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Frontiers of Earth Science

, Volume 13 Issue 2

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RESEARCH ARTICLE
Chemical and minero-petrographical changes on granulite rocks affected by weathering processes
Carmine APOLLARO, Francesco PERRI, Emilia LE PERA, Ilaria FUOCO, Teresa CRITELLI
Front. Earth Sci.. 2019, 13 (2): 247-261.  https://doi.org/10.1007/s11707-018-0745-5
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The purpose of this work is to study the weathering processes of the granulite rocks of the Serre Massif (southern Calabria, Italy) using a multidisciplinary approach based on field studies, geochemical modeling, and minero-petrographical analyses. The granulite rocks are plagioclase-rich with minor amphibole, clinopyroxene, orthopyroxene, biotite, and garnet and their texture are coarse-grained. The reaction path modeling was performed to simulate the evolution of groundwaters upon interaction with local granulite by means of the software package EQ3/6, version 8.0a. Simulations were performed in kinetic (time) mode under a closed system at a constant temperature of 11.5°C, (which reproduces the average temperature of local area) and fixing the fugacity of CO2 at 10−2.34 bar (mean value). During the most advanced stage of weathering the main mineralogical changes are: partial destruction and transformation of biotite and plagioclase associated with neoformation of ferruginous products and secondary clay minerals producing a change in the origin rock fabric. The secondary solid phases observed during the geochemical modeling (kaolinite, vermiculite and ferrihydrite) are similar to those found in this natural system. Thus, the soil-like material mainly characterized by mostly sand to gravel grain-size fractions is the final result of the weathering processes.

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Evolution model of a modern delta fed by a seasonal river in Daihai Lake, North China: determined from ground-penetrating radar and trenches
Beibei LIU, Chengpeng TAN, Xinghe YU, Xin SHAN, Shunli LI
Front. Earth Sci.. 2019, 13 (2): 262-276.  https://doi.org/10.1007/s11707-018-0740-x
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While deltas fed by seasonal rivers are common in modern sedimentary environments, their characteristics remain unclear as compared to those fed by perennial rivers. This study identifies a small delta discharged by a seasonal stream flowing into Daihai Lake, in northern China, which is driven by ephemeral and high-energy flood events. Detailed 3D facies architecture was analyzed using ground-penetrating radar (GPR) and sedimentary logs from outcrop and trenches. Four types of radar surfaces, including truncations of underlying inclined strata, weak reflections, and depositional surface of downlap and onlap, were identified. Six radar facies (high-angle oblique-tangential, low-angle subparallel, gently plane parallel, plane-parallel, chaotic, and continuous strong reflection) were identified based on distinctive reflections, including amplitude, continuity, dip, and termination patterns. Five depositional units (Unit A to E) were documented from proximal to distal delta. Seasonal discharge signatures include significant grain-size decrease over short distance, abundant Froude supercritical flow sedimentary structures, poorly developed barforms, and small-scale scour and fill structures. Records of lake-level and sediment budget were evaluated over the past 60 years. In highstand stage (1960–1980), amalgamated channel (Units A and B), and delta front (Unit C) were deposited. In slope stage (1980–1996), the lower deposits (Units A, B, C) were eroded by Unit D with a distinct truncation surface. In lowstand stage, most eroded sediments bypassed the incised channel and accumulated in the distal part, in which a new depositional unit was formed (Unit E). The model demonstrates that deltas fed by seasonal rivers tend to accumulate large amounts of sediments carried by high magnitude floods within short periods.

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Bias characterization of ATMS low-level channels under clear-sky and cloudy conditions
Qi LI, Xiaolei ZOU
Front. Earth Sci.. 2019, 13 (2): 277-289.  https://doi.org/10.1007/s11707-019-0750-3
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The Advanced Technology Microwave Sounder (ATMS) onboard the Suomi National Polar-Orbiting Partnership satellite is a cross-track scanning instrument containing 22 sounding channels in total. In this study, the bias characteristics of channels 1–6, which could have significant cloud contamination in heavy precipitation, are first analyzed based on the differences between ATMS observations (O) and model simulations (B) under clear-sky conditions over oceans. Latitudinal dependencies of the biases of window channels 1–3 are greater than those of channels 4–6. Biases of all nadir-only observations examined in different latitudinal bands [μ1(ϕ)] are positive and no more than 7.0 K. Biases at higher latitudes are larger. Channels 1–5 have a generally symmetric scan bias pattern [μ2(α)]. The global distributions of brightness temperature differences after subtracting the biases, i.e., O-B-m1(ϕ)-μ2(α), for channels 3–6 spatially match the liquid water path distributions. Excluding ice-affected observations, channel 3–6 O-B differences systematically increase as the liquid water path increases under cloudy conditions. Further investigation is needed to apply these findings for ATMS data assimilation under both clear-sky and cloudy conditions.

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The relationships between urban-rural temperature difference and vegetation in eight cities of the Great Plains
Yaoping CUI, Xiangming XIAO, Russell B DOUGHTY, Yaochen QIN, Sujie LIU, Nan LI, Guosong ZHAO, Jinwei DONG
Front. Earth Sci.. 2019, 13 (2): 290-302.  https://doi.org/10.1007/s11707-018-0729-5
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Interpreting the relationship between urban heat island (UHI) and urban vegetation is a basis for understanding the impacts of underlying surfaces on UHI. The calculation of UHI intensity (UHII) requires observations from paired stations in both urban and rural areas. Due to the limited number of paired meteorological stations, many studies have used remotely sensed land surface temperature, but these time-series land surface temperature data are often heavily affected by cloud cover and other factors. These factors, together with the algorithm for inversion of land surface temperature, lead to accuracy problems in detecting the UHII, especially in cities with weak UHII. Based on meteorological observations from the Oklahoma Mesonet, a world-class network, we quantified the UHII and trends in eight cities of the Great Plains, USA, where data from at least one pair of urban and rural meteorological stations were available. We examined the changes and variability in urban temperature, UHII, vegetation condition (as measured by enhanced vegetation index, EVI), and evapotranspiration (ET). We found that both UHI and urban cold islands (UCI) occurred among the eight cities during 2000–2014 (as measured by impervious surface area). Unlike what is generally considered, UHII in only three cities significantly decreased as EVI and ET increased (p<0.1), indicating that the UHI or UCI cannot be completely explained simply from the perspective of the underlying surface. Increased vegetative cover (signaled by EVI) can increase ET, and thereby effectively mitigate the UHI. Each study station clearly showed that the underlying surface or vegetation affects urban-rural temperature, and that these factors should be considered during analysis of the UHI effect over time.

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Effects of sea level rise on storm surge and waves within the Yangtze River Estuary
Yongming SHEN, Gefei DENG, Zhihao XU, Jun TANG
Front. Earth Sci.. 2019, 13 (2): 303-316.  https://doi.org/10.1007/s11707-018-0746-4
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Sea level rise (SLR) can cause water depth increase (WDI) and coastal inundation (CI). By applying the coupled FVCOM+SWAN model, this study investigates the potential impacts of WDI and CI, induced by a 1.0 m SLR, on storm surge and waves within the Yangtze River Estuary. A 1.0 m WDI decreases the maximum storm surge by 0.15 m and increases the maximum significant wave height by 0.35 m. The CI effect size is smaller when compared with WDI. CI decreases the maximum storm surge and significant wave height by 0.04 and 0.07 m, respectively. In the near-shore area, WDI significantly alters the local hydrodynamic environment, thereby stimulating changes in maximum storm surges and wave heights. Low-lying regions are negatively impacted by CI. Conversely, in deep-water areas, the relative change in water depth is minimal and the effect of CI is gradually enhanced. The combined effect of WDI and CI decreases the maximum surge by 0.31 m and increases the maximum significant wave height by 0.21 m. As a result, CI may be neglected when designing deep-water infrastructures. Nonetheless, the complex interactions between adoption and neglect of CI should be simulated to achieve the best seawall flood control standards and design parameters.

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A fast and simple algorithm for calculating flow accumulation matrices from raster digital elevation
Guiyun ZHOU, Hongqiang WEI, Suhua FU
Front. Earth Sci.. 2019, 13 (2): 317-326.  https://doi.org/10.1007/s11707-018-0725-9
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Calculating the flow accumulation matrix is an essential step for many hydrological and topographical analyses. This study gives an overview of the existing algorithms for flow accumulation calculations for single-flow direction matrices. A fast and simple algorithm for calculating flow accumulation matrices is proposed in this study. The algorithm identifies three types of cells in a flow direction matrix: source cells, intersection cells, and interior cells. It traverses all source cells and traces the downstream interior cells of each source cell until an intersection cell is encountered. An intersection cell is treated as an interior cell when its last drainage path is traced and the tracing continues with its downstream cells. Experiments are conducted on thirty datasets with a resolution of 3 m. Compared with the existing algorithms for flow accumulation calculation, the proposed algorithm is easy to implement, runs much faster than existing algorithms, and generally requires less memory space.

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Land use and land cover classification using Chinese GF-2 multispectral data in a region of the North China Plain
Kun JIA, Jingcan LIU, Yixuan TU, Qiangzi LI, Zhiwei SUN, Xiangqin WEI, Yunjun YAO, Xiaotong ZHANG
Front. Earth Sci.. 2019, 13 (2): 327-335.  https://doi.org/10.1007/s11707-018-0734-8
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The newly launched GF-2 satellite is now the most advanced civil satellite in China to collect high spatial resolution remote sensing data. This study investigated the capability and strategy of GF-2 multispectral data for land use and land cover (LULC) classification in a region of the North China Plain. The pixel-based and object-based classifications using maximum likelihood (MLC) and support vector machine (SVM) classifiers were evaluated to determine the classification strategy that was suitable for GF-2 multispectral data. The validation results indicated that GF-2 multispectral data achieved satisfactory LULC classification performance, and object-based classification using the SVM classifier achieved the best classification accuracy with an overall classification accuracy of 94.33% and kappa coefficient of 0.911. Therefore, considering the LULC classification performance and data characteristics, GF-2 satellite data could serve as a valuable and reliable high-resolution data source for land surface monitoring. Future works should focus on improving LULC classification accuracy by exploring more classification features and exploring the potential applications of GF-2 data in related applications.

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Analysis of the relation between ocean internal wave parameters and ocean surface fluctuation
Yufei ZHANG, Bing DENG, Ming ZHANG
Front. Earth Sci.. 2019, 13 (2): 336-350.  https://doi.org/10.1007/s11707-018-0735-7
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The relation between ocean internal waves (IWs) and surface fluctuation is studied using a quasi-incompressible two-dimensional linear ocean wave model. The main conclusions are as follows: the IW parameters can be obtained by solving the boundary value problem of ordinary differential equations with the frequency, wave number, and amplitude of the surface fluctuation. When the ocean surface fluctuation state is given, the ocean IW presents a different structure, i.e., the uncertainty of the solution, which reflects the characteristics of the inverse problem. To obtain a definite solution, this study proposes constraint conditions for the inverse problem, namely, the relationship among background flow, buoyancy frequency, sea surface height, and geostrophic parameters. The necessary and sufficient conditions for the existence of IWs and external waves (surface wave) can be obtained according to the different constraint conditions. The amplitude of the surface fluctuation is positively correlated with IWs, and they share the same frequency and wave number. We also examined the relationship between the vertical structure, the maximum amplitude, and the constraint conditions. For a certain wave number, when the ocean environment is defined, the natural frequency (characteristic frequency) of IWs can be obtained. If the frequency of the surface fluctuation is similar or equal to the natural frequency, the resonance phenomenon will occur and can result in very strong IWs. The presented theory can serve as a basis for the analytical estimation of IWs.

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Comparison of C- and L-band simulated compact polarized SAR in oil spill detection
Xiaochen WANG, Yun SHAO, Fengli ZHANG, Wei TIAN
Front. Earth Sci.. 2019, 13 (2): 351-360.  https://doi.org/10.1007/s11707-018-0733-9
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This paper presents the compact polarized (CP) pseudo quad-pol parameters for the detection of marine oil spills and segregation of lookalikes using simulated CP SAR data from full-polarized (FP) SAR imagery. According to the CP theory, 11 polarized parameters generally used for the detection of oil spills were derived from reconstructed pseudo quad-pol data for both C and L bands. In addition, the reconstruction performance between C and L bands was also compared by evaluating the reconstruction accuracy of retrieved polarized parameters. The results show that apart from σHV and RH, other polarized parameters of σHH, σVV, H, α, ϕH−V, r, ρH−V, and γ can be reconstructed with satisfactory accuracy for both C and L bands. Furthermore, C band has a higher reconstruction accuracy than L band, especially for ϕH−V. Moreover, the effect of reconstruction of polarized parameters on oil spill classification was also evaluated using the maximum likelihood classification (MLC) method. According to the evaluation of kappa coefficients and mapping accuracy, it is recommended to use σHH, σVV, H, ρH−V, and γ of the C band CP SAR for marine oil spill classification.

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Metal accumulation in Asiatic clam from the Lower Min River (China) and implications for human health
Yue ZENG, Zhongtao LI, Qianfeng WANG, Changcheng XU, Yunqin LI, Jia TANG
Front. Earth Sci.. 2019, 13 (2): 361-370.  https://doi.org/10.1007/s11707-018-0724-x
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Considering growing concerns regarding polluted estuaries and their adverse effects on public health, this study aimed to identify concentrations of metal (Zn, Fe, Cr, Ni, Cd, Mn, As, Cu, and Pb) in Asiatic clams sampled along the Lower Min River, China. Multivariate methods were used to identify and apportion pollution sources. Noncarcinogenic and carcinogenic health risk assessments were performed to gauge adverse consumer health effects. Results showed that Cr, Pb, and Zn concentrations were higher than the limits prescribed in Chinese government guidelines. In comparison with concentrations of selected metals in other rivers, Cr, Pb, Zn, and As concentrations in clams were generally higher. Pollution assessment using the metal pollution index showed that sampling sites surrounding developing industrial and residential areas were the most polluted. Principal component analysis indicated significant anthropogenic metal contributions in clams. Health risk assessment indicated significant risk for clam consumers along the Lower Min River in terms of hazard quotient and carcinogenic risk and, thus, clam consumption from the study area should be avoided. The present findings would help in establishing environmental monitoring plans and contribute to preserving public health as well as the development of water conservation strategies to alleviate the metal pollution.

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Development of a groundwater flow and reactive solute transport model in the Yongding River alluvial fan, China
Haizhu HU, Xiaomin MAO, Qing YANG
Front. Earth Sci.. 2019, 13 (2): 371-384.  https://doi.org/10.1007/s11707-018-0718-8
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The Yongding River in the western suburbs of Beijing has been recharged with reclaimed water since 2010 for the purpose of ecological restoration. Where the reclaimed water is not well treated, it poses a danger to the aquifer underneath the river. To provide a reliable tool which could be used in future research to quantify the influence of reclaimed water in the Yongding River on the local groundwater environment, a transient groundwater flow and reactive solute transport model was developed using FEFLOWTM in the middle-upper part of the Yongding River Alluvium Fan. The numerical model was calibrated against the observed groundwater levels and the concentrations of typical solutes from June 2009 to May 2010 and validated from June 2010 to December 2010. The average RMSE and R2 of groundwater level at four observation wells are 0.48 m and 0.61, respectively. The reasonable agreement between observed and simulated results demonstrates that the developed model is reliable and capable of predicting the behavior of groundwater flow and typical contaminant transport with reactions. Water budget analysis indicates that the water storage in this aquifer had decreased by 43.76×106 m3 from June 2009 to December 2010. The concentration distributions of typical solutes suggest that the middle and southern parts of the unconfined aquifer have been polluted by previous discharge of industrial and domestic sewage. The results underscore the necessity of predicting the groundwater response to reclaimed water being discharged into the Yongding River. The study established a coupled groundwater flow and reactive solute transport model in the middle-upper part of the Yongding River Alluvium Fan, one of the drinking water supply sites in Beijing city. The model would be used for risk assessment when reclaimed water was recharged into Yongding River.

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Ecological vulnerability analysis of Beidagang National Park, China
Xue YU, Yue LI, Min XI, Fanlong KONG, Mingyue PANG, Zhengda YU
Front. Earth Sci.. 2019, 13 (2): 385-397.  https://doi.org/10.1007/s11707-018-0726-8
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Ecological vulnerability analysis (EVA) is vital for ecological protection, restoration, and management of wetland-type national parks. In this study, we assessed the ecological vulnerability of Beidagang National Park based upon remote sensing (RS) and geographic information system (GIS) technologies. To quantify the ecological vulnerability, 10 indices were collected by the ‘exposure-sensitivity-adaptive capacity’ model and spatial principal component analysis (SPCA) was then applied to calculate the ecological vulnerability degree (EVD). Based on the numerical values, EVD of the study area was classified into five levels: moderate, light, medium, strong, and extreme. Results showed that the average EVD value was approximately 0.39, indicating overall good ecological vulnerability in Beidagang National Park. To be specific, 80.42% of the whole area was assigned to a moderate level of EVD with the highest being the tourism developed areas and the lowest being the reservoirs and offshore areas. Ecological vulnerability of the region was determined to be affected by the natural environment and anthropogenic disturbance jointly. The primary factors included tourism disturbance, traffic interference, exotic species invasion, land use/land cover, and soil salinization. We expected to provide some insights of the sustainable development of Beidagang National Park and would like to extend the results to other wetland-type national parks in the future.

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Impact of seasonal water-level fluctuations on autumn vegetation in Poyang Lake wetland, China
Xue DAI, Rongrong WAN, Guishan YANG, Xiaolong WANG, Ligang XU, Yanyan LI, Bing LI
Front. Earth Sci.. 2019, 13 (2): 398-409.  https://doi.org/10.1007/s11707-018-0731-y
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Water level fluctuations (WLF) are natural patterns that are necessary for the survival of various plants, and WLF guarantee both the productivity and the biodiversity of wetlands. However, the underlying mechanisms of how changes in vegetation are linked to seasonal WLF remain unclear. Using vegetation and hydrological data from 1989 to 2009, we identified the key seasonal fluctuations and their impacts on vegetation in the Poyang Lake wetland by utilizing a tree-based hierarchical model. According to our results: 1) WLF in summer had significant impacts on both sedges and reeds. The severe summer floods promoted the expansion of sedges, while they inhibited the expansion of reeds; 2) WLF in autumn also greatly impacted sedges, while reeds were severely affected in spring. Specifically, we found that low water levels in autumn led to the expansion of sedges, and low water levels in spring led to the expansion of reeds. The results were well corroborated through comparisons of the vegetation distribution patterns over the last two decades (i.e., the 1990s and 2000s), which may shed light on corresponding water resource and wetland management.

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Terrain relief periods of loess landforms based on terrain profiles of the Loess Plateau in northern Shaanxi Province, China
Jianjun CAO, Guoan TANG, Xuan FANG, Jilong LI, Yongjuan LIU, Yiting ZHANG, Ying ZHU, Fayuan LI
Front. Earth Sci.. 2019, 13 (2): 410-421.  https://doi.org/10.1007/s11707-018-0732-x
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The Loess Plateau is densely covered by numerous types of gullies which represent different soil erosion intensities. Therefore, research on topographic variation features of the loess gullies is of great significance to environmental protection and ecological management. Using a 5 m digital elevation model and data from a national geographic database, this paper studies different topographical areas of the Loess Plateau, including Shenmu, Suide, Yanchuan, Ganquan, Yijun, and Chunhua, to derive representative gully terrain profile data of the sampled areas. First, the profile data are standardized in MATLAB and then decomposed using the ensemble empirical mode decomposition method. Then, a significance test is performed on the results; the test confidence is 95% to 99%. The most reliable decomposition component is then used to calculate the relief period and size of the gullies. The results showed that relief periods of the Chunhua, Shenmu, Yijun, Yuanchuan, Ganquan, and Suide gullies are 1110.14 m, 1096.85 m, 1002.49 m, 523.48 m, 498.12 m, and 270.83 m, respectively. In terms of gully size, the loess landforms are sorted as loess fragmented tableland, aeolian and dune, loess tableland, loess ridge, loess hill and loess ridge, and loess hill, in descending order. Taken together, the gully terrain features of the sample areas and the results of the study are approximately consistent with the actual terrain profiles. Thus, we conclude that ensemble empirical mode decomposition is a reliable method for the study of the relief and topography of loess gullies.

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The 2015/16 El Niño-related glacier changes in the tropical Andes
Bijeesh Kozhikkodan VEETTIL, Jefferson Cardia SIMÕES
Front. Earth Sci.. 2019, 13 (2): 422-429.  https://doi.org/10.1007/s11707-018-0738-4
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Significant changes in the area and snowline altitude of two glacierized mountains – Nevado Champara (Cordillera Blanca, Peru) and Cerro Tilata (Cordillera Real, Bolivia) – in the tropical Andes, before and after the recent El Niño in 2015/16 period, have been analysed using Sentinel 2A and Landsat data. It is seen that the recent El Niño has been accompanied by higher fluctuation in glacier coverage on Nevado Champara and the loss of glacier coverage on Cerro Tilata was very high during the past 16 years. Rise in snowline altitude of selected glaciers was very high after the 2015/16 El Niño. Increase in the area covered by snow and ice during the La Niña periods were not enough to cover the ice loss occurred during the previous El Niño events and the strongest El Niño in 2015/16 was followed by a significant loss of ice-covered areas in the tropical Andes. Freshwater resources in this region will be affected in the near future if the current trends in glacier decline continue. Adaptation strategies needs to be implemented to reduce the impacts of the continuing loss of glacierized on regional communities in the tropical Andean region.

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Vegetation and soil wind erosion dynamics of sandstorm control programs in the agro-pastoral transitional zone of northern China
Zhitao WU, Mingyue WANG, Hong ZHANG, Ziqiang DU
Front. Earth Sci.. 2019, 13 (2): 430-443.  https://doi.org/10.1007/s11707-018-0715-y
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To combat soil erosion and desertification, large-scale sandstorm control programs have been put in place since 2000 in the agro-pastoral transitional zone of northern China. Vegetation dynamics as well as soil wind erosion control effects are very important for assessing the ecological success of sandstorm control programs in China. However, no comprehensive evaluation of vegetation dynamics and soil wind erosion control effects in this region has been achieved. In this study, we illustrate the vegetation and soil wind erosion dynamics of sandstorm control programs in the northern Shanxi Province using remote sensing data and soil wind erosion models. There was a significant increase in vegetation cover for 63.59% of the study area from 2001 to 2014 and a significant decrease for 2.00% of the study area. The normalized difference vegetation index (NDVI) showed that the largest increase occurred in autumn. Soil wind erosion mass decreased from 20.90 million tons in 2001 to 7.65 million tons in 2014. Compared with 2001, the soil wind erosion moduli were reduced by 43.05%, 36.16%, and 62.66% in 2005, 2010, and 2014, respectively. Spatially, soil wind erosion in most of the study area was alleviated between 2001 and 2014. The relationship between NDVI and soil wind erosion mass showed that the increased vegetation coverage reduced the soil wind erosion mass. In addition, wind was the main driving force behind the soil wind erosion dynamics. The results indicate that the vegetation coverage has increased and soil wind erosion mass has been reduced following the implementation of the sandstorm control programs. However, the ecological effects of the sandstorm control programs may vary over different periods. While the programs appear to be beneficial in the short term, there may be unintended consequences in the long term. Research on the sustainability of the ecological benefits of sandstorm control programs needs to be conducted in the future.

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