Urban Expansion in Major Grain Producing Area from 1978 to 2017:A Case Study of Zhengzhou Metropolitan Area,China

The spatial form of urbanization in China has developed from single-core city expansion to a multi-center metropolitan area.However,little attention has been paid to the growth process of the emerging metropolitan area situated in major grain producing locations in the central China.Taking the Zhengzhou metropolitan area(ZZMA)as a case study,we developed an inverse S-shape model to characterize the spatial distribution of urban land density,and constructed an urban expansion core index,urban expansion intensity index,and urban compactness index to quantify the spatial structure change that has taken place from 1978 to 2017 during the process of urban expansion.Moreover,cropland contribution rate(CR)was constructed to evaluate the impacts of urban expansion on croplands.We uncovered four key findings.First,over the past 40 yr,the ZZMA has experienced dramatic expansion,and the central city of Zhengzhou expanded faster than other cities.The gravity centers of urban expansion of surrounding cities were moving toward to Zhengzhou City.Second,the urban land density decreased with the distance from the city center to the outskirts.As the only large city,Zhengzhou has experienced the fastest and most compact centralized urban expansion,especially after 2000,while other medium-and small-sized cities have experienced low-intensity decentralized expansion.Third,the urban core has been gradually expanding outward.From 1978 to 2017,the hot-zone of urban growth has moved progressively with the acceleration of urbanization.All cities except Jiaozuo had a single peak in different periods.Forth,the cities in national core grain-producing areas has higher cropland contribution rates and lower urban expansion areas,which was closely related to cropland protection.Further analysis showed that large city was relatively better positioned than smaller cities in the efficiency of their urban infrastructure and the effectiveness of wealth creation efficiency in the urbanized area could be tested in all cities,and the policy factor seemed to play an important role in the urban expansion process.

Agricultural Production Structure Optimization: A Case Study of Major Grain Producing Areas, China

A large number of mathematical models were developed for supporting agricultural production structure optimization decisions; however, few of them can address various uncertainties existing in many factors （e.g., eco-social benefit maximization, food security, employment stability and ecosystem balance）. In this study, an interval-probabilistic agricultural production structure optimization model （IPAPSOM） is formulated for tackling uncertainty presented as discrete intervals and/or probability distribution. The developed model improves upon the existing probabilistic programming and inexact optimization approaches. The IPAPSOM considers not only food security policy constraints, but also involves rural households’income increase and eco-environmental conversation, which can effectively reflect various interrelations among different aspects in an agricultural production structure optimization system. Moreover, it can also help examine the reliability of satisfying （or risk of violating） system constraints under uncertainty. The model is applied to a real case of long-term agricultural production structure optimization in Dancheng County, which is located in Henan Province of Central China as one of the major grain producing areas. Interval solutions associated with different risk levels of constraint violation are obtained. The results are useful for generating a range of decision alternatives under various system benefit conditions, and thus helping decision makers to identify the desired agricultural production structure optimization strategy under uncertainty.

Performance evaluation of ecological compensation policy for cultivated land in China

The paper evaluates the changes in the ecological environment of cultivated land in the major crop-producing areas major crop-producing areas in the past 20 years by constructing an ecological pollution index;and quantitatively analyzes the effects of the existing policies and their main influencing factors by applying the PSM-DID method based on the frequency of policy enactment.The results are as follows:first,the existing ecological compensation policies for cultivated land are effective but not significant in improving the ecological environment in the major crop-producing areas.The economic development level and grain cultivation area of the major crop-producing areas are significantly and positively correlated with the improvement of the arable land ecological environment,while the level of agricultural infrastructure construction is significantly and negatively correlated with the improvement of the arable land ecological environment.Second,the reason for the ineffectiveness of the current arable ecological land compensation policy in protecting the arable land ecological environment in the main grain-producing regions is that the existing arable ecological land compensation policy in China has its own institutional defects and needs to be further improved.At the same time,the level of environmental pollution of cultivated land in the main grain-producing regions is positively correlated with the level of income from cultivated land and cultivated area.