Study On Land Use Change And Early Warning Of Ecological Security In Qiqihar City

In recent years,the ecological environment problems caused by human factors have gradually come into people’s view.The change of land use intensively reflects the influence of human activities on land ecosystem,and its ecological and environmental effects have become the ideal entry point for the natural and human processes,biochemical cycles and global environmental changes.With the increasingly prominent contradiction between land use and ecological environment,more and more scholars begin to explore the process and law of land ecological security.The study on early warning of land ecological security is to measure and evaluate the warning situation of land ecological security by building an early warning index system,which can effectively prevent the land use to disorderly development,and has the great significance to the optimization of land use layout,ecological environment protection and regional sustainable development.This paper takes Qiqihar City as the study area,based on the theories and methods of land use,land ecological security and early warning to analysis regional land use quantity and structure,the speed of change,degree of utilization and land use types transfer quantitatively;And combined the internal relationship between land use and ecological environment change,integrated multi-source data to select indicators.And then an early warning index system for land ecological security was established on basis of “Pressure-State-Response” model;On the 500 m×500 m raster scale,comprehensive index evaluation method was used to measure and evaluate the early warning of land ecological security of Qiqihar City.The research analyzed the spatial and temporal variation characteristics of the warning situation,reflected the status and evolution trend of regional land ecological security.Finally,countermeasures and suggestions were put forward according to the actual situation of the study area.The main conclusions are as follows:(1)Cultivated land was the main land use type in Qiqihar City.The surface water resources were rich and the land use degree was high.During the past 25 years,the area of cultivated land,forest land and unused land kept increasing,water area continued to reduce and became the largest reduction.The change area of grassland and construction land was small,the former increased first and then decreased,the latter decreased first and then increased;The main types of land use transfer were the conversion of cultivated land to forest land and the conversion of water,cultivated land and unused land.Compared with the two study periods,the land use types changed rapidly and converted frequently in 1990-2001.And the land use change tended to be gentle in 2001-2015.Land use has transformed from the adjustment period to the development period.Land use structure was optimized and water loss and soil erosion has slowed down.(2)The status of land ecological security in the study area showed an improvement trend during the period from 1990 to 2015.The warning situation composite index increased from 0.462 to 0.526.The warning grade has transformed from the medium alarm to light alarm,and gradually approached the early alarm interval.The warning situation composite index in different regions has increased in varying degrees.In addition to the municipal district stayed at the grade of medium alarm,the warning grade has been improved in most areas.During the past 25 years,the continuous improvement of each index of the response layer has significant effect on the pressure and state layer.The results were achieved in the ecological constructive input of returning cultivated land to forest and grassland,water loss and soil erosion control and so on.It improved the state of ecosystem while alleviating the pressure of ecological environment and promoting the overall level of ecological security to enhance smoothly.(3)The temporal and spatial variation characteristics of warning situation were significant in study area.In 1990-2001,the ratio of medium alarm area was the largest and about 43% of the total area.The high values of the composite index was concentrated in the central region,the main river basin and forest region,the low values were widely distributed in the municipal district and the eastern and western regions.In 2001-2015,the ratio of medium alarm area fell to 13.47%.The area with low values of warning situation composite index reduced in a large scale,only arose at the municipal district,Baiquan and Keshan County.The area with high values was expanded smally on the original basis.The ratio of light alarm grade area increased to 54.58% and gradually replaced the dominant position of the medium alarm grade.(4)In order to curb the deterioration of the ecological environment,maintain the ecological system in a safe and stable development of the good trend.This paper combined the characteristics of land use and the trends of warning situation in Qiqihar City.And then some countermeasures and suggestions were put forward to solve the main problems of land ecological security from the visual angle of land use zoning,strengthening the protection of cultivated land,optimizing land use and layout,comprehensive management of ecological environment and building ecological security barrier.