Research On Temporal And Spatial Change Of Arable Land And Grain Production Security In Shaanxi Province

With the acceleration of industrialization and urbanization, the confliction between decreasing arable land and increasing population has become more serious based on a large population with relatively little scarce arable land in China. Although numerous policies were applied, the decreasing trend of arable land has not been effectively controlled. The main factor which resulted in decreases of arable land was always irreversible construction occupation. China has implemented the arable land dynamic balance system to ensure the enough food, which did play an important role in guarantee the quantity of arable land. However, measures are quite rare about its quality balance. Although scholars have noticed the fact that qualities of supplementary arable land were worse than those occupational ones and have carried on some beneficial exploration in terms of grade conversion, quantitative study of its impacts on spatial food production is still almost blank.This study revealed the changes in arable land’s quantity and quality and analyzed its impacts on grain production from the year2000to2011through taking Shaanxi Province as a typical case. Two methods were adopted to predict the changes of arable land from2012to2020. In the107counties (districts),20sample counties (districts) and5764sample points were selected to calculate the arable land requisition-compensation coefficients using the methods of samples’actual output, farmland classification and productivity. Some protection measures aiming at different scales were also put forward. The following progress and results were obtained:(1) The impacts of spatial changes in arable land use on grain production has been analyzed on a quantitative based for the first time. Virtual production and typical sample investigation method were used to estimate the total grain lost from2000～2011and increment respectively, through which the change of grain productivity has been calculated because of the changes of Arable Land. (2) The concept of virtual production has been defined. It is an important index to measure the effects upon grain production when arable land changes to constructive use. Virtual production is the balance of actual output and net loss of grain in a certain year, the grain production which is under the assumption that there is no loss or supplement. The net loss of grain is the balance of grain production resulting from loss and supplement. The rate is the ratio between net loss of grain and virtual production, Positive rate implies increased grain production while negative means decreased one when arable changes occurs. The larger the greater influence occurs. Negative rate means decreased grain production. A negative rate can be named as the net loss ratio of grain, the larger the absolute value is, the greater the damage to grain production occurs.(3) From2000to2011, the main reasons of arable land decrease have transformed from ecological restoration to construction occupation. Shaanxi Province can achieve an overall requisition-compensation balance, but varies among different regions. Ecological restoration has been the first factor from2000to2005before the turning point year2006when construction occupation became dominant. The net decrease of arable land in Shaanxi Province tended to slow down between2000and2011. To view from the three regions, northern and southern Shaanxi can achieve requisition-compensation balance while the central Shaanxi plain cannot.(4) The main reason which causes the decreasing of arable land quality is due to difference quality between arable loss and new development ones. Construction land was mainly converted from arable land. The average level was60.8%in Shaanxi Province for the12years. Phenomena that construction occupied arable land happened mainly in the central Shaanxi plain, where irrigable and other high quality land was occupied. Arable land supplement with poor quality was mainly in the regions of northern Wei River and northern Shaanxi. Thus, differences in arable land occupation and supplement led to the decline of qualities as a whole. The average natural quality grades of occupational and supplementary land were7.05and12.76, respectively, with a difference of5.71. Compared with the year2000, the average natural quality grade of arable land decreased by0.11and the utilization grade decreased by0.15in the year2011in the whole province.(5) The net loss of grain was638024tons in Shaanxi Province in the past12years. Virtual production was used to estimate the grain reduction owing to cultivated land occupation, which turned out that the loss of grain was743125tons, among which Xi’an and Xianyang ranked top, accounted for41.95%and14.47%of the whole province respectively. Cultivated land supplementary increased a total of105101tons of grain. Although the requisition-compensation balance was realized in quantity in the whole province, the net loss of grain was638024tons because of the spatial and qualitative differences in cultivated land occupation and supplementary.(6)Construction use was the main factor improving the quality decrease of regional arable land. Residential and industrial land uses have been the primary demand factors. Phenomena that construction occupied arable land happened mainly in the central Shaanxi plain, where irrigable and other high quality land was mainly occupied. Arable land supplement with poor quality which was dominated by land development was mainly in the regions of northern Wei River and northern Shaanxi. Differences in arable land occupation and supplement led to the decline of quality as a whole. From2000to2011, there was about80.64%of arable land converting to residential and industrial uses among all the arable land occupation in Shaanxi Province.(7) To keep stable grain productivity, it is necessary to implement grade conversion between arable land occupation and supplement. Based on the grade transfer coefficient of the essay, from2012～2020, the average added on arable land area should be six times than loss arable area to keep the balance within the city. It is different from one to another that Hanzhong city is the highest while Yan’an city is the lowest. Figures will range from1to4.73for Arable Land utility Grade from4to14to keep the balance across cities.(8) Adhere to the concept of sustainable development, arable land production measures in different scales have been established in accordance with differences between regions. The occupation of arable land should be strictly controlled according to the regional characteristics in various scales. Urban Growth Boundary and Primary Agriculture Protection areas should be lined clearly. In addition, authorities in arable land conversion need to be narrowed eagerly and cost in occupation need to be improved reasonably. Under the concept of sustainable development, we have to correctly handle the development and protection of land resources as well as the relationship between the current and long-term development. Arrangements for all types of land should be reasonable and balanced. For those constructions that must occupy arable land, the ones with low-quality should be taken into account firstly to ensure sustainable and long-term use of those high-quality arable land and at the same time to protect the ecological environment.