Land Function And Its Change

As the material basis of human survival and development,the importance of land is self-evident.However,the use of land resources has been emphasized on economic output for a long time,and the other functions of land have been weakened for a time,resulting in a series of problems,such as serious land quality degradation,aggravation of soil erosion,loss of biodiversity and so on.The external reason for this phenomenon is the strong demand for land in the development of human society and economy,while the internal reason is that human beings do not fully understand the functions of land itself.At the same time,with the rapid development of urbanization and industrialization and the continuous growth of population,the demand for land is increasing,and the development of unused land has become an important way to supplement the land demand gap.Therefore,it is of great significance to understand and master the land function and explore the changes of land function before and after the development of unused land.At present,the research on land function has become a hot topic in the society.Scholars at home and abroad have conducted extensive research on the classification,evaluation and influencing factors of land function.However,due to the high complexity,strong comprehensiveness and difficult identification of land function,there are some problems,such as the definition of land function is not unified,the classification is not comprehensive,and the function identification is relatively weak,It has not yet formed a systematic theoretical system of land function.At the same time,there are relatively few researches on the change of land function before and after the development of unused land.In view of this,based on system theory,dissipative structure theory,synergy theory,sustainable development theory,this paper carries out theoretical research on the aspects of land function concept connotation,land element-structure-order-function theoretical system and land function classification,and carries out case study on the change of land function before and after the development of unused land in Tang County of Hebei Province from macro and micro perspectives,mainly using the methods of literature analysis,mathematical model method,survey research method,spatial analysis method and statistical analysis method,etc.The purpose is to promote the theoretical research of land function and provide a theoretical basis for the improvement of regional land comprehensive function.The main conclusions are as follows:(1)Through the exploration of land function theory,the theoretical framework of land element-structure-order-function is established.Based on system theory,dissipative structure theory and synergy theory,this paper defined the concepts of land,land structure,land order and land function by using literature analysis method,systematically analyzes the relationship between land elements,land structure,land order and land function,and establishes the functional relationship and conceptual relationship diagram between land elements,land structure,land order and land function.Land function is the ability of the system itself under the interaction of various elements within the land system.The relationship between land elements,land structure,land order and land function was summarized as follows:land function is determined by land elements,land structure,land order and external environment.The land system is a whole formed by the organic connection of elements,and the land structure is the internal manifestation of the organic connection between elements,which affected by the environment(fluctuation factors)to form a certain land order,determines the land function.(2)The land function was classified,and the land function identification system and land function measurement system were constructed.Following the principles of scientific,dominant,systematic,quantifiable,practical and expandable land function classification,according to the differences of products and services provided by land,the land function was divided into six categories,including production function,raw material supply function,carrying function,ecological function,landscape function and historical record function,and 20 sub categories.Based on the framework of element-structure-order-function,the index system of various land function elements was determined.This paper deeply analyzed the characteristics of land function,which were mainly manifested as obvious dynamic,strong regional,active man-made and influenced by many factors.Based on the land elements of climate,geology,topography,hydrology,soil and biology,the land functions in different regions were identified and analyzed,the land function identification system was constructed,and the key elements of land function identification were optimized and extracted.On the basis of previous research results,this paper determined the main quantitative indicators and influencing factors to evaluate various functions,analyzed the calculation methods of individual functions from macro and micro perspectives,and constructed the calculation system of land functions.(3)This paper used the method of "leading factors+limiting factors" to determine the land function types in the study area;The spatial and temporal changes of land use in the study area were analyzed,and the source and direction of unused land change were grasped.The results showed that A1CDEF was the largest proportion of land function types,that is,land plant growth function+carrying function+ecological function+landscape function+historical record function.This kind of function type accounted for 26.94%of the regional land area,and the corresponding land conditions were unused land with slope less than 25 degrees and soil layer thickness more than 10 cm.The combination of land function types in the south of the research area were mainly A1C2DC1EF?CEDA1F and A1CDEF,which was mainly based on land production function and carrying function,supplemented by ecological function,landscape function and historical record function;The combination of land function types in northwest of the study area was mainly A1CDEF?A1DEC1C2F and A1CEDF,that is,the main functions were the land production function,ecological function and landscape function.From 2000 to 2018,the land use in Tang county changed significantly.The area of cultivated land,woodland,grassland,urban and rural residential areas increased significantly,the area of traffic land and water area also increased in varying degrees,and the area of unused land decreased sharply.From 2000 to 2018,the area of unused land decreased by 25.87%.The transfer direction of unused land was mainly grassland,cultivated land,forest land,urban and rural residential land,accounting for 97.28%of the total transfer out area of unused land.The main transfer sources were woodland,grassland and cultivated land,accounting for 91.68%of the total area transferred into unused land.(4)This paper took the unused land in Tang County as the research object,quantified the land production function and ecological function before and after the development of the unused land at the county level,and defined the key influencing factors.Production function was mainly characterized by net primary productivity(NPP)of vegetation,and ecological function was quantified by In VEST(Integrated Valuation of Ecosystem Services and Trade-offs)model from the perspectives of water conservation function,soil conservation function,climate regulation function and biodiversity maintenance function.Taking the unused land in 2000 as the research object,the changes of land production function and ecological function before(2000)and after(2007,2018)development of unused land in Tang County were compared and analyzed.In 2000,2007 and 2018,the total amount of NPP before and after unused development in the study area was 38.45×10¹⁰g C?36.44×10¹⁰g C and 41.05×10¹⁰g C.From 2000 to 2018,NPP first decreased and then increased.Elevation,temperature and precipitation had great influence on the spatial distribution of NPP.The water conservation function,soil conservation function,climate regulation function and biodiversity function were all on the rise from 2000 to 2018.The key factors affecting the water conservation function were precipitation,evapotranspiration and elevation;The key influencing factors of soil conservation and climate regulation were precipitation,slope,elevation and vegetation cover;Biodiversity function was mainly affected by land use types and biological factors(human activities).The change of each function was directly related to the change of land use type.(5)On the scale of plot,the paper quantified the production function and ecological function of unused land before and after development,and clarified the change trend of related factors after reclamation.Taking the unused land before reclamation(mainly waste grassland)as the control,the changes of production function and ecological function were studied from the perspectives of cultivated land for different years and garden land,forest land and cultivated land for different utilization modes.The results showed that from the perspective of land production function,the crop yield showed a parabolic change with the increase of reclamation years,and reached the maximum value of 7172.51kg/hm² after 10 years of reclamation,and then decreased and stabilized.The product value of cultivated land was significantly lower than that of garden land and woodland.From the perspective of land ecological function,with the increase of reclamation years,the water conservation function of cultivated land showed an increasing trend,the climate regulation function showed a trend of increase-decrease-increase,and the biodiversity function showed a decreasing trend.Compared with the grassland before development,the water conservation function of cultivated land after reclamation decreased in the early stage of reclamation(1-6 years),and the water conservation function of cultivated land in the late stage of reclamation(15-20 years)was equivalent to that of waste grassland;the climate regulation function and biodiversity function of cultivated land after reclamation were higher than those of waste grassland.Compared with the ecological functions of different land use patterns,cultivated land and woodland were generally higher than garden land and waste grassland.Soil porosity,aggregate,organic matter and total nitrogen content in soil physical and chemical properties were the key factors affecting the production and ecological functions of land in micro scale.The theoretical framework of land element-structure-order-function and the identification and measurement system of land function constructed in this paper provide a theoretical basis for further understanding and mastering land function.From the perspective of the combination of factors,the determination of land function types can provide the basis for the future direction of regional land use.The changes of land production function and ecological function before and after the development of unused land in the study area showed certain regularity,and the key influencing factors were different at different scales.