Arid Northwest Research Articles

The Biophysical Climate Mitigation Potential of Riparian Forest Ecosystems in Arid Northwest China

The Biophysical Climate Mitigation Potential of Riparian Forest Ecosystems in Arid Northwest China

地下水埋深和季节性干旱对古尔班通古特沙漠南缘梭梭生理和生长的影响

PDF HTML阅读 XML下载 导出引用 引用提醒 地下水埋深和季节性干旱对古尔班通古特沙漠南缘梭梭生理和生长的影响 DOI: 10.5846/stxb202101190206 作者: 作者单位: 作者简介: 通讯作者: 中图分类号: 基金项目: 新疆维吾尔自治区天山青年计划项目（2020Q025）；国家自然科学基金项目（32171874）；新疆维吾尔自治区自然科学基金项目（2019D01A98） Effects of groundwater depth and seasonal drought on the physiology and growth of Haloxylon ammodendron at the southern edge of Gurbantonggut Desert 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:干旱区因降水稀少，地下水成为荒漠植被重要且稳定的水源。选取古尔班通古特沙漠南缘建群种植物梭梭（Haloxylon ammodendron）为研究对象，通过测量不同地下水埋深（3.45、9.08、10.47、13.27 m和15.91 m）下生长季前期和后期同化枝生理生化指标（黎明水势、正午水势、含水量、氯离子、钠离子、脯氨酸和非结构性碳水化合物）和生长与形态特征（生长速率和胡伯尔值），旨在认识荒漠植物对地下水埋深增加和季节性干旱的响应特征和调节适应机制。结果表明：（1）梭梭应对地下水埋深变化的生理调节对策，是采取先降低后升高黎明前同化枝水势、降低新枝形成期同化枝生长速率、增大胡伯尔值和积累非结构性碳水化合物的策略；（2）梭梭应对生长季大气干旱的生理调节对策，是通过降低黎明前同化枝水势、维持较高胡伯尔值、积累钠离子和消耗淀粉抵御季节性干旱；（3）在大气干旱与地下水水文干旱交互作用下，梭梭是采取降低正午同化枝水势、维持较高的同化枝含水量和积累可溶性糖的生态策略。综上所述，梭梭在响应地下水水文干旱和季节性大气干旱的生理特征间存在差异。研究结果丰富了水文和大气干旱对梭梭生理和生长影响的认知，可以为基于地下水资源管理的干旱区荒漠植被保育提供参考。 Abstract:Groundwater is an important and stable water source for desert vegetation due to the scarcity of precipitation in arid areas. Currently, anthropogenic withdraw of groundwater and climatic drought further limits the water availability for phreatophytic vegetation in arid regions and results in the decline of native vegetation. However, how phreatophytic plant response and adaptation to reduced water availability along the groundwater depth gradient are not clear. Haloxylon ammodendron was widely distributed in northwest arid zone of China and played an important role in desertification control. Groundwater was an important water resource for H. ammodendron. The declining groundwater depth has caused the partially decline even death of H. ammodendron in their native distribution area. In this study, we selected H. ammodendron, one of the main constructive species, at the southern edge of Gurbantonggut Desert as the taget species. In order to understand the response characteristics and regulatory adaptation mechanisms of desert plants to increasing groundwater depth and seasonal drought, we measured physiological and biochemical traits (including predawn water potential, midday water potential, water content, sodium ion, chloride ion, proline and non-structural carbohydrates), growth and morphological characteristics (including growth rate and Huber value) of assimilation branches in the early and late growing season under different groundwater depths (3.45, 9.08, 10.47, 13.27 and 15.91 m). The results showed that:(1) H. ammodendron adopted the strategy of first decreasing and then increasing predawn assimilation branch water potential, decreasing assimilation branch growth rate during new branch formation, increasing the Huber value and accumulating non-structural carbohydrates in response to increase in groundwater depth. (2) With the prolonged drought, H. ammodendron reduced predawn assimilation branch water potential, maintained high Huber values, accumulated sodium ions and consumed starch to resist seasonal drought during the growing season. (3) Reducing midday assimilation branch water potential, maintaining high assimilation branch water content and accumulating soluble sugars are ecological strategies in H. ammodendron to acclimate atmospheric and hydrological drought. In summary, there are differences in the physiological characteristics of H. ammodendron in response to groundwater hydrological drought and seasonally atmospheric drought. The results of the study enriched the knowledge of the effects of hydrological and atmospheric drought on the physiology and growth of H. ammodendron, and provided a reference for the conservation of desert vegetation based on groundwater resource management in arid areas. 参考文献 相似文献 引证文献

Influence of Acid Mine Drainage Leakage from Tailings Ponds on the Soil Quality of Desert Steppe in the Northwest Arid Region

Influence of Acid Mine Drainage Leakage from Tailings Ponds on the Soil Quality of Desert Steppe in the Northwest Arid Region

Influence of Acid Mine Drainage Leakage from Tailings Ponds on the Soil Quality of Desert Steppe in the Northwest Arid Region

Influence of Acid Mine Drainage Leakage from Tailings Ponds on the Soil Quality of Desert Steppe in the Northwest Arid Region

Influence of Acid Mine Drainage Leakage from Tailings Ponds on the Soil Quality of Desert Steppe in the Northwest Arid Region

Influence of Acid Mine Drainage Leakage from Tailings Ponds on the Soil Quality of Desert Steppe in the Northwest Arid Region

Influence of Acid Mine Drainage Leakage from Tailings Ponds on the Soil Quality of Desert Steppe in the Northwest Arid Region

Influence of Acid Mine Drainage Leakage from Tailings Ponds on the Soil Quality of Desert Steppe in the Northwest Arid Region

Estimation of Surface and Near-Surface Air Temperatures in Arid Northwest China Using Landsat Satellite Images

Near-surface air (Ta) and land surface (Ts) temperatures are essential parameters for research in the fields of agriculture, hydrology, and ecological changes, which require accurate datasets with different temporal and spatial resolutions. However, the sparse spatial distribution of meteorological stations in Northwest China may not effectively provide high-precision Ta data. And it is not clear whether it is necessary to improve the accuracy of Ts which has the most influence on Ta. In response to this situation, the main objective of this study is to estimate Ta for Northwest China using multiple linear regression models (MLR) and random forest (RF) algorithms, based on Landsat 8 images and auxiliary data collected from 2014 to 2019. Ts, NDVI (Normalized Difference Vegetation Index), surface albedo, elevation, wind speed, and Julian day were variables to be selected, then used to estimate the daily average Ta after analysis and adjustment. Also, the Radiative Transfer Equation (RTE) method for calculating Ts would be corrected by NDVI (RTE-NDVI). The results show that: 1) The accuracy of the surface temperature (Ts) was improved by using RTE-NDVI; 2) Both MLR and RF models are suitable for estimating Ta in areas with few meteorological stations; 3) Analyzing the temporal and spatial distribution of errors, it is found that the MLR model performs well in spring and summer, and is lower in autumn, and the accuracy is higher in plain areas away from mountains than in mountainous areas and nearby areas. This study shows that through appropriate selection and combination of variables, the accuracy of estimating the pixel-scale Ta from satellite remote sensing data can be improved in the area that has less meteorological data.

Urea Application Rate for Crop Straw Decomposition in Temperate China

Returning straw to the field has become the most important straw utilization method in China. The aim of this research was to study the appropriate amount of nitrogen fertilizer applied when returning the straw of three major crops (wheat, rice, and corn) to the field in areas under low to high yield levels based on the demand of nitrogen for microbial decomposition of straw. Under the condition of returning 100% straw to the field, we developed the formula for calculating the nitrogen application rate and estimated the urea application rate for the three major grain crops. The results showed that returning straws of wheat, early-season rice, middle-season rice and late-season rice, and corn to the field with urea application at the rate of about 150 kg/ha, 120～135 kg/ha, 75 kg/ha, and 75～90 kg/ha, respectively, can provide sufficient nitrogen for microbial decomposition. The urea application rate for returning 100% wheat straw to the field in Huang-Huai-Hai region, Middle-Lower Yangtze region, Loess plateau region, and Northwest arid region was 135–230 kg/ha, 110–190 kg/ha, 85–145 kg/ha, and 95–165 kg/ha, respectively. 52.5–98.5 kg/ha of urea was used for 100% early rice straw returning to the field in Middle-Lower Yangtze region and South China. In addition, the urea application rate for 100% middle-late rice straw returning to the field was 95–180 kg/ha, 100–185 kg/ha, 95–175 kg/ha, and 75–140 kg/ha, respectively. The rate of urea application for 100% corn straw returning to the field in Northeast China, Huang-Huai-Hai, Northwest arid region, and Southwest China was 60–135 kg/ha, 50–115 kg/ha, 60–135 kg/ha, and 45–105 kg/ha, respectively. The amount of nitrogen fertilizer required for the total return of crop straw is not only affected by crop straw C : N, yield per unit area, and ratio of grass to grain but also affected by straw returning mode, regional nitrogen application level, and other factors. Therefore, the amount of nitrogen fertilizer should be adjusted according to the type of cropping system, soil, and climatic conditions of the specific location. This substantial N input for stimulating straw decomposition may favor N losses with nitrate leaching and nitrous oxide emissions and hold a potential for soil N eutrophication in the long term if the level is not carefully adjusted to the N requirement of the subsequent crops and changes in soil organic matter levels.

DESERT SOLAR POWER INDIA: A SYSTEMATIC STUDY OF POTENTIAL DEVELOPMENT OF SOLAR POWER IN THE INDIAN DESERT

The deserts of Rajasthan have long been known for their spare beauty and their intense sunshine. Now that sun is being turned into a surge of solar power expansion that may one day power not just Rajasthan but a wide swath of India with clean energy. Rajasthan, with its 300 days a year of sunshine and relatively cheap desert land, has set a goal even more ambitious than Indias. In this years state budget, the newly formed state government announced it hoped to install 25,000 megawatts of solar energy in the state within the next five years, and infrastructure to transmit that power to the national grid. Rajasthan is no newcomer to renewable energy. Since the 1990s, the state has been home to a range of wind energy projects, with about 2,800 megawatts of wind capacity now installed, out of an estimated potential capacity of 5,000 megawatts. Altogether wind power in Rajasthan accounts for about 13 percent of Indias wind energy production. But Rajasthans Great Indian Thar Desert, the test site for Indias first underground explosion of a nuclear weapon 15 years ago, may now help make India a solar power as well. The desert set in Rajasthans largest district Jaisalmer, near the border with Pakistan, it is a place of sand dunes and shrub thickets – but also, increasingly, solar installations that could help change the character of Indias energy development. India committed at the U.N. Framework Convention on Climate Change negotiations in Copenhagen in 2009 to reduce its climate-changing emissions, per unit of GDP, by 20 to 25 percent by 2020, compared to 2005 levels. The country is currently the worlds seventh largest emitter of global warming pollution and the fifth biggest producer of emissions from burning fossil fuels. Sixty-eight percent of those emissions from fossil fuel use come from creating energy for the worlds second most populous country, according to Indias energy ministry. Today the country has 2.28 million megawatts of power generating capacity, and about 12.4 percent of that comes from renewable energy. Of the 2,632 megawatts of solar power now installed in India, Rajasthan so far has only 730 megawatts, putting it in second place behind the state of Gujarat, with 916 megawatts, according to Indias Ministry of New and Renewable Energy. But Rajasthan, Indias largest state and 60 percent covered by sunny desert, is now attracting the worlds interest as a solar hotspot. Around 1 lakh (100,000) square kilometers of barren land is available in the northwest arid belt of the state at cheaper rates that could be utilized for large scale solar projects. The government is formulating the policy to harness the enormous solar potential of the region to meet the countrys growing energy requirements. Besides large solar installations, the government is studying the possibility of grid-connected rooftop solar photovoltaic units for households. The Solar Energy Corporation of India estimates that 130 million homes could potentially be equipped with the units, creating 25,000 megawatts of generating capacity. said Alok, Rajasthans Energy Secretary.

Below-Cloud Evaporation of Precipitation Isotopes over Mountains, Oases, and Deserts in Arid Areas

AbstractAs raindrops fall from the cloud base to the ground, evaporation below those clouds affects the rain’s isotope ratio, reduces precipitation in arid areas, and impacts the local climate. Therefore, in arid areas with scarce water resources and fragile ecological environments, the below-cloud evaporation is an issue of great concern. Based on 406 event-based precipitation samples collected from nine stations in the Shiyang River basin (SRB) in the northwest arid area, global meteorological water line (GMWL) and local meteorological water line (LMWL) are compared, and the Stewart model is used to study the effect of spatial and temporal variation of below-cloud evaporation on isotope values in different geomorphic units at the SRB. Furthermore, factors influencing below-cloud evaporation are analyzed. The results show that 1) the change of d-excess (Δd) in precipitation at the SRB and the residual ratio of raindrop evaporation (f) vary in time and space. With regard to temporal variation, the intensity of below-cloud evaporation is described by summer < autumn < winter < spring. Regarding spatial variation, the below-cloud evaporation in mountain areas is weaker than in oases and deserts. The intensity of below-cloud evaporation in mountain areas increases with decreasing altitude, and the below-cloud evaporation in oasis and desert areas is affected by local climatic conditions. 2) Below-cloud evaporation is also affected by local transpiration evaporation, especially around reservoirs. Reservoirs increase the relative humidity of the air nearby, weakening below-cloud evaporation. This study deepens our understanding of the water cycle process in arid areas.

Response of NDVI of Natural Vegetation to Climate Changes and Drought in China

Temporal and spatial changes in vegetation and their influencing factors are of great significance for the assessment of climate change and sustainable development of ecosystems. This study applied the Asymmetric Gaussians (AG) fitting method, Mann-Kendall test, and correlation analysis to the Global Inventory Monitoring and Modeling System (GIMMS) third-generation Normalized Difference Vegetation Index and gridded climate and drought data for 1982–2015. The temporal and spatial changes to NDVI for natural grassland and forest during the growing season were analyzed. Relationships among NDVI, climate change, and droughts were also analyzed to reveal the influence of vegetation change. The results showed that: (1) Land use/cover change (LUCC) in China was mainly represented by increases in agricultural land (Agrl) and urban and rural land (Uril), and decreases in unutilized land (Bald), grassland, forest, and permanent glacier and snow (Snga). The increase in agricultural land was mainly distributed in the western northwest arid area (WNW) and northern North China (NNC), whereas regions with severe human activities such as southern South China (SNC), western South China (WSC), and eastern South China (ESC) showed significant decreases in agricultural land due to conversion to urban and rural land. (2) The start of the growing season (SOS) was advanced in WNW, SNC, WSC, and ESC, and the end of growing season (EOS) was delayed in WNW, NNC, and SNC. The growing season length (GSL) of natural vegetation in China has been extended by eight days over the last 34 years. However, the phenology of the Qinghai-Tibet Plateau (TP) was opposite to that of the other regions and the GSL showed an insignificant decreasing trend. (3) The NDVI increased significantly, particularly in the SNC, WSC, ESC, and the grassland of the WNW. Precipitation was found to mainly control the growth of vegetation in the arid and semi-arid regions of northwest China (WNW and ENW), and precipitation had a much greater impact on grassland than on forests. Temperature had an impact on the growth of vegetation throughout China, particularly in SNC, ESC, and WSC. (4) The Standardized Precipitation Evapotranspiration Index (SPEI) showed a downward trend, indicating an aridification trend in China, particularly in ENW, NNC, and WNW. Similar to precipitation, the main areas affected by drought were WNW and ENW and grassland was found to be more sensitive to drought than forest. The results of this study are of great significance for predicting the response of ecosystem productivity to climate change under future climate change scenarios.

Projecting Future Vegetation Change for Northeast China Using CMIP6 Model

Northeast China lies in the transition zone from the humid monsoonal to the arid continental climate, with diverse ecosystems and agricultural land highly susceptible to climate change. This region has experienced significant greening in the past three decades, but future trends remain uncertain. In this study, we provide a quantitative assessment of how vegetation, indicated by the leaf area index (LAI), will change in this region in response to future climate change. Based on the output of eleven CMIP6 global climates, Northeast China is likely to get warmer and wetter in the future, corresponding to an increase in regional LAI. Under the medium emissions scenario (SSP245), the average LAI is expected to increase by 0.27 for the mid-century (2041–2070) and 0.39 for the late century (2071–2100). Under the high emissions scenario (SSP585), the increase is 0.40 for the mid-century and 0.70 for the late century, respectively. Despite the increase in the regional mean, the LAI trend shows significant spatial heterogeneity, with likely decreases for the arid northwest and some sandy fields in this region. Therefore, climate change could pose additional challenges for long-term ecological and economic sustainability. Our findings could provide useful information to local decision makers for developing effective sustainable land management strategies in Northeast China.

Estimation of Evapotranspiration and Its Components across China Based on a Modified Priestley–Taylor Algorithm Using Monthly Multi-Layer Soil Moisture Data

Although soil moisture (SM) is an important constraint factor of evapotranspiration (ET), the majority of the satellite-driven ET models do not include SM observations, especially the SM at different depths, since its spatial and temporal distribution is difficult to obtain. Based on monthly three-layer SM data at a 0.25° spatial resolution determined from multi-sources, we updated the original Priestley Taylor–Jet Propulsion Laboratory (PT-JPL) algorithm to the Priestley Taylor–Soil Moisture Evapotranspiration (PT-SM ET) algorithm by incorporating SM control into soil evaporation (Es) and canopy transpiration (T). Both algorithms were evaluated using 17 eddy covariance towers across different biomes of China. The PT-SM ET model shows increased R2, NSE and reduced RMSE, Bias, with more improvements occurring in water-limited regions. SM incorporation into T enhanced ET estimates by increasing R2 and NSE by 4% and 18%, respectively, and RMSE and Bias were respectively reduced by 34% and 7 mm. Moreover, we applied the two ET algorithms to the whole of China and found larger increases in T and Es in the central, northeastern, and southern regions of China when using the PT-SM algorithm compared with the original algorithm. Additionally, the estimated mean annual ET increased from the northwest to the southeast. The SM constraint resulted in higher transpiration estimate and lower evaporation estimate. Es was greatest in the northwest arid region, interception was a large fraction in some rainforests, and T was dominant in most other regions. Further improvements in the estimation of ET components at high spatial and temporal resolution are likely to lead to a better understanding of the water movement through the soil–plant–atmosphere continuum.

Understanding the Mechanisms of Summer Extreme Precipitation Events in Xinjiang of Arid Northwest China

AbstractAs one of the aridest regions in the mid‐latitudes, arid Northwest China (ANC) has scarce water resources year‐round, its annual total precipitation is mainly contributed by summer extreme precipitation events, which may also cause disastrous flash floods. However, the physical mechanism and climatic features of extreme precipitation events in ANC are not fully understood and warrant in‐depth investigations. Taking Xinjiang as an example, this study investigates the underlying mechanisms and long‐term trend of extreme precipitation events in ANC during 1961–2019 using observational and reanalysis data sets. Results suggest that summer extreme precipitation events in ANC are characterized by a zonal wave pattern with the deepening of the western Siberian trough, central Asian high, and Mongolian high. Under the effects of the zonal wave pattern, the westerly and the easterly airflows anomalously intensify and converge in ANC, transporting a large amount of water vapor from the Arctic Ocean, the Caspian Sea, the Aral Sea, the Arabian Sea, and eastern China to ANC. Meanwhile, a deep anomalous cyclone center induced by the deep wave pattern appears over ANC, thus providing favorable conditions for the occurrence of extreme precipitation events in ANC. Over the long‐term period, total summer precipitation and the frequency of extreme precipitation events in ANC show significant increasing trends, indicating that summer climate in ANC is becoming more humid, and extreme precipitation events are becoming more frequent. These findings provide scientific insights for understanding the formation mechanism of summer extreme precipitation events and mitigating the corresponding disasters in arid regions.

Quantifying the relative contribution of climate variability and human activities impacts on baseflow dynamics in the Tarim River Basin, Northwest China

Study regionTarim River Basin (TRB)- the largest inland basin of China and essential part of the water supply to northwest arid region of China. Study focusInformation on baseflow dynamics and attributions is needed to develop sustainable water management strategies in cold and arid regions. The study separates baseflow with multiple separation methods, and analyzes the regional patterns and changes of baseflow and baseflow index (BFI). Furthermore, we quantitatively evaluate response of baseflow and BFI to climate variabilities and anthropogenic activities through the concept of climate elasticity under the water-energy balance framework. The purpose is to understand the dynamics and attributions of baseflow in the TRB. New hydrological insights for the regionWe found that climate variabilities play leading roles in the increase of baseflow in the headstreams. Among them, temperature is decisive climatic factor controlling baseflow variation. Changes of potential evapotranspiration have significant negative impacts on baseflow variations across the TRB. Besides, precipitation and inflow possessed great positive impacts on baseflow increasing. However, the decline across the basin BFI is found with increasing precipitation and inflow, indicating the increasing precipitation and inflow can promote more surface runoff, particularly in late spring and early summer. Attribution analysis indicates that climate change and human activities (e.g., engineering construction, agricultural activities, etc.) have the opposite impact on baseflow variation. Human activities are the main factors reducing baseflow in the mainstreams. Furthermore, the combined effects of climate change and human activities have caused the decline of BFI.

Water-carbon relationships and variations from the canopy to ecosystem scale in a sparse vineyard in the northwest China

Ecosystem water and carbon fluxes are inherently coupled through stomata. A deep understanding of the water-carbon relationship contributes to model development, water and carbon management, and decision-making. This study investigated the pattern of the water-carbon relationship, the difference in water-carbon relationship at both the ecosystem and canopy scales in different growth stages in a vineyard in arid northwest China for three consecutive years (2017–2019) via an eddy covariance system combined with sap flow sensors and microlysimeters. The results showed that the significant increase in soil evaporation (E) controlled by high surface soil water content (SWC, 10 cm) led to a transformation from a linear to nonlinear relationship between daily water and carbon fluxes from the canopy to ecosystem scale. Moreover, the water-carbon relationship varied with growth stages at both the ecosystem and canopy scales. The water-carbon coupling strength (the determination coefficient of the water-carbon correlation) was higher in the early and late growing seasons than in the middle growing season. Additionally, water use efficiency (WUE) was more dependent on the carbon flux in the early and late growing seasons. However, WUE was mainly determined by water flux in the middle growing season, and the control of E surpassed that of transpiration (T) in ecosystem WUE. The results of the structural equation model (SEM) indicated that canopy development in the early and late growing seasons together with the water and radiation conditions in the middle growing season played vital roles in controlling the water-carbon relationship. This study highlighted the critical role of SWC in controlling the water-carbon relationship and the differences in the coupling in various growth stages of an irrigated vineyard in the arid northwest China.

Drought monitoring in arid and semi-arid region based on multi-satellite datasets in northwest, China.

Drought is a complex natural disaster affected by multiple climate factors and underlying surface. In recent years, drought monitoring indices of remote sensing have been widely applied to monitor drought in a certain region or global. However, some remote sensing drought monitoring indices do not consider the drought-causing factors enough to reflect the comprehensive drought situation of a region fully. In this paper, a new remote sensing drought monitoring index, called Remote Sensing Drought Evaluation Index (RSDEI), was constructed by combining Vegetation Condition Index (VCI), Temperature Condition Index (TCI), Precipitation Condition Index (PCI), and Soil Moisture Condition Index (SMCI) using the spatial principal component analysis (SPCA) method. The reasonableness of RSDEI was test and verified using Net Primary Productivity (NPP), Standardized Precipitation Evapotranspiration Index (SPEI), and unit area crop yield. The RSDEI was also applied to the drought condition monitoring of the northwest arid and semi-arid region from 2001 to 2019.The result demonstrated that the results showed that the RSDEI had a high correlation coefficient with SPEI-12 (R=0.85, p<0.01). It is concluded that the correlation coefficient between RSDEI and NPP is 0.74 at 95% confidence level, which indicates that RSDEI and NPP have a strong correlation. Then, the correlation between RSDEI and crop yield per unit area is 0.89. The results of RSDEI showed that the drought in northwest China started in May and lasted in September from 2001 to 2019. The lowest value of RSDEI appeared in May, which inflected the significant difference of drought level in different month in northwest China. The result of CV (coefficient of variation) showed that the drought variation in the study area had a stable low fluctuation condition as a whole, in the northwest and northeast of study area, which indicated that the changes of drought were different in the past 19 years. The Hurst exponent analysis showed that the area with the positive evolution of Hurst index (0.5<H<1) is 1,845,046.669 km2,which accounts for 75.9% of the total area, while the area with reverse evolution characteristics (H<0.5) accounts for 24.1% of the total area. The result obtained above reflected that the drought changes in most regions are better than that in the past 19 years. The trend gradually changes from drought to humid.

Estimation of Crop Water Requirement Based on Planting Structure Extraction from Multi-Temporal MODIS EVI

Estimation of crop water requirement (CWR) is key to the rational water use and agricultural water conservation in arid regions. Using remote sensing data to obtain long-term CWR over large areas helps water resources management in water-scarce areas. This study, taking the Kaidu-Kongqi River basin in arid northwest China as the study area, investigated the feasibility of synergistically using phenological characteristics, Savitzky-Golay filter, harmonic analysis and decision tree to extract crop planting structures (CPS) from MODIS EVI, and meanwhile analyzed the spatiotemporal variation in the estimated CWR. The results show that the integrated method for CPS identification and extraction is feasible and reliable with the classification accuracy over 80%. The mid-season stage requires the most water and cash crops need more water than cereal crops. Summer accounts for 69% the total growing season water use. The significant increase in the area of high water demand crops such as cotton raised the total CWR of the basin surging from 14.91× 108m3 in 2000 to 34.92×108m3 in 2017. The spatial distribution of CWR was more related to crop types and area than to climatic conditions. Controlling the expansion of arable land and optimizing the agricultural planting structure remain important tasks for the sustainable management of water resources in the basin.

Effects of mulching with crushed wheat straw padding and plastic film on sunflower emergence, yield, and yield components under different irrigation intensity in the northwest arid regions, China

Crops in the northwest arid region of China frequently suffer from low emergence and poor yield due to high water deficit. Mulching is an important approach to reduce irrigation amount while increasing productivity but faces the challenge of ecological adaptability in this region. A field experiment was carried out in the three growing seasons from 2011 to 2013 to study the effects of mulching with crushed wheat straw padding and plastic film on sunflower seed emergence and yield under different irrigation intensities. A two-factor (mulching and irrigation intensity) completely randomized block design was applied, resulting in a total of 12 treatments repeated three times. Mulching treatments include zero mulch (N), straw mulching at the beginning of the experiment (S), plastic film mulching when sowing (F; a commonly used mulching by local farmers), and double mulching with plastic film on the crushed wheat straw layer (SF). Irrigation intensity includes high (H = 900 m3·ha−1), medium (M = 750 m3·ha−1), and low (L = 600 m3·ha−1). Results showed that all mulching treatments promoted the early emergence of seedlings compared with N, with SF and F performing better than the rest. SF was the best-performing mulching approach in this study, and it had significantly improved sunflower yield and yield components compared with other treatments. In SF, medium irrigation level had significantly increased sunflower 100-seed weight. Therefore, SF with M irrigation level showed the most positive effect on sunflower production, and it is now the recommended agronomic solution for sunflower production in the northwest arid regions and, potentially, other irrigated areas with similar ecological conditions.

Using geochemistry and environmental tracers to study shallow unconfined aquifer recharge and mineralization processes in the Yinchuan Plain, arid Northwest China

Abstract Irrigation water extracted from the Yellow River plays a key role in water resource management in the Yinchuan Plain (YCP), arid Northwest China. Investigating the soluble matters (ion and gas) of groundwater provides information to explain the unconfined shallow aquifer recharge and groundwater mineralization processes after long-term flood irrigation activity. Environmental tracing with the elements, 2H, 18O, 3H, and CFCs, combining geochemistry using major ions and selected trace elements, was conducted for 43 water samples from September to October 2019 in the YCP. Evaporite and silicate weathering dominate the shallow unconfined groundwater geochemical compositions. Water–rock interactions control the mineralization characteristics regularly along the groundwater flow paths from the southwest toward the northeast. Stable isotopes suggest that Yellow River water and precipitation in winter and/or from Helan Mountainous area are the main recharge sources. The shallow unconfined aquifer mixed young (post-1940) and old (pre-1940) water with young water ratios from 53.1 to 73.5% inferred from the CFC concentrations and 3H activities. Water reinfiltrations extracted from the Yellow River and from the old groundwater are confirmed. Lateral flow recharge for the shallow unconfined aquifer is less indistinctive than that from the water re-infiltration in the plain areas.