with the results of the indoor tests and analyses. subsequently, the resistivity and soil properties have been measured in the field at specific locations in Northwest China where railway roadbeds are diseased. The study's findings can theoretically support a deeper comprehension of the law and mechanism of soil resistivity change, as well as provide assistance for building infrastructure in Northwest China.

Increasing sensitivity of dryland water use efficiency to soil water content due to rising atmospheric CO2

Examining the intricate interplay between ecosystem carbon-water coupling and soil moisture sensitivity serves as a crucial approach to effectively assess the dilemma arising from escalating global carbon emissions and concomitant water scarcity. Using the Lund–Potsdam–Jena Dynamic Global Vegetation Model (LPJ), this study investigated the potential effects of climate change and soil water content (SWC) on terrestrial ecosystem water use efficiency (WUE) across China from 1982 to 2060. The results revealed that: (1) WUE was higher in South China and Northeast China, but lower in Northwest China and it had shown a significant upward trend in the past 40 years, especially in Northwest China where grasslands were widely distributed. The increase in WUE was mainly closely related to the greening of vegetation. In the past 40 years, the area of net primary productivity (NPP), evapotranspiration (ET), and WUE showing an upward trend accounted for 85.85 %, 63.66 %, and 83.88 % of the total area of the country, respectively. Although ET also showed an increasing trend nationwide, the increase of NPP was more obvious; (2) The control experiment showed that WUE showed a significant increase trend in arid and semi-arid areas of Northwest China with the increase of CO2 concentration, while SWC showed a significant drying trend, but both WUE and SWC showed an increasing trend in humid areas. The sensitivity of WUE to SWC was enhanced in arid and semi-arid areas, and the effect of soil drought was partially offset by the increase of WUE; (3) Future climate projections also indicated that the CO2 fertilization effect will contribute to an increase in WUE while causing drier soil moisture conditions in the arid and semi-arid regions. Especially under the SSP5-8.5 scenario, CO2 fertilization in Northwest China contributed more than 14 % to WUE from 2015 to 2060, while the impact on SWC depletion exceeded 3 %. This highlights the potential implications of rising atmospheric CO2 concentration, as it may promote a significant rise in WUE and exacerbate the drying of soil moisture in these areas. These findings emphasize the need for careful attention and consideration in managing water resources in arid and semi-arid regions in the face of future climate change.

Quantifying the Impact of Coal Mining on Underground Water in Arid and Semi-Arid Area: A Case Study of the New Shanghai No. 1 Coal Mine, Ordos Basin, China

The new Shanghai No. 1 Coal Mine is located in arid and semiarid area of northwest China, which is characterized by scarce rainfall, intense evaporation, and limited water resources. High-intensity coal mining has caused severe damage to groundwater resources. The Baotashan sandstone aquifer of the Jurassic system has abundant water resources, and they are stored in the floor strata of mining coal seams. This poses the risk of high-pressure build-up and water inrush hazards during the mining of coal. To avoid these, the Baotashan sandstone aquifer needs to be drained and depressurized, which can result in a huge waste of water resources. Thus, taking the New Shanghai No. 1 Coal Mine as the basis for the case study, the impact of coal mining on the underground water resources was quantified. Large-scale water release tests were performed under the shaft to determine the hydrogeological properties of the Baotashan sandstone aquifer and a three-dimensional numerical model of the groundwater system was established. The dynamic phenomenon of water drainage was simulated and the drained water discharge was predicted under the condition of safe mining.

Nitrogen inhibitors improve soil ecosystem multifunctionality by enhancing soil quality and alleviating microbial nitrogen limitation

Soil quality (SQI) is a comprehensive indicator reflecting the agricultural productivity of soil, and soil ecosystem multifunctionality (performing multiple functions simultaneously; EMF) can reflect complex biogeochemical processes. However, the effects of enhanced efficiency nitrogen fertilizers (EENFs; urease inhibitors (NBPT), nitrification inhibitors (DCD), and coated controlled-release urea (RCN)) application on the SQI and soil EMF and their relationships are still unclear. Therefore, we conducted a field experiment to study the effects of different EENFs on the SQI, enzyme stoichiometry and soil EMF in semiarid areas of Northwest China (Gansu, Ningxia, Shaanxi, Shanxi). Across the four study sites, DCD and NBPT increased SQI by 7.61–16.80 % and 2.61 %–23.20 % compared to mineral fertilizer, respectively. N fertilizer application (N200 and EENFs) alleviated microbial N limitation, and EENFs alleviated microbial N and C limitations to a greater extent in Gansu and Shanxi. Moreover, nitrogen inhibitors (Nis; DCD and NBPT) improved the soil EMF to a greater extent than N200 and RCN, DCD increased by 205.82–340.00 % and 145.00–215.47 % in Gansu and Shanxi, respectively; NBPT increased by 332.75–778.59 % and 364.44–929.62 % in Ningxia and Shanxi, respectively. A random forest model showed that the microbial biomass carbon (MBC), microbial biomass nitrogen (MBN) and soil water content (SWC) of the SQI factors were the main driving forces of soil EMF. Moreover, SQI improvement could alleviate microbial C and N limitations and promote the improvement of soil EMF. It is worth noting that soil EMF was mainly affected by microbial N limitation rather than C limitation. Overall, NIs application is an effective way to improve the SQI and soil EMF in the semiarid region of Northwest China.

Soil water depletion patterns in rainfed apple orchards and wheat fields.

Agricultural production in the Weibei rainfed highland, Northwest China, is challenged by severe drought and water shortages. While the land use pattern has shifted gradually from crop production to orchard farming in Weibei, little is known about the influence of fruit industry development on regional water resources and the rationality of planting orchards. Here, we characterized soil water depletion patterns in rainfed orchards and farmlands to evaluate the occurrence of soil desiccation under land use conversion from farmlands to orchards in Weibei. Soil moisture dynamics were monitored in the 0-150cm soil profiles of different aged Red Fuji apple orchards (young: 7 years, mature: 13 years, old: 22 years) and long-term cultivated winter wheat fields. We measured soil moisture content by oven-drying method in the middle of each month during the growing season of apple trees (March-September 2019). The over-depletion and depletion of soil water were analyzed to evaluate water stress and differential water depletion by distinct vegetation, respectively. The soil desiccation index was used to determine the occurrence of dry soil layers. Water stress was only observed at the 0-70-cm soil depths in the old orchards (mid-June) and farmlands (mid-May-mid-July). Water depletion took place at deeper depths for longer periods in the older orchards than in the younger orchards. Soil desiccation was absent in the young orchards, with mild desiccation at the 0-80-cm soil depths in the mature and old orchards in mid-June. The desiccation intensity was mild at the 0-60-cm soil depths in mid-April-mid-May, intense at the 0-150-cm soil depths in mid-June, and moderate at the 20-150-cm soil depths in mid-July. Results of this study demonstrate the mitigation of water stress and soil desiccation following conversion from wheat fields to apple orchards, which verifies the rationality of planting orchards in the rainfed highland area. Our findings provide strong support for developing a novel model of agro-industrial development, ecological construction, and sustainable economy in the vast arid and semi-arid areas of Northwest China.

Inversion of soil moisture and its feedback on ecological restoration in arid and semi-arid areas of northwest China

Soil moisture (SM) plays an important role in regulating the global water cycle, especially in arid areas, and is one of the main indicators of ecological environmental health. Although traditional methods can accurately measure SM at a single sample site, they are limited in large-scale and dynamic SM monitoring. Therefore, we used the Landsat images as the data source and the soil adjusted vegetation index (SAVI) to build the adjusted SAVI (aSAVI) index by modifying the soil adjustment parameter [...]

Temporal and spatial variation characteristics of vegetation coverage and quantitative analysis of its potential driving forces in the Qilian Mountains, China, 2000–2020

• The proportion of vegetation improvement area in QLMs reached 65.06% in the past 21 years, while 52% of the area will be continuously improved in the future. • The distribution of the NDVI in the QLMs maintained a high spatial agglomeration. • Annual sunshine duration is the main meteorological factor affecting vegetation change in Qilian Mountains. • The interaction between different driving factors can improve the explanatory power of vegetation changes compared with a single driving factor. Vegetation is an important indicator reflecting ecological environment stability, and monitoring vegetation change and understanding its potential driving force have important guiding significance for the adjustment and implementation of ecological restoration measures. As an ecological security barrier in northwest China, the Qilian Mountains (QLMs) play an important role in promoting the green development of social and economic development. Currently, the comprehensive driving effects of natural and anthropogenic factors on vegetation change in the QLMs are not clear. Based on the normalized difference vegetation index (NDVI), the spatiotemporal characteristics and trend changes in vegetation in the QLMs were systematically analyzed from 2000 to 2020 in this paper. The effects of natural and anthropogenic driving factors on vegetation change were explored using a geographic detector (GeoDetector). The results showed that the vegetation has improved continuously in the past 21 years, but the overall vegetation coverage was still low. The vegetation distribution was highly clustered, with a decreasing trend from east to west. Annual sunshine duration ( q statistic = 0.3347) and distance to the rivers ( q statistic = 0.2649) had the greatest explanatory power for vegetation change, while slope, aspect, and landform type had the least explanatory power. The interaction between elevation and sunshine duration, temperature and precipitation, temperature and sunshine duration, elevation and precipitation had the most explanatory power for vegetation change. Finally, we determined the ranges or categories of driving factors that were most suitable for vegetation growth by using a risk detector. The results of this study can help us further understand the potential driving mechanism of vegetation coverage variation in the QLMs and provide theoretical guidance for relevant managers to formulate ecological restoration measures and land management policies in the next step. It is of great significance to maintain the stability of the fragile ecological environment and prevent land degradation in arid and semiarid areas of Northwest China.

The Impact of Insect-Proof Screen on Microclimate, Reference Evapotranspiration and Growth of Chinese Flowering Cabbage in Arid and Semi-Arid Region

Despite the steadily increasing area under protected agriculture there is a current lack of knowledge about the effects of the insect-proof screen (IPS) on microclimate and crop water requirements in arid and semi-arid regions. Field experiments were conducted in two crop cycles in Ningxia of Northwest China to study the impact of IPS on microclimate, reference evapotranspiration (ET0) and growth of Chinese Flowering Cabbage (CFC). The results showed that IPS could appreciably improve the microclimate of the CFC field in the two crop cycles. During the first crop cycle (C1), compared with no insect-proof screen (NIPS) treatment, the total solar radiation and daily wind speed under the IPS treatment were reduced by 5.73% and 88.73%. IPS increased the daily average air humidity, air, and soil temperature during C1 by 11.84%, 15.11% and 10.37%, respectively. Furthermore, the total solar radiation and daily wind speed under the IPS treatment during the second crop cycle (C2) were markedly decreased by 20.45% and 95.73%, respectively. During C2, the daily average air temperature and air humidity under the IPS treatment were increased slightly, whereas the daily average soil temperature was decreased by 4.84%. Compared with NIPS treatment, the ET0 under the IPS treatment during C1 and C2 was decreased by 6.52% and 21.20%, respectively, suggesting it had great water-saving potential when using IPS. The plant height, leaf number and leaf circumference of CFC under the IPS treatment were higher than those under the NIPS treatment. The yield under the IPS treatment was significantly increased by 36.00% and 108.92% in C1 and C2, respectively. Moreover, irrigation water use efficiency (IWUE) was significantly improved under the IPS treatment in the two crop cycles. Therefore, it is concluded that IPS can improve microclimate, reduce ET0, and increase crop yield and IWUE in arid and semi-arid areas of Northwest China.

Distribution of soil available nutrients and their response to environmental factors based on path analysis model in arid and semi-arid area of northwest China

The study on the distribution of soil available nutrients and their response to the natural environment can provide valuable data and theoretical guidance for supporting human agricultural activities, especially in arid and semi-arid area where the ecological environment is extremely fragile. Based on the soil sampling and survey data set, this study established the path analysis model of SANs (soil available nutrients, including ammonium nitrogen (AN), available phosphorus (AP) and available potassium (AK)) with topography, climate and vegetation in order to explore how environmental factors interact to affect the content of SANs. Then, we combined Pearson correlation analysis and statistical analysis to explore the distribution of SANs under different environmental conditions and the response of vegetation growth to climate changes, in order to further reveal the availability of soil nutrients. The results showed that vegetation was the most important direct factor affecting AN and AP, and AK was the most sensitive to climate changes. The indirect effects of topography and climate on SANs were much greater than their direct effects. Elevation largely predicted the change of climate environment, and the regional climate directly controlled the growth of vegetation. These indirect effects strengthened the connection between topography as well as climate factors and SANs. It is worth noting that the response of vegetation to temperature and precipitation had time lag, which would have a certain impact on the content of SANs response to the environmental changes. This study is of great significance for improved understanding of soil nutrients supply and how ecosystems respond to soil nutrients availability in arid and semi-arid area.

The Compression Behavior of Undisturbed and Compacted Loess Under the Controlling of Total Suction and Injected Solutions

Thousands of square kilometers of habitable land have been created on the Loess Plateau in China. In arid and semi-arid area of Northwest China, the mechanical behavior of structural loess is sensitive to water intrusion and human engineering activities. Meanwhile, the higher water salinity in loess and seasonal variation of ambient humidity are common in this area. Due to different physical and mechanical properties of natural and compacted loess, the impacts of ambient humidity and saline water migration on their deformation are still unclear. This paper developed an oedometer test to investigate the compression behavior of natural and compacted loess under environmental humidity (represented by total suction Ψ) and injection water salinity (represented by osmotic suction Ψπ) changing. The results showed that the void ratio variation Δe of compacted loess (the dry density is 1.8 g/m3) under the impact of total suctions (from 14.01 to 146.23 MPa) and salinities of injected solution (0.17 mol/L NaCl, 0.29 mol/L Na2SO4 and distilled water) were under 0.01. The variation of void ratio for undisturbed loess increased about 8 times with 10 times decreasing of total suction, which was corresponding to the increase of relative humidity (RH). In the stage of solution injection, the deformation of undisturbed loess increased with the Ψ-Ψπ increasing, and the differences between different samples reached to nearly 20 times. The mechanism was that the salt inside undisturbed loess would deliquescence when the RH was higher than DRH (Deliquescence Relative Humidity), and the natural structure collapsed. The compression index Cc of samples generally decreased with Ψ-Ψπ, and the compressibility of undisturbed loess was higher. The swelling indices Cs of samples slightly decreased with Ψ-Ψπ, but the variation was not significant. The strain-stress relationships of loess can be well described by Duncan-Chang constitutive model. Interestingly, the difference of initial deformation modulus ΔEs of two loesses, which represented the structural compression under the coupling of total suction and osmotic suction, linearly related to the Ψ-Ψπ. The Δεmax between the structural loess and compacted loess exponential increased with Ψ-Ψπ. In the engineering practice, the humidity and saline water intrusion should be considered in the long-term behavior of loess in shallow layer.

Multisize particulate matter and volatile organic compounds in arid and semiarid areas of Northwest China

To investigate the chemical components, sources, and interactions of particulate matter (PM) and volatile organic compounds (VOCs), a field campaign was implemented during the spring of 2018 in nine cities in northwestern (NW) China. PM was mainly contributed by organic matter and water-soluble inorganic ions (41% for PM10 and approximately 60% for PM2.5 and PM1). Two typical haze patterns were observed: anthropogenic pollution type (AP-type), wherein contributions of sulfate, nitrate, and ammonium (SNA) increased, and dust pollution type (DP-type), wherein contributions of Ca2+ increased and SNA decreased. Source appointment suggested that regional sources contributed close to half to PM2.5 pollution (40% for AP-type and 50% for DP-type). Thus, sources from regional transport are also important for haze and dust pollution. The ranking of VOC concentrations was methanol > acetaldehyde > formic acid + ethanol > acetone. Compared with other cities, there are higher oxygenated VOCs (OVOCs) and lower aromatics in NW China. The relationships between VOCs and PM were discussed. The dominating secondary organic aerosols (SOA) formation potential precursors were C10–aromatics, xylene, and styrene under low–nitrogen oxide (NOx) conditions, and benzene, C10–aromatics, and toluene dominated under high–NOx conditions. The quadratic polynomial was the most suitable fitting model for their correlation, and the results suggested that VOC oxidations explained 6.1–10.8% and 9.9–20.7% of SOA formation under high–NOx and low–NOx conditions, respectively.

气候变化情景下孑遗植物绵刺在中国的潜在地理分布

PDF HTML阅读 XML下载 导出引用 引用提醒 气候变化情景下孑遗植物绵刺在中国的潜在地理分布 DOI: 10.5846/stxb202106111553 作者: 作者单位: 作者简介: 通讯作者: 中图分类号: 基金项目: 国家自然科学基金项目（32060095） Potential changes in the geographical distribution of the relict plant Potaninia mongolica Maxim. in China under climate change scenarios Author: Affiliation: Fund Project: 摘要 | 图/表 | 访问统计 | 参考文献 | 相似文献 | 引证文献 | 资源附件 | 文章评论 摘要:绵刺（Potaninia mongolica Maxim.）为我国西北干旱、半干旱地区孑遗濒危荒漠植物，具有重要的生态作用。预测过去、当代及未来气候变化情景下绵刺植物在中国的潜在地理分布区和迁移路线，将为绵刺的保护利用及种群合理建立提供一定的科学依据。基于绵刺在中国的73个有效分布点和8个环境因子变量，利用MaxEnt模型和ArcGIS软件预测末次间冰期、末次盛冰期、当代及未来绵刺在中国的潜在地理分布变化，综合分析影响绵刺分布的主要环境因子及其适宜范围，并用检验受试者工作特征（ROC）曲线下面积（AUC）评估模型的精确度。结果表明：（1） MaxEnt模型预测精确度极高，受试者工作特征（ROC）曲线下面积（AUC）值为0.988，预测显示当代绵刺主要分布在内蒙古中西部地区（阿拉善地区）、宁夏东北部和西北部、甘肃中东部、新疆中部和西部少量狭长分布区，潜在地理分布的总适生区面积约是51.94×104 km2；（2）影响绵刺潜在地理分布的重要环境因子变量是降雨（最干月降雨量、年均降雨量、最湿月降雨量、最冷季度平均降雨量）和温度（最热月的最高温）；（3）从末次间冰期到末次盛冰期，绵刺不同等级潜在适生区面积大幅度缩小；末次盛冰期到当代，绵刺不同等级潜在适生区面积有所增加，但未恢复到末次间冰期面积；未来四种气候情景下，绵刺潜在适生区面积除未来2070年典型浓度路径（RCP8.5）情景下少量减少外，其他三个气候情景（2050年RCP4.5、2050年RCP8.5和2070年RCP4.5）均增加，但高适生区和中适生区面积均减少，低适生区面积大幅增加，且绵刺分布中心有向西南迁移的趋势。 Abstract:Potaninia mongolica Maxim. is a relict and endangered desert plant in arid and semi-arid areas of Northwest China, which plays an important ecological role. Predicting the potential geographical distribution areas and migration routes of Potaninia in China under climate change scenarios in the past, contemporary and future will provide a certain scientific basis for the protection and utilization of Potaninia and the reasonable establishment of populations. This study was based on 73 effective distribution sites and 8 environmental factor variables of P. mongolica in China, The MaxEnt model and ArcGIS software were used to simulate the potential distribution of P. mongolica in the Last Interglacial, the Last Glacial Maximum, the current and the future. Comprehensive analysis of the main environmental factors affecting the distribution of P. mongolica and its suitablerange, and the response curve was used to determine the suitable range of environmental factor variables. The accuracy of model was tested and evaluated by area under the curve (AUC) of the test subject working characteristic (ROC).The results showed that (1) the prediction accuracy of the Maxent model is extremely high, area under the curve (AUC) of the test subject working characteristic (ROC) is 0.988. The prediction shows that current P. mongolica is mainly located in the central and western regions of Inner Mongolia (Alashan Region), northeastern and northwestern Ningxia, Central and eastern Gansu, a small number of narrow and long distributions in Central and western Xinjiang. The total suitable area of the potentially geographical distribution of P. mongolica is about 51.94×104 km2. (2) The main environmental factor variables affecting the potential geographical distribution of P. mongolica are precipitation (the driest monthly precipitation、annual average precipitation、the wettest monthly precipitation and coldest quarter average precipitation) and temperature (hottest monthly highest temperature). (3) From the Last Interglacial to the Last Glacial Maximum, the suitable area of potentially geographical distribution of P. mongolica was greatly reduced; From the Last Glacial Maximum to the current,the suitable area of potentially geographical distribution of P. mongolica was increased, but did not recovered;Under the four future climate scenarios, the suitable area of potentially geographical distribution of P.mongolica increase under the condition of RCP4.5 and RCP8.5 in 2050 and RCP4.5 in 2070, which was reduced slightly under the condition of RCP8.5 in 2070. But the most and moderately suitable areas decreased, while the lowly suitable areas increased significantly. Furthermore, the distribution center of P. mongolica tended to migrate to the southwest. 参考文献 相似文献 引证文献

What is the past, present, and future of scientific research on the Yellow River Basin? —A bibliometric analysis

China's Yellow River Basin (YRB) has large watershed but scarce water resources. More importantly, most parts of the YRB are located in semi-arid areas of Northwest China, where the ecology and environments are fragile. So, ecological restoration and agricultural production always are the key research topics of the YRB. However, the specific research interest of YRB changed over time and was always closely related to the implementation of government policies. Hence, we conducted a comprehensive analysis of YRB's research topics based on the methods of bibliometrics. The results showed that the number of papers about YRB’s research experienced a change from slowly increasing (1998–2010, 83 papers) to rapidly increasing (2011–2015, 128 papers), and then to exponentially rising (2016–2020, 369 papers). Secondly, the main research fields of the YRB included farming, crops, water, soil, environment, and etc. The journal of Agriculture Water Management had the highest global total citations and H-index, even local cited references were the highest among all of the reference papers about the YRB. Through summarizing the most cited papers and references, we found the most important research hotspots about the YRB were: the impacts of climate change and human activities on the amount of sediment in the YRB, the management of soil erosion and vegetation restoration in the YRB, and the relationship between crops and environment and management in the Loess Plateau of China. In addition, “Loess Plateau” was the most frequent keyword in the past ten years and the popularity of “climate change” rose sharply in the past five years. For YRB’s research in near future, how to effectively control carbon emissions, greenhouse gas (GHG) emissions, and carbon surplus is becoming an important implication for YRB's agricultural production and ecological restoration in the future. In general, this research is expected to promote a comprehensive and quantitative understanding of the past, present and future of YRB’s research.

The trend towards a warmer and wetter climate observed in arid and semi-arid areas of northwest China from 1959 to 2019

The observed trend towards a warmer and wetter climate in northwest China is a controversial issue lacking sufficient scientific research. Based on monthly meteorological data from 201 weather stations in northwest China and surrounding regions from 1959 to 2019, we calculated potential evapotranspiration using Penman-Monteith (PM) equation. By analyzing the spatial–temporal variations in temperature and precipitation and by studying changing drought trends, we systematically explored the climate trends in northwest China over the past 60 years. Our findings include: (1) From 1959 to 2019, during the growing season, there was a significant upward trend in temperature across northwest China. The most obvious trend, ranged between 0.4 °C–0.6 °C per decade, was observed in northern Qinghai and northeastern Xinjiang. On a per-month basis, the average temperature increased in all months, with April showing a maximum rate of 0.41 °C per decade. (2) The amount of precipitation in the growing season increased in most regions, especially in western Xinjiang and Qinghai. The areas of reduced precipitation were mainly concentrated in the south of Gansu and Ningxia, the west of Shaanxi and the northeast of Xinjiang. The average precipitation also increased in all months, with June showing a maximum change rate of 1.8 mm per decade. (3) There were obvious spatial differences in the climate trends in northwest China with the warming shifting from areas of bare land to grassland and the trend towards increased rainfall shifting from grassland to bare land. These effects were most obvious in Xinjiang’s Tarim Basin. (4) From 1959 to 2019, the degree of drought in northwest China significantly decreased in most areas. The areas where drought decreased and precipitation increased were fairly consistent, which produced a strong spatial correlation between them.

Phytoremediation Potential of Four Native Plants in Soils Contaminated with Lead in a Mining Area

Metal pollution in soils is an issue of global concern, and lead (Pb) pollution is considered to be the most serious type. The arid and semi-arid areas of Northwest China are rich in Pb ore resources. In this study, four native crops [wormwood (Artemisia capillaris), dandelion (Taraxacum mongolicum), alfalfa (Medicago sativa), and plantain (Plantago asiatica L.)] that grow naturally around tailings slag in a mining area in Northwest China were selected to screen their ecological restoration impacts on Pb-contaminated soil. In pot experiments, four different metal lead pollution gradients (0, 2, 3, and 5‰ w/w) were set, and crop growth indexes such as plant height, root length, and biomass, together with the changes of soil Pb content in different tissues and organs before and after planting were analyzed. The results showed the difference in the amount of accumulated Pb in relation to the level of Pb content in the soil. It was found that wormwood and plantain have great potential as remediation plants for soil metal lead pollution in the arid and semi-arid lead bearing mining areas of Northwest China.

Soil Organic Carbon Stocks and Its Driving Factors Under Different Land-Use Patterns in Semiarid Grasslands of the Loess Plateau, China

Fencing for grazing exclusion and grazing are common land-use methods in the semi-arid areas of the Loess Plateau in China, which have been widely found to change grassland soil organic carbon (SOC); however empirical studies that evaluated driving factors of soil carbon (C) stocks under the different land use are still weak. In this study, we investigated soil physicochemical and soil respiration (Rs) in the fenced and grazed grassland, to study the soil C stock variations and the main driving mechanism of soil C accumulation. The results showed that bulk density (BD), soil moisture content (SMC), and soil porosity (SP) had no significant difference between fenced and grazed grassland. Fencing increased the SOC, total nitrogen (TN), and C/N ratio, and significantly increased the aboveground biomass (AGB), belowground biomass (BGB), and the amount of soil large macro-aggregates in the topsoil layer (0-10 cm), and the soil stability was improved. Meanwhile, grazing increased soil temperature (ST) and Rs. The soil C stock in the topsoil layer (0-10 cm) of fenced grassland was significantly higher than that of grazed grassland. The soil C/N ratio, BD, and MWD explained large proportions of the variations in soil C stocks. Our results indicate that fencing can improve the stability of soil structure, and reduce Rs, then increase soil C stocks, which is an effective way to improve soil C stocks of grassland ecological in semi-arid areas of northwest China.

Effects of Cumin/Maize Intercropping on Crop Productivity, Interspecific Interaction and Water Use Efficiency in the Semi-arid Area of Northwest China

In the semi-arid areas of Xinjiang in China, the agricultural community is facing long-term challenges in improving crop productivity and economic profits. A potential way to improve crop productivity is by intercropping food crops with cash crops. In this two-year field experimental study, we analyzed the advantages of the cumin/maize intercropping system as compared to cultivating them separately from three perspectives: crop growth, interspecific interactions, and water use efficiency. At the experimental site, each cropping systems (i.e., the cumin/maize intercropping system, monocropping cumin system, and monocropping maize system) had three replicates. In the experimental of 2019 and 2020, the three cropping systems showed significant differences in plant height, stem diameter, and leaf area index (LAI). The yields of the cumin/maize intercropping system were both lower than monocropping maize and cumin. However, the cumin/maize intercropping system had a higher land equivalent ratio (LER) than either of the monocropping systems, with a two-year average value of 1.65. Intercropped cumin was less dominant; as shown by aggressivity (Acm; averaging—0.22) and relative crowding coefficient (Rcm; averaging—3.15). In addition, the cumin/maize intercropping system significantly improved the Water equivalent ratio (WER) as compared to the monocropping systems, with a two-year average value of 1.67. Therefore, the cumin/maize intercropping system is a promising agricultural strategy to improve the utilization rate of agricultural resources and economic benefits in Xinjiang.

Signal Intensity of Stem Diameter Variation for the Diagnosis of Drip Irrigation Water Deficit in Grapevine

Precise irrigation management of grapevines in greenhouses requires a reliable method to easily quantify and monitor the grapevine water status to enable effective manipulation of the water stress of the plants. This study describes a study on stem diameter variations of grapevine planted in a greenhouse in the semi-arid area of Northwest China. In order to determine the applicability of signal intensity of stem diameter variation to evaluate the water status of grapevine and soil. The results showed that the relative variation curve of the grapevine stem diameter from the vegetative stage to the fruit expansion stage showed an overall increasing trend. The correlations of MDS (maximum daily shrinkage) and DI (daily increase) with meteorological factors were significant (p < 0.05), and the correlations with SWP, RWC and soil moisture were weak. Although MDS and DI can diagnose grapevine water status in time, SIMDS and SIDI have the advantages of sensitivity and signal intensity compared with other indicators. Compared with MDS and DI, the R2 values of the regression equations of SIMDS and SIDI with SWP and RWC were high, and the correlation reached a very significant level (p < 0.01). Thus, SIMDS and SIDI are more suitable for the diagnosis of grapevine water status. The SIMDS peaked at the fruit expansion stage, reaching 0.957–1.384. The signal-to-noise ratio of SIDI was higher than that of MDS across the three treatments at the vegetative stage. The value and signal-to-noise ratio of SIDI at the flowering stage were similar to those of SIMDS, while the correlation between SIDI and the soil moisture content was higher than that of SIMDS. It can be concluded that that SIDI is suitable as an indicator of water status of grapevine and soil during the vegetative and flowering stages. In addition, the signal-to-noise ratio of SIMDS during the fruit expansion and mature stages was significantly higher than that of SIDI. Therefore, SIMDS is suitable as an indicator of the moisture status of grapevine and soil during the fruit expansion and mature stages. In general, SIMDS and SIDI were very good predictors of the plant water status during the growth stage and their continuous recording offers the promising possibility of their use in automatic irrigation scheduling in grapevine.