| Food is an important basis for a country’s long-term peace and stability,water and cultivated land resources are the most important resources to support food production.Northeast China is a major grain-producing area in China,also a key region for planting structure optimization.It is of great significance to study its water-land-food nexus to promote the sustainable production of regional grain and sustainable utilization of land and water resources.In this study,time series data from 1990 to 2017 and GIS spatial analysis methods were used to analyze the temporal and spatial changes of water,cultivated land and grain.LMDI,virtual cultivated land,comprehensive irrigation quota was used to explore the impact of grain production on the utilization of cultivated land and water resources.The water-land-food nexus model(WLF)was constructed to illustrate the correlation among the three elements.The LSTM model was established to predict the future scenarios of water-land-food nexus.Finally,the corresponding control strategies were proposed.The main conclusions are as follows:The study diagnosed the basic situation and spatio-temporal evolution characteristics of water,cultivated land and grain in northeast China.Since 1996,the cultivated land area had been decreasing slowly.The decreased cultivated land shifted from ecological land to construction land,and the increased cultivated land was mainly from forest land,grassland and other ecological land.The change of farmland utilization structure was mainly from dry land to paddy field,and paddy field area and proportion both increased.The spatial distribution of total water resources was inconsistent with the utilization of water resources,which the utilization rate of development in hilly areas were low and the three plains were generally high.From 1990 to 2017,the grain area increased by 9.10×10~6 hm~2;Among them,rice and corn increased by 11.09 and 14.00 percentage points respectively,while that of soybean,wheat and coarse grains decreased by 3.16,13.42 and 8.51 percentage points respectively.Rice was mainly concentrated in sanjiang and Songnen Plain areas,while maize was developing rapidly in central and southern regions.The study analyzed the binary associations between water,cultivated land and grain.The correlation analysis of grain-cultivated land showed that the low-yield crops turned to high-yield crops,then the grain virtual cultivated land was deceasing from 0.24 hm~2/t in 1990 to 0.17 hm~2/t in 2017,the grain planting structure developed towards land saving direction.Grain-water correlation analysis showed that,rice area proportion increased and dry land crops area proportion decreased,then grain comprehensive irrigation quota increased from 1838.30 m~3/hm~2 in 1990 to 2192.52 m~3/hm~2 in 2017,grain planting structure developed towards more water consumption direction.The analysis of water and land matching showed that there was a big gap between the two types matching coefficient based on the natural water background and the total water use control indicators.A water-land-food nexus model was constructed to measure the correlation in multiple situations.Based on the total area of land used for planting grain,no matter in the situation of water resources or in the situation of total water use control,the water-land-food nexus was in an unbalanced state at provincial scale and all of them were short of water.At the prefecture-level,87.96%and 82.41%%cities were in unbalanced state,mainly short of water.It showed that it was unrealistic to develop all cultivated land for irrigation.Based on the existing irrigated cultivated land area for planting grain,no matter in the situation of water resources or in the situation of total water use control,the water-land-food nexus was in balanced state at provincial scale,indicating that the water-land-food nexus was balanced without increasing the irrigated area.At the prefecture-level,47.22%and 44.44%cities were short of land with redundant water,indicating that there was a certain potential to increase the irrigation area,which were mainly concentrated in mountainous areas,so the water right transfer could be adopted to realize the regional balance between mountainous areas and plain areas.The study predicted the future water-land-food nexus Scenarios and put forward the precision control strategy.The LSTM model was built to predict the future water-land-food nexus.The results show that by 2030,under the condition of total irrigation water control,based on the total land area for grain production,the water-land-food nexus will still be in the state of water shortage.Based on the cultivated land area under grain irrigation,the water-land-food nexus in Jilin province and Liaoning Province will continue to maintain an overall balance,and Heilongjiang Province will become slightly short of water.Changes in cultivated land resource,water resource,coefficient of effective utilization of irrigation water and irrigation quota had a direct impact on the relationship between water-land-food nexus.According to the water-land-food nexus characteristics in different cites,adjustment of the grain crops structure and water-land allocation will be the most direct and effective means for regional balance.The main innovations are the follows:(1)The water-land-food nexus model was constructed to evaluate the suitability and satisfaction degree of water,cultivated land and grain production;(2)The LSTM comprehensive prediction model of water-land-food nexus was established,which improved the prediction accuracy;(3)The relationship between the adjustment of grain structure and water-cultivated land utilization was revealed in northeast China,and precision control strategies were put forward from four perspectives. |
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