Study On Ecological Security Of Cultivated Land In Coastal Area Based On The Distribution Of Agrogeochemical Elements

Excessive exploitation and utilization of land resources will lead to the imbalance of the land ecosystem,and also threaten human health and life safety because of the quality of the products provided by land.At present,the land security issues have been upgraded to land ecological environment and functional safety issues from the land carrying security issues in the long-term irrational development and utilization.The research on land ecological security has become the focus of social concern.Among them,the research on the field of cultivated land ecological security has not reached consensus on the definition of connotation,evaluation index system and evaluation method.The spatial scale of most studies is too large,and because of lacking geochemical elements distribution information which is reflecting the soil nutrient content,environmental quality and health function of cultivated land,it is difficult for the research results to touch the deep essence of the ecological security of cultivated land.In view of this,Utilization of agrogeological geochemical background survey,and combined with field sampling detection,the research obtained detailed data and information.By the research of the theoretical connotation of cultivated land ecological security,the paper constructed a conceptual model and evaluation system,and took Huanghua City in Bohai Rim region as the research object to implement the evaluation and regionalization of cultivated land ecological security,and carried out the research on the monitoring and protection strategy system of cultivated land ecological security.It aimed to promote the theoretical study of land ecological security,guide the practice of agricultural ecological security production,and accelerate the construction of agricultural ecological civilization.Main conclusions were as following:(1)Defined the connotation of cultivated land ecological security and constructed a conceptual model of cultivated land ecological security.Based on the theory of “ecological security”,“land resource security” and “land ecological security”,the paper analyzed the system dynamics principle of cultivated land ecological security by considering Man-Land Relationship,characteristics and requirements of cultivated land use in China.The ecological security connotation of cultivated land was defined as: carrying security,land(soil)environmental security,system function safety,reserve support security,time and space balance,system security and property rights security,and constructed a conceptual model of ecological security assessment at county scale.Carrying security,ecological security and system function safety in the conceptual model are the basic and core elements.Reserve support security determines the subsequent supply of cultivated land.Space-time security requires that the benefits of cultivated land ecological security should be fairly distributed among different generations and regions,and it emphasizes that the allocation of cultivated land resources should provide the same right to development at the scales of time and space.Institutional security and property right security determine the periphery system and policy environment of cultivated land protection.(2)Carried out ecological security utilization survey and monitoring evaluation of cultivated land Taking Huanghua City as an example.The study carried out comprehensive and systematic investigation of the cultivated land in Huanghua City by various means and methods.Based on the results of agrogeological geochemical background survey,combined with field interviews and surveys,a large number of soil samples were collected to obtain testing data.and combined with land use change survey,agricultural land natural quality grading results and multi-year socioeconomic statistics,the paper established the 2015’ cultivated land ecological security database of Huanghua City.The study choose the single factor evaluation method,established reasonable safety evaluation standards and classification standards according to relevant regulations,technical standards and published research conclusions,and evaluated the ecological security of cultivated land in Huanghua City.Evaluation result display:The per capita arable land occupation in the county is relatively safe,which offfsets the inferiority of low grain yield and makes the per capita grain possession and cultivated land carrying rate in most areas more secure.The overall organic matter content of cultivated land is low,and 96.75% of the area belongs to the critical and moderate insecurity level.Most of the cultivated land has insufficient alkali nitrogen content,highly insecurity area is 76.55%,and the moderate unsafe area is 23.09%,which is in sharp contrast with the large use of nitrogen fertilizer.Groundwater has a shallow depth and high groundwater mineralization,which is a factor limiting the environmental safety of cultivated land.And 37.81% of cultivated land is in moderately salinized,and more than 20% of the cultivated land is seriously salinized,which belongs to the moderate and highly insecurity level.The correlation between the depth of groundwater and the degree of salinization of cultivated land is higher in spatial distribution.More than 90% of the cultivated land in Huanghua City has a highly pH value and in the critical safe state.The shortage of freshwater resources greatly restricts the guarantee rate of cultivated land irrigation in Huanghua,and only 2.62% of irrigated land can get 75% irrigation guarantee rate.The drainage conditions of cultivated land are poor,and 12.06% of the cultivated land drainage conditions are at the level of highly insecurity.The amount of fertilizer applied to cultivated land in Huanghua is generally too high,but the utilization efficiency of fertilizer is too low.In addition to As element and Ni element content,there is moderate level of security,the other six heavy metal elements are at highly security level.(3)Delineation of remediation division of cultivated land and corresponding construction of the district remediation strategyBased on the evaluation results,an ecological security monitoring system was constructed.And the areas where the indicators were un security were extracted,in accordance with the principles of consistency in technical and regulatory measures,the study used the spatial superposition method to superimpose the evaluation results and implemented the regionalization of ecological security.Four types of cultivated land strictly restricted occupancy area,fertility enhancement area,saline soil remediation and salt-tolerant crop improvement area,heavy metal pollution prevention area were identified,and corresponding regulation and supervision measures were arranged.(4)Proposed the improved utilization of saline soil by category in Huanghua CityThe study evaluated the degree of soil salinization in Huanghua City and analyzed the causes and influencing factors of salinization.Combined with the existing improvement methods of salinization,the paper discussed the suitable techniques for improving and utilizing light salinized soil,medium salinized soil and heavy salinized soil in Huanghua City.The paper proposes that the management of coastal saline-alkali land should follow the "adaptation" as the main strategy and the "salt control" as the auxiliary strategy,and eliminate the large-scale implementation of water-soil engineering.It also advocate vigorously promoting the cultivation of salt-tolerant crops,optimizing the cultivation system in coastal areas,and screen trees,shrubs,forages and grain crops with production and ecological benefits to improve the landscape and ecosystem of a large number of unused saline-alkali land.(5)Put forward cultivated land reserve resources security and property right security strategyThe study indicated two ways to ensure the security of cultivated land reserve resources in Huanghua City.First,through the development and utilization of salt-tolerant plants resources to improve the utilization efficiency of unused salinized land,alleviate the production pressure of cultivated land resources and shape the unique salinized soil landscape ecosystem of the county.The second is to explore the structural and spatial adjustment potential of land use through the construction of new countryside and small towns,and increase the supply of cultivated land and expand the scale of cultivated land management.By analyzing the deficiencies of the existing land property rights registration management system and protection performance,the paper put forward that the security of the land property rights system should be guaranteed by stabilizing the current rural land use system and promoting the transfer of land use rights,cultivating new subjects of safe use and protection,incorporating cultivated land into the unified land ownership registration audit system of towns and villages,make full use of new technology to establish dynamic monitoring system of cultivated land ecological security,and at the right moment and zone,suitably carry out land consolidation work to improve the level of agricultural industrialization and innovate the protection mechanism of cultivated land ecological security.