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Now showing items 1 - 5 of 5

  • Assessing changes in wind erosion climatic erosivity in China’s dryland region during 1961–2012

    Fengbo Yang   Changhe Lu  

    China’s dryland region has serious wind erosion problem and is sensitive to climate change due to its fragile ecological condition. Wind erosion climatic erosivity is a measure of climatic factors influencing wind erosion, therefore, evaluation of its intensity and response to recent climate changes can contribute to the understanding of climate change effect on wind erosion risk. Using the FAO equation, GIS and statistical analysis tools, this study quantified the climatic erosivity, analyzed its spatiotemporal variations, and detected the trend and sensitivity to climate factors during 1961–2012. The results indicate that mean annual climatic erosivity was 2–166 at 292 stations and 237–471 at 6 stations, with the spatial distribution highly in accordance with wind speed (R2 = 0.94). The climatic erosivity varied greatly over time with the annual variation (CV) of 14.7%–108.9% and monthly variation (concentration degree) of 0.10–0.71 in the region. Meanwhile, annual erosivity showed a significant downward trend at an annual decreasing rate mostly above 1.0%. This significantly decreasing trend was mainly attributed to the obvious decline of wind speed during the period. The results suggest that the recent climate changes were highly possible to induce a decrease of wind erosion risk in China’s dryland region.
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  • Sustainable value of degraded soils in China's Loess Plateau: An updated approach

    Lingling Hou   Dana Hoag   Catherine M.H. Keske   Changhe Lu  

    Abstract China's Loess Plateau is a highly distressed region where intensive crop production has been undermined by high soil erosion rates that threaten the long-term livelihood of its inhabitants. Regional policy goals aim to balance economic performance with the sustainable use of natural resources. From a practical perspective, challenges arise when measuring sustainability levels that mix multiple dimensions, scales, and benchmarks. This study addresses these challenges by comparing the sustainability of agricultural systems across varied crops, land types, and cropping techniques in China's Loess Plateau. Sustainability levels for each system are compared to benchmarks using data envelopment analysis, which is then used to calculate a sustainable value (SV). The SV approach provides a monetary measure of sustainability that includes economic, environmental and social dimensions. Results demonstrate that the most sustainable agricultural systems in the Loess Plateau involve machine intensive cropping systems, a corn–soybean–corn rotation, mulching, furrows ridging, and bench terracing. Highlights • Sustainable value (SV) can be used to evaluate sustainability of cropping systems. • The SV was compared for more than 2000 cropping systems in China's Loess Plateau. • On average, SV was −$264/ha. Sustainable efficiency was 69%. • Terracing, mulching, furrow ridging, and rotations increased sustainability. • SV can be enhanced by estimating custom benchmarks with data envelope analysis.
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  • Alpine Glacier Change in the Eastern Altun Mountains of Northwest China during 1972-2010

    XinYang Yu   Changhe Lu  

    Accurately mapping and monitoring glacier changes over decades is important for providing information to support sustainable use of water resource in arid regions of northwest China. Since 1970, glaciers in the Eastern Altun Mountains showed remarkable recession. Further study is indispensable to indicate the extent and amplitude of glacial change at basin and individual glacier scale. In this study, spatiotemporal glacier changes referring to the year 1972, 1990, 2000 and 2010 were studied for the Eastern Altun Mountains using Landsat MSS/TM/ETM; images and glacier volume-area scaling. The results demonstrated that the total area and volume of glaciers in EAMs decreased significantly by 10.70±0.57 km² (19.56±10.41%) and 0.61±0.03 km³ (23.19±11.40%) during 1972-2010, respectively. More than half of the total receding area occurred during 1990-2000, primarily due to higher temperature increasing. However, varied response of individual glaciers indicated that glacier change was also affected by glacier dynamics, which was related to local topography. In addition, five glaciers unrecorded in the glacier inventory of China were reported in this study.
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  • Spatiotemporal variation and trends in rainfall erosivity in China's dryland region during 1961–2012

    Fengbo Yang   Changhe Lu  

    Abstract This study evaluated rainfall erosivity and its changes in China's dryland region during 1961–2012, using a daily rainfall erosivity model, ArcGIS based spatial interpolation tools, and the Mann–Kendall and Sen's methods. It was found that mean rainfall erosivity was 2–4098 MJ mmha − 1 h − 1 a − 1 in the region, with the regional average of 794 MJ mmha − 1 h − 1 a − 1 , showing a significant increase trend accordingly with an increase in rainfall from northwest to southeast. Rainfall erosivity varied annually with the CV of 32.4–491.3%, and varied seasonally with about three-quarter distributed in summer. During 1961–2012, a statistically significant increase/decrease trend in rainfall erosivity was detected only for 24/10 stations or about 4.6/0.4% of the region, and a non-significant increase/decrease trend was observed for 32/45 stations or 16.5/10.0% of the region at the 50 to 90% confidence level. No statistically confidential trend was found for other 126 stations or 68.5% of the region. At regional level, mean annual erosivity of the arid zone indicated an upward trend, while the sub-humid zone a downward, but the semi-arid zone generally had no evidential trend. Comparing the 26 year's averages during 1987–2012 and 1961–1986, mean erosivity of the arid zone increased by 17.4%, the sub-humid zone decreased by 6.1%, and the semi-arid zone reduced slightly by 0.45%. The results suggest that change in the rainfall characteristics during the past half century had no significant influence on water erosion in the majority of the region, but it could probably induce an increase of water erosion risk in parts of the drier west and a slight decrease in parts of the wetter east including the Loess Plateau. Highlights • Rainfall erosivity increased with increasing rainfall from northwest to southeast. • Rainfall erosivity showed an increase/decrease trend in 21/10% of the region. • Mean annual rainfall erosivity of the arid and sub-humid zone showed an opposite trend.
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  • Evaluation of land‐use change effects on runoff and soil erosion of a hilly basin — the Yanhe River in the Chinese Loess Plateau

    Kaijie Yang   Changhe Lu  

    Starting in 1999, the Grain‐for‐Green Programme has been implemented in the Loess Plateau to alleviate the severe soil erosion by converting steeply sloping croplands to forestlands or grasslands. To quantify the effects of these conservation efforts, this study identified the land‐use changes between 2000 and 2015 and quantified their impacts on runoff and erosion using the Soil and Water Assessment Tools (SWAT) and a typical hilly basin, the Yanhe River basin as a case‐study. To heighten the applicability of SWAT to the region, major model parameters were localized and calibrated for the period of 1975–1980 and were then validated for 1981–1987. The R2 and NS validation indices were 0.70 and 0.65 for the monthly runoff and 0.67 and 0.61 for the sediment load, indicating that the model performance was acceptable. Between 2000 and 2015, the slope croplands were reduced by 39.9%, the forestlands increased by 90.2%, and the grasslands increased by 12.9%. These land‐use changes were simulated using SWAT to reduce the basin runoff by 13.8% and the sediment load by 50.7%. Spatial analyses using ArcGIS indicated that the simulated reduction in water yield due to cropland conversion to forestland was more obvious than that due to the conversion to grassland, but the reductions in the sediment yields were similar. The results suggest that the Grain‐for‐Green practice during this period was effective for preventing soil and water losses.
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