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Development of a high-accuracy method to extract arable land using effective data sources is crucial to detect and monitor arable land dynamics, servicing land protection and sustainable development. In this study, a new arable land extraction index (ALEI) based on spectral analysis was proposed, examined by ground truth data, and then applied to the Hexi Corridor in northwest China. The arable land and its change patterns during 1990–2020 were extracted and identified using 40 Landsat TM/OLI images acquired in 1990, 2000, 2010, and 2020. The results demonstrated that the proposed method can distinguish arable land areas accurately, with the User’s (Producer’s) accuracy and overall accuracy (kappa coefficient) exceeding 0.90 (0.88) and 0.89 (0.87), respectively. The mean relative error calculated using field survey data obtained in 2012 and 2020 was 0.169 and 0.191, respectively, indicating the feasibility of the ALEI method in arable land extracting. The study found that arable land area in the Hexi Corridor was 13217.58 km2 in 2020, significantly increased by 25.33% compared to that in 1990. At 10-year intervals, the arable land experienced different change patterns. The study results indicate that ALEI index is a promising tool used to effectively extract arable land in the arid area.
Xinyang Yu; YoungGu Her; Xicun Zhu; Changhe Lu; Xuefei Li. Multi-Temporal Arable Land Monitoring in Arid Region of Northwest China Using a New Extraction Index. Sustainability 2021, 13, 5274 .
AMA StyleXinyang Yu, YoungGu Her, Xicun Zhu, Changhe Lu, Xuefei Li. Multi-Temporal Arable Land Monitoring in Arid Region of Northwest China Using a New Extraction Index. Sustainability. 2021; 13 (9):5274.
Chicago/Turabian StyleXinyang Yu; YoungGu Her; Xicun Zhu; Changhe Lu; Xuefei Li. 2021. "Multi-Temporal Arable Land Monitoring in Arid Region of Northwest China Using a New Extraction Index." Sustainability 13, no. 9: 5274.
Grassland covers 54% of the Tibetan Plateau (TP) and suffered overgrazing and degradation problems during past decades. To alleviate these problems, a series of policy measures have been implemented during recent two decades and inevitably caused changes of the grassland. To this end, this study quantitatively analyzed the grassland changes and the effects of reduced grazing intensity, and identified the hot plots of grassland degradation in the TP during 2000–2019. The grassland status was indicated by the Fractional Vegetation Cover in the green grass period (GP), i.e., FVCGP, and its changes and spatial variations were detected by analyzing the FVCGP trends and their distribution, using the Mann–Kendal, Sen’s Slope, and ArcGIS buffering methods, and data of the MOD13Q1 Collection 6 products and other sources. The results showed that 62.12% of the grasslands were significantly increased in the FVCGP, and 28.34% had no apparent changes. The remaining 9.54% of the grassland significantly decreased in the FVCGP, mainly occurring in the areas nearby roads, rivers, and lakes, and distributed mostly in a point pattern. Of the total FVCGP decreased grassland area, 27.03% was clustered and identified as the hot plots of grassland degradation in six main regions. Decreased grazing intensity and increased precipitation contributed to the increase of grassland FVC in the TP, while local overgrazing could be the main cause of the FVC decrease. To strength the grassland restoration in the TP, the government supports and supervision should be enhanced to further mitigate the grassland pressure of animal grazing, particularly in the hot plot areas of degradation.
Yaqun Liu; Changhe Lu. Quantifying Grass Coverage Trends to Identify the Hot Plots of Grassland Degradation in the Tibetan Plateau during 2000–2019. International Journal of Environmental Research and Public Health 2021, 18, 416 .
AMA StyleYaqun Liu, Changhe Lu. Quantifying Grass Coverage Trends to Identify the Hot Plots of Grassland Degradation in the Tibetan Plateau during 2000–2019. International Journal of Environmental Research and Public Health. 2021; 18 (2):416.
Chicago/Turabian StyleYaqun Liu; Changhe Lu. 2021. "Quantifying Grass Coverage Trends to Identify the Hot Plots of Grassland Degradation in the Tibetan Plateau during 2000–2019." International Journal of Environmental Research and Public Health 18, no. 2: 416.
Yield growth stagnation in grain crops has been reported worldwide over recent decades. To understand this recent crop yield trend and its causes in China, we conducted an analysis of maize (Zea mays L.) in the North China Plain (NCP) as a case study. First, we analyzed the change characteristics of maize yield for the whole region during 1998–2015, then identified trend patterns at county level via an approach based mainly on the Mann–Kendall and Sen’s slope methods, and finally, analyzed the contribution of major causal factors to maize yield changes based on multiple linear regression (MLR) function. The results indicated that regional mean maize yield in the whole NCP increased by 0.02–2.03% per year before 2011, then declined by—0.83% during 2011–2015. Regionally, maize yield in the southern NCP did not improve greatly; in the north, it increased before 2011, then declined or stagnated thereafter. Only 40 counties showed a continuous increasing trend (IN), whereas 180 counties displayed an increasing–stagnating trend (IN-ST); 52 and 40 counties showed trend patterns of stagnating (ST) and decreasing (DE) in yield, respectively. On the whole, the maize yield in 87.8% of the counties tended to stagnate or even decrease. The reason was mainly attributed to the reduced net returns due to the quickly rising costs of labor and production material. To stimulate yield growth, it is essential to increase the profitability of maize by adopting appropriate policy measures to improve production efficiency.
Zemin Zhang; Changhe Lu. Identification of Maize Yield Trend Patterns in the North China Plain. International Journal of Plant Production 2020, 15, 125 -137.
AMA StyleZemin Zhang, Changhe Lu. Identification of Maize Yield Trend Patterns in the North China Plain. International Journal of Plant Production. 2020; 15 (1):125-137.
Chicago/Turabian StyleZemin Zhang; Changhe Lu. 2020. "Identification of Maize Yield Trend Patterns in the North China Plain." International Journal of Plant Production 15, no. 1: 125-137.
The production gap of soybean (Glycine max L. Merr.) has been expanding in China recently, due to the increasing demand and decreasing production. Identifying soybean production dynamics is contributable to appropriate adjustment of crop rotation system and efficient use of agricultural resources—and thus to ensure food security. Taking the North China plain (NCP) as a case area, this study first analyzed the spatiotemporal dynamics of soybean production during 1998–2015 based on the spatial autocorrelation method, and then calculated contributions to the total production by yield and sown area using the factor decomposition method. The results indicated that total soybean production in the NCP decreased dramatically from 1998 to 2015 and showed a decreasing trend in 80.4% (263) of the counties, mainly (83.9%) contributed by the shrinkage of sown area, largely caused by decreasing benefit. Two regions were found with significantly spatial clustering degree of soybean production. In the south part of NCP, soybean production was highly clustered in Anhui province, and in north it was mainly clustered in western Hebei plain. It was found that soybean production in the NCP was rather sensitive to the return gaps of soybean from maize (Zea mays L.). These imply that the reduced area of soybean production can be restored if the return is improved by adopting appropriate policies such as appropriate subsidies. These findings could be helpful for the policymakers to make soybean production planning in the NCP, contributing to the national revitalization strategy of soybean production.
Zemin Zhang; Changhe Lu. Clustering Analysis of Soybean Production to Understand its Spatiotemporal Dynamics in the North China Plain. Sustainability 2020, 12, 6178 .
AMA StyleZemin Zhang, Changhe Lu. Clustering Analysis of Soybean Production to Understand its Spatiotemporal Dynamics in the North China Plain. Sustainability. 2020; 12 (15):6178.
Chicago/Turabian StyleZemin Zhang; Changhe Lu. 2020. "Clustering Analysis of Soybean Production to Understand its Spatiotemporal Dynamics in the North China Plain." Sustainability 12, no. 15: 6178.
Since the Grain for Green (GFG) program was implemented in 1999, most steeply sloping farmlands in the Loess Plateau of China have been returned to forestland and grassland. To understand its impact on the food production, this study analyzed the spatiotemporal changes of food crop production (FCP) in the plateau and quantified the contribution of sown area and yield changes to the total FCP during 1998–2014 using factor decomposition models, and then discussed the impact of GFG program on the FCP based on literature data. With the implementation of GFG program, total sown area in the Loess Plateau quickly deceased by 17.3% from 1998 to 2003, and then gradually restored to 1.03×107 hm2 in 2010. Thereafter, it slightly decreased to 1.02×107 hm2 (94.6% of the area in 1998) in 2014. By contrast, total FCP generally showed an apparent growth trend, averagely increased by 1.71% per year in the whole plateau during 1998–2014. This increase was jointly contributed by the improved yield of individual crops, and the adjustment of cropping structure, i.e., the expansion of high yield maize crop. The factor decomposition analysis results indicate that the sown area shrinkage only reduced the growth rate of total FCP by 0.29% per year during 1998–2014, although a significant impact was found for the early stage of 1999–2003. The results suggest that the implementation of GFG program would not induce an obvious risk of the food security. Therefore, it is suggested that the GFG program should be set as a long-term strategic policy, by not only supporting the conversion of slope farmlands, but also helping local farmers to seek sustainable ways of land use to improve the income and livelihood. It can be combined with the poverty eradication program, to simultaneously achieve the national goals of ecological civilization building and the livelihood improvement of rural people in the Loess Plateau. Considering rainfall limitation, the conversion of slope farmlands should be prioritized to grasslands.
Changhe Lyu; Zhiyuan Xu. Crop production changes and the impact of Grain for Green program in the Loess Plateau of China. Journal of Arid Land 2020, 12, 18 -28.
AMA StyleChanghe Lyu, Zhiyuan Xu. Crop production changes and the impact of Grain for Green program in the Loess Plateau of China. Journal of Arid Land. 2020; 12 (1):18-28.
Chicago/Turabian StyleChanghe Lyu; Zhiyuan Xu. 2020. "Crop production changes and the impact of Grain for Green program in the Loess Plateau of China." Journal of Arid Land 12, no. 1: 18-28.
Associated with population and income growth, grain consumption in China is expected to increase, and thus has inevitably influenced the food security. Using statistical data of the Food and Agricultural Organization of the United Nations (FAO) from 1978 to 2017, this study adopting the vector auto-regression (VAR) model and implied demand approach, projected the future consumption of major grains (rice, wheat, maize, and soybean) for food, feed, and other uses in China during 2018–2030. On this basis, it further discussed their implications on grain security. The results showed that during 2018–2030, the Chinese dietary structure would continue to shift from food grain to animal foods. As a result, the grain’s food consumption will decrease slightly (1.5%), while the feed consumption will increase significantly (31.4%), contributing 71.4% to the total increase of grain consumption. By 2030, the total grain consumption will increase by 20.2% to 846.2 million tons, of which 50.2% will be consumed for feeding animals. In the total consumption, maize will be the largest consumed grain variety, accounting for 39.2%. The security of rice and wheat would be optimistic in the future, while the security of maize and soybeans is likely to decline, and thus needs to be given high priority. These findings have great policy implications for improving the grain security, suggesting that in addition to promote the expansion of maize and soybean growing area by adjusting the cropping structure of the arable land, great efforts should be paid to improve the yield of both crops. In addition, residents should be guided to adjust the dietary structure, and also, it is important to improve the animal feeding efficiency.
Yuanyuan Chen; Changhe Lu. Future Grain Consumption Trends and Implications on Grain Security in China. Sustainability 2019, 11, 5165 .
AMA StyleYuanyuan Chen, Changhe Lu. Future Grain Consumption Trends and Implications on Grain Security in China. Sustainability. 2019; 11 (19):5165.
Chicago/Turabian StyleYuanyuan Chen; Changhe Lu. 2019. "Future Grain Consumption Trends and Implications on Grain Security in China." Sustainability 11, no. 19: 5165.
The North China Plain (NCP) is the most important winter wheat production region and an area of water shortage in China. The stability of winter wheat (T. aestivum L.) production in spatial pattern and the sustainability of water resources have been a major policy concern in China. This study explored the barycenter shift and change trends of wheat total production during 1998–2015, using methods of barycenter model, Sen’s slope, and Mann Kendall test, and analyzed the influence of external factors and the response of water resources. Results indicated that the barycenter of wheat production moved southwards by 115.16 km during 1998–2015, with an average speed of 6.77 km/year. For the entire NCP, the total production showed phased changes during the study period: It decreased during 1998–2003, and then continuously increased during 2004–2015. Of the wheat production increase in the NCP, yield increase and sown area expansion averagely contributed 64.5% and 35.5%, respectively, and the contribution proportion of yield increase continuously increased since 2003. At county level, total wheat production showed a significant increase and decrease trend in 87 and 29 counties, mainly distributed in the southern and northern NCP, respectively. The increase of total production at county level was mainly contributed by yield growth in the southern NCP, while the decrease in the north was due to the reduction of sown area to great extent. The southward shift was jointly resulted by the spatial variation of input factors, benefit, and water prices. These spatial pattern changes alleviated the water pressure in the north region to some extent, in the case of ensuring the production increase of winter wheat. Therefore, the current spatial shift should be continuously promoted in the future.
Zemin Zhang; Changhe Lu. Spatio-Temporal Pattern Change of Winter Wheat Production and Its Implications in the North China Plain. Sustainability 2019, 11, 3028 .
AMA StyleZemin Zhang, Changhe Lu. Spatio-Temporal Pattern Change of Winter Wheat Production and Its Implications in the North China Plain. Sustainability. 2019; 11 (11):3028.
Chicago/Turabian StyleZemin Zhang; Changhe Lu. 2019. "Spatio-Temporal Pattern Change of Winter Wheat Production and Its Implications in the North China Plain." Sustainability 11, no. 11: 3028.
Land expansion of mountain cities in China is not systematically studied yet. This study identified 55 major mountain cities at and above prefecture level, and analyzed the land expansion characteristics and driving forces, based on visually interpreted data from TM images in 1990, 2000, 2010 and 2015. From 1990 to 2015, total built-up land area of the mountain cities increased by 3.87 times, 5.56% per year. The urban land growth was apparently accelerated after 2000, from 4.35% per year during 1990–2000 increased to 6.47% during 2000–2010 and 6.2% during 2010–2015. Compared to the urban population growth, the urban land expansion rate was 44% higher. As a result, the urban land area per capita increased, but it was still within the government control target, and also was much lower than the average of all cities in China. Urban development policy, changes to administrative divisions, GDP and population growth, and road construction were identified as the major driving forces of land expansion. Terrain conditions were not found a relevance to the urban land expansion rate during 1990–2015, but had a significant impact on the layout and shape, and also probably on the urban land efficiency.
Ziwei Wang; Changhe Lu. Urban land expansion and its driving factors of mountain cities in China during 1990–2015. Journal of Geographical Sciences 2018, 28, 1152 -1166.
AMA StyleZiwei Wang, Changhe Lu. Urban land expansion and its driving factors of mountain cities in China during 1990–2015. Journal of Geographical Sciences. 2018; 28 (8):1152-1166.
Chicago/Turabian StyleZiwei Wang; Changhe Lu. 2018. "Urban land expansion and its driving factors of mountain cities in China during 1990–2015." Journal of Geographical Sciences 28, no. 8: 1152-1166.
In 2013, China proposed the Bangladesh–China–India–Myanmar Economic Corridor initiatives to enhance the economic cooperation between Bangladesh, India, and Myanmar. To serve the priority setting of agricultural cooperation in the initiatives, an analysis is necessary to understand the food security situation and its key influencing factors in the three countries. For this purpose, this study applied a food security index (FSI) to measure the food security level at state scale and analyze its changes in the three countries during 1990–2013. Further, a factor decomposition method was used to quantify the contribution of major factors to the FSI changes. The results showed that the food demand was generally secured in Myanmar and India during 1990–2013 but in shortage by around 10% in most years before 2008 in Bangladesh. The annual FSI values showed a rather obvious periodic variation and a slightly increasing trend during the whole period. Although the grain production in the three countries increased significantly, the FSI was not accordingly improved, as a result of the simultaneous increase of grain consumption. In Bangladesh and India, the grain production increase was mainly driven by the improvement of crop yield, while the grain consumption increase was mainly caused by the population growth. In Myanmar, the production increase was largely caused by the expansion of cropping area, and the consumption growth was mainly due to the increased grain requirement per capita. To meet the increasing food demand in the future, it is essential to improve the irrigation and drainage systems and crop management to increase the land use efficiency and crop yield. In addition, the adaptation of appropriate policy for family planning could be important to slow down the quick population growth and thus the food demand.
Yuanyuan Chen; Changhe Lu. A Comparative Analysis on Food Security in Bangladesh, India and Myanmar. Sustainability 2018, 10, 405 .
AMA StyleYuanyuan Chen, Changhe Lu. A Comparative Analysis on Food Security in Bangladesh, India and Myanmar. Sustainability. 2018; 10 (2):405.
Chicago/Turabian StyleYuanyuan Chen; Changhe Lu. 2018. "A Comparative Analysis on Food Security in Bangladesh, India and Myanmar." Sustainability 10, no. 2: 405.
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.
Fengbo Yang; Changhe Lu. Assessing changes in wind erosion climatic erosivity in China’s dryland region during 1961–2012. Journal of Geographical Sciences 2016, 26, 1263 -1276.
AMA StyleFengbo Yang, Changhe Lu. Assessing changes in wind erosion climatic erosivity in China’s dryland region during 1961–2012. Journal of Geographical Sciences. 2016; 26 (9):1263-1276.
Chicago/Turabian StyleFengbo Yang; Changhe Lu. 2016. "Assessing changes in wind erosion climatic erosivity in China’s dryland region during 1961–2012." Journal of Geographical Sciences 26, no. 9: 1263-1276.
The North China Plain (NCP) is the most important food grain producing area in China and has suffered from serious water shortages. To capture variation water availability, it is necessary to have an analysis of changing trends in precipitation. This study, based on daily precipitation data from 47 representative stations in NCP records passed the homogeneity test, analyzed the trend and amplitude of variation in monthly, seasonal and annual precipitation, annual maximum continuous no-rain days, annual rain days, rainfall intensity, and rainfall extremes from 1960 to 2007, using the Mann-Kendall (M-K) test and Sen’s slope estimator. It was found that monthly precipitation in winter had a significant increasing trend in most parts, while monthly precipitation in July to September showed a decreasing trend in some parts of NCP. No significant changing trend was found for the annual, dry and wet season precipitation and rainfall extremes in the majority of NCP.A significant decreasing trend was detected for the maximum no-rain duration and annual rain days in the major part of NCP. It was concluded that the changing trend of precipitation in NCP had an apparent seasonal and regional pattern, i.e., precipitation showed an obvious increasing trend in winter, but a decreasing trend in the rainy season (July to September), and the changing trend was more apparent in the northern part than in the southern and middle parts. This implies that with global warming, seasonal variation of precipitation in NCP tends to decline with an increasing of precipitation in winter season, and a decreasing in rainy season, particularly in the sub-humid northern part.
Lan Fan; Changhe Lu; Biao Yang; Zhao Chen. Long-term trends of precipitation in the North China Plain. Journal of Geographical Sciences 2012, 22, 989 -1001.
AMA StyleLan Fan, Changhe Lu, Biao Yang, Zhao Chen. Long-term trends of precipitation in the North China Plain. Journal of Geographical Sciences. 2012; 22 (6):989-1001.
Chicago/Turabian StyleLan Fan; Changhe Lu; Biao Yang; Zhao Chen. 2012. "Long-term trends of precipitation in the North China Plain." Journal of Geographical Sciences 22, no. 6: 989-1001.